Tram D201 mod that included a 6146B-8298A tube in final?

[capn357]

Anyone familiar with a modification for the Tram D201 that replaced the normal tube in the output section with a 6146B-8298A tube? Way back when in 1976, my father sent our Tram D201 to a guy to have it modified so that it would transmit on the "manual" tuning selection. At the same time, I remember the guy saying that he bumped up the power, but I didn't know the details. 40+ years later, I fired it up and compared the inside of mine to pictures of units being sold on Ebay. It was only then that I noticed the extra cord connected to the top of the rear most tube in my Tram's chassis (see photo). After examining that tube, I saw that it was a 6146B-8298A. The unit dead keys about 25 watts on AM according to my bird wattmeter.

Attachments:

[Sandbagger]

Feb 13, 2017 14:13:59 GMT -5 capn357 said:

Anyone familiar with a modification for the Tram D201 that replaced the normal tube in the output section with a 6146B-8298A tube? Way back when in 1976, my father sent our Tram D201 to a guy to have it modified so that it would transmit on the "manual" tuning selection. At the same time, I remember the guy saying that he bumped up the power, but I didn't know the details. 40+ years later, I fired it up and compared the inside of mine to pictures of units being sold on Ebay. It was only then that I noticed the extra cord connected to the top of the rear most tube in my Tram's chassis (see photo). After examining that tube, I saw that it was a 6146B-8298A. The unit dead keys about 30 watts on AM according to my bird wattmeter.

That's interesting. It's not an easy swap and will take a bit of work. Besides the wiring for the plate cap, the socket has to be rewired as the pin outs for the 6146 and the 6L6 are not the same. I don't doubt that once properly set up that it'll dead key 30 watts. But I have to wonder if the modulator has enough "oomph" to fully modulate that much carrier. I know the Tram has some of the best punchy audio at 4 watts. I wonder if it's still that strong with a 30 watt carrier. I would expect that a little modification work probably had to be done to the modulator to do so..

Personally, I never understood the appeal of these type of mods. I guess back in the good old days, if you never planned on ever running an amplifier, this kind of mod would probably net you a couple of S-units of signal boost over a "barefoot" 4 watt radio. But these mods come at a cost. And that cost is in reliability and longevity of the radio. The D201 already generates a lot of heat, due to the design of the power supply. Resistors change value and caps dry out, and crystals drift way off frequency. A power mod like that will only add to the heat and put extra strain on the power supply.
The real problem comes in if and when (and when is more likely), you finally decide to buy an amp, you find that most amps meant for CB are designed to be driven with no more than 5 watts of power. Putting 30 watts into that type of amp will toast it in short order. Nowadays, they do make amps for "high drive", due to the proliferation of higher powered "export" type radios. But back when that Tram was the king of the airwaves, you didn't have such a luxury. You'd then have to either un-modify the radio and put it back to stock, or maybe try to adapt a ham amplifer to work with it. 30 watts into a pair of 572B's will give you around 150 watts carrier out with a 600 watt PEP.

But hey it's all good. That's what's fun about this hobby. All sorts of interesting things to do to different radios......

[capn357]

We never did run an amp in combination with this unit, but we did have a Wilson 12 element laser on the roof.  What a monstrosity that was!  I remember being amazed that my mother let us put that thing up.  It made the little ranch house we lived in look like the fuselage of a helicopter.  I think my mother still has an old photo that I'll have to try to find the next time I'm up there.  We lived west of D.C. and I was able to talk all over the U.S. although I recall most of the contacts were east of the Mississippi.  There was a boatload of noise on every channel (all 23 of them:D) back in those days.  I still have a stack of the postcards I received from the folks I spoke to; I can't believe all the trouble we went to back then just to "prove" we talked skip somewhere.

Anyway, regarding your comments about the modulation,  I don't know whether this mod to the RF final included any modification to the modulation section or not.  I do know that the system sounded great with the standard non-amplified D104 back then.  I'm not sure it has the same punch today although I don't (yet) have a decent antenna to do it justice.

Your comments about the compromised reliability are duly noted.  I doubt we would have had this modification performed if either my father or I had really understood what was involved.  Then again, here I am 41 years after the fact and the rig still works, although I'm sure it is on borrowed time.  I had an Agilent Fieldfox analyzer that belonged to a former business partner of mine on hand that allowed me to align the synthesizer.  There were some banks of channels that were way out of whack and the USB was all over the place.  I was able to bring all but one of the crystals into alignment so channels 5-9 are still just a bit off on AM and LSB, but I can bring 'em back with the clarifier set to 9 o'clock.

Speaking of all of this, I recall one particular annoying "feature" of this radio back in the day that I want to run by you for comment.  I did a lot of talking on sideband back then and I was always under the impression that this unit transmitted on a slightly different frequency than it received on in SSB mode.  The reason I say that is because when I would tune someone in so that they sounded right, that person would always need to retune to get me to sound right.  I eventually just got in the habit of letting whoever I spoke to do the tuning and then I just lived with him or her sounding like a chipmunk.  Ever heard of this happening with other D201s?

[Sandbagger]

Feb 14, 2017 1:17:27 GMT -5 capn357 said:

We never did run an amp in combination with this unit, but we did have a Wilson 12 element laser on the roof.  What a monstrosity that was!  I remember being amazed that my mother let us put that thing up.  It made the little ranch house we lived in look like the fuselage of a helicopter.  I think my mother still has an old photo that I'll have to try to find the next time I'm up there.  We lived west of D.C. and I was able to talk all over the U.S. although I recall most of the contacts were east of the Mississippi.  There was a boatload of noise on every channel (all 23 of them:D) back in those days.  I still have a stack of the postcards I received from the folks I spoke to; I can't believe all the trouble we went to back then just to "prove" we talked skip somewhere.

Anyway, regarding your comments about the modulation,  I don't know whether this mod to the RF final included any modification to the modulation section or not.  I do know that the system sounded great with the standard non-amplified D104 back then.  I'm not sure it has the same punch today although I don't (yet) have a decent antenna to do it justice.

