UHF question

[outback]

I have just got a Uniden 7760NB UHF radio and a Uniden AT-870 aerial.

The aerial comes with 5m of cable and a small connector that screws into a normal PL259 connector in the back of the radio.
I don’t need 5m of cable so is it ok to cut the cable and at what increments should this be done?
Also does the UHF aerial need to be trimmed/tested for max output?

Back in the old 27Mhz CB radios cable length was not something you just cut as fits it had to be a fixed relationship.
Again to maximize the 27Mhz output you SWRed the aerial in either by trimming or using an SWR unit.

Do these UHF aerial need SWRing to get max output?


Still have an old 27Mhz set but seems none is using them. Pity SSB was fantastic.

[Hodge]

G'day mate. Can't comment or help with cutting the cable at certain increments, but I do know that you should never have the cable coiled up, like for example if you have excess length.

[NissanGQ4.2]

Hi mate, this site should cover your questions: http://www.mobileone.com.au/antennas/cb477info.html

[Drewboyaus]

Hi mate, this site should cover your questions: http://www.mobileone.com.au/antennas/cb477info.html

I argue that first tip is rubbish. A high gain antenna is not always your friend. In mountainous terrain a lower gain antenna is best or you will not get reception from the bloke on the other side of the hill.
High gain is fine in flat terrain but rubbish in the hills

[outback]

Hi mate, this site should cover your questions: http://www.mobileone.com.au/antennas/cb477info.html
Thanks for that link solved a few questions.


I argue that first tip is rubbish. A high gain antenna is not always your friend. In mountainous terrain a lower gain antenna is best or you will not get reception from the bloke on the other side of the hill.
High gain is fine in flat terrain but rubbish in the hills

Yes I remember about the different effect hii vs low and terrain.
This radio came with the hi gain 6 Db aerial. I am getting a low one later.

[Drewboyaus]

Thanks for that link solved a few questions.



Yes I remember about the different effect hii vs low and terrain.
This radio came with the hi gain 6 Db aerial. I am getting a low one later.

I have a 6db on mine and I drive the high country all the time. Works fine.

[outback]

The UHF is more of a convince than a need. It all good on the main roads for me but outside that is an extra.
Since I tend to run solo I am looking more at a sat phone and/or HF.

At present just doing step 1 in the comms area.

[GQ TANK]

1. Shorten the cable to the length you need, add a little bit in case you need to replace the connectors.

2. Pre-made UHF cb cables are usually ok. But we always check the VSWR and trim the antenna if needed.

3. The VSWR check will also indicate if you have a faulty connector (I have had factory assembled cables fail)

4. The other aspect of antenna gain is the height of the antenna (higher the gain - bigger the antenna), and the greater the chance of hitting a tree with the antenna. I personably use a RFI 3 dB GPI antenna that is appox 30cm