VHF operation and the associated antennas, and especially propagation are what interests me.
I have written before in this blog about where I think I fit into the broad spread of amateurs. Here is some of it ...
It seems to me that the amateur radio world is divided into three camps. Category A has those who have a simple set-up, a wire antenna with a "VHF co-linear" vertical and who shun any further development or learning. At the other end of the scale, Category C pursue their hobby with deep pockets, obsession and determination to out-punch the ionosphere and out-buy anyone who dares to challenge them. And in between is Category B, who are the ones who want to learn and progress beyond the simple, but who stop short of relentless pursuit endless contacts.
I know that I am in Category B, but I only know of two other amateurs in the world who think the way I do. So there are only three of us. Only three of us who cannot stick the mundane boring nature of aimless CQs by the unknowing Category As. And the same three of us have no need of "premium brand" radios, huge linears and towers turned from the bottom which the Category C folks think are essential. We just want to learn from our hobby. All three of us.
That comes from here http://gm4fvm.blogspot.com/2017/06/out-of-rat-race-bikes-and-update.html
Maybe there are more than 3 of us now.
I say again, it is not that I am against the way others get their radio thrills, I just prefer to do it differently.
I am driven back to thinking about this by the discussion recently about planning permission. Do I want/ need a better/ bigger/ higher antenna?
Does anyone? (Erm, that is for them to decide Jim).
Take the past two days on 4m.
|70MHz stations worked at GM4FVM on 24 and 25 May 2019|
Was I happy? No. I couldn't work SV2DCD. I heard him, and checking with PSK reporter I could see that he heard me. We never heard each other's CQ, so no contact resulted.
WHY CAN I NOT WORK GREECE ON 4M WHEN I CAN ALMOST REACH IT?
|70MHz band as shown on PSK reporter on 25 May 2019|
If I hadn't compromised by pairing up the 4m and 6m antennas for some test, I could have done it. I could have been a contender.
Those last two paragraphs are nonsense. This had nothing to do with my antenna and everything to do with my over enthusiasm (Don't you mean everything to do with your ego, Jim?).
I have done the sums and I know that I have as good a station as I can have. Sure I keep swapping about the antennas, but then that is what keeps me interested.
Here are the conclusions I came to ages ago...
1) Output power
As readability increases as a logarithm of power and not proportionately, there comes a point where adding more power becomes financially pointless. So many radios come with 100Watts, the legal UK limit is 400W, and 200W is a handy stopping point. 100W is fine, 200W is moderately affordable and has twice the result, but 400W costs rather a lot to do. The first 100W added to the rig adds double the result, but to double it again needs another 200W, and that is too far for me. Anyway, on 70MHz the power limit is 160W.
If you end up with lots more power than the weak DX station you are trying to work you will fail anyway - you won't be able to hear them.
2) Antenna size
This is not quite so simple, but nevertheless doubling the length of the antenna might bring about 3dB gain. The complication is the number of elements, which alter things in a complex way. It does not help that some manufacturers quote silly gain figures. Changing from the 3m boom 70MHz beam to the 2m boom 50/70MHz dual band beams might have lost me about 1dB on 70MHz. I don't really believe that 1dB was stopping me working SV2DCD.
I have done the sums. A maximum 3m boom length is the best practical length for me - it fits my masts, it gives a good compromise of gain versus length and it does not look too dominating on the skyline. I could still do a lot with 2m booms if I had to, and the difference would not be that great. I will probably go back to a 3m boom on 70MHz because I have one stored away, but a bigger antenna than that is just not worth it.
3) Antenna Height
I have a copy of the RSGB VHF/UHF Handbook which has a height gain chart. It shows "typical mast heights" between 25 and 50 feet and suggests that doubling antenna height between these limits will mean about difference of about 6dB gain. That certainly has not been my experience, and to be fair the book does say that a lot of different factor are at play.
My Tennamast, with the maximum height of just short of 8m and with mast and rotator above that, provides a top height of about 10m, where the 2m antenna is usually placed. I can raise it from about 6.5m up to 10m. The main factor I have found is that when it is lowered it is below the roof ridge line to the South, but raising by a metre or so clears this. At 10m it is above next door's roof line to the East. In the other directions there is no roof to clear. So far, clearing the roof line has been the only thing to produce a significant effect. Generally speaking I want it as high as I can when working DX, but it doesn't make much difference how much higher once the obstructions have been cleared.
My MM0CUG mast raises to about 12m at the antenna but as it is above the roof line at all times I never found much need to raise it. I have tried, but despite the figures in the book it makes little difference.