Your comments about the compromised reliability are duly noted.  I doubt we would have had this modification performed if either my father or I had really understood what was involved.  Then again, here I am 41 years after the fact and the rig still works, although I'm sure it is on borrowed time.  I had an Agilent Fieldfox analyzer that belonged to a former business partner of mine on hand that allowed me to align the synthesizer.  There were some banks of channels that were way out of whack and the USB was all over the place.  I was able to bring all but one of the crystals into alignment so channels 5-9 are still just a bit off on AM and LSB, but I can bring 'em back with the clarifier set to 9 o'clock.

Speaking of all of this, I recall one particular annoying "feature" of this radio back in the day that I want to run by you for comment.  I did a lot of talking on sideband back then and I was always under the impression that this unit transmitted on a slightly different frequency than it received on in SSB mode.  The reason I say that is because when I would tune someone in so that they sounded right, that person would always need to retune to get me to sound right.  I eventually just got in the habit of letting whoever I spoke to do the tuning and then I just lived with him or her sounding like a chipmunk.  Ever heard of this happening with other D201s?

The Tram D201 is one of the finest CB radios ever made. I enjoy mine immensely. But the Tram does not age well. Because of the heat issues and the design of the power supply, there are more components that need to be replaced than similarly aged radios when that 100,000 mile overhaul comes up. Most of the tube rigs I've restored can get by just replacing a small handful of electrolytic filter caps. While the Tram also frequently needs 1 and 2 watt resistors, tube sockets etc. replaced to bring it completely back to its former glory.

But yea, in the 1970's, if you didn't have a Browning Golden Eagle, the Tram was just as good, especially if you ran on SSB with any regularity (The Browning sucked as a SSB rig). You just had to give it a little "love" to keep it in top form.

As to your question on split transmit and receive frequencies on SSB, it's not a "design flaw". My D201's do not exhibit the problem. If I were to hazard a guess, I would say that your issue has something to do with how the "manual tuner VFO" mod was performed. There were literally a half dozen different procedures on how to do this mod. Some were better than others. I had to undo the initial mod that was done on mine and redo it in a more sensible way. Mine was so bad initially that it was actually transmitting on both the crystal and the VFO at the same time, which was not a good thing.

[2600]

Using the manual side on SSB is a waste of time. We did a lot of this and that trying to stabilize the VFO. A zener diode to regulate the B+ to the VFO has no effect on this. Tried it.

Finally found what causes it. When you key the mike, the transmit circuits draw more current from the power transformer. This causes the filament voltage to fall, just slightly. The only tube that is affected by this is the VFO side of V302. The tiny drop in heater temperature in the tube is what causes it to shift frequency on SSB. When you unkey, it slides right back to the frequency it gave you on receive before keying the mike.

A fanatic could probably regulate the heater power to V302 and fix this. Never had a customer fanatical enough to ask how much it would cost, let alone offer to pay for having it done.

But that's what we discovered.

Bear in mind that there is more than one way to wire up the "Xtl-Man" switch for using the VFO to transmit. Some hookups cause the frequency to jump when you transmit. Nobody notices on AM. The simplest hookups will cause this frequency shift and the AM operators won't notice or care. The hookup we worked out is more complex, but still won't fix the heater-voltage problem.


Oh, and that 6146 mod for the final was circulated on the 'net ten or fifteen years back. Best I can remember it was a guy named Gary Bedell in California who worked that out. He has been gone for nearly ten years, IIRC.

Maybe. Been a while. To run a bigger final you need more audio wattage to modulate it. Gotta figure that the audio level would be reduced with this setup unless you also make the modulator section bigger as well.


73

[capn357]

Feb 15, 2017 15:53:05 GMT -5 2600 said:

Using the manual side on SSB is a waste of time. We did a lot of this and that trying to stabilize the VFO. A zener diode to regulate the B+ to the VFO has no effect on this. Tried it.

Finally found what causes it. When you key the mike, the transmit circuits draw more current from the power transformer. This causes the filament voltage to fall, just slightly. The only tube that is affected by this is the VFO side of V302. The tiny drop in heater temperature in the tube is what causes it to shift frequency on SSB. When you unkey, it slides right back to the frequency it gave you on receive before keying the mike.

A fanatic could probably regulate the heater power to V302 and fix this. Never had a customer fanatical enough to ask how much it would cost, let alone offer to pay for having it done.

But that's what we discovered.

Bear in mind that there is more than one way to wire up the "Xtl-Man" switch for using the VFO to transmit. Some hookups cause the frequency to jump when you transmit. Nobody notices on AM. The simplest hookups will cause this frequency shift and the AM operators won't notice or care. The hookup we worked out is more complex, but still won't fix the heater-voltage problem.


Oh, and that 6146 mod for the final was circulated on the 'net ten or fifteen years back. Best I can remember it was a guy named Gary Bedell in California who worked that out. He has been gone for nearly ten years, IIRC.

Maybe. Been a while. To run a bigger final you need more audio wattage to modulate it. Gotta figure that the audio level would be reduced with this setup unless you also make the modulator section bigger as well.


73

That is extremely interesting (about the heater power)!  Thanks so much for taking the time to share that.  Regarding that 6146 mod, mine was performed by a fellow in Fairfax (or possibly Falls Church), Va in '76 or so.  I can vaguely remember riding to the guy's house with my father to pick up the unit.  What I can't recall is if I ever operated the D201 unmodified or if we had it shipped directly to this guy for modification at the time of purchase.

Regarding your and Sandbagger's comments that the AM modulation must be reduced, I suspect that is indeed the case.  Whereas a recently purchased unmodified D201 will dead key at 4 watts and swing a bit higher when speaking into the mike (as shown on a bird 43) my 6146 based unit dead keys around 25 watts, but then shows a decrease in power (again on the Bird 43) when speaking into the mike.  I wish I still had my buddy's Agilent Fieldfox so that I could see exactly what's going on with the carrier and sidebands, but I just sent that back to him about a week ago.  If only I had stayed at HP a while longer in the 80's AND if only I had not then lost complete interest in CB's in general at that time, I could have acquired an entire HP bigfoot test system (8903 audio analyzer, 8656 sig gen, 8902 measurement receiver) for nothing!  The guy that took my place now has that setup in his house in Richmond.

