Use of Ground Tuning Units and 1/4w verticals

I have been interested in Ground Tuning Units since working G4AKC/PM groundwave from a SOTA summit, the Old Man of Coniston - he was operating trolley based pedestrian mobile utilising salt water groundplane to maximum effect - I broke in after a conversation with an Australian, and this was May this year. He must be getting out well with 1.2 million hits on QRZ.

Has anyone experimented with Ground Tuning Units during SOTA activations? My most recent web scan resulted in reading the following article which really does a very good job of explaining ground tuning units, how they are constructed, how they work - and in particular the difference in operation over salt water and on rocky summits.

Regards, Mark. M0NOM

That’s an interesting article Mark. For me the comment about the performance of the unit away from the sea is the key - The performance enhancement of the salt water diminishes rapidly as we move out or away from the “fresnel zone”

Personally I would rather carry 4 pieces of wire to give me 4 elevated radials rather than a GTU which would weigh more and require adjustment on site. To date I have used my vertical over a variety of ground types including made up ground (Hensbarrow Downs) without the need to spend time adjusting the antenna. However I like the idea for beach sites as it removes potential trip hazards and may well consider one for my /A site up in Northumberland which has miles of unspoilt and largely unoccupied beach close by.

Thanks for bringing this to our attention.

73, Gerald G4OIG

Regarding my experience, Gerald said it all!

Vy 73 de Pedro, CT1DBS

There is a misunderstanding of how the GTU actually works… The principle is that it “couples” the return common line to the surrounding ground… Unlike radials that provide the earth return current within the radial wires the GTU creates a low impedance connection to true ground and therefore is very dependent upon the performance of the ground that sits below the vertical antenna… So yes it does perform better close to sea water as that is an ideal ground plane but it is also a very efficient method of ground coupling over inferior ground as well and if the station is moving, for example… bicycle or pedestrian mobile it then eliminates the need for trailing wires and produces a far more stable and efficient true ground to work against… Hope that helps… Dave G4AKC

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