GMRS / CB antenna locations - near A pillar or mid point on hood

[chorky]

The height in the last picture looks ok to me. If you have an ohmmetter connect it across the coax center conductor and whip then check continuity while you unscrew the antenna off the mount. If you get two turns or more before it looses continuity it should be ok.

Some antenna bases have a bendable contact that you can grab and pull out a little to make better contact. Some have a spring loaded pin that can't be moved.

So I got the bracket and antenna on today and as you suggested I first tested continuity from of just the coax, then the antenna and then the coax and antenna together. I probably should test again now that the coax is routed to the final destination.

The coax and antenna combination varied between .01 and .03 and I think that was just because I couldn't get a good solid connection on the antenna itself with the multimeter leads. The antenna is coated in something black.... and the tip had a rubber covering, so I pealed that off and found some fresh metal (assuming it is stainless steel). There was a little gash up there probably from the manufacturer process that showed just a touch of bear metal. So I think the lead just couldn't touch the metal fully to have a good enough connection for no resistance. All the components separately measured flat 0

However, one thing I found interesting is that little metal bracket with the teeth on it underneath the bracket isn't touching metal. I'm not sure if it is supposed to or not? I did tighten it down quite well, and probably could go more but it doesn't feel right doing that. It seems the plastic isolator is what is preventing it from crushing into the metal bracket.

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[chorky]

I'm also curious what to do with the extra coax. I have a lot more than anticipated. I saw somewhere recently that you should wrap it up in the form of a bow? like a bowtie? Not sure if that's accurate or not?

 

[Radio Guy]

On the ohmmeter test if you measure less than an ohm consider it a short. When the antenna is screwed on you should show a short between the whip and coax center conductor. My test was to slowly unscrew the antenna and see how many turns you can go before it looses continuity between the whip and center conductor. If it goes open within a half turn that means the center pin of the mount could be recessed too much and not making good contact with the antenna. If you can unscrew several turns before loosing continuity its good.

The brass threaded part of the mount should have very good continuity to the metal bracket which should have good continuity to the sheet metal of the vehicle around the bracket which is part of the ground plane. With the coax disconnected from the radio you can place the ohmmeter across the brass threaded part of the mount to a screw or bare metal spot on the vehicle near the mount. It should show a short or .2-.3 ohms if that is what your meter reads when the leads are shorted.

For excess coax I would run it to your radio and leave a little more, maybe a foot or two then cut and install a connector. Too much excess coax at UHF is loss and you want to eliminate that. Its not that critical for CB but I still cut to fit with a just a little extra.

 

[chorky]

On the ohmmeter test if you measure less than an ohm consider it a short. When the antenna is screwed on you should show a short between the whip and coax center conductor. My test was to slowly unscrew the antenna and see how many turns you can go before it looses continuity between the whip and center conductor. If it goes open within a half turn that means the center pin of the mount could be recessed too much and not making good contact with the antenna. If you can unscrew several turns before loosing continuity its good.

The brass threaded part of the mount should have very good continuity to the metal bracket which should have good continuity to the sheet metal of the vehicle around the bracket which is part of the ground plane. With the coax disconnected from the radio you can place the ohmmeter across the brass threaded part of the mount to a screw or bare metal spot on the vehicle near the mount. It should show a short or .2-.3 ohms if that is what your meter reads when the leads are shorted.

For excess coax I would run it to your radio and leave a little more, maybe a foot or two then cut and install a connector. Too much excess coax at UHF is loss and you want to eliminate that. Its not that critical for CB but I still cut to fit with a just a little extra.

I had a feeling you were gonna say that. I really didnt want to cut and re-do a new connector... But do you have a suggestion of a particular one? or are they all the same? Manufacturer wise that is....

I did measure the depth of the inside of the antenna base, and the protrusion of the center pin above the bracket. It looks like the cetera pin will be compressed about 1/4 of an inch. I dont have anybody to help me so doing the unscrewing method would be difficult.... But it sounds like I have a solid connection from the tip of the whip to the end of the coax on the radio side. I just can't confirm with certainty how much compression the center pin on the antenna is getting.