[Sandbagger]

Feb 16, 2017 0:31:38 GMT -5 capn357 said:

Feb 15, 2017 15:53:05 GMT -5 2600 said:

Using the manual side on SSB is a waste of time. We did a lot of this and that trying to stabilize the VFO. A zener diode to regulate the B+ to the VFO has no effect on this. Tried it.

Finally found what causes it. When you key the mike, the transmit circuits draw more current from the power transformer. This causes the filament voltage to fall, just slightly. The only tube that is affected by this is the VFO side of V302. The tiny drop in heater temperature in the tube is what causes it to shift frequency on SSB. When you unkey, it slides right back to the frequency it gave you on receive before keying the mike.

A fanatic could probably regulate the heater power to V302 and fix this. Never had a customer fanatical enough to ask how much it would cost, let alone offer to pay for having it done.

But that's what we discovered.

Bear in mind that there is more than one way to wire up the "Xtl-Man" switch for using the VFO to transmit. Some hookups cause the frequency to jump when you transmit. Nobody notices on AM. The simplest hookups will cause this frequency shift and the AM operators won't notice or care. The hookup we worked out is more complex, but still won't fix the heater-voltage problem.


Oh, and that 6146 mod for the final was circulated on the 'net ten or fifteen years back. Best I can remember it was a guy named Gary Bedell in California who worked that out. He has been gone for nearly ten years, IIRC.

Maybe. Been a while. To run a bigger final you need more audio wattage to modulate it. Gotta figure that the audio level would be reduced with this setup unless you also make the modulator section bigger as well.


73

That is extremely interesting (about the heater power)!  Thanks so much for taking the time to share that.  Regarding that 6146 mod, mine was performed by a fellow in Fairfax (or possibly Falls Church), Va in '76 or so.  I can vaguely remember riding to the guy's house with my father to pick up the unit.  What I can't recall is if I ever operated the D201 unmodified or if we had it shipped directly to this guy for modification at the time of purchase.

Regarding your and Sandbagger's comments that the AM modulation must be reduced, I suspect that is indeed the case.  Whereas a recently purchased unmodified D201 will dead key at 4 watts and swing a bit higher when speaking into the mike (as shown on a bird 43) my 6146 based unit dead keys around 25 watts, but then shows a decrease in power (again on the Bird 43) when speaking into the mike.  I wish I still had my buddy's Agilent Fieldfox so that I could see exactly what's going on with the carrier and sidebands, but I just sent that back to him about a week ago.  If only I had stayed at HP a while longer in the 80's AND if only I had not then lost complete interest in CB's in general at that time, I could have acquired an entire HP bigfoot test system (8903 audio analyzer, 8656 sig gen, 8902 measurement receiver) for nothing!  The guy that took my place now has that setup in his house in Richmond.

An average reading wattmeter like a Bird 43 is a great indicator of modulation unbalance. If you have more positive peak modulation, than negative trough modulation, the meter will swing forward when you talk. The converse is also true. And it looks like you are seeing a backward swing when you talk, which means your negative modulation is stronger than your positive. A good rule of thumb is to observe what the power reading drops to when you fully modulate, and that level should be where you set the dead carrier power in order to not back swing when modulating.

A 25 watt carrier will need to swing to 100 watts PEP to make 100% positive modulation. The 6L6 audio tube should have enough power to support that. But the rest of the circuitry may not be completely up to snuff considering it was only designed to deliver maybe 20 watts of peak modulation. The other factor may be the 6146 itself. Usually, in ham rigs, it takes a pair of those tubes to put out 100-120 watts give or take. So a single 6146 may not be able to deliver 100 peak watts.

[capn357]

Feb 16, 2017 7:20:48 GMT -5 Sandbagger said:

Feb 16, 2017 0:31:38 GMT -5 capn357 said:

An average reading wattmeter like a Bird 43 is a great indicator of modulation unbalance. If you have more positive peak modulation, than negative trough modulation, the meter will swing forward when you talk. The converse is also true. And it looks like you are seeing a backward swing when you talk, which means your negative modulation is stronger than your positive. A good rule of thumb is to observe what the power reading drops to when you fully modulate, and that level should be where you set the dead carrier power in order to not back swing when modulating.

A 25 watt carrier will need to swing to 100 watts PEP to make 100% positive modulation. The 6L6 audio tube should have enough power to support that. But the rest of the circuitry may not be completely up to snuff considering it was only designed to deliver maybe 20 watts of peak modulation. The other factor may be the 6146 itself. Usually, in ham rigs, it takes a pair of those tubes to put out 100-120 watts give or take. So a single 6146 may not be able to deliver 100 peak watts.

You got me to wondering if indeed something else was modified along with the RF final section when the 6146 was dropped in so I took the bottom off of my unit and the newly acquired "standard" unit and compared the two.  It certainly appears that my audio board has some extra components added to it, at least compared to this other unit. I put a high-res photo of my audio board in my box account at:

app.box.com/s/j4cus5rc1cumm2160vqafow08ouoryo4  

If you guys are curious at all and have the time to take a look at that photo, I figure you can easily tell if this looks standard or not.

I will say this, from a heat damage point of view, my unit sure looks a lot better than this one I picked up recently.  The only sign of any heat related damage on my juiced up unit is about a half-dollar sized discoloration in the upper corner of the BA board; everything else looks great.  On the other hand, this standard unit that I just bought shows a fair amount of heat damage on the receiver board and the BA board is completely discolored.  Maybe the previous owner let his cat sleep on top of the unit while he was talking on it.
 

[2600]

The math to determine the audio power your modulator must deliver for 100% modulation is fairly simple. Starts with the input power to the final tube. A class-C tube final gets you about 70% efficiency, so 10 Watts input power gets you a 7-Watt carrier. The RMS audio power needed is HALF the final tube's INPUT power. So, for that 7-Watt carrier on the wattmeter you need 5 Watts of audio power from the modulator, half the 10-Watt input power to the final.

