UHF Base Aerial for house

Hi Ingo

I don't recall where we got our base antenna, but it is a lot longer (at least twice) than a car antenna. It is attached onto the top of the television antenna.

On another property we had in a flatter region, being able to talk to people and businesses in excess of 50 kms direct line was common.

What channel will you need for the fire station? Our experience in trying to find information during fires is that the emergency services operate on channels outside of the 40 on our UHF sets.


Motherhen

When we set up our base station a few years back this is what we were advised.6db gain for short distance comm, 10db for longer distance hilly terrain(all purpose) and 12db for long distance flat terrain comm.The 6db is about 6ft, 9db 9ft and 12db 12ft.Try and use as shorter length of coaxil as possible and put a loop in the top of the cable to allow for movement in the wind.
We use a 9db and get good coverage in hilly terrain.
Ours is also a GME branded one and the base of the aeriel grounds onto the mast where it clamps on.Oh, and use plenty of silicone around where the cable joins onto the aerial as water is its worst enemy.

Go for the base station type antenna.....6 dbi gain suits most terrain unless extremely flat for many many kilometers then go a 9 or even 12 dbi gain......all these don't require a ground plain (ground plain independant). Try to keep coax length less than 10 mtrs if possible, use RG-213 coax as a minimum and go to a specialist communications supplier, have them crimp or solder (there call) the 2 plugs on for you....... The radio end plug is reasonable straight forward, however the Antenna end plug "N" type is the reason most "Home Handyman" installs fail or are lacking......don't forget to use "zippy" ties around mast to prevent weight of coax pulling out of bottom of antenna......($250) approx. A cheaper( but not better) alternative is to use a 6bd "Megablaster" 4ft mobile antenna which dosn't need a ground plane mounts to a standard 5/16 Tpi base, lead and plug (4mtrs coax) $ 100 approx

Cheers

Ingo,

I'd go for a 9 or 12 dB aerial, with the best co-ax you can afford.

However the quality co-ax can cost more than the aerial! Heliax or LDF-4 co-ax can cost around $500 for 20 metres, but it's worth an extra 10-30 kms extra range, both in Tx & Rx. RG-213 is a cheaper alternative.

If you're only communicating 10-15 km to fire station, then you could get away with a 6 or 9 dB aerial, and mount it as high as possible. Height is might, with UHF.

Bob

Thanks to all your replies

much appreciated

The important bit is to use a thick cable of high quality. The 1/4" cable like RG58 will have too much loss at the lengths you require. Use 1/2" (or bigger if you can afford it) cable RG213 as a minimum. Talk to one of your two way radio installers rather than a CB only types - they will be able to supply better cable and terminate the correct plugs for you.

PeterD

Some good advice above Ingo - I'll just add that the aerial is a very important factor and good cable and installation is so important.

As you go up in antenna gain , particularly above 9dbi then the antenna has to kept quite vertical and the product needs to be able to resist bending by the wind otherwise the signal won't be sent in a horizontal plane.