But going back to the continuity between the metal bracket. Referring to my picture above, just to clarify I understand you correctly, if I remove the antenna, and place one lead on the large threaded brass portion that goes around the inner brass center pin, and another lead on a ground - there should be continuity? I will check that tomorrow, but based on my picture it sounds like I don't have enough compression of that large brass threaded.....puck I guess I'll call it... so maybe I need to tighten it down a little more. It does touch the bracket - of course the bracket is painted. but on the bottom side, those little 'teeth' really aren't even touching the bracket at all, but the inner 'smooth' teeth are. I'll try to draw on that picture and re-post

 

[chorky]

On the ohmmeter test if you measure less than an ohm consider it a short. When the antenna is screwed on you should show a short between the whip and coax center conductor. My test was to slowly unscrew the antenna and see how many turns you can go before it looses continuity between the whip and center conductor. If it goes open within a half turn that means the center pin of the mount could be recessed too much and not making good contact with the antenna. If you can unscrew several turns before loosing continuity its good.

The brass threaded part of the mount should have very good continuity to the metal bracket which should have good continuity to the sheet metal of the vehicle around the bracket which is part of the ground plane. With the coax disconnected from the radio you can place the ohmmeter across the brass threaded part of the mount to a screw or bare metal spot on the vehicle near the mount. It should show a short or .2-.3 ohms if that is what your meter reads when the leads are shorted.

For excess coax I would run it to your radio and leave a little more, maybe a foot or two then cut and install a connector. Too much excess coax at UHF is loss and you want to eliminate that. Its not that critical for CB but I still cut to fit with a just a little extra.

in red are the teeth that are not touching.

in green is the half moon thing that still protrudes that does seem to touch.

the brass threaded portion on top also does touch.

I probably would need to bend those teeth up more if they are supposed to be digging into the bracket.

 

[Radio Guy]

I had a feeling you were gonna say that. I really didnt want to cut and re-do a new connector... But do you have a suggestion of a particular one? or are they all the same? Manufacturer wise that is....

I did measure the depth of the inside of the antenna base, and the protrusion of the center pin above the bracket. It looks like the cetera pin will be compressed about 1/4 of an inch. I dont have anybody to help me so doing the unscrewing method would be difficult.... But it sounds like I have a solid connection from the tip of the whip to the end of the coax on the radio side. I just can't confirm with certainty how much compression the center pin on the antenna is getting.

But going back to the continuity between the metal bracket. Referring to my picture above, just to clarify I understand you correctly, if I remove the antenna, and place one lead on the large threaded brass portion that goes around the inner brass center pin, and another lead on a ground - there should be continuity? I will check that tomorrow, but based on my picture it sounds like I don't have enough compression of that large brass threaded.....puck I guess I'll call it... so maybe I need to tighten it down a little more. It does touch the bracket - of course the bracket is painted. but on the bottom side, those little 'teeth' really aren't even touching the bracket at all, but the inner 'smooth' teeth are. I'll try to draw on that picture and re-post

There should be continuity between the threaded brass part and the mount and the vehicle body.

 

[kd1yt]

I had a feeling you were gonna say that. I really didnt want to cut and re-do a new connector... But do you have a suggestion of a particular one? or are they all the same? Manufacturer wise that is....

Don't remember what radio you are installing or what antenna connector on your radio is.

But if you have a radio with a super-common "UHF" connector (with the ridges at the forward face of the threaded section on the radio) . . . . The overwhelming majority of "standard" "PL 259" UHF coaxial connectors offered for sale are of terrible quality - bad alloy, bad dimensions, poor quality insulator, plating on the main body that won't 'wet' well to make a good solder connection. . . .

If you get a top-grade (Amphenol, etc) "real" PL-259 . . . . even those are kind of infamous to be difficult to install fully properly (making a good solder connection to the full braid of the coax ... but without so much heat that it melts the internal insulation on the coax) unless (maybe) you have a bunch of practice. . . . which is sometimes gained after some fails along the way.