A simplified version of this math is that your minimum audio power for 100% modulation is just over 7/10 of the carrier power on the wattmeter.


In my experience, A D201 starts to lose full modulation percentage around 6 or 7 Watts of carrier on the wattmeter. This implies that the 6L6 is delivering at best 5 Watts of audio power. The mods in the pic might double that, but no more than double. Probably not even that. Working backwards from a 25-Watt carrier, the input power to the final would be just under 36 Watts. Perfectly safe for a 6146. But the audio needed for full modulation is 18 Watts. No way a single 6L6 is giving you that. The modulation transformer will also hold you back, though I don't know how much.

Something I threatened to do years ago and never did was to pull the 6L6 tube from a D201 and hook up an external PA amplifier in its place. The guys who wanted to short across the carrier-set resistors and get a 12-Watt carrier asked how to keep from losing modulation percentage, and that's what I told them. That and I told them to turn the carrier back down and get an amplifier if they wanted more wattage.

We have used a 6550 tube in place of the 6L6 in a few D201s. You have to add some fixed bias to the cathode bias. Never tried to measure any increase in audio wattage, but it's a larger tube and spreads the heat over a larger surface area. That's the whole reason I put one in the D201 we used for years as a bench radio. Any increase in audio power is not that large, and only serves to improve "headroom" and maybe he forward swing. But not a lot. Not nearly enough to satisfy the needs of that 6146.

That radio will get you some bragging rights, but not a lot of audio on the air. Oh, and the dark spot on the BA board is from radiated heat off the 6L6 tube. I'll guess that the plate cherries up just a bit if you key it too long.

73

[Sandbagger]

Feb 16, 2017 20:56:42 GMT -5 capn357 said:

Feb 16, 2017 7:20:48 GMT -5 Sandbagger said:

An average reading wattmeter like a Bird 43 is a great indicator of modulation unbalance. If you have more positive peak modulation, than negative trough modulation, the meter will swing forward when you talk. The converse is also true. And it looks like you are seeing a backward swing when you talk, which means your negative modulation is stronger than your positive. A good rule of thumb is to observe what the power reading drops to when you fully modulate, and that level should be where you set the dead carrier power in order to not back swing when modulating.

A 25 watt carrier will need to swing to 100 watts PEP to make 100% positive modulation. The 6L6 audio tube should have enough power to support that. But the rest of the circuitry may not be completely up to snuff considering it was only designed to deliver maybe 20 watts of peak modulation. The other factor may be the 6146 itself. Usually, in ham rigs, it takes a pair of those tubes to put out 100-120 watts give or take. So a single 6146 may not be able to deliver 100 peak watts.

You got me to wondering if indeed something else was modified along with the RF final section when the 6146 was dropped in so I took the bottom off of my unit and the newly acquired "standard" unit and compared the two.  It certainly appears that my audio board has some extra components added to it, at least compared to this other unit. I put a high-res photo of my audio board in my box account at:

app.box.com/s/j4cus5rc1cumm2160vqafow08ouoryo4  

If you guys are curious at all and have the time to take a look at that photo, I figure you can easily tell if this looks standard or not.

I will say this, from a heat damage point of view, my unit sure looks a lot better than this one I picked up recently.  The only sign of any heat related damage on my juiced up unit is about a half-dollar sized discoloration in the upper corner of the BA board; everything else looks great.  On the other hand, this standard unit that I just bought shows a fair amount of heat damage on the receiver board and the BA board is completely discolored.  Maybe the previous owner let his cat sleep on top of the unit while he was talking on it.
 

It's difficult to tell exactly what those added components are for, but it's possible it could be some form of fixed bias (a clue to tell if that's the case is if the two 220 ohm 2 watt resistors on the BA board are jumpered out). After looking at the tube specs for the 6L6, you can get a few more watts of audio power out if you configure it with fixed grid bias over the standard cathode bias. I was actually surprised at what I saw. I thought the 6L6 was rated for more than it can actually deliver. It has a 30 watt plate dissipation, but in class A operation with cathode bias (at 300 volts on the plate) your power output is only 6.5 watts. That's plenty of modulation power for anywhere up to about 10-12 watts of RF carrier power. But not so much for 25 watts. Changing from cathode bias to fixed grid bias will up the max audio power to 10.8 watts, which then should just about get you to the 18-20 watt RF level. But you are still going to fall short at 25 watts carrier, which explains the backswing you are seeing.

Of course, you have to remember the times we lived in back then. Very few people understood the relationship between carrier power and peak modulation. They only saw what their watt meters showed them, and the thing back in the 70's was big carrier power. People wanted their radios peaked up so they would drive their amplifiers harder so that the big number on the wattmeter would be even higher. Never mind that they often sounded mushy that way, as long as they pushed your S-meter into the red when they keyed up. Today, we've gone entirely in the opposite direction. Now it's all about "swing". People want their setups to dead key 10 watts and swing to a kilowatt. That's equally insane, but CB'ers always did like to push the envelope, and if a little is good, a lot must be much better .

Your radio does look clean, which would imply that it wasn't used all that much, which is good, as it will probably not need as much for the 100,000 mile overhaul. Both of mine have circuit boards that are far more discolored. A lot of hours were logged on mine. Which probably explains the number of out of tolerance resistors I ran across.

[capn357]

Alright, so let's presume my rig is undermodulated.  Suppose I wanted to back down the carrier power to a level where my Audio section (however modified) can more adequately modulate the carrier.  Can that be done without a wholesale change of components or without completely detuning the RF final section?  (I'd like to just add a volume pot to the input of V700:D).

[Sandbagger]

Feb 17, 2017 11:28:44 GMT -5 capn357 said:

Alright, so let's presume my rig is undermodulated.  Suppose I wanted to back down the carrier power to a level where my Audio section (however modified) can more adequately modulate the carrier.  Can that be done without a wholesale change of components or without completely detuning the RF final section?  (I'd like to just add a volume pot to the input of V700:D).

