C1 wonderbar radio reception problem

[Gary L.]

Re: C1 wonderbar radio reception problem

Got new antenna from paragon. It is labeled 120 omh instead of 75 ohm that corvette central sells. It is a stiffer cable also. It did not fix problem. A potato on the antenna works well. You can touch the antenna and the volume increases 100% along with all kinds of stations and wonderbar stopping on all stations with good signal. Works perfect with cheap antenna with 4 ft lead. Very confused!

[Dan D.]

Re: C1 wonderbar radio reception problem

Hi Gary,

Did you try re-peaking the trimmer capacitor in the radio? If touching the antenna gives a good response it sounds like the circuit just needs a little capacitance change in order to make it happy. That is what you are doing when you touch the antenna, you are changing the overall capacitance of the circuit.

The cable should not be 120 ohms - it should be 93 ohms. Don't know about that one. Don't know about the spud either. Maybe it is hungry.

-Dan-

[Gary L.]

Re: C1 wonderbar radio reception problem

Have not tried adjusting the trimmer capacitor. Last two lead wires made no difference. I can try that again. Thanks

[Steven B.]

Re: C1 wonderbar radio reception problem

Dan and Jerry, what is best source for '56-'57 cable? Will the '58-'62 cable work? Dan, too bad Edison killed the elephant or Tesla would have prevailed---and got paid what Edison owed him.

Thanks!

Steve

[Gary L.]

Re: C1 wonderbar radio reception problem

Adjusting trimmer did not help with new paragon cable.

[Dan D.]

Re: C1 wonderbar radio reception problem

Steve, lets see what Gary reports back when he adjusts the trimmer. That might just fix it. Jerry Rudbeck says the Paragon cables work good. I did not find that to be true. They sold me a RG-59 cable and it is nearly deaf. I bought one from Corvette America and it tuned, but with the trimmer all the way in (max C). Reports are Corvette Central is RG-59 and will not work.

I suggest 2 things. If you have or can obtain an original cable, use it. They are by far the best and if not damaged they usually work good. If not try Paragon first, Corvette America second, and Grossmuellers third. You can call these vendors first and ask them what RG number their cable is, and if they have a series cap built in. If they say RG-59, then run - do not walk. My experience with these sources is two years old, and things do change. Keep us posted. -Dan-

[Jerry R.]

Re: C1 wonderbar radio reception problem

Hard to find some of this old info as I never get around to archiving it...

Paragon must have given up on the winner and changed cables. The last one they sent to Greg T was labelled "COMMSCOPE AMC-62 MOD PVC-V 125 OHM AN24062". He told me that he got it to work and I paid no more attention. Here's the number stamped on the Paragon cable that worked beautifully - "RE3697 LF 62MF BM24172". Greg mentioned that the RG59 and 58 cables measure over 350pf center to ground (10') and the Commscope cable measures 42pf (16'). When I measured the RE3697 cable I didn't write it down, sorry...

So, you have the wrong type cable Gary. Call Paragon and ask for the second cable number or, as I mentioned in the email, send the radio/cable and an antenna length to your service guy and have him trim the radios matching network. It's easy. I don't even use the noise bridge anymore to bring it into range.

That's how I do it for guys that have just bought a new cable and send their radio in for rebuilding. Saves them a hassle and me a lot of time explaining and seeing a radio again later due to another incorrect aftermarket vendor part. So far, either the mod'ed radios have all tuned in range or guys are being nice and not telling me. If the trimmer doesn't peak it in range, it's just not going to work.

I'm going back to vacationing - have fun guys. _Jerry_

[Gary L.]

Re: C1 wonderbar radio reception problem

Thanks for your vacation time. I'll give them a call.

[Dan D.]

Re: C1 wonderbar radio reception problem

Hard to find some of this old info as I never get around to archiving it...

Paragon must have given up on the winner and changed cables. The last one they sent to Greg T was labelled "COMMSCOPE AMC-62 MOD PVC-V 125 OHM AN24062". He told me that he got it to work and I paid no more attention. Here's the number stamped on the Paragon cable that worked beautifully - "RE3697 LF 62MF BM24172". Greg mentioned that the RG59 and 58 cables measure over 350pf center to ground (10') and the Commscope cable measures 42pf (16'). When I measured the RE3697 cable I didn't write it down, sorry...

