Sunday, 26 May 2019

Biggest isn't necessarily best.

As usual, I have to say that just because I do not do some aspect of amateur radio, I am not suggesting that there is anything wrong with it. I do not do much with Summits on the Air, LF, home brew, contests, CW, Club Nets (any nets really), vintage equipment, direction finding contests, SHF ... probably means that I do not have the time. If you do them, well done. I admire the efforts of others in these fields, I am interested in hearing about them and reading articles, but I simply cannot spread myself thin enough to cover them all.

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
This, by any standard, is pretty good. By the standard of my performance on the 4 metre band of 5 or 10 years ago it is fantastic. I saw several familiar callsigns being worked so I know several readers of this blog were in on the action too.

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
I could see everybody doing remarkably well, but why couldn't I work SV2DCD? It must be that dual band antenna. I need a bigger/ higher antenna.

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.

73 

Jim
EDIT BELOW

2 minutes after I posted that ---

First SV on 4m this year, plus a new square ... and without changing anything.

Patience dear boy.
73 Jim

Monday, 20 May 2019

Feeling jaded, plus antenna planning permission in Portugal

"When a man is tired of radio, he is tired of life, for in radio there is all that life can afford."

A comment attributed to Dr Samuel Johnson (1707 to 1784). Well, he might have written it had radio been known in the Eighteenth Century.

I think he may have been thinking about radio when he referred to London. Most things I hear seem to relate to radio.

Oh dear, am I becoming radio-obsessed?

Surely not.

I have been feeling out of sorts. As I have said before on this blog, I have a love/hate relationship with radio. Sometimes I cannot get enough of it, and then minutes later I want to give it all up, go QRT and take up quilting instead. Making quilts seems like a more restful hobby.

Usually some challenge will make me perk up. I have several challenges underway right now, for example two projects to improve the performance of my 2m and 70cms stations. These are also part of the "simplification" strategy which seems to involve getting more gear, but anyway ....

For some reason all these plans have failed to lift my gloom. Perhaps a break away would help. Mrs FVM was also enduring a bout of indecision. Hers was in case we might go away and find that Brexit had been resolved while we were away and we found ourselves locked out of the country when we tried to return. However, as it became clear that waiting for Brexit to resolve might take longer than the Summer (not saying which year) she decided to take me to Portugal for a week, with some help from the fine people at Jet2.

All this lack of enthusiasm for radio brought about a ground breaking decision. For the first time in my life I would leave these islands for a holiday without a radio. OK, I know my phone is a radio, as is the wi-fi on my tablet computer, but you know what I mean. The faithful Roberts stayed stored away at FVM Towers. This was to be a radio-free holiday.

After a 03:00 start from a cheap hotel in the Northumberland tourist trap that is Ashington (rugby events in Newcastle having raised the airport  hotel rooms from £50 to £300 a night), we were pretty groggy by the time it came to navigating a hire car out of Faro Airport. Mrs FVM asked "Are you sure this is the right road?". "Yes", I replied "I recognise that mast", pointing to an amateur's Earth-Moon-Earth capable array which I had noted several times before.

So it was that type of "no radio" holiday: the sort that spots every antenna, hand portable or reference to radio.

As a holiday it worked well at every level, with 33C temperatures and clear skies for the whole time. Excellent food and even a little drink. Those plus points even got me onto a cliff top - well if you call a crumbling bank a cliff. It was nothing like the local cliffs at Burnmouth.
GM4FVM above Fal├ęsia Beach (that is what passes for relaxed looking).
The view might look OK from the top with Albufeira in the distance, but the cliff really was not much more than a mound. I dare say that they have dramatic cliffs in Portugal, but these were a pretty ordinary ones.

"Cliffs" on the Algarve near Villamoura
Quite a few domestic Portuguese TV antennas caught my eye. This one below did not a take a good photo, but you can see that it is quite a bit higher than the surrounding buildings (click image to enlarge if necessary).
TV reception antennas in Portugal
Clearly Portugal has a different approach to this than the UK. The system the UK adopted when we went progressively higher in frequency for TV broadcasts has been to install more and more subsidiary transmitters to fill in gaps in the coverage. While the US and other jurisdictions tended to adopt cable TV,  the UK preferred repeaters. The geographical facts of this country mean that fill-in stations are usually easy to site on hilltops. As a result, these days indoor antennas are pretty well standard in UK cities, and of course the increasing use of streaming TV services increases the trend towards the absence of antennas.

Also worth considering is that because the UK did not go for cable TV (who remembers Associated Rediffusion which started out in the 1920s as a cable radio network?) we did not have existing TV cables on which to build up a fibre internet network. Apart from what became the geographically limited Virgin Media network, we have had to rely on the copper twisted pair in the telephone system.

It wasn't always that outdoor antennas were unusual. I well remember the time when just about every house had a 50MHz beam on the chimney to receive 405-line VHF television signals. Even though Band 1 transmissions ended here 30 years ago, and they were largely ignored long before that, there are still a few of those old behemoths stuck on local chimneys.

