would they 6" antenna cone shaped one screw into one of those tabs on the top of the Bull Bar?
Jeep Jamboree: CB to be replaced by FRS/GMRS two-way radios in 2021
- Thread starter Hulk
- Start date
DaveInDenver
Rising Sun Ham Guru
Are you thinking about the phantom antennas? They mount on NMO bases. There are ways to get one on an ARB antenna tab. I've had good success mechanically with an Opek AM-207C but realize that the tab doesn't give much of a surface around the NMO so not all antennas will be weather-tight depending on the diameter of the base and how they are designed to seal. Only the inner o-ring on my Larsen will sit fully on the tab, for example.
Antenna Mount Series - Autotek AM-207C Model
Autotek, manufacturer of two way radio antennas and accessories, main products including antenna mounts, coaxial switches, and more.
www.opekantenna.com
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I ordered the MXT275 bundle with the Ghost antenna. Plan on mounting the antenna on the tab on the top of the Bull Bar
I read the 6db expands the power horizontally so better for flat landing. The 3db may be better for off-roading
In any case, I will still have HAM and the ability of the 3dB antenna should cover separation on a trail run. Farthest distance isnt a concern since we all (Romer's) also have HAM
I read the 6db expands the power horizontally so better for flat landing. The 3db may be better for off-roading
In any case, I will still have HAM and the ability of the 3dB antenna should cover separation on a trail run. Farthest distance isnt a concern since we all (Romer's) also have HAM
DaveInDenver
Rising Sun Ham Guru
Midland says both the 3 dB ghost and the 6 dB whip antenna are 5/8λ so it's not clear how they differ electrically for the gain claims. If it's true they're both 5/8λ then they'll be ground plane dependent as to how well they tune and the actual gain and pattern.
FWIW the only antenna I've had much luck with on the bull bar was a Laird 2m 1/2λ NGP (model BB1442N). The GMRS equivalent is the BB4502N (there's other variants in chrome and with base springs).
FWIW the only antenna I've had much luck with on the bull bar was a Laird 2m 1/2λ NGP (model BB1442N). The GMRS equivalent is the BB4502N (there's other variants in chrome and with base springs).
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I don't normally like antennas in your front view. This one is short so shouldnt be in the way at all. If it doesnt work well enough, then I will route to the back
Couldn't you just use a firestick? I was thinking about repurposing my CB antenna for the GMRS radio.
That would be a sparky Dave question . That would be good to know
Any ham can answer that one...
Firesticks from CB are not good for GMRS. CB is closer to HF where GMRS is closer to UHF.
Dual band or UHF ham antennas are generally good for GMRS/FRS though so lots of you have those around.
Firesticks from CB are not good for GMRS. CB is closer to HF where GMRS is closer to UHF.
Dual band or UHF ham antennas are generally good for GMRS/FRS though so lots of you have those around.
Ken - I've got the Midland ghost antenna mounted to the top tab of my ARB front bumper. I haven't done any sort of tuning, but the performance has been excellent.
Thanks Ryland, Thats great to know
DaveInDenver
Rising Sun Ham Guru
CB antennas are of no use on GMRS.
OTOH for comparison this is a full height 1/4λ whip tuned for amateur 70cm, which ends up being about 6.5" tall. For GMRS it would be barely shorter, like a couple of mm.
The equivalent CB antenna would be 9 feet (108 inches, e.g. those monster whips you used to see) tall.
For anyone interested in the actual radio stuff, this antenna will show 2.15 dBi (0 dBd) of gain, so could be fed with 5 watts with respect to the GMRS channels 1 to 7 ERP rules. However it doesn't actually perform well due to the lack of decent ground plane. When you measure will likely show high SWR that indicates you should keep cutting it shorter.
That SWR is likely a red herring because the bumper isn't a good plane unless you've grounded the mount well to the bumper (exposed bare steel under it) and bonded it to the frame to keep the body itself from coupling indirectly across rusty bolted connections. Doing that at least prevents the coax shield starting to act like the ground, which is what will happen if the mount isn't grounded well. So while eventually you could keep cutting until you get a reasonably low SWR that is actually indicating you're approaching a nonresistive dummy load rather than efficient antenna.
