UHF and SWR

Hi Philip,

As far as I have seen all UHF antennas come pre tuned, you really only needed an SWR meter for the am 27 Mhz radios.

If its a ground plane antenna you can move it to any location you like,

But I could be wrong :-)

No need to SWR in the UHF antennas unless you area purist they are ready to go as supplied.

Hi Phillip,

If the ariel is one where you have to put the connector on yourself then check the connector with an ohm meter to make sure it is not shorted (non dc grounded ariel) between the centre pin and outer connector. We see around 50% of all customer fitted connectors short or open in some way.

Also we have received 2 x 477MHz pre-tuned ariels from a reputable company in the past month that were out of tune and showing a VSWR of 2.6:1 (elevated feed so easily checked by swapping whips)

A VSWR test will show up not just an out of tune antenna but stretched/damaged cable and incorrectly installed connectors. We do a VSWR test as a free service on customer installed equipment so once you installed it, take it into where you bought the gear (if local) and ask if they would mind checking. It really is peace of mind.

I have seen some horrors.

Regards
David

SWR (Standing Wave Ratio or the suitability of the antenna to match to the radio) is a pretty complex area. Whilst any commercial UHF CB antenna will be tuned for minimum SWR at 477MHz (I think that's UHF CB frequency) that is only a theoretical tuning because the designers cannot control the installation conditions and as every installation is different you will, almost certainly, not have an SWR of 1:1 or thereabouts. How far away the match is from ideal is impossible to say without checking with an SWR meter. I suggest you do the installation and make a few on-air checks to see if all is working OK then find a professional installer to do an SWR test for you - he'll probably charge about $20?

Mike Harding