54 antenna wire

[Guy M.]

Grossmulers have a wire but i.m wondering if it will work before I buy it. Any know if the connections are good?. Thanks folks

[Guy M.]

Re: 54 antenna wire

Anyone know the diamiter of the wire???

[Jerry R.]

Re: 54 antenna wire

Here's the link with the answers from 7 days ago Guy. Same topic...

https://www.forums.ncrs.org/showthre...80287&uid=6364

A tip: I have an almost day one 53 radio on the bench now (same as yours) and if the antenna trimmer will not tune within its range, the radios ability to stop on stations (signal seek) will be significantly impaired. That's just a quick check for any C1 Wonderbar. The cables available that are made from RG-59 TV cable (most vendors these days except Paragon and Corvette America) are the wrong impedance to match the radio RF input stage.

[Dan D.]

Re: 54 antenna wire

Jerry, RG-59 is 75 ohm cable. Is that not the correct impedance for the radio? At first I thought RG-59 was correct, but based on what you say and the fact that Corvette Central states their cable is RG-59 and has a built in series capacitor to match the radio input impedance. I did not understand this series cap at first, but it is now making sense. So I'm sure you are correct. Just wondering what the correct impedance for the radio is. 53-55 antennas are built into the trunk lid, 56 up are conventional dipoles. Don't know if the trunk antennas are difference impedance or not. Any education would be appreciated. Thanks -Dan-

[Jerry R.]

Re: 54 antenna wire

This could be a long answer Dan but I'm going to condense it significantly. The evolution of auto antennas from the 20's on is a fascinating study. Surprisingly, it is not something you'll ever hear mentioned in the typical EE electro-magnetics college studies through the grad level. Kind of a lost art...

No, RG59 is not correct (but it could be)... The most obvious clue is that our original feedlines are stiff and have a large outside diameters and a very thin (and fragile) solid core center conductor. That ratio establishes the impedance. The RG-59 outside diameter is flexible and thin by comparison and has a large (and usually) stranded center conductor.

RG-59 is, as you noted, 75 ohms but RG-62 was a default for many years. That has a characteristic impedance of 93 ohms. Some earlier installations (not necessarily in the vette era) used RG-63 at 125 ohms. The installations from the mid 20's through the late 30's comprised a very creative hodgepodge of adaptations. One vette parts supplier, possibly two, appear to have a vendor that uses RG-62 (coded in their parts house number) and has selected a series cap which is almost a perfect match for the 56-62's. I've seen good AM signal transfer success with that aftermarket product.

Wire loss is irrelevant due to the cable length and frequency involved for this situation. And I'm ignoring FM since C1's didn't have it.

So, RG-59 could work if the radio input circuit saw the "match" it was designed to see. To simplify that, the series cap you mentioned is a part of the formula. And in some cases, I've found that adding a smaller series cap inside the radio in series with the external cap yields resonance. At other times, adding a parallel cap at the connector inside the radio fills the bill. To summarize that further; to use the RG-59 cable from most of our currrent vendors, the input circuit of the radio must be modified for maximum signal transfer. That is just not an acceptable solution...

I can't answer the 53-55 question yet Dan. The comments above are mainly directed at the 56-76's. But so many 53-55's are crossing the bench these days that I'm going to do a bit of testing on those vehicles at a friends shop out of curiousity. If you have ever seen an RG or equivalent number on an original 53-55 cable, please pass it along. I rarely see anything but the radios. My suspicion is that the cable is RG-62.

One last comment for the non radio guys that will help put things in perspective: AM signals are very long in wavelength. An optimum length antenna for 1000 on the dial is 234 feet (1/4 wavelength). Imagine that on your fender! That's why the cable, which in this case is an integral part of the whole system and not just a signal carrying pipe, is so critical. It's also why the series cap is in the cable path. The radio must be fooled into thinking it is seeing 234 feet of wire.

By comparison, 100 on the FM dial desires an antenna 2.34 feet long; almost a perfect match for a fender whip. That's why FM suffers little from the RG-59 cable. You'd almost think the aftermarket cables were designed for it...

For guys who have suffered this far into our exchange, the bottom line is: if you have a signal seek circuit and the antenna trimmer does not peak in it's travel range, some portion of your AM signals are going into the trash and your radio is not stopping on as many stations as it is capable of sensing.

Sorry for the wordiness Dan... it's a sizable subject.

[Dan D.]

Re: 54 antenna wire

Don't worry about the wordiness Jerry, I appreciate it. I understand 1/4 wave, d-d ratio, etc. I was thinking when I wrote it that it might be 92 ohm. Your response is a big help for me.

I will look at my 54, but I don't think it will have any RG markings. I don't recall seeing any markings. Like you say the best thing to do is measure one. Terminate one end in a resistive load and look at the transfer.

Guy, sorry if we hijacked your post. Hopefully your question was answered okay. -Dan-

[Dan D.]

Re: 54 antenna wire

Well Jerry, I bought one from Corvette America, one of the 2 'preferred' sources. RG59U! They do not say RG59 up front like Corvette Central does, they just enclosed a note saying not to try and measure continuity on the center lead, so that implies a series capacitor. Oh well. My car is a driver so it will not matter much. Just trying to keep it as correct as possible.
I bought an antenna too - I am going to take the whole thing down to the shop and see if it will tune on the bench. Got to rebuild the radio first though. Will let you know. -Dan-

[Jerry R.]

Re: 54 antenna wire

That tells me it came from Corvette America by default as Paragon is still selling the cable with the house number with the 62 in it; as of 8 days ago anyway. The second guess would be that the diameter of the cable in the picture on their web site (CA) is larger than what you received Dan. That's just annoying...

