Other SOTA sites: SOTAwatch | SOTA Home | Database | Video | Photos | Shop | Mapping | FAQs | Facebook | Contact SOTA

Activation Report GWB-003 The Stiperstones 16.02.1

Thought I would get up early and make a start. Quite warm when I left a dark Stoke on Trent at 06.30 today, flask full and batteries charged.
Never been to The Stiperstones before and suprised how far it is from Shrewsbury. The closer I got, the nicer the villages sounded (Snailbeach, The Bog)and the icier the roads became.
As the sun started to rise, I left the warmth of my van and started an idyllic walk on my own. A light covering of untouched snow allowed me to follow a fox track most of the way, and the light was magical…Should have taken my camera, but perhaps I had enough to carry.
Started earlier than planned on 144Mhz ssb. My thanks to Roger, G0TRB and Brian G8ADD for coming back to my original call.
Swopped to FM and managed to contact Peter, G8CQH. One more to go…and then Matt, 2E0XTL/A made my day with a nice QSO from Wooferton Transmitting Station, near Ludlow.
Thanks to all stations. Appologies to those who tried calling me, but I could not hear.
Then started to play around on HF with my Mirical Whip. It turns out that it is not such a mirical after all…it is going back in the loft.
Many thanks to everybody,
73’s
John
G1STQ

In reply to G1STQ:

It turns out that it is not such a mirical

There’s a man in the Lake District who thinks they’re not that bad. But he’s wrong! :wink:

The thing to remember about all super compact HF antennas is the following: if super compact HF antennas were really any good then commercial broadcasters would use them rather than constructing enormous arrays of antennas out of gazillions of miles of wire.

Put it where it belongs John, on eBay!

Andy
MM0FMF

In reply to MM0FMF:

Put it where it belongs John, on eBay!

Exactly! It’s a re-incarnation of the “Joystick”, and just as useless.

73,
Walt (G3NYY)

In reply to G3NYY:
What easy and simple hf antenna would people suggest,
It must be quick to set up and as I do this on my own (no friends) it must be small and light enough for me to carry along with the rest of my kit.
Not asking for much am I?
With only 5 watts out, I need to make the most of what I’ve got.
Any ideas,

In reply to G1STQ:

Er… dipole?

Andy
MM0FMF

In reply to G1STQ:

Most people will suggest a dipole which will have removeable links for the different bands that you want. This is optimum for efficiency but is a nuisance if you change bands a lot.

When I was using an FT817 I used a doublet with it, and tuned it with a dinky little homebrew Z-match with the coils wound on a toroid and the tuners a couple of polyvaricons, very small and light. This meant that I could work on any band 80 to 10 metres without leaving the operating position. Some say that you lose some of your output in the tuner but in my experience the losses were negligable: using the same rig and tuner with a 102-foot doublet at home I got close to my DXCC and worked five continents so it can’t be too bad! It is, however, more gear to carry and set up.

I would listen to what people say and then experiment to find what suits you.

73

Brian G8ADD

In reply to G1STQ:
Resonant dipole configured as a inverted V supported by a single fibre glass roach pole/SOTA pole. These pack away to a small package and are light to carry, can also make them self guy by adding a third leg of guy line. Sean M0GIA

In reply to M0GIA:

In reply to G1STQ:
Resonant dipole configured as a inverted V supported by a single fibre
glass roach pole/SOTA pole. These pack away to a small package and are
light to carry, can also make them self guy by adding a third leg of
guy line. Sean M0GIA

I’ve wondered about that, Sean, since I saw the video of it being set up in a very short time. Does it make the antenna directional at all, after the manner of a V-beam? A few dB of gain would make it worthwhile setting it up to favour Europe.

73

Brian G8ADD

In reply to G8ADD:
Brian if you read this article

http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/IVee80.htm

It says: The inverted vee has the additional characteristic that it is far more omni-directional than the dipole.

I take it that is over a horizontal dipole, V beams use longer legs (3/4 wave) and this would change the patterns of the radiating RF. I dont think there is much if any direction favoured from a inverted V. Any experts know? Sean M0GIA

In reply to G1STQ and G8ADD and M0GIA:

My tuppence worth:

Inverted V supported at the top of a collapsible (mine has very rarely) pole, definitely. Use string (pegged in the ground) or other non-conducting stuff off the ends of the dipole to get them off the ground since they’re high voltage bits. I often take a couple of lightweight garden canes (the green things) to poke in the ground and wrap the string round near the dipole ends, that way I need shorter strings. The idea of a third line is a good one, though I’ve not used it, if there’s a bit of a breeze I set the dipole up with the arms at a shallow angle to hold the pole straight against the wind.

