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Post by capn357 on Mar 8, 2017 8:54:12 GMT -5
I hooked up some test equipment in order to measure, among other things, the distortion level on the transmitted audio at 1KHz. When the test equipment registered 7% distortion on the first of my three D201s that I tested, I thought, "Holy smoke, that's high! There's no way that's right!" I immediately went to the manual only to find that the specification for the audio output is "4 watts at 10% T.H.D."
The other two d201s I have produce similar results. Admittedly, all of my units are in need of the "100,000 mile service" (to borrow a phrase from Nomad).
I'm curious to know what distortion levels you guys have seen or have been able to achieve with these units.
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Sandbagger
Administrator/The Boss 
Posts: 6,250 
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Post by Sandbagger on Mar 8, 2017 10:19:47 GMT -5
I hooked up some test equipment in order to measure, among other things, the distortion level on the transmitted audio at 1KHz. When the test equipment registered 7% distortion on the first of my three D201s that I tested, I thought, "Holy smoke, that's high! There's no way that's right!" I immediately went to the manual only to find that the specification for the audio output is "4 watts at 10% T.H.D." The other two d201s I have produce similar results. Admittedly, all of my units are in need of the "100,000 mile service" (to borrow a phrase from Nomad). I'm curious to know what distortion levels you guys have seen or have been able to achieve with these units. You have to take the term "distortion" in context. At the core, the definition of distortion is any deviation from the original signal. But tube amplifiers have an inherent distortion that makes the audio sound "warmer" or "more rich". So having 7% distortion may not be a bad thing. Distortion is also hard to quantify without accurate test equipment. |
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Post by capn357 on Mar 8, 2017 12:46:02 GMT -5
I hooked up some test equipment in order to measure, among other things, the distortion level on the transmitted audio at 1KHz. When the test equipment registered 7% distortion on the first of my three D201s that I tested, I thought, "Holy smoke, that's high! There's no way that's right!" I immediately went to the manual only to find that the specification for the audio output is "4 watts at 10% T.H.D." The other two d201s I have produce similar results. Admittedly, all of my units are in need of the "100,000 mile service" (to borrow a phrase from Nomad). I'm curious to know what distortion levels you guys have seen or have been able to achieve with these units. You have to take the term "distortion" in context. At the core, the definition of distortion is any deviation from the original signal. But tube amplifiers have an inherent distortion that makes the audio sound "warmer" or "more rich". So having 7% distortion may not be a bad thing. Distortion is also hard to quantify without accurate test equipment. Y-e-a-h, that's kind of what I figured. Two worlds are colliding for me now: My teenage CB days operating our tube based D201 and my subsequent adult life as an engineer. More recently, when considering and evaluating stereo audio equipment, I've flatly dismissed subjective evaluation in favor of hard measurement results. I've found myself put off by the un-quantifiable characterizations of some audiophiles such as "punch", "presence", "life", and yes, "warmth". Instead, I always took the positions of "give me equipment that produces the waveform as it was originally recorded" and "if it can't be measured, it isn't real". Not surprisingly, all of my stereo equipment is solid state based and I'm sure lacks warmth, life, punch, and presence  That said, I think I can make an exception now when it comes to CB's. I suppose I can go along with the idea of "coloring" the audio here since there is nothing particularly interesting about maintaining the absolute fidelity of someone yapping on the radio. Still, I am interested to know what type of distortion is typical and/or achievable with these units. For my part, I'm using an HP 8903B Audio Analyzer to supply the audio to the mic input of the D201 (2mV is what I chose), and then using an HP 8568B as a tuned receiver to demodulate the transmitted signal from the D201 (8568 tuned to carrier frequency and set to zero span, linear scale). I then feed the demodulated signal (i.e. video output of 8568B) into the 8903B. The 8903B measures the frequency, amplitude, and distortion level (either percentage or amplitude) of the demodulated signal. The 8903B