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23cm antenna?


#21

Thanks Andy - just found a short lump of 141 with an SMA on it.
Ready to head for the hills!
73
Tim
(Sorry for hi-jacking the thread)


#22

I assume that there is no hard fast rule on polarisation on 23cm, it depends on the chaser? Matt M0IAW


#23

Adjust antenna orientation for best signal received.


#24

Hi Matt

You’re spot on there.

Of the chasers I spoke about in a previous post

Black Country - all Vertical
Bolton - Bit of both
Cheltenham - Mostly Horizontal

Generally you will meet them on another band, and as Andy said, you can quickly adjust the antenna for best RX signal once you decide to QSY to 23cm. However, most folk on 23cm are SSB users, so the chances are they’re all going to be horizontal. That certainly is the theory that I use.

One of the most succesful activators for 23cm, bucked all the ideas above, she used the Alinco DJG7, a vertical omin direcetional colinear and had great success, her name and callsign is Karen 2E0XYL. So antenna theory is a hard one to guess!! Alot of her contacts were also on the stock rubber duck!

Says how little use the band gets when after 15 years of SOTA the highest score is 396! Maybe you can topple them all!

73

Matt G8XYJ


#25

The polarisation question interests me.

On 2m FM we have frequently compared the performance of horizontal and vertical polarisation. Horizontal always seems to be better, even with hand held radios and short antennas. That is, I do not recall any test where vertical was better.

It will be interesting to do the same comparisons on other bands. But going out on a limb (with the metaphors too), I will eat my hat (a very tasty one) if vertical ever wins.

Andrew vk1da/vk2uh


#26

That score table may not be reporting what you think. When I run a similar report, it includes all activations where there was at least one contact on the 1240 mhz band. But most of the contacts were on other bands.

Andrew vk1da/2uh


#27

Having done many V/U set ups in the bush in NSW around Sydney with our equivalent of RACES/RAYNET etc we have concluded that horizontal is best. The theory is that the signal doesn’t get attenuated as much by tree trunks which are predominately vertical. We have only anecdotal evidence for this, no empirical measurements available to support the conclusion we have reached. The gun chaser stations are almost always H in my part of the world on 23cm.

Compton


#28

“most of the contacts were on other bands.”

That is certainly true of 70cm contacts; M6BWA has spent some time trying to establish her true 70cm score. I am not sure whether she found a convenient method; she is not currently around to ask.

73,
Rod


#29

There was a study done some time back (late 70s or early 80s) to determine this which I think was done by amateurs. They used low band VHF (50/70/144) to see if there was anything between the polarisations. Evidence suggested horizontal was better. A good result as mounting large Yagis vertically is a challenge. However, it was low VHF and at 432 and higher, scattering and reflections become more prominent. The principle should still hold true that horizontal should be better until the received signal becomes so badly affected by scattered components that you can no longer find a polarisation maximum.

My contest group uses reflection on 13cms regularly to get a signal from Southern Scotland to the IOM. We cannot go over GD-001 Snaefell so we bounce around it using LD-030 Black Combe as a mirror. ISTR we need to play with the polarisation of our transmit feed horn because the signal arrives at the other station rotated to some degree after reflection. No direct signal with about 60W to a 2m dish but 58/59 when bounced off the mountain.

As long as one station can fanny about with the antenna, you can accommodate these effects.


#30

Download the complete activation log and load it into Excel or LibreOffice. Sort the activation QSOs by date then summit ref then band then strike out the non-70cms QSOs. You should be able to knock up a macro to this task quickly and can also find all occasions where there are 4 QSOs or more per date/summit ref combo.


#31

Thank you Andy.
73,
Rod


#32

Rod, Vicky, I was playing about and this is what I get using only the 70cms QSOs currently in Vicky’s log.


#33

Andy, many thanks for this; I will draw her attention to it when Vicki returns from her travels. Presumably this technique requires admin access to the database and is therefore not generally available.