One of my earliest childhood memories is the arrival of "UTV" in the late 1950s, which was the local Independent Television ("ITV") service. I was only a child at the time, but I remember the brand new TV which arrived to receive it, with the unusual device, a channel selector. Our previous set, which only had Band I, and thus only BBC reception, was transferred to my Grandmother's house and became here first TV. Later she was given a down converter which went into the antenna downlead and came with a switch to select Band 1 (BBC ~50MHz) or Band 3 (ITV ~ 174-230MHz). Needless to say receiving on two bands required multi-band antennas and the ironmongery on the rooftops got even heftier.

The earlier arrival of Band I TV saw the installation of many 50MHz yagis and crossed dipoles. These were particularly conspicuous where the signal came from a repeater station as these were (and still are) usually vertically polarised. By comparison my radio antennas are small beer, especially if they could be set alongside the TV masts and antennas of rural Ireland. There it was not uncommon to see 100 tall foot guyed masts topped with yagis, log periodics, dishes and all sorts of things, pointing to GI or GW in order to receive UK broadcasts. Where we lived in GI we had a local main transmitter, but we still had both Band I and Band III yagis on the chimney.

When we moved in 1962 we had to update the TV antennas on the chimney of our new house. My father was scathing about the radio antenna, which most houses had pre-War (our house was built in 1937). We found a neat Belling-Lee socket by the living room window frame, through which an "Inverted L" wire antenna rose to the chimney and across to a tall mast down the garden. My father took great glee in chopping down the mast with a hacksaw, now that modernity had arrived in the shape of our 405-line black and white TV. I later wished he had left it. The cable of the radio antenna, carefully fed through the window frame but now cut on either side of the frame, was still there 40 years later when the house was demolished.

The fact that houses had tall, long, wire receiving antennas and masts before TV arrived is often forgotten these days.

Later we got a multi-standard TV for the new 625 line BBC 2 standard, and I remember at some stage taking it apart to convert the 405 line BBC 1 and ITV reception to 625 line. This brought congratulations from my father who immediately noticed the improvement in sound quality (405 line TV had AM sound) and picture resolution. Some years later that TV did what so many of them did in those days - it caught fire helped by the hot valves, and set fire to the curtains behind it. Luckily we put the fire out.

Anyway, the point I am getting at is that here in the UK was have moved from a world where antennas were large, high and commonplace, to a place where such things are unusual. Nowadays our Town and Country Planners frown upon antennas (except domestic satellite dishes which are largely exempt from the Planning laws!).

In the UK planning is administered by local authorities (i.e. municipalities).There are 343 "Councils" in England, 44 in Wales, 32 in Scotland and 11 in Northern Ireland. Most of these have planning powers. If that wasn't enough, in general they consult lower tier institutions about planning issues, such as "Parish Councils" in England and "Community Councils" in Scotland ... and so forth.

It is hardly surprising given the complexity of the local government system that what constitutes a reasonable development, and what is a blot on the landscape, varies enormously. If you happen to live in a conservation area, like an ancient town centre, the planning authority is likely to regard whatever antenna you plan to put up as an insult to local aesthetics. Elsewhere, some councils would not regard some antennas as subject to planning at all. Many councils do not want to get involved with minor issues, preferring to get them resolved locally. At the other extreme some local councillors, eager to get re-elected, will take personal umbridge at any pimple on the roof line. I recall a case where a councillor assured the amateur that he would make it his personal goal in life to get the antennas removed, and so he did.

There is no common definition as to what is a "structure". Sure, everybody knows that a new house is a structure, but is a shed or a greenhouse? Is a pole for a clothes line different from a mast? Is an antenna a structure at all? Well, it depends on which council area you live in. It also depends a lot on whether your neighbours object to it. It is generally accepted that a wire antenna is not a structure for this purpose (there the agreement about antennas ends). Some councils are not concerned about modest antennas attached to houses, or those which are less that a certain height about the roof line. Very much "it depends".

Some councils are very keen to run a side-line in issuing "letters of comfort" to anyone who has something like an antenna which the council has decided (often because the antenna has been in place for four years or more) is not subject to the planning rules. They charge sums like £60 for these - I know I bought one at a previous house. What a nice earner for the council who did not even come to look at what it was they were granting me comfort for.

So there is no simple answer. I have heard of several UK amateurs who have had to process expensive and slow planning applications for 2m and 70cms antennas which are no more noticeable than a television antenna. On the other end of the scale, some have put up free-standing lattice towers with HF beams and had no trouble at all. The variation is caused by the fact that they live in different council areas or are covered by different planning authorities (and they have different neighbours).

The Radio Society of Great Britain runs a service to help amateurs deal with planning problems. I have not needed to use it (yet!) but it gets good reviews. National radio societies do have their uses, and this is a good one.

My Portuguese antenna-spotting trip is now over. I think it is clear that the planning rules in Portugal seem to allow these things, or that permission can be granted. Here, we used to have so many antennas that we stopped noticing them. Now we have so few that any amateur antenna at all seems to attract local objections.

If you look up "TV antenna" on Wikipedia you get an article and this photo of a multi-band set-up.
"Antenna" - by Yonatan Horan - Own work, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=1642466
Clearly in some places, maybe not just Portugal, multiband antennas are common place. However, in the UK they now seem to be frowned upon.