Yes, you can drop he RF power by simply doing what Tram did in the first place with the original tube, by dropping the plate voltage to the final tube. The original circuit used a total of 4.2K (7-10 watt resistors) between the B+ and the modulation transformer leading to the final. You probably only have to drop the power down to between 15 and 20 watts and you should be able to regain 100% positive modulation.

[capn357]

Nice, thanks!  I tested the sound out today (not para-metrically, just what it sounded like through another relic of mine (Browning LTD)), and it sounded plenty loud to me as I drove around town while my assistant yapped on the tram.  I'm anxious to actually measure the modulation %, but I don't have the equipment to do so at the moment.  I'll likely wait to dive into the carrier power adjustment until I'm able to see the results of that measurement.

Now my challenge is that I don't think my property is very "CB base station friendly".  I'm kind of in a hole so I don't think I'll be able to achieve much range here locally.  Then again, it was always talking skip that interested me as a kid and I suppose I should be able to manage that reasonably well, even from the hole (assuming I put up a decent beam antenna, which I'm sure the snooty neighbors here will love).

[Sandbagger]

Feb 17, 2017 22:41:18 GMT -5 capn357 said:

Nice, thanks!  I tested the sound out today (not para-metrically, just what it sounded like through another relic of mine (Browning LTD)), and it sounded plenty loud to me as I drove around town while my assistant yapped on the tram.  I'm anxious to actually measure the modulation %, but I don't have the equipment to do so at the moment.  I'll likely wait to dive into the carrier power adjustment until I'm able to see the results of that measurement.

Now my challenge is that I don't think my property is very "CB base station friendly".  I'm kind of in a hole so I don't think I'll be able to achieve much range here locally.  Then again, it was always talking skip that interested me as a kid and I suppose I should be able to manage that reasonably well, even from the hole (assuming I put up a decent beam antenna, which I'm sure the snooty neighbors here will love).

The radio can still sound somewhat "loud" even if the peak positive modulation falls short of the 100% mark. I ran a strapped (Plate voltage dropping resistors jumped out) Lafayette Comstat 25 for my first several years in CB, with a 6 watt carrier and 80% modulation, and it still sounded "loud" enough to the locals. It was only when you moved further out of the area where my signal dropped down to S5 or lower did it become apparent that I lacked the amount of modulation "punch" that would have made me more copyable at that signal level.

I can also relate to living "in a hole". I did that for the first 29 years of my CB experience. I lived in a creek valley and 3 out of the 4 major directions, my signal had to climb hills to get out. Only to the SW did I have a shot that didn't run right into the side of a hill. I didn't do too badly for where I was, or at least I didn't think so compared to the other locals who lived in the area. You don't realize how much you're missing out until you move to a better area. Towers, big beams and some extra power help to make up for the shortfall in signal level. But living in the hole is a 2 way street and if you can't hear them, you can't talk to them either.

Hopefully you have a decent group of locals where you live, or you'll lose interest in CB real quickly. Skip is hit or miss, and right now we're just about to the bottom of the sunspot cycle, so the chances of good F layer skip is just about nil for the next 6 or 7 years. E-layer skip will hit again in the early summer months, but then that will fade away until next January or so. You'll get sporadic hits of it here and there but nothing predictable.

[capn357]

Feb 18, 2017 10:19:25 GMT -5 Sandbagger said:

I can also relate to living "in a hole". I did that for the first 29 years of my CB experience. I lived in a creek valley and 3 out of the 4 major directions, my signal had to climb hills to get out. Only to the SW did I have a shot that didn't run right into the side of a hill. I didn't do too badly for where I was, or at least I didn't think so compared to the other locals who lived in the area. You don't realize how much you're missing out until you move to a better area. Towers, big beams and some extra power help to make up for the shortfall in signal level. But living in the hole is a 2 way street and if you can't hear them, you can't talk to them either.

Hopefully you have a decent group of locals where you live, or you'll lose interest in CB real quickly. Skip is hit or miss, and right now we're just about to the bottom of the sunspot cycle, so the chances of good F layer skip is just about nil for the next 6 or 7 years. E-layer skip will hit again in the early summer months, but then that will fade away until next January or so. You'll get sporadic hits of it here and there but nothing predictable.

Acknowledged.  Just from the monitoring I've done here over the past few weeks, I have heard a fair amount of skip roll in (seems like at least once a day), and I'm getting plenty of signal from some of these guys that I'm sure are running impressive power.

When it comes to the CB airwave experience, I'm the guy who's been buried in a time capsule.  I can speak to three points in time:
1. Mid to late seventies where everybody and his brother had one of these things plus high sunspot activity = S9 baseline noise on every channel.
2. 1986 when I gave a mobile CB that I was no longer using to my then boss.  After hooking it up and turning it on, I initially thought it was broken because there was absolutely no noise and no signal level.  A combination of low sunspot activity, a dramatic decrease in users from the '70s peak, and no interference from computers and/or wireless transceivers (there were none) made for what had to be the golden age of quiet CB.
3. 2017.  I think I'll refer to this as the interference age.  From the moment I first hooked up the old D201 to a dipole here in the house I was immediately confronted with "noise" and this was different from the CB traffic related noise I heard 40 years ago.  This was interference that had to be mitigated with a combination of deployment of the noise blanker and full throttle on the ANL.  These were two features I never even used 40 years ago because I couldn't see that they made any difference whatsoever back then.  When I later put the old Browning LTD in the truck and drove around town with the unit on, I heard very little in the way of actual CB chatter.  I did hear the same type of interference noise except that in this case, the interference increased at every intersection.  The overall baseline signal level is certainly lower than it was in the seventies, but nowhere near as quiet as I heard there in Richmond in 1986.  My gut tells me this interference is due to the proliferation of CPUs and wireless transceivers even though both the CPUs and the transceivers operate at much higher frequencies.

[spitfire441]

Feb 17, 2017 22:41:18 GMT -5 capn357 said:

Nice, thanks!  I tested the sound out today (not para-metrically, just what it sounded like through another relic of mine (Browning LTD)), and it sounded plenty loud to me as I drove around town while my assistant yapped on the tram.  I'm anxious to actually measure the modulation %, but I don't have the equipment to do so at the moment.  I'll likely wait to dive into the carrier power adjustment until I'm able to see the results of that measurement.