provides no insight into where, in frequency, the distortion is, just the extent (amplitude) of it. I can certainly get a sense of the where from viewing the 8568 results in a more traditional swept frequency mode. One potential weakness of my current setup is the way in which I'm coupling the output from the D201 into the input of the 8568 spectrum analyzer. I've simply inserted a paper clip into the center conductor of the input of the 8568 to serve as a bad antenna to pick up the leakage from the D201 that is transmitting into a dummy load. This "works" and serves to address the incompatibility of the 4-25 Watt direct output of the D201 (depending upon which one I'm using) and the 1 Watt maximum input allowed on the 8568. Ideally, it would be nice to have a 40 dB directional coupler that I could insert inline to pick off the signal directly, but I don't have one of those presently. Incidentally, I also used this basic setup as described to characterize the distortion produced by the combination of a D201 + old Elkin 6 tube amplifier. Here again, the Elkin is all original and I'm sure is in need of some cap replacement at a minimum. At the low output setting the of Elkin, I get about 80-90 Watts on the Bird 43 and about 15-18% distortion on the 8903B (again, the input to the Elkin coming from the D201 contains about 6% distortion level). On the high setting of the Elkin, the Bird registers somewhere north of 150, but the distortion goes through the roof at 35% or higher and the video trace on the 8568 no longer resembles a sine wave. My next alteration to the test setup is to put a speaker or headphones in place of the 8903B analyzer so that i can hear all of that good (and bad) distortion. In school, I always took a liking to electromagnetics and radio wave propagation, but never liked or really understood the electronic design part of it. Consequently, I'm very comfortable analyzing and evaluating the modulated radio wave, but have little clue how exactly it is produced and what affects the performance of it, at least not down below the block diagram level. I really wish I could look at a schematic and clearly understand what the circuit was doing and how it would behave strictly from a glance at the topology and values of the discrete components, but I cannot. These recent experiments with my old radios are forcing me to confront my weakness in electronic design and I greatly appreciate the help and insight you and others have provided along those lines. |
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Post by bill on Mar 8, 2017 14:58:56 GMT -5
WOW... Sounds pretty Technical to me... Sure, I suppose everyone wants the best Output, but what difference does it or will it make to a Crappy Receiver of the Signal ? I don't know a lot admittedly... Here's the most Technical Video of a Tram's performance that I know of... www.youtube.com/watch?v=pYGYxbXZrcII'm not sure if it falls in line with anything you are doing, or not... |
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Post by capn357 on Mar 8, 2017 15:23:17 GMT -5
WOW... Sounds pretty Technical to me... Sure, I suppose everyone wants the best Output, but what difference does it or will it make to a Crappy Receiver of the Signal ? I don't know a lot admittedly... Here's the most Technical Video of a Tram's performance that I know of... www.youtube.com/watch?v=pYGYxbXZrcII'm not sure if it falls in line with anything you are doing, or not... Bill, thanks for providing that link. After watching that video, the weakness I see in that analysis is that it didn't include any modulation; that is where all of the distortion I'm speaking of and that I've measured comes into play. The unmodulated carrier is indeed pristine just as can be seen on that video. He should have put the spectrum analyzer in "max hold" mode, keyed the mike, and exclaimed, "Break o-n-e n-i-n-e! How 'bout that Rubber Hose, you got a copy?" into the mic. That's when the splatter, if any, would occur. |
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Post by bill on Mar 8, 2017 17:01:14 GMT -5
I'd probably be more apt to perform the 1000,000 Mile Tune-Up before I did any Technical Evaluation(s) on the Radio... Make sure all the Circuit Voltages were up to Specs... Then again, as far as Distortion, I do not believe all Manufacturers' Tubes are created equal either... You can do an Online Search or search this Forum, for Tram Modifications and some of which are Audio Tailoring Mods grumpy.proboards.com/thread/5814/un-happy-tramPlenty of Tips and Tricks have been done to these Radios... I own a couple of D201A Radios and both are Electrically Different from the Factory... Nomad I am sure will have a few Ideas, as he is quite familiar with these Radios and more... I own a couple of sets of Brownings, a R27 / S23 and a MK IVA... The D201A and the MK IVA are like Night and Day... The Tram is a keeper, the Brownings, not so much in my opinion... |
