40 channel Mod for Cobra 132a?

[BladeRunner now OLD FLASH!!!!!]

I have a Cobra 132A that works very good. It is a 23 Channel radio. I have read on the ne thtat there is a Mod to add the additional CB channels by adding a 13 mhz crystal and use the niose blanker switch to swithch between that crystal and the existing 12 mhz chip that controls the original 23 channels. My problem is that I cant find a 12 mhz crystal. The closest I can find is a 12.8 mhz crystal. I also find that crystal on the schematic in cbtricks.com, but no just plain, 12mhz crystal. Does anyone have any idea if the 12.8 mhz crystal is the one the instructions are referring to and is there anyone out there that is familiar with this change and has actually performed the mod?

Thanks in advance

[Sandbagger]

Oct 30, 2008 8:31:42 GMT -5 BladeRunner now OLD FLASH!!!!! said:

I have a Cobra 132A that works very good. It is a 23 Channel radio. I have read on the ne thtat there is a Mod to add the additional CB channels by adding a 13 mhz crystal and use the niose blanker switch to swithch between that crystal and the existing 12 mhz chip that controls the original 23 channels. My problem is that I cant find a 12 mhz crystal. The closest I can find is a 12.8 mhz crystal. I also find that crystal on the schematic in cbtricks.com, but no just plain, 12mhz crystal. Does anyone have any idea if the 12.8 mhz crystal is the one the instructions are referring to and is there anyone out there that is familiar with this change and has actually performed the mod?


Thanks in advance

That's it. The 12.8 Mhz crystal is the one you put on a switch. Obtain a 13.1 Mhz crystal, and that will give you from channel 26 (on channel 1 on the dial) up to channel 55 (on channel 23 on the dial). You'll need some method to fill in the gap channels (3,7,11,15,19 A and channel 25), either sliding the clarifier or adding a 6.030 Mhz crystal on another switch .

[BladeRunner now OLD FLASH!!!!!]

Thanks Sandbagger, I appreciate the info. I picked up one of thse old radios for 10 bucks an it works perfectly. I'll do the channel mode and there are a couple other changes that will boost the output. Have a great day.

[Sandbagger]

Oct 30, 2008 20:44:29 GMT -5 BladeRunner now OLD FLASH!!!!! said:

Thanks Sandbagger, I appreciate the info. I picked up one of thse old radios for 10 bucks an it works perfectly. I'll do the channel mode and there are a couple other changes that will boost the output. Have a great day.

You'll like that radio. It was a great performer in its day, and it'll still hold its own against the modern stuff.....

[BladeRunner now OLD FLASH!!!!!]

I had an identical one in the 70's and three months before I was married (30 years ago) I was relocated 110 miles away. I had a cobra 132a and a amp under the seat and I talked skip all the way home every sunday afternoon. It was amazing. I think i taled more skip from my car than i ever did from my base. Of course back then I was much younger and virtually lived in my car. I was always on the way to somewhere...

[BladeRunner now OLD FLASH!!!!!]

I have looked at several radio mod sits adn there is a modulation mod and a power mod that can be made to the radio. The info is on several sites and it's identical since the information was copied exactly the same from one site to the next. To me , the inexperienced, I'm not sure what they intend you to do to the radio . here is the information and how it is listed ......Cobra 132 A .......Modulation Mod CUT CD39 & CD40 ......Power Mod R79 (ssb) R87 ...My question is what exactly do you do ....On the Modlation mod do you just cut CD39 and cd40 out? On the power modulation, what do you do with the two resistors? remove them? jumper across them? I read and read and can find no information anwhere on just what exactly to do. If anyone can elighten me, I will appreciate it. Thanks
BladeRubnner

[Tombstone (R.I.P.)]

Bladerunner, There isn't enough information on the power modded resistors so I don't know if they want you to jump across them or clip them. When they say to cut a component it's usually called clipping, Normally you don't have to remove the component, just cut the wire lead and move the component away from the connection. When clipping it's a good idea to cut where you can easily solder the connection back together if need be. I don't see where you said anything about dead key. It probably isn't a good idea to power mod and modulation mod that radio anyway, the power supply might not hold up, so I wouldn't clip, esdecially in the modulation. Why don't you try peaking the AM up (R79) and putting a decent power mic on the radio? That's the best I can answere you questions and I hope it helps you.

Tombstone

[BladeRunner now OLD FLASH!!!!!]

