Saturday, 19 June 2021

Mostly about antennas and masts

I have had to go away for a few days. The long waffle I was writing about conditions now seems old hat. So I will cut almost all that wonderful creative writing, and just summarise it. Most of the rest is about antennas and masts. Antennas like these ones:-

Old 23cms Wimo on the left, new Dual 36el on the right.

First the round up:-

6m... I managed to work trans-Atlantic on 6m barefoot. This surprised me but a linear was not required to work a handful of stations and indeed add a new square.

4m... I managed to work a new country to bring the total to 49. The latest one was Gibraltar. Given that Gibraltar was the pinnacle of 4m DX when I started on the band it is odd that it has taken me since 1977 to work it. Still, it is in the book at last. And an elusive square in the Balearic Islands - JM29 -  was worked today.

2m... I managed to work a new country (OE) during one of several Sporadic E openings. Not sure how OE had evaded me for so long. Once again the basis of "doing the treble" works even if I feel less moved to actually work stations on all bands. I just need to see what is coming in on 6m, wait on 4m for signal to peak about about +05dB, then go for 2m. It does not work on 6m alone, I have to move up to 4m and listen there. Today I have worked EA and DL on 2m that way, and just missed 9A.

70cms... Old news, I worked a new country in the shape of Spain. That was back in March but I have only got round to mentioning it. There were several good tropo openings in late April with some new squares on offer.

23cms... Those tropo openings allowed me to have a couple more long rag chews with OZ2ND. I continue to be astounded by what I can work on 23cms.

Secondly - moving on to antennas and masts:-

This complicated re-organisation, whereby everything ended up back more or less where it was ages ago, started with moving the 2m/70cms dual band vertical.

2m/70cm vertical at GM4FVM, back where it used to be years ago

There was nothing particularly startling about this as that mounting was the first one I used when I moved here in 2009. It was there for years. However, by putting the vertical back up in that place I was able to free up the location it used to use and that allowed me to reuse the coax route to that one for the further developments which I then made later.

This was the first use I have made of Hyperflex 7 coax. I wanted to try it for a lower specification run like this, hoping that if it worked I could use it later for other things. It certainly does work, and the M&P plugs specifically made for it are very good.

The vertical is working very well in its new/old location.

I have mentioned before that I have had problem with mains breakthrough on 70cms. This has rendered my almost new nice high powered Tajfun 1000 linear pretty well redundant. I can use 100W safely with no problems. While moon bounce on 70cms is probably terminally affected, I am doing more work on 23cms instead.

To reduce problems with the 70cms breakthrough I moved its antenna to the mast furthest away from my neighbour's house. To allow for that move I took my 4m and 6m antennas down from that CUG mast. It seemed to me that I could not get both the combined 4m/6m antenna and the 2m/70cms antennas on the one mast. I was wrong about that and I had to reverse the initial thinking and get all four bands onto the one mast.

The problem was that I would need to get four runs of coax to that mast. Previously there were only two. After making a few compromises it worked because of this:-

1) by using Hyperflex 7 (H7) for the 4m antenna it would all fit through my conduits and it is much cheaper that Hyperflex 10 (H10),

2) by moving a run of H10 from the Tennamast and putting in an N-type joint I could save the cost of another run - and an N-type joint is acceptable to me on a lower frequency so that is for 50MHz

3) by using tails of H7 instead of H10 from the 2m and 70cm preamps I can squeeze in enough space to fit both antennas onto the existing stub mast (making the stub mast longer would cause neighbour problems). H7 has a much tighter minimum radius and this made the whole thing possible.

Trying the H7 on the vertical proved I could use it on 4m, and it is a lot cheaper. It is much easier to fit through the conduits in and out of the house. This may open the door to squeezing more runs through in future, though I expect 70MHz is my H7 limit for dx-type antennas. It is fine for the vertical too.

The result looks better to me than what I had before. Previously, as I was using coax with a longer minimum radius I felt that I had to take the coax down vertically from the antenna. This is because the Dual antennas have N-type sockets mounted below the boom, and it was really difficult to bend the coax back towards the boom. Such a problem does not arise with the thinner coax, so I could loop the coax round and run the leads along the boom rather as you might in a conventional single band antenna. Looking at the Dual website revealed that others have done the same.

Dual 2m/70cms yagi about the Dual 4m/6m yagi, with the CUG mast lowered

This gives me 4 elements on 6m, 5 on 4m, 7 on 2m and 12 on 70cm. Boom length is around 3m in total but used length is slightly shorter on 4m and 70cms.

Moving the vertical freed up the Ecoflex coax which fed that antenna in its previous location. The Ecoflex is now eight years old, and it is stiff and rigid. Ecoflex has been a disappointment to me, as it is inclined to form kinks and get stuck in places. When it came on the market it was the best coax I could use. Now I would not use it again.

Then it was time to put up my 36 element Dual yagi for 23cms. This goes up on the Tennamast and is double the length of the previous Wimo. The plan was to get a 10m dipole up there too but a snag developed and I have since taken it down again. For now 23cms is the only band on that mast.

36 element Dual 23cms yagi on the lowered Tennamast

I have to accept that this is the best combination of antenna locations that I can do at the moment. Given that I work five bands, having four on one mast and one on the other is not ideal. I have to point all four of the lower band yagis in the same direction, which rarely happened when I could do it differently. The two double band yagis are mounted on the weaker of the two masts, and they are all turned by the weaker of the two rotators. At least 23 cms has the more accurate rotator, which is useful for such a long antenna.  

I am working on all five bands again. I have antennas that many amateurs would think are pretty good. So I should be happy. 

I have been wondering whether a dish would be better for 23 cms but where would I mount it? I did see this idea while I was away recently.

Tree mounted dish seen at Grantown on Spey

All I would need to do would be to chop the top off one of Mrs FVM's trees.

I read that Blogger is going to stop email notifications for new blog postings from next month. That would be a problem for me. We need to see how that pans out.




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