ive got a gme tx3200 uhf radio running through the crapy arieal my truck came with and i have stuff all range (my mates $20 handheld beats it). i want to replace it and need to know what is the best Db. needs to be ground impiedent as it will be mounted on my alloy bullbar. the kind of trips i do are duoble island, frazer, landcruiser park, black duck valley, ect. radio is mostly for convoy chat and comunication. any sugestions and oppinions would be great.
cheers
SASS
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CB arieal? 4.5db or 6.5db?
Moderators: toaddog, TWISTY, V8Patrol, Moderators
CB arieal? 4.5db or 6.5db?
Stick it in low and NAIL IT !!!!!!!!!!
Dick Smith are currently stocking the RFI 6.5db elevated feed for $79 or thereabouts. I'm running one of these on the mrs' car and a mate has one on his 4wd and i reckon it's the best out there. Just make sure you get the one with RFI stamped all over it and don't cut the cable any shorter and don't coil it - run up and down to use up length. Range from this aerial ranges from about 5-6klm max in heavily timbered or extremely hilly country, 6-7klm max for heavily populated urban areas or average hilly areas, 7-15 klm rural landscape and i've managed 22-24klm on the beach at Fraser and out on the darling downs. I've tested thes ranges with a Uniden 013, and several Icom 400 pro's so the GME should be excellent with that aerial.
As a guide, the lower the dB value, the shorter distance horizontally they will transmit/recieve (radiation pattern like a doghnut with a hole in it), but the better able they are to handle hills and valleys ("vertical off axis"). The low dB ones are good for convoys as it limits the reception/transmission to your local area, and you don't get interference from other users several km away.
Higher dB values give a radiation pattern more like a frisbee (wide, flat, but not very tall) These are basically only good for long distance driving on flat roads, and will give you apparent "dead spots" in hilly country.
They are not that expensive or difficult to change that you can't buy one of each and change them while you air down/up. Benefit is if you break one, you still have the other as a spare (although not ideal).
Higher dB values give a radiation pattern more like a frisbee (wide, flat, but not very tall) These are basically only good for long distance driving on flat roads, and will give you apparent "dead spots" in hilly country.
They are not that expensive or difficult to change that you can't buy one of each and change them while you air down/up. Benefit is if you break one, you still have the other as a spare (although not ideal).
George Carlin, an American Comedian said; "Think of how stupid the average person is, and realise that half of them are stupider than that".
Hi guys,
I had a similar problem with a Uniden UHF. The Antenna I have is just a cheap wire whip style, ground plane independant, pre-tuned. After a couple of trips of frustration I found and followed this little patch of info.
Aerial is the same, mounted on bullbar still though I did remove the coax connector and re-attach it as per the second instructions.
Now the thing works 100 times better and it only cost me about 30 minutes of my time and 10cm of solder
UHF Reception checklist
1. Run separate power and earth leads direct to the unit from the battery to reduce voltage drop
2. Earth the radio case to the chassis or earth lead direct from battery
3. Directly Earth the aerial base, not just via the coax
4. Mount the aerial as high as possible
5. No sharp kinks in the coax
Terminating the Co-Axial cable and wiring
Tools Required
1. Soldering iron
2. Sharp knife
Steps
A. Carefully cut the black insulation away about 3 cm then cut the outer conductor leaving about 1cm
B. Fold back the outer conductor
C. Cut the inner insulation about 5 mm from the outer conductor
D. Slide some heat shrink and the outer piece of the connector or the entire area, then screw the fitting over the exposed outer conductor
E.
F. Solder the inner conductor to the end of the fitting
G. Slide up to other parts and screw it together then place the heat shrink over the end and heat it
I had a similar problem with a Uniden UHF. The Antenna I have is just a cheap wire whip style, ground plane independant, pre-tuned. After a couple of trips of frustration I found and followed this little patch of info.
Aerial is the same, mounted on bullbar still though I did remove the coax connector and re-attach it as per the second instructions.
Now the thing works 100 times better and it only cost me about 30 minutes of my time and 10cm of solder
UHF Reception checklist
1. Run separate power and earth leads direct to the unit from the battery to reduce voltage drop
2. Earth the radio case to the chassis or earth lead direct from battery
3. Directly Earth the aerial base, not just via the coax
4. Mount the aerial as high as possible
5. No sharp kinks in the coax
Terminating the Co-Axial cable and wiring
Tools Required
1. Soldering iron
2. Sharp knife
Steps
A. Carefully cut the black insulation away about 3 cm then cut the outer conductor leaving about 1cm
B. Fold back the outer conductor
C. Cut the inner insulation about 5 mm from the outer conductor
D. Slide some heat shrink and the outer piece of the connector or the entire area, then screw the fitting over the exposed outer conductor
E.
F. Solder the inner conductor to the end of the fitting
G. Slide up to other parts and screw it together then place the heat shrink over the end and heat it
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I install allot of RFI gear and i have never read anywhere not to cut the coax. RG58 coax has a very high loss, over 10M you loose 3Db which is close to half of your tx power (eg tx 5 watts and only 2.5-3watts at the antenna) so the shorter the better, but remember that is on 10M of coax and antennas only come with 5M so the loss is not as bad but is still noticeable, you will also get slight losses through the Connector(PL259's are rated the worst for loss).
There is no direct connection between SWR and coax length excepth the SWR will look better with longer coax because the reflected power is all relative to the power at the antenna so reduced power at the antenna means a better SWR or reflected power reading.
My suggestion is to make the coax as short as possible and get some one with a Thru-Line Meter or SWR meater to tune your antenna, i would never rely on Factory tuned or Pre-Tuned antennas to be correct unless it is a coliner type which have no way of tuning.
Cheers
Simon
There is no direct connection between SWR and coax length excepth the SWR will look better with longer coax because the reflected power is all relative to the power at the antenna so reduced power at the antenna means a better SWR or reflected power reading.
My suggestion is to make the coax as short as possible and get some one with a Thru-Line Meter or SWR meater to tune your antenna, i would never rely on Factory tuned or Pre-Tuned antennas to be correct unless it is a coliner type which have no way of tuning.
Cheers
Simon
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