I'd start a rant on the current spiraling quality of Trimparts (radio related components specifically) and the aftermarket chrome face kits whose mounting holes don't even line up and the amount of Dremel work required to install the selector bar parts so that they will even slide. But on second thought...

Once you have it rebuilt, go to the antenna connector in the radio and tinker with both series and parallel caps. It's easier to work there. Parallel values should be around 20pf (+10 -5) and a series cap should be less than 120pf. Start with parallel.

A short ground clip lead from the antenna base to your cars frame is more than adequate. Once you hit resonance you'll start to wonder why there's so much talk about getting the grounding plates perfect. Of course if we could drag 250' of ground radial behind the car (1/4 wave), the antenna circuit might actually notice it. For testing I just stick the antennas in a vice and set it on the floor near the car. The change when mounted has always been within the trimmers range.

Holler if you want someone to commiserate with when tweaking. Peak the trimmer for max noise near 1600. A modulated sig gen with an AC VOM across the speaker works even better. Good luck Dan, it's not hard.

((And my thanks to Guy also!)) _Jerry_

[Dan D.]

Re: 54 antenna wire

On second thought Jerry, why don't I just send this thing back to Corvette America and buy Paragon. At least Corvette Central tells you up front that their cable is 59. Corvette America just hands it to you. I think I am going to do that.
I'm with you on the quality of this repro stuff. I am starting to get the car back together now and for the last month and all I have been doing is battling repro stuff that doesn't fit and/or doesn't work. I end up reworking just about everything and its going at a snails pace.
The problem is we are very resourceful and we make almost everything work. What we should be doing is sending this stuff back. That's the only way to get things fixed.
Off my soap box for now, I have a good selection of lab quality HP test equipment and I will align the whole radio after I replace all the paper and electrolytic caps, solid state vibrator, 1N4007s inside the OZ4, etc. (Radio is 1956 Cadillac - not correct-I know - its all I have to work with).
I'll let you know how I make out with Paragon. Maybe I should call them first and confirm their antenna offering.
My 54 is stored off site and I have to get over there and see if I can find any markings on the cable for you.
-Dan-

[Dan D.]

Re: 54 antenna wire

Hi Jerry, I did visit my 54 today. I do not see any writing on the cable. It looks to me to RG-62. The wire is cut and no good, so if I had a wire cutter with me I would have cut a piece out and tried to measure the characteristic impedance. 54s are not grounded at the antenna as it is built into the trunk cover. For ground, the outer insulation is removed near the back of the passenger side seat and a ground braid going down to a body mount frame bolt. Next visit I will remove a section and bring home. I can clean it better and look closer for any writing. It is original cable - I know that for sure.

I looked at Paragon today, but did not buy it yet. -Dan-

[Jerry R.]

Re: 54 antenna wire

Great on all Dan and thanks for the info. If you do a micrometer check of the original cable, you'll probably figure out it's RG62 easier than firing up a network analyzer/impedance bridge. Even if we just knew how many turns and the dimensions, we could compute the loop's impedance fairly well.

But for your purpose, and assuming you can salvage the antenna end connector, you could just use RG-62 and trim in the series cap. Problem solved.

I'll drive over and borrow a 53/54 trunk lid later this week and put the subject to rest in my mind. It's time for a little fun break anyway; too many radios in the queue.

BTW, if you leave the 0Z4 in and add the 4007's at the base, it will still work fine, save you time and get you an extra 10+ vdc of high voltage.

Also, change the red rectangular mica AGC coupling caps (100PF) in the 56 when you swap the wax jobs. Then align the 262KHz string carefully. That's where you'll get the biggest bang for your buck.

I've worked with many guys who have installed the Paragon cable and none has said it did not trim within range when their radios came back. Quite the opposite. Many called to say their radios passed judging just fine, even stopping on the lowest sensitivity range. The cable mismatch of the RG-59 subs just turns the 58-62's into hearing impaired bricks.

I'd suggest we take the rest of this off forum. I doubt many guys are going to be very interested and Guy has been very patient with the techie talk.

You can contact me at jerry@electrodesign.us Dan. Don't hesitate.

_Jerry_

[Jim L.]

Re: 54 antenna wire

I'd suggest we take the rest of this off forum. I doubt many guys are going to be very interested and Guy has been very patient with the techie talk.

I understand everything you two have discussed and I'd like to see the discussions continue on line. I can't be the only other one with an electronics background; there have to be others who are following along.

Jim

[Guy M.]

Re: 54 antenna wire

Thanks guys for all the great info. I still dont know if what grossmuller is selling will do the trick. I included the pics if it works for review. It sell for $125 and I dont want something that wont work. You guys are great. One other question......was the wiring harnesses installed before or after paint??

[Dan D.]

Re: 54 antenna wire

The rear harness was glued in place over the wheel well when the body was assembled, so that most likely was before paint. The front harness I believe was installed after paint. Someone else may have more knowledge on this than me. If you could measure the OD of the cable Jerry or I could tell you if it is RG62 or not. RG-59 is smaller and more flexible. Didn't mean to hijack your post Guy - glad you are okay with it. Jerry, lets continue on line with it. Jim has a good point. There are many other high level technical discussions on this forum. The current one on bearing journal size being one of them.

[Guy M.]

Re: 54 antenna wire

Thanks Dan, my cable measures a hair over 1/4 inch OD. This one is cut in the rear, can it be latched on to or is it ruined? The radio connection is good. cant see any markings.