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Post by bill on Mar 8, 2017 19:20:18 GMT -5
Question is.... WHICH Manufacturer(s) supplied the Tubes for Trams  All the Tubes in 1 of my 2 D201A Radios are Factory Originals... Many have Tram Logos upon the Glass... Of course, I know that Tram did not make them... I've asked the Question as to which Tube Manufacturer supplied Tram and it was said one's suspicion was General Electric... It was said that GE had a habit of being somewhat sneaky in their placing "Tell-Tale; Dots" on the Glass of all their Tubes... Yes, Different Manufacturers made different Tubes that were then Sold and Relabeled and Marketed once again... SO.... WHO made your Tube(s) ? Here's one's opinion related to 6L6GC Tubes that works on these Radios and more and also has New Old Stock Parts for Tram and Browning Radios... He cautions against some Chinese and Russian Tubes... stores.goldeneagleradios.com/6l6gc-6n3ce-may-be-in-white-boxes/I don't know, as I am NO "Expert'... Nor do I claim to be.... BUT, To me, NOT ALL Tubes are created equal... I see the possibility / probability, that any Modulation / Distortion Tests would vary depending on the Tube(s) the Radio uses... Isn't Electronics and the Radio Hobby FUN LOL .... |
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Post by 2600 on Mar 8, 2017 22:59:02 GMT -5
Who made this tube?
Who sold this tube?
Two different questions. Sometimes with the same answer, sometimes not.
It's not so different from other businesses. One business unit of corporation "G" runs a factory making tubes. Another business unit markets and distributes them. Not so different from the auto business in this sense. You can't drive up to a car factory, hand them a wad of cash and drive away in a new one. The factory only ships to the sales division of the parent company.
Now, if you are buying in wholesale lots, you could deal with the factory's sales division.
If you want just one, or a few you'll have to go one level down from the manufacturer's wholesale division to a retailer.
Tubes were made in bulk at a factory, and sold that way in trays of 144 with no brand markings on them. Just the indelible type number. This way they could be sold to any sales company, whether for corporation "G" who owns both, or to any other. Those bulk trays of un-branded tubes would be sold to whoever had the money, not just the 'other' division of the same corporation.
If the GE Sales division ran out of 6L6 tubes, and the Owensboro factory would not be making another production run for a month, they would fill that sales order any way they could. Sure, the GE Sales division would prefer to buy from the GE factory, but they would buy trays of unmarked tubes from whatever factory had them to sell.
The sales division would paint a name on the tube, and package it for retail sale in a printed carton.
Or put them back into bulk trays of 144 with the customer's name printed on them, instead of the GE Sales division's name.
RCA, Sylvania and Amperex would all do this if you bought enough of one type at a time. Didn't matter to them what name got painted onto the tubes they shipped, so long as the setup fee for the artwork got covered.
But about that indelible (usually) type number? GE sandblasted the type number. RCA would have an octagon border around the type number. Sylvania used a dark ink with no border. And Amperex used the nastiest, sloppy gobby ink of them all.
And if you bought a tube in a GE carton with their logo painted on the tube in white, and the tube says "Made in USSR" on one side of the glass, it was to fill an order before the GE factory was ready to ship the next batch.
Pretty sure this was the deal with Tram. Even if they had their tubes painted "TRAM" by GE Sales Division, there was no guarantee that GE made those tubes. They came from wherever the GE sales division could get them to fill the order on time.
73
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All the Tubes in 1 of my 2 D201A Radios are Factory Originals... Many have Tram Logos upon the Glass... Of course, I know that Tram did not make them... I've asked the Question as to which Tube Manufacturer supplied Tram and it was said one's suspicion was General Electric... It was said that GE had a habit of being somewhat sneaky in their placing "Tell-Tale; Dots" on the Glass of all their Tubes... Yes, Different Manufacturers made different Tubes that were then Sold and Relabeled and Marketed once again... SO.... WHO made your Tube(s) ? 
