54 antenna wire

[Dan D.]

Re: 54 antenna wire

Hi Guy,

RG-59 measures right around .235. RG-62 comes in right around .275. Maybe Jerry can confirm these measurements.

I am going to be out of town for a few days starting tomorrow morning, so if I don't respond back for a few days don't think that I don't love ya any more. Can't believe the schedule here now that I am retired. I think it's worse than when I was working. -Dan-

[Gary C.]

Re: 54 antenna wire

Guy, Jerry and Dan, FWIW checked Sam's for 56-7 Wonderbar radio and it does not show the antenna impedance. Gary....

[Jerry R.]

Re: 54 antenna wire

Just a couple comments... (I'll check the thread as often as I can.)

Guy, the cable "eyeballs" fine in your pictures. Of course most of the stocks, banks and politicians available today meet the same criteria.

The bottom line, if I were in your situation and making a decision, would be to install the cable and find a radio guy (who may not eyeball fine but actually has some savvy) close by and tell him to match the system to your radio input network. After you determine that the antenna trimmer will or will not peak the signal within its range yourself, then tell a tech to add series capacitance in series with the lead in at the antenna jack in the radio. He can actually put a variable compression trimmer capacitor in series and rough it in. If that does not work, he can move that trimmer to be in parallel with the lead in. That takes the rocket science out of it. This should take an hour or two including tinker time and not cost a fortune at all. Or, find a ham operator from the old days that builds his own stuff. He'll know what to do and have fun doing it.

I jump to this suggestion because there seem to be no other suppliers of the cable with the proper connector on the end (and I'm assuming the connector is the right one).

RG-62 "U" was the de facto for auto aerials in the 50's from my limited research. It provided a very low capacitance, high Q (and Delco called it High Q) cable. For communications antenna systems on vehicles, RG-58 was the preferred cable (think two way radio). It has a much higher capacitance value per foot.

There are several flavors of RG-62 but the one we're interested in seems to be the RG-62 U ASP (air space polyurethane). The insulation just inside the braided (armored) shield was very firm to support the outer wire and external black polyurethane because an air dielectric was used and the center conductor was extremely thin and sat in a pretty large void compared to its own diameter. In other words, your original cable is undoubtedly relatively "hollow".

The piece I have here is close to .25" OD. From the center of the cable to the inside of the inner poly tube is slightly over .1". That leaves ~.025" for the inner and outer and braided layers.

But, the kicker is that the characteristic impedance is determined by a ratio and if the diameter of your center conductor varies from the RG-62 stock I have here, the OD will vary.

I've almost rambled enough but one other topic and I'll stop... on various forums I've read that the antenna trimmers tune broadly or not at all and "that's OK". Not so. Just above we talked about high Q circuits. The evolution of the tuning circuits in auto radios changed from using variable capacitors for main tuning to ferrite slug permeability tuned circuits as they were simpler. The manuals will confirm that there should be a very noticeable peak in signal strength when the trimmer is adjusted correctly. That tweaking is a part of what was called stagger tuning or band spreading back in my day. Usually the tuning coil (slug) determined the low end of the range resonance and the trimmer cap set the high end (based on mixer injection frequency). So, if the trimmer tuning is sloppy or broad, the cable has become contaminated by water/chemical leaching or something else is wrong.

Dan, the manual I have here shows the OD on RG-62U at .242".

For those who are still awake and reading, you just qualified for a "nerd" window sticker. Display it proudly (if your vette has a real window that is...).

[Dan D.]

Re: 54 antenna wire

Okay, one more shot at this before I go away for a few days. Sam's photofacts never give antenna impedance. But most, if not all, auto radios in the 50s used similar antennas and coax. If fact the antenna tuning circuit in all car radios of that vintage were very similar in design, regardless of the vehicle manufacturer.

Jerry, I measured the cable in my 57 to be .275 - not original cable. When I get back I will measure the OD of my 54 cable, which I know is original. But again, that does not mean a lot. It is the ratio of the center conductor diameter to the diameter of the braid that determines the impedance.

I ordered the Paragon cable for my 57 yesterday. Will report back when I get it. -Dan-

[Guy M.]

Re: 54 antenna wire

Thanke guys for all your advice. I guess Ill work with Grossmullers cable, doesnt seem to be a better choise. This is a great string and will print this one!

[Jerry R.]

Re: 54 antenna wire

Here's a little more... I drove over and looked at a couple 54 trunk lids today. Nothing magic there, they are simply a sheet of chicken wire (hopefully galvanized AFTER they were woven) under fiberglass. They were also called panel and mesh antennas. It's still chicken coup wire and functions just like a whip.

It was way too hot to dig into the back of the 53/54 parts trailer for an original feedline cable today but next trip... and I'll take the hardtop off before driving the BB back there for sure!