Directional? Yes, it’s a dipole so there are nulls off the ends (probably not as deep as a straight dipole), otherwise it’s pretty broad. You want to keep the nulls NOT pointing at Europe if you want to favour that direction, so set up with the dipole roughly aligned between north-to-south and north-east-to-south-west. The dipole is very close to ground in terms of wavelengths anyway, so a lot of radiation gets squirted up into the sky, but that’s what you want for NVIS. I guess if you’re on a very rocky (low conductivity) pointy summit then it would be more like an isolated dipole. However the exact configuration won’t matter too much since local ground conditions will always be different.

For higher frequencies (20m? - this is a VHF and up bloke talking!) maybe a vertical would be better - I’ve rarely used my HF verticals on SOTA, since I have them with three radials and they’re more effort than a dipole (and my view is that they need the radials). They also really need a longer pole than a SOTA pole. As the sunspots increase it’s going to be fun to see what these higher HF bands are like.

For all of these, I use resonant aerials so I don’t need to bother with an ATU. I’ve never got round to building one and it would be more weight. I also haven’t got round to making a dipole with add-on sections for the different bands (links) - I have one for each band and usually just take a couple if I’m doing HF. Yes, the linked dipole would be lighter.

I have used a choke balun (half a dozen turns of coax about 20cm diameter) at the top of the feeder; it helps to stop the feeder radiating and spoiling the dipole radiation pattern. However for SOTA conditions I’m not sure if it makes a lot of difference and I’ve certainly worked HF fine without one.

No, the dipole length is not changed for an inverted V. It’s not very much of a V anyway for 80m / 40m and even 20m, given the length of a SOTA pole. At least, mine aren’t any different from a straight dipole and they work just fine. The resonant length is a little bit shorter than the half wavelength in free space (all the usual references for the exact values).

73
John GM8OTI

In reply to M0GIA:

I’m not sure my point got across, Sean. Using an inverted V as two arms of a tripod puts the vertex well to one side of the ends so that in plan it looks vaguely like a V beam. It is known that putting the arms of a dipole at an angle in the horizontal plane will have a small effect on the polar pattern but I don’t know if this effect will still apply in the case where the angled dipole is also an inverted V. It probably isn’t too significant but the thought intrigues me!

73

Brian G8ADD

In reply to G8ADD:
Been looking at making myself a simple inverted V dipole, attached via a tie wrap or similar - to a SOTA pole. I appreciate that if I trim it to resonant frequency, I can leave the ATU and SWR bridge at home.
However, is it sufficient to simply feed the dipole in a light coax, eg RG174 and have a few turns at the top to act as a balum? Or would you suggest a current balum be used.
I am trying to avoid the use of balanced feed line if possible. Simple is good - as if it takes hours, it will end up in the loft, next to my not-so miricle whip :slight_smile:
Or am I being a bit thick?
John

In reply to G1STQ:

I would suggest that no balun of any sort be used, in order to reduce the windage. The worst that will happen is that you get some radiation off the feeder, which might even be useful! As for the attachment, I carry a roll of duct tape with me, I tape the wire to the top of the mast and tape the mast to any handy post or projecting rock - on Watchcroft DC-007 I even taped the pole to an ancient standing stone…perhaps the ley lines helped with the output! :slight_smile:

Did you use a counterpoise with the Miracle Whip?

73

Brian G8ADD

In reply to G8ADD:
Thanks for the quick reply Brian.
The more I think about operating portable, the more questions I have. Takes me back 20 years and has definately increased my enjoyment of our hobby.

Do you simply use coax then, not bothering with a balanced feeder?

No counterpoise used with the unmiracle whip…perhaps I should have done! Silly really, as I had 20ft of cable with me - doh!

In reply to G8ADD:

tape the mast to any handy post or projecting rock

Hah! You should try some of the boggy flat summits in south west Scotland - not a fencepost or rock to be seen for miles :wink:

73
John GM8OTI

In reply to G8ADD:

I even taped the pole to an ancient standing
stone…perhaps the ley lines helped with the output! :slight_smile:

Brian

Taping things to ancient monuments is almost certainly illegal - and not very environmentally friendly either. I seem to remember you suggesting that duct tape was not such a good idea a few weeks ago when you recalled the delights of having a sticky ball of tape in your pocket afterwards!