I was going to follow up the suggested procedure from your previous post on the subject but you have beaten me to it. As she has quite a few activations to upload she must be getting quite close to the 70cm Goat. I will try to have a go before she does this so my figures and yours should be comparable.

There do not seem to be many of our activations when she has been unable to somehow squeeze out the 4th 70cm contact (apart from the earlier ones when she was doing 2m FM only and it was me doing 70cm with rather less success).

Thanks again.

73,
Rod


#34

Sadly it’s not a standard feature of the DB that you can all access. I was trying some ideas out and it’s not yet in a form that could be deployed so anyone could use it. I wanted to try a few things whilst I had the time. If you and Vicki pay attention to the logs you have to enter you can see how far off the all 70cms Goat level.

Now to answer all the emails I’ve put off for the last week.


#35

and just think of the load on the system if we all tried to use complex SQL filters.


#36

My vhf dx operations are always on horizontal polarisation. Nearly always this is using tropospheric paths.

Es may produce different results as it involves the ionosphere. There has been a rash of articles and comments about what happens to polarisation in a plasma subjected to a magnetic field (ie. when a signal hits the ionosphere) and basically if I understand it correctly, the outcoming signal is circularly polarised, or at least has horizontal and vertically polarised components, whatever polarisation was used at the transmitter. This is also subject to conditions, hence the HF receiving antenna article in QST (with dual dipoles at 90 degree phase shifted combinations) that allowed you to receive signals as either Right hand circular or Left. With big differences in received signals and in QSB levels compared with a single polarisation antenna such as a dipole. Presumably these circular polarisation effects also apply to Es.

But my original comments were about using hand held radios and simple verticals on them. We have established a very reliable record of using horizontally polarised hand held radios (and hence, antennas) to get a massive improvement in signal level over non-line-of-sight paths. And this applies to both the compact helicals often provided as standard antennas and also the telescopic quarter waves that I now use as the normal antenna on my IC-V85.

This observation may well be contradicted by experiences people have when contacting repeaters that are typically vertically polarised and more significantly, cannot be changed to horizontal polarisation for such tests. It would be interesting to see how much better coverage was achieved by a circularly polarised antenna on repeaters. Given that typical commercial practice for the FM stereo system is to use a kind of elliptical polarisation, (ie H and V, not necessarily 90 degrees phase shifted) to make signals more readily receivable on various antennas people have stuffed behind their FM tuner, or on their ghetto blaster, or on their car, maybe this is something our repeater builders should consider. But none would be reading this…

Hence my thought that horizontal should be at least tested by people using HTs on 23cm FM. FM is not naturally associated with vertical polarisation and experiments are needed, folks. One instance is just an anecdote as Dr Karl says. Repeatable results, recorded in your log.

73 Andrew VK1DA/VK2UH


#37

Your evidence backs up the article I read. (I wish I could find it, I’m sure the reference to it was in RadCom but the actual article may be from the ARRL ). As a matter of course when out SOTAing I always wave the handheld about to see which orientation gives the best result.

We have just had a major disaster chez FMF. I have Vermouth, I have Vodka. But I’m out of Olives :cry: How can you make a proper Vodka Martini without an Olive? It’s just not right without an Olive. The evening was nearly perfect, Martini, The Roy Haynes Quartet absolutly nailing “Fly Me To The Moon” and now this. Disaster!


#38

Have a whisky instead :smile:

Interesting thread.

The scrap bin at work is stuffed with those cables in the pictures. The stuff that gets thrown away would make some cry! Maybe I should take up microwave operating :slight_smile:


#39

Did that on my last 3 activations where I had 23cm with me, I now carry it all the time, 1W FM. It makes a difference. I will often pull my 2 m J Pole over a bit away from verticval and that also makes a difference.


#40

I may have also made another purchase for 23cm… http://www.sg-lab.com/TR1300/tr1300.html ideal for being driven via the 817! Matt