If you had a crimp tool designed for RG58 coax connectors ... there are decent crimp connectors for crimp-able PL-259 connectors - but not worth buying the crimp tool for a one time job.

A solution, though you may wince at the up-front cost, is a version of a PL-259 that adopts a different way of attaching the coax braid, via clamp, borrowed from the design of a later, much better-designed "N" military-spec coax connector. This lets you need to solder only the center conductor (easy) and is relatively goof-proof for the installation and highly reliable, for the long haul, after installation. You can almost certainly buy a bargain-grade PL259 for 1/10 this price but if you want low hassle, low room for error, and high reliability over time, the better connector, for a one-connector install, is negligible in cost compared to aggravation or erratic operation later.
https://www.pasternack.com/uhf-male...41-rg142-rg223-rg400-connector-pe44052-p.aspx
It's also a way better connector at higher frequencies. And the instructions show you exactly the dimensions to strip to, for proper installation. There may be other sources at lower prices but the other source I was looking at as I compose this message is out of stock.

The "standard" "UHF" PL-259 coax connector is a 1930s design that has endured mainly because it's very cheap and overwhelmingly omnipresent - not because it is good.

There will be hundreds of people who will say that they just jammed together a cheap PL259 and it worked ... and maybe it did . . . . and maybe it'll stay working . . . . or . . . . not . . . . for who knows how long

In a vehicle comm setting, my mindset is "when you want (or need) it to work, you want it to work ... not probably work " - and not detour into a need for a surprise troubleshooting endeavor before you can actually use the radio.

 

[kd1yt]

This one is also way better, and easier to install, than a "usual" PL-259 but I think the one above with the clamp is sturdier and more reliable
https://www.solidsignal.com/ampheno...MsNKM-3Hftj7jIB4SVkvc92Z88Ov24ccaAgdmEALw_wcB
or
https://www.mouser.com/ProductDetail/Amphenol-RF/083-58FCP-RFX?qs=py4qCovljJ%2BZueQ0CYx64A==

 

[Radio Guy]

This would be for UHF so you want to make sure the connector is good quality and properly installed. If your not sure of which one to buy or have no experience or tools for installing them I would suggest you get someone who is qualified to do it.

A good silver plated Teflon insulated solder type is fine but easily screwed up during soldering unless you have lots of experience. A crimped connection is usually superior if you have the specific crimp tools for the connector. Just for the record, for critical RF connections in aircraft or spacecraft, etc, no soldering is allowed, only crimped. Been there and done that working in aerospace and I've also built complete cable harnesses for military aircraft.

If you want to make the journey to So Cal I have every connector type imaginable, the proper tools and experience. Plus all the test equipment to measure anything in your antenna system and radio. And I'm free for Jeep owners!

 

[chorky]

Don't remember what radio you are installing or what antenna connector on your radio is.

But if you have a radio with a super-common "UHF" connector (with the ridges at the forward face of the threaded section on the radio) . . . . The overwhelming majority of "standard" "PL 259" UHF coaxial connectors offered for sale are of terrible quality - bad alloy, bad dimensions, poor quality insulator, plating on the main body that won't 'wet' well to make a good solder connection. . . .

If you get a top-grade (Amphenol, etc) "real" PL-259 . . . . even those are kind of infamous to be difficult to install fully properly (making a good solder connection to the full braid of the coax ... but without so much heat that it melts the internal insulation on the coax) unless (maybe) you have a bunch of practice. . . . which is sometimes gained after some fails along the way.

If you had a crimp tool designed for RG58 coax connectors ... there are decent crimp connectors for crimp-able PL-259 connectors - but not worth buying the crimp tool for a one time job.

A solution, though you may wince at the up-front cost, is a version of a PL-259 that adopts a different way of attaching the coax braid, via clamp, borrowed from the design of a later, much better-designed "N" military-spec coax connector. This lets you need to solder only the center conductor (easy) and is relatively goof-proof for the installation and highly reliable, for the long haul, after installation. You can almost certainly buy a bargain-grade PL259 for 1/10 this price but if you want low hassle, low room for error, and high reliability over time, the better connector, for a one-connector install, is negligible in cost compared to aggravation or erratic operation later.
https://www.pasternack.com/uhf-male...41-rg142-rg223-rg400-connector-pe44052-p.aspx
It's also a way better connector at higher frequencies. And the instructions show you exactly the dimensions to strip to, for proper installation. There may be other sources at lower prices but the other source I was looking at as I compose this message is out of stock.

