CB not transmitting?
- Thread starter alkarich
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I'm with Brent, I still think there is a DC ground issue.
However, given the information regarding your mounting location (sorry I didn't ask about this earlier) you also have the issue of a poor image plane. Basically, the truck surface needs to act as a ground radial for your antenna, and your location doesn't allow this very well. You could correct somewhat by using a taller antenna to get above the vehicle more, but it won't make a large difference.
Instead, you could use a 1/2 wave antenna which acts like a dipole and uses the coax as the other half or ground radial. I've seen some surprising improvements by moving to a 1/2 wave for locations with a poor image plane (both with 11m CB and 2m/70cm Ham).
The best result though would probably come from a change to a no-ground-plane antenna system (which is specifically designed to use the coax as a ground plane). I know Firestick offers these and I'm guessing others do also. I've never had to go this far though, so I can't offer any personal experience.
As for why one radio worked and another didn't - that's confusing. An intermittent DC ground problem would certainly explain it, but you would need a lot more test data to confirm this (couple hundred attempts with each radio).
However, I've also seen marked differences between radios when connected to the same poor image plane antenna, even though there is little noticeable difference in the two radios when connected to a quality antenna with a perfect DC ground and excellent image plane. So in short (no pun intended) the poor image plane magnifies any weakness in the radio's transmit ability.
An antenna analyzer would help here, but I wouldn't recommend the expense if this is your only purpose. However, I would recommend you find a local Ham radio club and get to know them, as someone there will likely have an antenna analyzer and be happy to help you out.
As a final note, the image plane issue is supported by the fact that your mag mount worked well. Though mag mounts generally have a poor dc ground, they often have a great image plane b/c they are generally placed in the center of the roof or very close thereto (and in any case much better placement than a low point on the front bumper).
Keep at it, you're getting close (I can feel it)!
However, given the information regarding your mounting location (sorry I didn't ask about this earlier) you also have the issue of a poor image plane. Basically, the truck surface needs to act as a ground radial for your antenna, and your location doesn't allow this very well. You could correct somewhat by using a taller antenna to get above the vehicle more, but it won't make a large difference.
Instead, you could use a 1/2 wave antenna which acts like a dipole and uses the coax as the other half or ground radial. I've seen some surprising improvements by moving to a 1/2 wave for locations with a poor image plane (both with 11m CB and 2m/70cm Ham).
The best result though would probably come from a change to a no-ground-plane antenna system (which is specifically designed to use the coax as a ground plane). I know Firestick offers these and I'm guessing others do also. I've never had to go this far though, so I can't offer any personal experience.
As for why one radio worked and another didn't - that's confusing. An intermittent DC ground problem would certainly explain it, but you would need a lot more test data to confirm this (couple hundred attempts with each radio).
However, I've also seen marked differences between radios when connected to the same poor image plane antenna, even though there is little noticeable difference in the two radios when connected to a quality antenna with a perfect DC ground and excellent image plane. So in short (no pun intended) the poor image plane magnifies any weakness in the radio's transmit ability.
An antenna analyzer would help here, but I wouldn't recommend the expense if this is your only purpose. However, I would recommend you find a local Ham radio club and get to know them, as someone there will likely have an antenna analyzer and be happy to help you out.
As a final note, the image plane issue is supported by the fact that your mag mount worked well. Though mag mounts generally have a poor dc ground, they often have a great image plane b/c they are generally placed in the center of the roof or very close thereto (and in any case much better placement than a low point on the front bumper).
Keep at it, you're getting close (I can feel it)!
- Thread starter
- #23
Hello Miescha, well I honestly don't know what a 1/2 wave antenna or a no ground-plane antenna is. So looks like I need to do a little research. Thanks.
Sorry about that, I try to avoid too much tech jargon as it often gets lost on me.
The wave length refers to the radio frequency wave. So a 2m ham transmits a 2m wavelength pattern. Likewise, the 11m CB bands transmit an 11m wavelength pattern. So an antenna designed to perfectly transmit or receive a 2m frequency would be a 2m straight whip - but that would be over 6 1/2 feet which is a bit awkward for city driving. On the 11m CB side, a full wavelength antenna would be a 36ft staight whip - this is REALLY difficult to have on your truck!
To get around this, manufacturers use a whip and loading coil to achieve thier desired need on the vhf/uhf bands where the whip is still pretty small even at 1/2 wave or 5/8 wave whips.
On 11m CB, manufacturers use loading, but also wind the wire around the fiberglass stick to get a longer length wire antenna in a shorter overall space.
Check out the firestick.com site for more details.
Hope this helps.
The wave length refers to the radio frequency wave. So a 2m ham transmits a 2m wavelength pattern. Likewise, the 11m CB bands transmit an 11m wavelength pattern. So an antenna designed to perfectly transmit or receive a 2m frequency would be a 2m straight whip - but that would be over 6 1/2 feet which is a bit awkward for city driving. On the 11m CB side, a full wavelength antenna would be a 36ft staight whip - this is REALLY difficult to have on your truck!
To get around this, manufacturers use a whip and loading coil to achieve thier desired need on the vhf/uhf bands where the whip is still pretty small even at 1/2 wave or 5/8 wave whips.
On 11m CB, manufacturers use loading, but also wind the wire around the fiberglass stick to get a longer length wire antenna in a shorter overall space.
Check out the firestick.com site for more details.
Hope this helps.
- Thread starter
- #25
Miescha, looks like an option. How much if any better performing would a NGP antenna be vs. a mag mount. I'm assuming that in performance we would be looking at distance signals travel. I'll try talk to the CB guy who has been helping me. I may just end up keeping the mag mount. It also would be nice to solve this though. Thanks, Alan.
- Thread starter
- #26
Well I'm running out of time before the snow flies. So will probably end up keeping the mag mount. Unfortunately haven't had a chance to fully test the range of this set-up. Heading to Grand Canyon soon. Thanks for all the help here.
Sorry I had to disappear off the board for a while (work keeps getting in the way of life 
).
I'm guessing you're gone, so I'll with you luck.
As for your last question, the NGP system should work very well if you don't otherwise have a ground (image) plane. I can't say with any certainty though beyond what I've read - as stated, I've never tried one as I've been fortunate to get a standard system working.
Good luck!
).I'm guessing you're gone, so I'll with you luck.
As for your last question, the NGP system should work very well if you don't otherwise have a ground (image) plane. I can't say with any certainty though beyond what I've read - as stated, I've never tried one as I've been fortunate to get a standard system working.
Good luck!
Kofoed
SILVER Star
FYI- The NGP antennas that firestik sells work if you have no metal to mount the antenna to. It uses the coax to form the image (the other 1/4 wave of the antenna) which is a poor solution--but one that is better than using a regular antenna without the "ground plane"
- Thread starter
- #29
Was out for awhile as well, hiking in the Grand Canyon. Snow should be flying soon. If I end up with poor performance next spring I'll explore these other options. Thanks for all the help with this. Alan.