Thursday, 12 March 2015

All change on the VHF antenna front ...

This is my new 6 element Yagi. Below it is my 10 element 2 metre beam, which now looks very small by comparison.



A few words of explanation. (few words? me? you are kidding!) On my Tenna mast I used to have a Vine 4/6m beam. That was 4 elements on 4metres, and 3 elements on 6meters. That was actually pretty good and it worked well because I have a restriction on the size of antenna I can have. It needs to be either maximum of 2 metres balanced across the mast, or shifted so that less than 1 metre extends on one side of the mast. So the Vine, which has a 2 metre long boom, was just fine. I could then lower it with the boom parallel to the ground. The 10ele worked too, as it is supported off centre and the short end is also less than 1 metre off to one side of the boom, so I could lower the mast IF the antennas were pointed just North of West.

I used to get annoyed about this as if I moved the mast I could use longer antennas, but is that really what I wanted to do? I really wanted a Tonna 9 element 2metre antenna, but with a boom just over 3metres it would not fit. However, I knew that I could do better than the 10 element, and in the end I bought a 6 element 2metre quad. That is a fine antenna, but I still felt restricted by the 2metre boom limit.

One day it finally dawned on me. The Vine was 2 metres by 3 metres (2m boom and 3m widest element.). But instead of 2x3 I could fit in 3x2. In other words, if I just had a 4metre beam instead of a 4/6metre dual band, it would only be 2m wide and could be 3m long in the boom (in fact any length of boom really). And a Tonna would then fit that way round!

This caused more head scratching. As the 4m beam I settled on, the Sandpiper one, has boom supports then the only thing I could fit under it was one other antenna. This would have to be the 2m one as the boom has to be pointing downwards when I lower it and thus a 6m would not fit (3m widest elements too long to fit). So for now I do not have a 6m antenna up. And the 2m quad no longer fits either.

Later I may put up a 6m vertical (I also have a 6m half wave vertical from Sandpiper).

So there you go. Lots of complicated stuff, but basically multiband 4/6m beam down, 2m quad down, 6ele 4m yagi up, 10ele 2m yagi up. Do I prefer this? Oh yes! Do I miss 6m --- yes.

OK, so the present antenna round down is
those two VHF yagis,
a 10/12m vertical dipole,
a 2m/70cms vertical and
a 4m vertical.

So far so good but I need to put something up for 6m. I have a Diamond 2 element (a sort of HB9CV) in the garage. that might go up soon.

If you are wondering why the 10element 2m went back up instead of the much wished for Tonna. Well, while I dithered Tonna stopped making them. Bah! Still, they may become available later. Maybe. Otherwise something better than the Diamond 10 element is due eventually.

Anybody want a used 4m/6m dual band yagi or a used 6 element 2m quad????

Jim

No comments:

Post a Comment