Tombstone I agree with you. i don't understand that there are so many sites with the same inforamtion., which is little to nothing. Like i said I got thi radio fr 10 bucks off ebay and I had one about 30 years ago and this one , like the one I had before is already a strong radio as far as output and very easy to tune even when talking Sideband. like I said earlier I use to spwnd a lot of time on the road and with a litttle help under the seat, talk skip all the time, and wht i didn't mention before it was usually sideband. It's a radio that's very easy to tune while driving 100 MPH jumping in and out around traffic on the freeway and cutting people off....LOL... Just kidding. I mentioned that because it's my pet peeve. I got nothing against people driving and talking on cel phones...or anything else as far as thats concerned if done responsibly.

I was in traffic on the freeway a few days back. Traffiic was moderately thick. i was on the inside lane doing about 65 in a 60 in a four lane area where two interstates merge than split again after about 1 mile. At this pint , the inside lane was not the fast lane but noe you needed to be i to take a particular split to a particular freeway. I had a woman in a moroon
dodge wiith the front left bumper cover flopping in the wind three feet off my bumper, with her her sunglasses on, her cowboy hat pulled down over her eyes, holding her cel to her left ear, flashing her lights and honking her horncutting from one lane to the next trying to get around anybody and everybody, sometimes swinging four lanes across barely missing many other cars. I would have let her go by but I had nowhere to go. I got her liscense plate number (from texas). I thought she was going to hit me when she came from two lanes from the right just squeezing between two cars ending up directly in front of me almost clipping my front right fender. I don't know if thay stil do but State Troopers here use to monitor Channel 9. I gave details of what was going on on 9 and got nor response, but in about a mile She was leaning against her car talking to a state trooper and whoever was on he phone.

I think I'm going to onvert it to 40 channels and put it in my sons truck. He's been wanting one. Thanks for the information Tombstone and everyone else that answered.

BR

[Sandbagger]

Nov 1, 2008 10:50:33 GMT -5 BladeRunner now OLD FLASH!!!!! said:

I have looked at several radio mod sits adn there is a modulation mod and a power mod that can be made to the radio. The info is on several sites and it's identical since the information was copied exactly the same from one site to the next. To me , the inexperienced, I'm not sure what they intend you to do to the radio . here is the information and how it is listed ......Cobra 132 A .......Modulation Mod CUT CD39 & CD40 ......Power Mod R79 (ssb) R87 ...My question is what exactly do you do ....On the Modlation mod do you just cut CD39 and cd40 out? On the power modulation, what do you do with the two resistors? remove them? jumper across them? I read and read and can find no information anwhere on just what exactly to do. If anyone can elighten me, I will appreciate it. Thanks
BladeRubnner

Those pot numbers for power adjustment don't sound right, at least not compared to the version schematic I have for the 132/135. You don't want to up the power on AM anyway, as you'll lose modulation punch.

As for cutting the modulation limiters, DON'T do it. That radio distorts badly when the limiters are cut and the mic is too high, and it becomes difficult to adjust the mic for best clarity and loudness. You are much better off leaving the limiter in and just changing the value of R200 to a higher value to bring the max modulation level up a little bit if needed, while allowing the limiter to hold that level. With the limiter in, the audio is smooth and clear.

[Tombstone (R.I.P.)]

I got the AM power pot number from my Master Edition repair manuals, it could be a misprint or just wrong, I haven't checked CB Tricks to find out what they have on it. On second thought, Sandbagger is correct, don't peak the AM power for max dead key. If you set it for about three watts it should give you more modulation swing.

Tombstone

[2600]

There is no "power pot" for the AM carrier on this radio. And no transistor for it to control, as in most post-1980 SSB CB radios.

The AM power is set by a pair of fixed resistors in parallel, if memory serves.

The extra-channel mod has one shortcoming. The crystal that you change is also the one that the clarifier is connected to. Getting the thing on frequency close enough for SSB may be tricky. And the clarifier's range will be affected by the new crystal, as well. Some crystals would adjust okay, but some would not. If what you care about is mostly AM, this probably won't be an issue.

73

[Tombstone (R.I.P.)]

My mistake. My manual reads R79 for AM power, not VR79. I must be getting old??

Tombstone

[BladeRunner now OLD FLASH!!!!!]

I appreciate the information Tombstone. I'm not sure I'll modify the radio or not. Like I said before I think) I had one of these in the 70's and it was a great skip talker on SSB and strong on AM. I've already Got an old JC Penny Radio tat's modified and has 80 additional frequencies and keeping up with switch positions and a paper list of what frequencies are on what channel numbers is too much for a mobile radio. I'd be much worse that someone on a cell phone....Let's se I'm doing 80 on the freeway....Looking down at the Frequency list. What channel is 26.865 on...Oh there it is (CRASH)....LOL...(changing to channel 9) Is there a policeman on this channel?