Half Square - feeding half way along horizontal section to achieve 180 degree phasing

[M3KXZ]

I wonder if anyone has tried this? I like the simplicity of the half square and will be using an inverted one on my next trip to the beach. But I like the idea of the elements being fed 180 degrees out of phase so that the distance between elements can be smaller while giving a narrower endfire pattern as opposed to a broadfire pattern (which becomes almost omnidirectional at closer spacing). Also, my preference for 180 degree phasing and an endfire pattern is that the pattern remains largely unchanged as frequency increases, thus making the antenna usable over a wider range of frequency.

If I feed the inverted half square at a point halfway between the two vertical elements then they are fed exactly 180 degrees out of phase, giving me what I want irrespective of frequency.

My question is this....I end up with Impedance = 1319 - J 2514 ohms (for my particular size antenna) at the halfway feedpoint - am I likely to be able to match this using a 4:1 balun (W1CG design Guanella balun) and an Elecraft T1 tuner (this combo has no trouble matching a 44ft inverted V doublet on 80 thru 6), or alternatively with an SGC237 ?

If anyone has any experience with doing this, I'd love to hear from you.

The reason for inverting the halfsquare? To give better low angle RF over salt water, and to make access to the horizontal section easier.

Thanks.

Pete

[M3KXZ]

No takers then? Well, I'm giving this a go today - 2 x 7m tall vertical sections joined by 7m long horizontal bottom section. Reason for running the vertical sections longer than 1/4 on 20, with total separation less than 1/2 wave is that it positions the high current part some way up the vertical section instead of being at the lower corner. This should reduce ground losses - although I'll be at the beach so not too worried. My only concern is whether it'll match with a 4:1 balun and Elecraft T1 atu at the feedpoint half way along the bottom section.

Don't even know if 20 will be open, but I@ll give it a go and report back.

Apologies for any spelling errors - I'm typing without my contact lenses in!

Pete

[M3KXZ]

Well, I had a bit of a problem matching - Wouldn't go below 3:1 with the balun and tuner. But it was still pulling signals in strong in the E-W direction and seemed to be nulling well N-S, confirmed by moving the antenna so it was facing N-S and then E-W signals disappeared. Anyway, as the SWR was still high I took half of it down and just used a 7.2m vertical with one 3.6m elevated counterpoise on on a fishing pole for the next couple of hours on the beach. Then it dawned on me why the Elecraft T1 atu was having trouble matching - I only had the FT817 on very low power (long time since I used it and I couldn't remember what the widgets meant) and it wasn't enough for the atu to find a match properly. Soon as I turned power up one notch to 1W then matching was much quicker. I'll give it a go again next time.

I didn't waste my time on the beach though - I had some great QSOs with the simple vertical and short cpoise with the LA0 expedition, a ham in southern Portugal and also a member of the XG Net in Florida. Very strong sigs coming in today on 20.