So, you have the wrong type cable Gary. Call Paragon and ask for the second cable number or, as I mentioned in the email, send the radio/cable and an antenna length to your service guy and have him trim the radios matching network. It's easy. I don't even use the noise bridge anymore to bring it into range.

That's how I do it for guys that have just bought a new cable and send their radio in for rebuilding. Saves them a hassle and me a lot of time explaining and seeing a radio again later due to another incorrect aftermarket vendor part. So far, either the mod'ed radios have all tuned in range or guys are being nice and not telling me. If the trimmer doesn't peak it in range, it's just not going to work.

I'm going back to vacationing - have fun guys. _Jerry_

Okay, my Paragon cable is labeled RE3697 LF 62MF AZ24291. This is the same number sequence as Jerry reports except for the last set of numbers. I wonder if this is some kind of a date code or something. The capacitance of the original cable measures 133pF. The new Paragon measures 62pF. The original tunes with the trimmer set near minimum - all the way out. The Paragon never really does peak, but it almost peaks with the trimmer at maximum - full clockwise.

Gary, are you sure the trimmer will not tune? Does it have any effect at all? Because if you can improve sensitivity by touching it, then I believe it is close.

If you still have no joy, then I could either lend you my cable to try, or even test and modify the circuit in your radio if you sent it to me. Not trying to short circuit Jerry, but I know he is very busy and being on holidays for a month, he should be swamped and probably would not mind me doing this.

Another thing here, yours is a 1958 and they are different than 56-57. Different tube types but similar design.

Try the trimmer adjust again, and tell be if it has any effect at all.

For anyone that has bought cables from any supplier that do not work - send them back. -Dan-

[Gary L.]

Re: C1 wonderbar radio reception problem

Owner picked up car for weekend. I turned the trimmer tuner slowly one full turn each direction from where is was set from repair shop. No effect. not sure how many turns there are from full in to full out. A 4 ft. antenna lead works great from a cheap antenna. i will try again when I get the car back, probably Tuesday.

[Jerry R.]

Re: C1 wonderbar radio reception problem

Add 20 or 25 pf's in parallel at the choke input Dan and you should be fine. Or, re-tune the associated inductor. You're close. And, thanks for the thought but you're right, I don't mind at all. I'd do things a lot different if this was food on the table (like I'd advertise) but I'd never do the work the way some of the shops do. There are shortcuts and then there are patches without band aides.

The AZ number is probably just a lot/batch number. The velocity factor, etc. should be the same through all production runs as you know. The variance in the cap readings is undoubtedly due to the length of cable measured and accuracy of the meter being used. 100 puff is not much and lead length and routing may be part of it. So many variables... But boy do those variables kill the seek function quickly.

As I remember, Gary's repair shop is close to him and sounded like they had above normal car antenna system knowledge. I bet they can help.

Stay out of trouble and away from the B+.

[Dan D.]

Re: C1 wonderbar radio reception problem

Hi Jerry,

Thanks for the info on the caps. FYI, the capacitance I measured was from one end of the cable center conductor to the other end. Cable lengths about the same. Measured both cables at the same time. Meter was HP4263A. Used a low frequency - 1kHz to minimize cable capacity.

Now, Jerry, what are you doing up at midnight? Go the bed, get some rest so you can get up early and DRIVE THAT VETTE!. It is Memorial day you know, and I bet the car is waiting for you!

Back in the days, been bit hundreds of times by that nasty ole B+. Usually resulted in some 4 letter words. -Dan-

[Gary L.]

Re: C1 wonderbar radio reception problem

Checked on paragon cable and all numbers are the same except theirs shows mod puc-u where yours was pvc-v. No idea what those stand for unless it is the type sheathing or conductor sheathing.

[Gary L.]

Re: C1 wonderbar radio reception problem

How many turs are there on antenna tuner?

[Dan D.]

Re: C1 wonderbar radio reception problem

I think 3 or 4, but I have not counted them and its been awhile. -Dan-