The "standard" "UHF" PL-259 coax connector is a 1930s design that has endured mainly because it's very cheap and overwhelmingly omnipresent - not because it is good.

There will be hundreds of people who will say that they just jammed together a cheap PL259 and it worked ... and maybe it did . . . . and maybe it'll stay working . . . . or . . . . not . . . . for who knows how long

In a vehicle comm setting, my mindset is "when you want (or need) it to work, you want it to work ... not probably work " - and not detour into a need for a surprise troubleshooting endeavor before you can actually use the radio.

Soldering is not a problem for me, I've done that a fair bit - but crimping would certainly be faster and easier. I'll have to see if I still have my coax crimp tools... used to do a bunch of that for low voltage stuff but it's been years. I do appreciate those links too!

This would be for UHF so you want to make sure the connector is good quality and properly installed. If your not sure of which one to buy or have no experience or tools for installing them I would suggest you get someone who is qualified to do it.

A good silver plated Teflon insulated solder type is fine but easily screwed up during soldering unless you have lots of experience. A crimped connection is usually superior if you have the specific crimp tools for the connector. Just for the record, for critical RF connections in aircraft or spacecraft, etc, no soldering is allowed, only crimped. Been there and done that working in aerospace and I've also built complete cable harnesses for military aircraft.

If you want to make the journey to So Cal I have every connector type imaginable, the proper tools and experience. Plus all the test equipment to measure anything in your antenna system and radio. And I'm free for Jeep owners!

Oh man - I really appreciate that offer. I do plan on doing some trips to Cali in the future - Brad from trail recon has shown some awesome trails there. But it's awful cold here still, so I might opt to just wait until spring/summer to trim down the coax. Wires don't like bending much when it's below freezing. So hopefully I dont cause any issues until then but once I get the redo itself mounted, and the dummy load I'll do some testing and see how it looks. It would be nice to have use out of it until I can trim down coax but that will be sometime in July I think.

 

[Radio Guy]

Soldering is not a problem for me, I've done that a fair bit - but crimping would certainly be faster and easier. I'll have to see if I still have my coax crimp tools... used to do a bunch of that for low voltage stuff but it's been years. I do appreciate those links too!




Oh man - I really appreciate that offer. I do plan on doing some trips to Cali in the future - Brad from trail recon has shown some awesome trails there. But it's awful cold here still, so I might opt to just wait until spring/summer to trim down the coax. Wires don't like bending much when it's below freezing. So hopefully I dont cause any issues until then but once I get the redo itself mounted, and the dummy load I'll do some testing and see how it looks. It would be nice to have use out of it until I can trim down coax but that will be sometime in July I think.

If you have a connector on now with just some extra coax it will work fine. Shortening the coax will just be a future enhancement.

 

[chorky]

If you have a connector on now with just some extra coax it will work fine. Shortening the coax will just be a future enhancement.

yeah but i have 5-6’ of extra coax

 

[Radio Guy]

yeah but i have 5-6’ of extra coax

It will work fine, just use and enjoy for now and when the time is right you can shorten it.

 

[chorky]

It will work fine, just use and enjoy for now and when the time is right you can shorten it.

i ended up ordering some solder connections from amazon since I had other things to order anyway

Would there be a concern about crossing signals if coax for gmrs and ch were parallel since i plan on mounting them next to each other? The coax I dont believe is shielded.

 

[Radio Guy]

i ended up ordering some solder connections from amazon since I had other things to order anyway

Would there be a concern about crossing signals if coax for gmrs and ch were parallel since i plan on mounting them next to each other? The coax I dont believe is shielded.

No problem, even running both cables wrapped tightly together the full length of the truck. All coax is inherently shielded, just some is better than others. There will be way more signal pickup between antennas compared to cable leakage.

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