In the UK power and telephone cables are buried in all new urban construction, and this provision has applied for many decades now. It is now normal to see UK town skylines looking very uncluttered. Only old-established town centres have above ground cables (thankfully, given the radio noise they emit). People are beginning to view anything above ground as abnormal.

What the future holds, I dread to think.

I am back now, refreshed and still a bit fed up with radio. Perhaps some radio operation would help.

73

Jim

GM4FVM

Thursday, 9 May 2019

Icom IC-9700 PTT switching - something I do not understand.

I have, of course, been watching developments on the IC9700 front for some time. It looks like and interesting radio for those of us who work on both 144MHz and 430MHz, and adds 1296MHz for good measure.

Maybe I have got this wrong, but it appears to me that the 9700 cannot switch different linear amplifiers on its different bands.

This is not such a hard thing to do. My IC7100 can do it. You can switch the two pins on the 13-pin socket between either working HF and VHF separately, or 2m/70cms separately. This is something I do. The IC-7100 has a "standard" 13 pin Icom output socket. However, the IC9700 seems only to have the other "standard" 7-pin socket. This has many things which I don't need, like RTTY switching, but it only has one PTT output pin.

Here is how the IC-7100 does it (one output is called HSEND, and the other VSEND) ...
IC-7100 manual showing clearly how to set the two separate PTT outputs.
As usual, click the images to enlarge if necessary.

You select what you want in the settings ...
IC-7100 manual showing how to select the automatic PTT band switching.

I do not own an IC-9700 and I have to rely on the "basic" version of the manual published by Icom UK. This does not show almost all of section 2 which would reveal the details. However that manual does show an explanation of the pin outs for the accessory plug ...
IC-9700 "basic" manual showing just one PTT output.

Now, as I say, I don't have an IC-9700 so I cannot verify if they are indeed being supplied with the 7 pin socket. However, elsewhere in the manual there is an explanation of how to set the single PTT output to work on specific bands
IC-9700 "basic" manual showing how to set the single PTT output.
This is, of course, consistent with the wiring details shown in the other part of the basic manual. It appears from this that you can set the single PTT output to on or off on any specific band, any combination of bands, or none.

It seems strange to me that a rig with three RF outputs only has one output for switching linear amplifiers. With the IC-7100, for instance, I can set it up with my 2m amplifier on one RF socket, and my 4m amp on the other socket, and it decides which amp to key. The same goes for 2m and 6m, and I have had it set that way too. You could also do this in the IC-7100 for 2m and 70cms, using a diplexer, but I have never tried that. I would have thought that this would have been a pretty obvious arrangement for the 9700 too.

I do wonder why the 9700, a radio with three RF outputs on the back, has only one PTT output, whereas the IC-7100 has two RF outputs and has full flexibility as to which PTT works with which. Why does the 9700 have the 7 pin plug when even the IC-7300, which has only one RF plug on the back, has the 13 pin plug. The IC-9700 seems to have taken a step backwards here.

From what I can see, the IC-9100 also had the 13-pin socket and the two PTT output, so if I was was replacing an IC-9100 with a IC-9700 I would be pretty miffed about this. It was a development of the 7100 system, allowing some limited choice between some of the bands. Shown below, from the 9100 manual, is the paragraph I would have wanted to see in the 9700s manual ...
The IC-9100 manual showing how it should be done.

OK, I have not seen a UK version 9700, nor even a full manual. Hopefully some 9700 owner can come on and tell me that the rig did, eventually, sell with the 13 pin plug and even the basic connectivity of the 7100 or 9100. If so, I can happily delete this post.

Is this a deal breaker for me? Probably in the sense that an IC-9700 would be a very good single band rig for me, but I could not use its multi-band capability. Sure I could rig up a switch to turn the PTT between the amplifiers, but I would only need to make one mistake with that to blow up my mast head pre-amps. I did not go to all the trouble of sequencing them to risk sending RF up to them with no PTT active.

I do not rule out getting an IC--9700, but it would be limited by this issue. I cannot see myself going into the menu to change the PTT settings every time I change bands, and the consequences of forgetting or getting it wrong are too expensive to contemplate. And anyway, isn't this what a multi-band radio is supposed to avoid? If the feature was worth putting in the 7100 and 9100, why leave it out of the 9700?

I have thought up a circuit which would RF sense the outputs and turn the PTT in line with that. This would mean that only the first transmission would go without the matching PTT - thereafter it would stay switched until I changed band again. But how often would I need to do that before the pre-amps died?

If you do not use amplifers and pre-amps this does not matter to you. Until you come to sell it of course, when such things make or break second hand sales.

It seems to me that it would have been sensible for Icom to have carried over the socket, the circuity and the software from the IC-9100 to the IC-9700 so that the very many VHF-ers who have multiple linear amplifiers could use them. After all, Icom had already figured out how to do it more than five years ago on the IC-7100.

But then again, are the production models supplied as the manual I have seen suggests? I hope not.

73

Jim

GM4FVM (EDIT - not just linears, but SHF transverter control is affect by this issue too)