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

[chorky]

The steps in a step bit are really shallow, you might need to go about 3/8" wider than the hole to make a rectangular recessed spot for the back side of the NMO mount to fit in. I did that once using a hand held grinder in similar thickness metal to the Evo mount and it was a big PIA. If you had a typical roof mount NMO mount you could use that as a guide on how much metal to remove to bring the top contact point up to needed height.

You could also use a "thick mount" NMO like this but you have to solder in your own coax and weather proof it. You also have to make sure the material is not too thin where you have to use spacers to leave the correct height on the center contact to the antenna.
https://www.ebay.com/itm/223457312586?hash=item340717ff4a:g:X7gAAOSwXL1clOzM&amdata=enc:AQAHAAAA4NhRdM4pMtgaYxXTYtiB4GhcUerZ50fjGli3JkmqhY7+inhdwZYKPYPwL35Nm//ioDw3uTEy2wAzm+4TbIpyf6JcOhrA4g2PIYg0VzPckRh2Ot1l+a3xEUW8GWyc2jziUq5BcNooPcnvrXeOvYnlyJKgZm/zE/CLfVSmYIGlEIOj5SKviRGNSlQGc+0BiG3rU300oW2aHKS1akxEMs/AbnnMNQCHLYduNdo6HQwY2CJv4CA7RzUG0/jEWpwcD5zIR1KPsAkagrlCdKBDNFfcorUX2r6O2qQ+rkji4NDJLVa7|tkp:Bk9SR_yo0fy_YQ

On the post above with the short antenna on the blue truck with 5mi range, I get well in excess of 20mi range down the open highway to most anyone and have done further depending on how good the antenna is at the other end. I easily do 75mi or more to GMRS and UHF amateur repeaters around here with my trunk lip mount on the hood.

For chorky you should get 20mi range down the highway on GMRS with a hood mounted antenna that is right on the hood not elevated and CB depends entirely on if the skip is in and how noisy the band is. If its a real quite day with no skip I would expect at least 5 to 10mi to other vehicles with good antennas and 10-20mi to base stations. On a real noisy day range can be just a mile or so and people on the other side of the country will be much stronger than the guy a mile up the road from you.

do you have an opinion on this guy? Just arrived today. Still waiting for the coax. Funny enough it was the only one in stock i found at the time of order so hoping it works good

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[Radio Guy]

do you have an opinion on this guy? Just arrived today. Still waiting for the coax. Funny enough it was the only one in stock i found at the time of order so hoping it works good

If your referring to the NMO thick mount I have used them many years ago and that particular one is made by Larsen which is good quality. Two things that need attention on that is the height of the center contact on top which you may have to adjust using a big washer or two on the underside of the cowl mount since your mount is thicker than a vehicle roof but thinner than what most people use these mounts for. The second thing is weatherproofing the coax connection after you solder the coax center conductor, crimp the braid and solder the cover over the hole for the center conductor.

I should have mentioned you will need a soldering iron and a proper crimping tool for the braid plus some coax of course.

 

[chorky]

If your referring to the NMO thick mount I have used them many years ago and that particular one is made by Larsen which is good quality. Two things that need attention on that is the height of the center contact on top which you may have to adjust using a big washer or two on the underside of the cowl mount since your mount is thicker than a vehicle roof but thinner than what most people use these mounts for. The second thing is weatherproofing the coax connection after you solder the coax center conductor, crimp the braid and solder the cover over the hole for the center conductor.

I should have mentioned you will need a soldering iron and a proper crimping tool for the braid plus some coax of course.

oops. Pic didnt post. I meant this

but I have soldered and crimped many things so pretty well versed in that. Im hoping the coax i have on the way will work but Ill know this weekend

 

[Radio Guy]

oops. Pic didnt post. I meant this

but I have soldered and crimped many things so pretty well versed in that. Im hoping the coax i have on the way will work but Ill know this weekend

I've never used that brand or model but its probably ok for the price. I would recommend a good 50 ohm resistive load rated for more power than your radio puts out. Any power measurements will only be accurate when using a 50 ohm resistive load and measuring power to your antenna will cause inaccurate readings. I would think the VSWR measuring side of that meter is ok. The frequency counter will be very crude and not suitable for tweaking any radio on frequency and your radio will probably be more on frequency than the frequency counter.

