Having spent most of my career in the Radio Communications field, I have built up a certain amount of knowledge and experience (I was able to put C.Eng., M.I.E.E. and M.I.E.R.E. after my name, and at various times I ran my own company supplying Amateur radio equipment, was Technical Director for one of the leading PMR manufacturers and Manager of the UK Government’s Radio Technology Laboratory.)
Here are some thoughts about various technical subjects that I hope you will find of interest…..G5RV, 1/2 G5RV, SWR,
G5RV HF Antenna
I have been a fan of the G5RV antenna for ever. It is simple and cheap to make and works moderately well on most bands between 10m and 80m.
There is also a “half-size” version which works between 10m and 40m.
There is loads of information on the internet about the antenna but I have found some of the best are:
- A talk given to the Surrey Radio Contact Club by Mike Parkin, M0JMI – the slide pack can be downloaded from Overview of the G5RV Antenna
- A series of videos by Peter Waters, G3OJV – the first is at Introduction to the G5RV antenna
with a short update at Part 3A
- And the second is at Antennas for the smaller garden
The G5RV is my “go to” antenna for Special Event and Portable stations if there is room for the 102ft horizontal section. It doesn’t need radials, you just put it up and it works (mostly). I say “mostly” because on one occasion, the antenna just didn’t seem to be loading up properly. We cut off the “balun”, through it away and replaced it with a “proper” high-power 4:1 balun; after that there was no trouble at all and the antenna was used for many different events.
[back to top]
1/2 size G5RV Antenna
The G5RV also has a “little brother” which is half the size (51ft horizontal section.). This works on the bands between 10m and 40m.
I use one at home but when I put it up last time, I carried out some SWR measurements which suggested it was most resonant at the lower and of the bands. As my main interest is Data and SSB (never had a CW QSO in my life), I decided to shorten it; I bent back on itself the end 6ins on both halves of the horizontal sections and now have a much more “centred” antenna.
Again, no radials required and it works on 6m!!
[back to top]
A lot is written about how important your antenna SWR is.
But, is it???
Yes, it is helpful to check a tuned antenna is, in fact, tuned to the correct part of the band (for example), but I suggest it is not worth loosing any sleep over trying to get the SWR down to 1;1 when you have it at 2:1.
After all, the easiest way to reduce your SWR is add some lossy coax – yes, that’s right, adding a lossy feeder will reduce your measured SWR!!!
On HF, you are probably using an ATU which ought to be able to tune out the reactance so the TX output “sees” a good match.
On VHF & UHF anything less than 3:1 and your transmitter can probably cope with anyway!
[back to top]