Now my challenge is that I don't think my property is very "CB base station friendly".  I'm kind of in a hole so I don't think I'll be able to achieve much range here locally.  Then again, it was always talking skip that interested me as a kid and I suppose I should be able to manage that reasonably well, even from the hole (assuming I put up a decent beam antenna, which I'm sure the snooty neighbors here will love).

I have an easy reduce power mod for you. Buy a 2E26 tube, it will directly replace a 6146. Its good for about 18 to 30 watts peak, depending on plate voltage. I did this to my Multi Elmac transmitter as the 6146 was too much power to drive my 8 pill. The 2E26 is perfect. BTW the Elmac uses a pair of 5881 tubes in "shove yank", they are industrial equivalent to 6L6

[Sandbagger]

Feb 19, 2017 8:29:59 GMT -5 capn357 said:

Feb 18, 2017 10:19:25 GMT -5 Sandbagger said:

I can also relate to living "in a hole". I did that for the first 29 years of my CB experience. I lived in a creek valley and 3 out of the 4 major directions, my signal had to climb hills to get out. Only to the SW did I have a shot that didn't run right into the side of a hill. I didn't do too badly for where I was, or at least I didn't think so compared to the other locals who lived in the area. You don't realize how much you're missing out until you move to a better area. Towers, big beams and some extra power help to make up for the shortfall in signal level. But living in the hole is a 2 way street and if you can't hear them, you can't talk to them either.

Hopefully you have a decent group of locals where you live, or you'll lose interest in CB real quickly. Skip is hit or miss, and right now we're just about to the bottom of the sunspot cycle, so the chances of good F layer skip is just about nil for the next 6 or 7 years. E-layer skip will hit again in the early summer months, but then that will fade away until next January or so. You'll get sporadic hits of it here and there but nothing predictable.

Acknowledged.  Just from the monitoring I've done here over the past few weeks, I have heard a fair amount of skip roll in (seems like at least once a day), and I'm getting plenty of signal from some of these guys that I'm sure are running impressive power.

When it comes to the CB airwave experience, I'm the guy who's been buried in a time capsule.  I can speak to three points in time:
1. Mid to late seventies where everybody and his brother had one of these things plus high sunspot activity = S9 baseline noise on every channel.
2. 1986 when I gave a mobile CB that I was no longer using to my then boss.  After hooking it up and turning it on, I initially thought it was broken because there was absolutely no noise and no signal level.  A combination of low sunspot activity, a dramatic decrease in users from the '70s peak, and no interference from computers and/or wireless transceivers (there were none) made for what had to be the golden age of quiet CB.
3. 2017.  I think I'll refer to this as the interference age.  From the moment I first hooked up the old D201 to a dipole here in the house I was immediately confronted with "noise" and this was different from the CB traffic related noise I heard 40 years ago.  This was interference that had to be mitigated with a combination of deployment of the noise blanker and full throttle on the ANL.  These were two features I never even used 40 years ago because I couldn't see that they made any difference whatsoever back then.  When I later put the old Browning LTD in the truck and drove around town with the unit on, I heard very little in the way of actual CB chatter.  I did hear the same type of interference noise except that in this case, the interference increased at every intersection.  The overall baseline signal level is certainly lower than it was in the seventies, but nowhere near as quiet as I heard there in Richmond in 1986.  My gut tells me this interference is due to the proliferation of CPUs and wireless transceivers even though both the CPUs and the transceivers operate at much higher frequencies.

I'm right there with you on the time capsule. For me I have 4 points in time. The first was early 70's when we all ran walkie-talkies and could actually talk 3 or 4 miles without any trouble because the "fad" hadn't started yet, the sunspot cycle was at the bottom, and the ambient noise was very low.

Then, like you, I have the mid-late 70's full on fad period, where the channels were packed with people, the skip was ever-present, bleed over was the biggest nemesis, and everyone was obsessed with obtaining big power and extra channels. Of course back then "big power" was anything over 200 watts.

Then there was the 80's into the 90's. It was a time of transition. Export radios hit the scene. The casual fad user lost interest and moved on, and those who were left were more serious radio operators. But the level of civility also dropped, as the language became much more abrasive, and the "CB Rambo" types became much more prevalent.

Then we have the 21st century. Radio Shack stops selling CB radios. There are very few places where you can buy them locally. Export and "10 meter" radios outnumber legal CB radios by a wide margin, and most radios are made in China or some Pacific Rim country. Old timers become nostalgic for the "good old days" and start collecting vintage radios which starts inflating their worth (a radio that you couldn't give away at a hamfest in the 80's is now fetching $50 - $100 or more on E-Bay). Yet another sunspot cycle has come and gone, and it was not nearly as strong as the last one, and most of the skip heard was south of the border Spanish speaking stuff (at least for those of us on the East coast). As you've noticed, the amount of noise generated from digital widgets, switching power supplies, LED's, and computer networks makes running mobile an exercise in frustration. And even from the base station, there are devices that cause receiver pain. And I suspect, it's only going to get worse. We now have trains being fitted with speed control systems which transmit on channel 13, and put out spurs on several other channels. The FCC doesn't seem to be all that interested in it, and I'd bet they're secretly happy about it, since they'd like nothing more than to have the CB band go away.

[capn357]

Feb 19, 2017 16:22:57 GMT -5 spitfire441 said:

I have an easy reduce power mod for you. Buy a 2E26 tube, it will directly replace a 6146. Its good for about 18 to 30 watts peak, depending on plate voltage. I did this to my Multi Elmac transmitter as the 6146 was too much power to drive my 8 pill. The 2E26 is perfect. BTW the Elmac uses a pair of 5881 tubes in "shove yank", they are industrial equivalent to 6L6

Great, thanks!  Do you have any recommendation on which 2E26 manufacturer(s) are good (or alternatively, which manufacturer(s) I should avoid)?

