1989 Buick Riviera Coaxial Cable Type

[CA1989Riv]

Good afternoon everyone. I previously had posted about the repair of the AC Delco power antenna unit. Unfortunately, when the nylon string broke inside of the unit, my dad ended up cutting the coaxial cable to remove the power antenna unit from the trunk, instead of disconnecting the coaxial cable via the two screws that go into the mast. I am now attempting to repair that coaxial cable, but I do not know what kind of cable it is. There are no markings on the outer jacked of the coaxial cable. It is just a black cable that ends in a metal piece that bolts into the antenna mast itself. If anyone knows the kind of cable this is, please let me know!

[Oldtech]

What is the diameter? different cables are different sizes.

[CA1989Riv]

My micrometer says .242 inches, or 6.14mm

[37_Roadmaster_C]

What you describe is very close to the diameter of RG59 75 ohm coax cable. This is the standard cable used for television signals within a home.  To be sure you will need to know a couple more things. First is the diabeter of the internal insulation around the center conductor. The second is whether the center conductor is solid or stranded wire. Assuming it is what I think it is the center conductor will be solid and the center insulation will be approximately 0.146 in or 3.71 mm. The solid center conductor is approximately  0.039 in or 1 mm.  Ok, with that out of the way the connector to use is a type F connector. This is the standard TV connector. Put a connector on each of the cut ends and connect with a type F 'barrel' or female splice. Screw it all together and enjoy radio. Even if the cable is not exactly this type, the splice method will work just fine for an automotive radio.  Good luck.in 3.71 mm

[Oldtech]

Thanks Roadmaster. I suspect though that is is actually RG 62/u  which is 93 ohm. but I think his fix will work.  

[Frank DuVal]

Is the center conductor loose inside the center conductor's insulation? Or is it tight inside the insulator like RG 62, RG 59, etc?

 

If loose, it is not like any RG spec cable, it is auto radio coax. Back when we had to change Nissan pickup right fornt fenders, I would cut the cable and repair it. Much easier than removing half the dash to release the cable from the radio!

 

Cut just enough of the inner insulation to make two small loops and hook the inner conductors together. Apply a little solder. Wrap with tape just the inner conductor. Splay the braids around the inner conductor splice and wrap with a little new copper wire of small gauge, like 24 to 28. With LITTLE heat, flow some solder to this new wire and the braids. You do not want to melt the braid into the center conductor!😲 Wrap with more tape when finished. For a more professional look, slide a piece of heat shrink large enough to cover the braid splice on one coax before starting the repair.😉

 

Yes, you need pretty good soldering skills, so practice first.

[37_Roadmaster_C]

I have not ever been around the RG62 cable so I do not what connectors are available for it. If you can kludge any F type connector it will work for a receiver.  The way Frank described is workable also. I never think that way as I made a career in the communications industry and have probably installed over 5000 coax connectors over the last 40 years. That type of repair just would not wash in my industry, but it would be fine if done well in this application. Franks way is very well thought out and is better than many fixes I have seen over the years 🤣.

[Frank DuVal]

The real problem is that fine inner conductor loosely fitting inside the insulation does not fit any connector except the Motorola connector (you may have the mini version by the late 80s. I know GM changed most to the mini Motorola by the late 90s.

 

The wire is so fine that it corroded in several places on my 66 Monza and I ran a new conductor through the original cable to fix it!😉 There is that much room inside the inner insulation that you can run a new wire through. Nothing like any other coax I have seen in the industry in 50 years. I've been a ham almost that long.

[37_Roadmaster_C]

9 hours ago, Frank DuVal said:

The real problem is that fine inner conductor loosely fitting inside the insulation does not fit any connector except the Motorola connector (you may have the mini version by the late 80s. I know GM changed most to the mini Motorola by the late 90s.

 

The wire is so fine that it corroded in several places on my 66 Monza and I ran a new conductor through the original cable to fix it!😉 There is that much room inside the inner insulation that you can run a new wire through. Nothing like any other coax I have seen in the industry in 50 years. I've been a ham almost that long.

 

@Frank DuVal,  That is amazing. I have never seen any coax like that either, except for the large "Air Line" types 7/8 inch and up. I to am a ham radio operator, W7MSE and have been a chief broadcast engineer and lastly the owner of a two-way radio shop and now retired.  I just do not see why the auto makers would desire a custom cable when there are so many low cost cables that would work just fine and already have connectors available. The engineering thoughts in regard to this is mind boggling.  Also, congrats on restringing the center conductor in your cable. I do not think I would have even thought of that or tried if I did 🤔.

[CA1989Riv]

Thank you everyone for your recommendations! I found a chart online that shows the type of cable based on the outside diameter. Appears to be RG62. It has a very thin conductor inside of a narrow plastic insulator, which is then wrapped in stranded copper conductor, all protected by a plastic/rubber outside insulation. I did a bunch of research and found both male and female “BNC” crimp connectors that work with RG59 and RG62 cable. The center conductor is super thin and the connectors each come with a small copper cover that must be soldered onto the thin conductor within the cable. I’ll give it a go next weekend as all the parts for the repair just arrived a few minutes ago. 

[Frank DuVal]

Yep, that thin center conductor makes it automotive radio coax. No where near the impedance of RG 62 (93 ohms) or RG 59  (75 ohms). Look at the OD of the center conductor on the RG 62 and RG 59 spec sheets. I have no idea what the results of using wrong impedance connectors on this coax will be. I've seen people mix up the 50 ohm and 75 ohm BNC connectors without much problem, but they are made different for a reason (look into the male end and see the difference, very noticeable), or only one impedance of BNC connector would be made. Of course my soldered repair didn't keep the impedance even through the repair either....🤔 And it is for receiving, not transmitting, so VSWR is not important, you should be OK.

 

OD means nothing, just relative to how much power it can carry without getting hot. RG 58, RG 143, RG 174,  LMR 400, and up to 4 1/16" pipe are all 50 ohm coaxes. I've used them all at work. Of course, a different career than collision work!😉

 

Frank

WA4CWM

Edited November 15, 2021 by Frank DuVal (see edit history)

[Bloo]

That auto radio stuff is maybe 93 ohm, or maybe even higher. It is made the way it is to lower capacitance. The impedance rating won't matter that much. Since there is really no way to impedance match it effectively with a typical antenna and a typical car radio, whatever capacitance exists in the cable just drains signal to ground, so the lower the pF/foot the better. I have had exactly zero success splicing this stuff, the loss was always horrendous afterwards. I can't explain why. The only times I have tried were for long runs and rear fender mounted antennas, so if the antenna is mounted up front and there is less cable I think you are more likely to come up with something that works. Good luck.

[Daniel Eldridge]

CA 1989 RIV, Can you contact me per PM @ ed34207@yahoo.com ?