So my simple rule of thumb here is that I need to clear the obstructions, after that more height matters but not much. Sure, if I could go to double next door's roof line - 20m - I might get another 6dB as the book promises, but I would need a new mast, which would need to be much heavier and free standing, new planning permission, more money ... and it isn't worth it to me.
So why am I finding that more power, bigger and higher antennas don't matter to me?
This seems to run counter to logic. Surely a better antenna is always a better antenna? Isn't more power always better - didn't I read an article suggesting that every UK amateur has a duty to run 400W so that they do not take that away from us?
Erm ... no Sir, not for me. Of course better is better by definition, but then what about the cost? Am I really losing much by having what I have? I cannot see that I am. I cannot say what I am missing because I cannot hear them, but when I look at what others do with their better (more expensive) set-ups I think I can do without it.
Maybe I am trying to justify my own choice of mediocre performance but frankly bigger linears, bigger antennas and higher masts make no sense to me. I think this is because of the propagation types I work.
You only need to take a look at the maps of 4m activity over the last two days which are posted above. I could probably have done all that on a dipole. Years ago I used a dipole before graduating to an HB9CV which could do almost everything I needed. Sporadic E is generally high signal strength, you don't need a beam or a high antenna.
You could make a case for most of the propagation methods I use - Tropo Ducting, Sporadic E (single hop anyway), Aurora, Meteor Scatter and EME - have been perfectly successful from here without exceeding my self-imposed power, boom and height limits. In fact you could make a case that in many situations smaller, lower antennas are more successful for these modes. Smaller antennas have wider beam width, and lower antennas bring ground gain and may connect into ducts which higher antennas or sites might not.
The only exception to this general rule for Es is "multi-hop Sporadic E" where 1dB might make the difference (to SV2DVD?). There is still plenty of fun to have without those extra dB though - I worked Canada on 50MHz with 50W SSB and an HB9CV boom length 0.8m at a height of 7 metres. Maybe I would not have worked Brazil with that, but when I did I was still using the 200W/3m boom rule with 7m height in that case.
And that just leaves plain and simple tropo. "Inter G" working. For that task a bigger, higher antenna fed with more power would help. Great ... spend lots more money and in some situation I might be able to work the next county. I might be competitive in a contest. Sorry, not interested, give me propagation science any day.
For the type of operation I do, I can see no point in going for the full power, max height big antenna set up. I know somebody with a high power super-station. On 144MHz he has a 4 yagi array with 7 elements each. I reckon he has 6dB more gain than I have, plus he lives on top of a hill. He is a nice guy and I admire what he does but that is not for me. He might be able to win contests and work more EME than me, but I reckon the price is too high. Not just the financial price, but also the planning issues, the neighbour relations and all the other aspects.
I am well aware that if it was not for super-stations with stacked arrays I might have very little DX to work. Their antennas do all the work for me. Yet I also do something for them. I am here to work them too. If it wasn't for my middle-ranking station they might have nobody to work. If we all waited until we could afford to set up a super-station there wouldn't be much activity.
So where does this leave me with SV2DCD?
I have already worked him on 4m. We had a contact on 18 June 2016 and exchanged QSL cards.
I think for a moment I got caught up in the frustration of it all. Who to blame? Must be the antenna, linear or mast. In reality, the propagation was probably against us. I have already worked out that bigger antennas are not for me.
Earlier that day I worked E76C for a new country on 70MHz (we worked last year on 50MHz). So that was country number 41 on 4m. That means more than anything else that day, and I did it with my modest set-up.
There are still lots of things to do. I could probably do most of them with my old HB9CVs. Wimo sell a dual 4m/6m band Moxon, there are multi-band log periodics, 2m/70cms yagis, verticals and all sorts of other good small antennas. I believe that nobody should be put off by pictures in books and catalogues of vast towers and antennas which few UK councils would tolerate under the planning rules. I would suggest instead get something simple up to start with. Even a 1/4 wave vertical has infinitely more gain than if having no antenna at all is keeping you QRT.
Over 40+ years I have built up a few better-than-simple antennas and bits of gear. That should be fine for me. The cold-headed me is happy with it, but the hot-headed me gets frustrated and wants to fall for the myth peddled by the VHF books - that huge towers and antennas are necessary.
I am not in this hobby to bulldoze my way through. My joyous radio memories stem from surprising contacts made with less power and with smaller antennas than you might expect. I might lose sight of that and need to prove it all to myself over again (see above), but I count myself lucky to do as well as I do.
Now, if I change the dual band 4m/6m yagi for a 4m stored one in the garage, and divide the 2m/70cm dual beam into two antennas, then ....
Rest assured, I will jiggle it all, about but "200W max/3m boom max/10m height max" is still the rule.
2 minutes after I posted that ---
First SV on 4m this year, plus a new square ... and without changing anything.
Patience dear boy.