In that case range will probably be impacted. But since the comparison is CB that can't make 1/2 mile using a dummy load (literally a big resistor) fed with 15 or 50 watts will radiate well enough to be heard a couple of city blocks away by a sensitive radio seems pretty good. In actuality 5 watts into a decent antenna should work more or less to the horizon (line of sight limited, not signal strength). Even 1 watt should work tens of miles to highly placed repeaters with good efficiency and line of sight. A poorly grounded antenna, be it 1/4λ like this or any other, will fall somewhere in the middle. Not as good as can be but not totally a dummy load.
If you do take the time to ground the mount to the bumper it could be a decent antenna electrically but highly directional. It'll produce two strong lobes side-to-side along the upper tube, might produce a weak lobe back over the hood (that will be substantially blocked or absorbed by the cab and meatbags inside in my case) and almost no energy radiates forward. You'd notice having trouble contacting and hearing stations maybe a mile ahead of you but still randomly hear a station tens of miles away that comes and goes as you drive around switchbacks.
The shortest No-Ground Plane antennas that solve this lack of sheet metal and nonuniformity are typically a few inches taller because they elevate the feedpoint such that it's in effect a dipole turned vertical or they put an artificial ground, a coil or capacitor-inductor circuit, in the base. Those will at least work more uniformly around all 360° of the whip although the external interference (the previously mentioned meatbags) will remain. That is dealt with by elevating the antenna to the highest practical.
They may also simply use an antenna that's 1/2λ long, which would be about 35 cm or ~14 inches tall and be inherently ground plane agnostic. It may also start to show a little gain (e.g. if you're worried about respecting ERP rules). Anything taller than 14" is actually multiple elements and will almost definitely have increasing gain. Such an antenna can be made shorter by putting a loading coil in the middle so it's electrically long enough but not physically.
That SWR is likely a red herring because the bumper isn't a good plane unless you've grounded the mount well to the bumper (exposed bare steel under it) and bonded it to the frame to keep the body itself from coupling indirectly across rusty bolted connections. Doing that at least prevents the coax shield starting to act like the ground, which is what will happen if the mount isn't grounded well. So while eventually you could keep cutting until you get a reasonably low SWR that is actually indicating you're approaching a nonresistive dummy load rather than efficient antenna.
In that case range will probably be impacted. But since the comparison is CB that can't make 1/2 mile using a dummy load (literally a big resistor) fed with 15 or 50 watts will radiate well enough to be heard a couple of city blocks away by a sensitive radio seems pretty good. In actuality 5 watts into a decent antenna should work more or less to the horizon (line of sight limited, not signal strength). Even 1 watt should work tens of miles to highly placed repeaters with good efficiency and line of sight. A poorly grounded antenna, be it 1/4λ like this or any other, will fall somewhere in the middle. Not as good as can be but not totally a dummy load.
If you do take the time to ground the mount to the bumper it could be a decent antenna electrically but highly directional. It'll produce two strong lobes side-to-side along the upper tube, might produce a weak lobe back over the hood (that will be substantially blocked or absorbed by the cab and meatbags inside in my case) and almost no energy radiates forward. You'd notice having trouble contacting and hearing stations maybe a mile ahead of you but still randomly hear a station tens of miles away that comes and goes as you drive around switchbacks.
The shortest No-Ground Plane antennas that solve this lack of sheet metal and nonuniformity are typically a few inches taller because they elevate the feedpoint such that it's in effect a dipole turned vertical or they put an artificial ground, a coil or capacitor-inductor circuit, in the base. Those will at least work more uniformly around all 360° of the whip although the external interference (the previously mentioned meatbags) will remain. That is dealt with by elevating the antenna to the highest practical.
They may also simply use an antenna that's 1/2λ long, which would be about 35 cm or ~14 inches tall and be inherently ground plane agnostic. It may also start to show a little gain (e.g. if you're worried about respecting ERP rules). Anything taller than 14" is actually multiple elements and will almost definitely have increasing gain. Such an antenna can be made shorter by putting a loading coil in the middle so it's electrically long enough but not physically.
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