 

[chorky]

I've never used that brand or model but its probably ok for the price. I would recommend a good 50 ohm resistive load rated for more power than your radio puts out. Any power measurements will only be accurate when using a 50 ohm resistive load and measuring power to your antenna will cause inaccurate readings. I would think the VSWR measuring side of that meter is ok.

hmm I've never heard of measuring with a resistive load before. can you offer a suggestion on an item?

does the same situation occur with measuring swr for CB? I have never heard of needing to do that before.

 

[Radio Guy]

hmm I've never heard of measuring with a resistive load before. can you offer a suggestion on an item?

does the same situation occur with measuring swr for CB? I have never heard of needing to do that before.

Even measuring a CB into an antenna will give inaccurate power readings, all wattmeter's are calibrated for use into a 50 ohm resistive load and when the load is a different resistance or impedance or has capacitive or inductive properties which antennas have, the meter cal is out the window.

Here is a cheap hobby load that should work, although you will have to use a PL to N adapter which adds some uncertainty.
https://www.ebay.com/itm/165808317828?hash=item269af22584:g:XmEAAOSwps5fkWCd&amdata=enc:AQAHAAAAoEgGX8Nje28x42mpve+dq5EIYO3ob+gy8pI5Yt3wv+KWFpnccnQLzzJ0I74HTTmLbCb7PQi93EO/76sJtMcjg6qmsnFHgIzVr+8oDp9y11RVCNmJRE9Pw0nMXdtxmhMspwE027Ovd6w8mIp/bBbx2HnrN1dMIwdkOc3iiDkiyclJdkT4TKxfHn6WA2d1MVVs+44knu20lz8FmxJktI0elM8=|tkp:Bk9SR8yjwN7AYQ


Here is a used commercial version with N connector that is slightly better and doesn't need an adapter for your meter.
https://www.ebay.com/itm/174417855095?hash=item289c1d4277:g:fGQAAOSwtrxfTq7o&amdata=enc:AQAHAAAAoAfHmEDErmY1VHZemSc2CcvoX/ZdBVNuGCkdLD3M5IAO2SvffyfzvFr+1YUj1eRCm78GEt6Lsvjy7dr3aZupegMClaNjKULWN12/g9xaVyn6ZDJy52svBwmRyJEHLd0/W75U8chl+hAjgd8MYY072roc3cDOqG5A90WiTZcyuyuhjBl38HUSiWXXaxAYfVts+g3hoW8lmkl82EvJjokqpIc=|tkp:Bk9SR8qjwN7AYQ

 

[chorky]

Even measuring a CB into an antenna will give inaccurate power readings, all wattmeter's are calibrated for use into a 50 ohm resistive load and when the load is a different resistance or impedance or has capacitive or inductive properties which antennas have, the meter cal is out the window.

Here is a cheap hobby load that should work, although you will have to use a PL to N adapter which adds some uncertainty.
https://www.ebay.com/itm/165808317828?hash=item269af22584:g:XmEAAOSwps5fkWCd&amdata=enc:AQAHAAAAoEgGX8Nje28x42mpve+dq5EIYO3ob+gy8pI5Yt3wv+KWFpnccnQLzzJ0I74HTTmLbCb7PQi93EO/76sJtMcjg6qmsnFHgIzVr+8oDp9y11RVCNmJRE9Pw0nMXdtxmhMspwE027Ovd6w8mIp/bBbx2HnrN1dMIwdkOc3iiDkiyclJdkT4TKxfHn6WA2d1MVVs+44knu20lz8FmxJktI0elM8=|tkp:Bk9SR8yjwN7AYQ


Here is a used commercial version with N connector that is slightly better and doesn't need an adapter for your meter.
https://www.ebay.com/itm/174417855095?hash=item289c1d4277:g:fGQAAOSwtrxfTq7o&amdata=enc:AQAHAAAAoAfHmEDErmY1VHZemSc2CcvoX/ZdBVNuGCkdLD3M5IAO2SvffyfzvFr+1YUj1eRCm78GEt6Lsvjy7dr3aZupegMClaNjKULWN12/g9xaVyn6ZDJy52svBwmRyJEHLd0/W75U8chl+hAjgd8MYY072roc3cDOqG5A90WiTZcyuyuhjBl38HUSiWXXaxAYfVts+g3hoW8lmkl82EvJjokqpIc=|tkp:Bk9SR8qjwN7AYQ

ok so the dummy load connects directly to the end of the SWR meter? I thought the point of the SWR meter was to help trim antenna to the right length. Or how else do you check integrity of the coax from radio to antenna? Or maybe I'm just getting myself mixed up.

