'61 radio antenna

[Richard P.]

The antenna cable I purchased from Paragon for my 1961 doesn't have a long enough "stud" that goes into the back of the radio, hence not enough signal. I took the radio to a shop and it worked great on his bench using his antenna. I am doing this NCRS, so any suggestions where I can get the correct antenna.

[John F.]

Re: '61 radio antenna

Does it push all the way into the radio? Do you need to slightly re-route the cable to reach? Make sure both ends are attached properly. Could be a bad cable. In that case, send it back for another one.

[Jerry R.]

Re: '61 radio antenna

Do you see the symbols RG-59 on the replacement cable? The aftermarket cable from Corvette Central is of this type (75 ohm cable tv line) and it was such a bad mismatch to the antenna on another NCRS members 62 radio that it was attenuating the signals horribly! The original cable is of a higher impedance (and larger diameter) than the RG-59. I'm pretty sure this is what you are experiencing.

There's a simple fix but it requires a modification to the radio antenna input in the radio if that's the problem you're experiencing. Apparently original cable sets with the correct impedance are very scarce. By the way, it is normal to not have DC continuity using an ohm meter from one end of the cable to the other. There's a small capacitor in the connector.

Don't forget to adjust the antenna trimmer.

[Stewart A.]

Re: '61 radio antenna

Jerry do the 58 -60 have the same problem. Stewy

[Richard P.]

Re: '61 radio antenna

Jerry:

What is the simple fix to the radio input you refer to? What and where is the antenna trimmer?

[Jerry R.]

Re: '61 radio antenna

Yes Stewy. A mismatch problem of the type I described would affect all model year radios. The affect would be most noticeable on the AM band but also impact FM to a less" noticeable" degree. Without getting all techie, a correct length antenna for the AM band is several hundred feet long. So to fool the radio into thinking it is seeing one that long (on a rear fender of all places), a "match" must be established to convince the circuitry it is hooked to a resonant circuit (like a tuning fork) on the AM band. The correct length for the FM band is more on the order of 4 to 5 feet (.5 wavelength) - thus, the mismatch is less severe. It's all an electrical balancing act.

I'm not condemning the Corvette Central replacement line. It has a series capacitor of some value in it to approximate the original GM cable and RG59 cable is readily available compared to 93 ohm coax cable which was probably used originally.

The antenna trimmer is in the circuitry to "balance the teeter totter" and compensate for some mismatch. In the case that I mentioned, the trimmer could not compensate for the variance between an original antenna and radio due to the cable supplied.

If someone wanted to check their installation, the easy way is to go to Auto Zone (or is it Aussie Zone down there? ) and buy the $10 replacement antenna. Plug it in the back or the radio and turn the trimmer. If the problem is present, the difference in signal strength (and just plain loudness) between the antennas can be extremely dramatic.

I don't know if this is a wide spread problem but I do know to look for it now. And for Wonderbars, this is like sticking cotton in their ears. If the signal strength is inadequate, they don't stop to hear the music (pun intended).

Sorry for the excess verbosity. Maybe it will help someone get a point or two down the road.

[Jerry R.]

Re: '61 radio antenna

The simple fix Richard is to add a hand selected correct value capacitor in the radio at the antenna input. I won't state a value as it will vary with the installation. Each vehicle has a varying length of antenna and also lead-in wire back to the radio and the input matching circuitry of the radio will vary also. Therefore, the value of the part "may" vary a bit. I can't say that one part value is correct to repair all situations without more exposure to the frequency of this problem.

In the case I mentioned, the NCRS member sent his new antenna wire along with the radio so I was able to pick a part value that tricked the circuit into transferring the energy with minimal loss. In retrospect, I wish I had his actual antenna in hand too. Anyway, that's how the cause of the poor reception was identified in the first place.

The antenna trimmer on your radio is a recessed screw head just below the case cover level (inside the radio) on the bottom close to where the antenna plugs into the set. Think of it as a mixture screw on a carburetor.

When you described your successful bench test and the antenna plug possibly not going in far enough, it triggered the association. Mainly because the plug center pin should be long enough and it also sounded like you were getting "some" stations.

For those folks reading this who still have their original lead in cables, don't just yank the wire out of the back of the radio when removing it. That regularly results in the male connector remaining in the connector socket and the wire breaking free from it. There's a capacitor in there and you're not going to be able to just solder it all back together.

Sorry that doesn't give you a fix that you can perform yourself Richard. It's not hard, just specialized.

[Roger W.]

Re: '61 radio antenna

What about the other way around? using an original antenna with a modern digital radio. Will it match OK?

[Jerry R.]

Re: '61 radio antenna

It should work just fine Roger. Go through the antenna trimmer alignment procedure that came with the radio - that will confirm it for you. I don't mess with digital car radios so they may not even have trimmers any more.

[Valeria H.]

Re: '61 radio antenna

Nice car Jerry! Good to see you post some of your vast knowledge about radios/antennas etc. You are the best when it comes to the restoration of old Wonderbar radios.
Valeria

[Jean C.]

Re: '61 radio antenna

Richard,
If the problem is that the plug on the radio end of the antenna wire is of the incorrect type that does not provide for a proper fit of the male stud into the radio's plug, why can't the radio shop you are dealing with replace the bad order plug with a correct plug, e.g. one with a longer stud?
Best regards,

[Jerry R.]

Re: '61 radio antenna

For those still following this thread, here's an update:

Richard stopped by and we set up his radio, his Paragon antenna cable and antenna using my 67 frame as the ground plane for the antenna. The initial results are that the connector is of the correct type and the Paragon cable presented a much better radio frequency match in a 58-62 installation than the Corvette Central replacement cable. Only a minor change to the radio internal matching network was necessary to increase the reception quality significantly. Does this mean the Paragon cable is better than the CC product? Not necessarily. There are many variables to be accounted for and the sampled cases so far are small. Also, the number on the Paragon cable was a unique house number so we couldn't determine if it has the higher characteristic impedance usually associated with auto antenna systems. But, it appears to be...

The real test will come when Richard has his radio back and everything is installed in his car but there is little question now but that it will work just fine. _Jerry_

[Roger W.]

Re: '61 radio antenna

I just put a new Soney digital radio in my Blazer. That did not have a trimmer.

[Valeria H.]

Re: '61 radio antenna

Jerry, You are the master!!!!
Valeria