[capn357]

Feb 19, 2017 18:20:16 GMT -5 Sandbagger said:

I'm right there with you on the time capsule. For me I have 4 points in time. The first was early 70's when we all ran walkie-talkies and could actually talk 3 or 4 miles without any trouble because the "fad" hadn't started yet, the sunspot cycle was at the bottom, and the ambient noise was very low.

Then, like you, I have the mid-late 70's full on fad period, where the channels were packed with people, the skip was ever-present, bleed over was the biggest nemesis, and everyone was obsessed with obtaining big power and extra channels. Of course back then "big power" was anything over 200 watts.

Then there was the 80's into the 90's. It was a time of transition. Export radios hit the scene. The casual fad user lost interest and moved on, and those who were left were more serious radio operators. But the level of civility also dropped, as the language became much more abrasive, and the "CB Rambo" types became much more prevalent.

Then we have the 21st century. Radio Shack stops selling CB radios. There are very few places where you can buy them locally. Export and "10 meter" radios outnumber legal CB radios by a wide margin, and most radios are made in China or some Pacific Rim country. Old timers become nostalgic for the "good old days" and start collecting vintage radios which starts inflating their worth (a radio that you couldn't give away at a hamfest in the 80's is now fetching $50 - $100 or more on E-Bay). Yet another sunspot cycle has come and gone, and it was not nearly as strong as the last one, and most of the skip heard was south of the border Spanish speaking stuff (at least for those of us on the East coast). As you've noticed, the amount of noise generated from digital widgets, switching power supplies, LED's, and computer networks makes running mobile an exercise in frustration. And even from the base station, there are devices that cause receiver pain. And I suspect, it's only going to get worse. We now have trains being fitted with speed control systems which transmit on channel 13, and put out spurs on several other channels. The FCC doesn't seem to be all that interested in it, and I'd bet they're secretly happy about it, since they'd like nothing more than to have the CB band go away.

No kidding about the inflated prices for old radios!  i won't call out the manufacturers here, but stuff that was considered to be junk or marginal back in the day is now suddenly sought after for some reason.

As far as the new lack of civility goes, I've already noticed that here in the last few weeks.  Admittedly we had our drunks and general pain in the butts back in the 70's, but there were enough people in the CB community listening at any given time that would intervene and keep that pretty well under control.  Moreover, the small town i grew up in (not so small now) made it much tougher to be an anonymous jackass on the air.

[Sandbagger]

Feb 19, 2017 20:55:12 GMT -5 capn357 said:

Feb 19, 2017 18:20:16 GMT -5 Sandbagger said:

I'm right there with you on the time capsule. For me I have 4 points in time. The first was early 70's when we all ran walkie-talkies and could actually talk 3 or 4 miles without any trouble because the "fad" hadn't started yet, and the ambient noise was very low.

Then, like you, I have the mid-late 70's full on fad period, where the channels were packed with people, the skip was ever-present, bleed over was the biggest nemesis, and everyone was obsessed with obtaining big power and extra channels. Of course back then "big power" was anything over 200 watts.

Then there was the 80's into the 90's. It was a time of transition. Export radios hit the scene. The casual fad user lost interest and moved on, and those who were left were more serious radio operators. But the level of civility also dropped, as the language became much more abrasive, and the "CB Rambo" types became much more prevalent.

Then we have the 21st century. Radio Shack stops selling CB radios. There are very few places where you can buy them locally. Export and "10 meter" radios outnumber legal CB radios by a wide margin, and most radios are made in China or some Pacific Rim country. Old timers become nostalgic for the "good old days" and start collecting vintage radios which starts inflating their worth (a radio that you couldn't give away at a hamfest in the 80's is now fetching $50 - $100 or more on E-Bay). Yet another sunspot cycle has come and gone, and it was not nearly as strong as the last one, and most of the skip heard was south of the border Spanish speaking stuff (at least for those of us on the East coast). As you've noticed, the amount of noise generated from digital widgets, switching power supplies, LED's, and computer networks makes running mobile an exercise in frustration. And even from the base station, there are devices that cause receiver pain. And I suspect, it's only going to get worse. We now have trains being fitted with speed control systems which transmit on channel 13, and put out spurs on several other channels. The FCC doesn't seem to be all that interested in it, and I'd bet they're secretly happy about it, since they'd like nothing more than to have the CB band go away.

No kidding about the inflated prices for old radios!  i won't call out the manufacturers here, but stuff that was considered to be junk or marginal back in the day is now suddenly sought after for some reason.

As far as the new lack of civility goes, I've already noticed that here in the last few weeks.  Admittedly we had our drunks and general pain in the butts back in the 70's, but there were enough people in the CB community listening at any given time that would intervene and keep that pretty well under control.  Moreover, the small town i grew up in (not so small now) made it much tougher to be an anonymous jackass on the air.

And no matter how heated a "discussion" got, the language never exceeded a "PG" rating. Nowadays there are people out there (fortunately not on our local channel) who throw out four letter words every other sentence. Part of that could be explained by the very real fear of the FCC back in the day. Every once in a while they would show up and take out a few bad eggs, and everyone else went into lock down mode, cleaned their acts up and hid away any illegal equipment. Now, no one cares about the FCC, because they know the FCC doesn't have the budget to run roughshod over the CB band. Unless you become a world class butthead and start wiping out commercial and municipal communications, chances are you'll never have the deal with the FCC.

But the drunks were funny. You never knew what they might do. They were a good excuse to keep the tape recorder warmed up and ready.....

[capn357]

Feb 17, 2017 12:44:46 GMT -5 Sandbagger said:

Feb 17, 2017 11:28:44 GMT -5 capn357 said:

Alright, so let's presume my rig is undermodulated.  Suppose I wanted to back down the carrier power to a level where my Audio section (however modified) can more adequately modulate the carrier.  Can that be done without a wholesale change of components or without completely detuning the RF final section?  (I'd like to just add a volume pot to the input of V700:D).

Yes, you can drop he RF power by simply doing what Tram did in the first place with the original tube, by dropping the plate voltage to the final tube. The original circuit used a total of 4.2K (7-10 watt resistors) between the B+ and the modulation transformer leading to the final. You probably only have to drop the power down to between 15 and 20 watts and you should be able to regain 100% positive modulation.