73

Richard
G3CWI

In reply to G1STQ:

Hi John

I have used inverted V’s on many activations to good effect. I use wire stripped from computer ribbon cable - incredibly strong and light. Feeding with RG174 and no balun is fine, I have not been able to detect any difference in performance with and without in tests on 5MHz (although it has to be said variations in propagation would probably mask any subtle effects).

I use three way tagstrips as the dipole centre, with the wire for the legs wrapped a couple of times through the outer tag fixing holes for strain relief and the coax looped round and attached to the centre tag with a tiny cable tie. I clip a fishing swivel through the eye of the middle tag, and attach to the pole by another cable tie which slips over the top of the pole and catches on the first joint. Coat the open end of the coax with some of SOTAbeam’s excellent liquid rubber to keep out moisture, and I recommend getting the proper BNC’s to fit RG174 - cobbled up arrangements to use the RG58 type have proved problematic in the field. And I would echo GM8OTI’s advice to keep the ends of the dipole as far as you can above the ground, preferably a metre but never less than 600mm to avoid catastrophic detuning.

Having said that, my current preference is for a balanced feed doublet based on the Norcal design but longer - google Norcal Doublet for clever construction details. I use a little MFJ ATU that gives me easy band changing and scope to compensate for varying ground conditions. A weak point is the highly-stressed area where the feeder becomes the element, following an aggravating incident on Easington Fell to avoid problems while out I try to make a new antenna every thirty activations or so. Since then the only breakages I have had have been when I have managed to inadvertantly yank the wire hard as a result of snagging.

Sorry to go on, hope that’s of some use!

73 de Paul G4MD

In reply to G4MD:

And I would echo GM8OTI’s advice to keep the
ends of the dipole as far as you can above the ground, preferably a
metre but never less than 600mm to avoid catastrophic detuning.

A useful rule-of-thumb is to keep the ends of a dipole at least 1/40th of a wavelength from the ground to avoid excessive detuning or losses. This rule was derived based on several papers written about the performance of low antennas and does seem to work out well in practice across a wide range of different ground types.

73

Richard
G3CWI

In reply to G1STQ:

I am trying to avoid the use of balanced feed line if possible. Simple
is good - as if it takes hours, it will end up in the loft, next to my
not-so miricle whip :slight_smile:
Or am I being a bit thick?

Hi John,
this subject has been discussed many times. The value of the reflector here is that all the posts have been saved. So you can search the reflector for previous posts and read all the discussions that took place. This means there is a wealth of both theoretical knowledge and actual practical results from applying that theory. There are descriptions of antennas, modeling results, pictures, materials used, construction methods, limitations and advantages, etc. etc. A veritable cornucopia of QRP (and not so QRP) antenna design facts.

From experience at what has been written, the vast majority of HF operators use an inverted-V dipole with links to alter the effective length of the antenna. A small minority use tuners (auto or manual) and balanced feeder with non-resonant antennas. Some commercial antennas like Buddipoles have been used as well as a few verticals. The overwhelming choice is the link dipole because it is cheap, light and damn effective.

As for choke baluns have excessive windage or pluging links requiring frequent moving about then all I can say is I must be doing something wrong on my small number (160) of activations. Whilst I feel my choke balun is on the small side to be truly effective, it’s windage is negligble compared the bleedin’ great runs of wire for the dipole legs and the 5m of fibreglass rod sticking up out of the ground. Likewise, I change bands once per activation normally and I don’t find that I’m up and down like a lady-of-the-night’s undergarments! I am stuck at only having 3 bands for HF until I add some more links. The biggest disadvantage of links is that they make winding the antenna legs on their respective winders a little fiddly so the link lays neatly with the wire. Sometimes it takes me 10-20 seconds to adjust the winding to solve this issue!

To be serious, it’s well worth checking the archives on this subject.

Andy
MM0FMF

In reply to MM0FMF:

Sometimes it takes me 10-20 seconds to adjust the winding to
solve this issue!

I’m sure that you will get better at it as you gain more experience Andy!

73

Richard
G3CWI