 

[Radio Guy]

ok so the dummy load connects directly to the end of the SWR meter? I thought the point of the SWR meter was to help trim antenna to the right length. Or how else do you check integrity of the coax from radio to antenna? Or maybe I'm just getting myself mixed up.

To test antenna VSWR you put the meter in line with your antenna. To test radio output power accurately or at least to the extent of the accuracy of the meter you replace the antenna with a 50 ohm resistive load right at the output of the meter. Testing power when connected to the antenna might be close or it could be perfect, but it could also be way off and you will never know. But it will let you know the radio is putting out some power in a pinch.

 

[Dls79]

This is how I attached my GMRS antenna at the driver’s A pillar. It is a magnetic base to MOPAR A pillar auxiliary light brackets. This set up works really well for me. The antenna mount stays put at 80+ MPH and through high pressure washing.

 

[Minty JL]

Simple answer to the thread title, higher is better in regards to LoS.

I will be mounting my antenna on my bed rack

 

[MPMB]

I may have already answered in this thread, but I have a JCR half roof rack and the antenna is mounted on that. If you plan on going topless this doesn't work, but I doubt I'll ever take off the back.

 

[chorky]

Even measuring a CB into an antenna will give inaccurate power readings, all wattmeter's are calibrated for use into a 50 ohm resistive load and when the load is a different resistance or impedance or has capacitive or inductive properties which antennas have, the meter cal is out the window.

Here is a cheap hobby load that should work, although you will have to use a PL to N adapter which adds some uncertainty.
https://www.ebay.com/itm/165808317828?hash=item269af22584:g:XmEAAOSwps5fkWCd&amdata=enc:AQAHAAAAoEgGX8Nje28x42mpve+dq5EIYO3ob+gy8pI5Yt3wv+KWFpnccnQLzzJ0I74HTTmLbCb7PQi93EO/76sJtMcjg6qmsnFHgIzVr+8oDp9y11RVCNmJRE9Pw0nMXdtxmhMspwE027Ovd6w8mIp/bBbx2HnrN1dMIwdkOc3iiDkiyclJdkT4TKxfHn6WA2d1MVVs+44knu20lz8FmxJktI0elM8=|tkp:Bk9SR8yjwN7AYQ


Here is a used commercial version with N connector that is slightly better and doesn't need an adapter for your meter.
https://www.ebay.com/itm/174417855095?hash=item289c1d4277:g:fGQAAOSwtrxfTq7o&amdata=enc:AQAHAAAAoAfHmEDErmY1VHZemSc2CcvoX/ZdBVNuGCkdLD3M5IAO2SvffyfzvFr+1YUj1eRCm78GEt6Lsvjy7dr3aZupegMClaNjKULWN12/g9xaVyn6ZDJy52svBwmRyJEHLd0/W75U8chl+hAjgd8MYY072roc3cDOqG5A90WiTZcyuyuhjBl38HUSiWXXaxAYfVts+g3hoW8lmkl82EvJjokqpIc=|tkp:Bk9SR8qjwN7AYQ

Looks like it will work…. ??

here is a pic of the plastic groment isolator next to the mount. Its not really that thick.

 

[chorky]

@Radio Guy

looks right to me unless im missing something

 

[Radio Guy]

@Radio Guy

looks right to me unless im missing something

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.

 

[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.

I will give that a try tomorrow. Yeah the center contact on the coax part won't move, it's pretty solid. also, the grounding plate on the bottom side was not touching the metal bracket however thats mostly because I didnt screw it down tight enough. I'm thinking it will work.

the big question though will be like you said earlier - the distance between the antenna and ground plane. I did not know until today when taking of the cowl that its not just the round cowl parts that are plastic but the whole cowl as well, and it's a good 3 inches or so under the plastic before there is metal, so that bracket will have the base of the antenna probably 4-6 inches above the metal under the plastic cowl.

If that does cause a problem, is there anything I can do to remedy the situation?

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