Alright, so I acquired some test resources and confirmed that the 25 watt carrier was indeed undermodulated.  Moreover, when looking at the unit itself I saw that as part of this modification, R642 and R643 were completely removed (I guess jumpering these two wasn't good enough for our tech as he must have decided he wanted to retain a few items for his trouble).  He also re-provisioned the 4 uF capacitor (C628) and used it as part of his funky modification to the audio board.  

So I purchased a 50 watt 10K pot and a 100 uF capacitor (I saw some reference to somebody's mods for the d201 that suggested the 100 uF as a replacement for the standard 4 uF) to insert back into the circuit in place of R642, R643, and C628, respectively.  This "worked" in so much as I can now adjust the pot and vary the carrier output power anywhere from a watt or two to about 28 watts.

I haven't yet figured out all of the details of the modifications this tech made to the audio board as part of the overall 6146 mod, but I don't think he accomplished much of anything with those mods other than adding a bunch of distortion to the audio output.  I have to back the carrier output level all of the way down to near the rated output of 4 watts in order to achieve full modulation with an acceptable (6-7%) distortion level.

About the only good thing I can think of to say about this modification at this point is that it didn't appear to cause any unique heat-related issues to my unit.  As I've stated previously, the ONLY board that shows any signs of heat damage is the upper right corner of the BA board; everything else looks great and I used to leave this radio on for many hours (if not days) straight back in the stone ages.

Other than that, all I'm left with at this point is a bit of a Frankenstein monster that I no longer know how to align properly.

[capn357]

Upon further analysis, the demodulated baseband signal emanating from this D201 is decidedly asymmetrical in the positive direction.  That explains the increased distortion level as compared to the other two Trams.  I'm wondering if this was a purposeful aspect of the audio board modifications that were performed by our tech or an undesirable artifact.  I can't see why he would have done this purposely given the high carrier level and relatively low modulation percentage.

[Sandbagger]

Mar 9, 2017 0:19:21 GMT -5 capn357 said:

Upon further analysis, the demodulated baseband signal emanating from this D201 is decidedly asymmetrical in the positive direction.  That explains the increased distortion level as compared to the other two Trams.  I'm wondering if this was a purposeful aspect of the audio board modifications that were performed by our tech or an undesirable artifact.  I can't see why he would have done this purposely given the high carrier level and relatively low modulation percentage.

Increased positive asymmetry would actually be a good thing. Many broadcast stations employ deliberate asymmetrical modulation to boost their "talk power". But what you've found doesn't make sense. In order to achieve a higher level of positive (peak) modulation, the modulator needs to be able to reproduce it at a power level to modulate a 25 watt carrier, which we determined falls short with the stock Tram modulator. Now at a lower carrier level, that might be a different story, and positive asymmetry should result in a forward deflection of an average reading wattmeter when modulation is applied. You also have to make sure the modulation limiter is working. If that is completely defeated, the modulator will push the power to its limits in the positive direction, but it will hard cutoff at the zero crossing point of the negative direction. Usually there is more positive than negative modulation (you can't go lower than zero). But you don't want the negative to cutoff, as that is what's responsible for splatter.

[bill]

1 6146 Mod I saw, which is within the Mods discussed here; Rifleman's Part 1, says the 6146 is for SSB and otherwise AM use would smoke the Audio Transformer
It's on Page 2 of Part 1... Nomad previously referenced a fellow Gary Bedell and the Initials of the Author of that Mod is G.B., so probably 1 and the same fellow, I presume...
grumpy.proboards.com/thread/5814/un-happy-tram
Also in Part 1 is more talk about 6146 use; Pg 10 there...

I have even seen photos of Trams with 2 pieces of 6146 tubes in them to replace both 6L6GC tubes, along with an additional transformer added...
These Radios are probably the most modified that I have seen...

[outbacktech]

Feb 13, 2017 14:13:59 GMT -5 capn357 said:

Anyone familiar with a modification for the Tram D201 that replaced the normal tube in the output section with a 6146B-8298A tube? Way back when in 1976, my father sent our Tram D201 to a guy to have it modified so that it would transmit on the "manual" tuning selection. At the same time, I remember the guy saying that he bumped up the power, but I didn't know the details. 40+ years later, I fired it up and compared the inside of mine to pictures of units being sold on Ebay. It was only then that I noticed the extra cord connected to the top of the rear most tube in my Tram's chassis (see photo). After examining that tube, I saw that it was a 6146B-8298A. The unit dead keys about 25 watts on AM according to my bird wattmeter.

I have modded mine with a 6DQ6B; One for one swap apart from the anode feed. The plate dissipation on the 6DQ6B is better than the 6DG6, (a whole lot easier to obtain also) a small hole has to be drilled through the chassis to enable a connecting wire from the plate capacitor which needs to be well insulated, the parasitic suppressor is also used again just need to source an anode cap.

[2600]

Umm, six-bee-kew-six?

Or six-DEE-kew-six?

Either tube would probably work, seems like.

But a puzzle. The 6L6GC we use for this has a plate rated for 30 Watts. The 6DQ6 says 18 Watts. 11 Watts for the 6BQ6.

6DG6 plate is rated for ten Watts, so any of the above tubes is an upgrade from factory-stock.

6L6GC is the simplest of all to use.

73

[outbacktech]

Yeah, typo, 6 DEE QUE 6, I like Anode caps & the 6L6 ( which is pretty much an Audio Tube) would not work... Yaesu used this Tube back in the days when the D201 was in production in the FT75-B, two of them gave 100w input, the 6DQ6 is better suited for RF applications and a little more rugged than the original, works like a treat in the D201A..

[2600]

Way cool! A solution that works is a good one, right?

Rock on and 73

[outbacktech]

Yes, appears so, no adverse effects, the power supply of the D201 is quite capable of operating this tube and quite well it seems, no real modification to the circuit required apart from lifting the parasitic suppressor off the valve socket, a small hole and a feed from the plate capacitor,