Guy, the threads on the urethane trunk lid connector are very fine as you know (better than I do). And, I have no idea what the metal connector threads on the cable from Grossmuller's cable is like - more course I would think. Check that carefully before you crank it down. And, an observation; don't screw it down far enough to let the connector shell touch the two screws on the rectangular plate on the trunk lid. It will short out the cable. I didn't see any ground connection on either trunk lid for the antenna. Electrically that's no big deal and your ground for noise suppression is apparently at the passengers seat as was mentioned.

So, if the connector shell threads correctly onto the trunk lid - go with it. If it doesn't, you could send it back - recover lots of money and buy the one from Paragon and spend a few of the hundred bucks you saved to whip up a connector or use the end of your old one if you still have it. As long as the wire doesn't fall out of the plastic connector on the lid, all is good. It appears that only the center conductor is doing any work back there.

When the 54 that's being restored here is further along, my friend will call me and I'll go over for a much closer look. But the matching of the radios antenna circuit to whatever carries the signal from the chicken wire is the key to the signal seek circuit having enough signal to stop when it should on all ranges.

This may all sound mystical if you're not a radio geek but it's no different than needle valves on old carbs or square pegs and round holes. "Trimmer" it to fit.

[Robert J.]

Re: 54 antenna wire

I was reading this thread thinking about replacing my old wire in the 55. I asked a friend in the radio field if he knew of any RG62 wire and he gave me about 30 feet.........RG62AU If that is the right wire I will have enough left after mine for someone else to do theirs. First to let me know gets it. Bob

[Dan D.]

Re: 54 antenna wire

Don't be to generous Bob, the 57 cable is 15-1/2 feet long. 53-55 should be about the same and RG-62 cable should be readily available. The trick is terminating the connectors, and you have to have the connector at the antenna end as to my knowledge that beast cannot be purchased. The radio end should be available as it was used throughout the industry. But terminating either end will not be easy.
I bought the Paragon cable, but have not done anything with it yet. Don't know if it is RG-62 - paperwork that came with it also states a series capacitor. It has the in-house P/N AE 3697 LF 62 MF AZ24291. Jerry R. - is this the P/N that you have for the Paragon cable?
I am going to take the Corvette America, Paragon, and my existing 57 cable into work and measure the return loss with 75, 93, and 125 ohm resistive loads. This will characterize all 3 cables and I will post the results. My existing 57 cable is not original to the car, but dates back to the early/mid 60s.
Radio has been on the back burner lately, working on little things like getting the engine back in the car. And I am going out of town again tomorrow - back sometime Sunday. -Dan-

[Robert J.]

Re: 54 antenna wire

OK; I am missing the last foot of cable and the female end that fits onto the inlaid trunk connector on a 55. I was hoping to splice them together. I guess that would really mess up the resistance..... Bob

[John S.]

Re: 54 antenna wire

cable from grossmueller's for a 53-55 is 160 inches. ground is 59 inches from trunk connection and the ground is approximately six inches long. the diameter of the trunk connector that grossmueller is selling is 7/16 inches and has the center wire extending out of it. what i need on my 55 is a connection on the cable that is approximately 11/16 inches and has a female connection in the center. the fitting on my trunk has the center wire extruding through it.

[Robert J.]

Re: 54 antenna wire

Sounds like a lot of us are missing the female trunk connector. Does anyone have a good Pic of it? Might help the search.

[Jerry R.]

Re: 54 antenna wire

Dan, yes, that's the cable number. Note the 62 in it FWIW.

The original cable I saw recently was thin, what I'd expect from RG62 A/U. It looked too thin for an air dielectric and significantly thinner than the large/stiff cable we've all seen before.

I'll look close when I go back, I was rushing that day. If they don't need it yet, I'll just borrow it. The ground pigtail was exactly where everyone described it and the standard Motorola type connector for the radio end was present.

RG62 is a common cable and still in use for networking purposes. Pre-made pieces usually are terminated in BNC connectors.

Robert/John - What I remember seeing was a tubular female "threaded plastic post" with center conductor hooked to the wire screen and held to the trunk by two bolts. Both trunk lids were made to accept the plate the "connector" was mounted onto. John, it sounds like yours is the reverse gender from what I saw. (PS: I misunderstood and thought you needed the connector on the end of the cable.)

Unless perfection is a requirement, the shell from a chassis mount TNC or similar connector modified to mount with the center conductor hooking to the chicken wire and the connector shell (ground) not connected to anything on the trunk electrically, would work just fine and look nice.

Something tells me the trunk lid connector is going to be "DIY" if it's missing.

[Brett H.]

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??

I have always used the cables from Grossmueller's. Probably used ten of them and they all worked well with reception and the wonderbar function.
The grounding connection in front of the passenger rear wheel has always been in the right location as well.

Good product. Carol is the best!