Re verticals, I used to work plenty of DX quite easily from southeast England (yes even with a humble G4 callsign!) using 100W into a Butternut HF6V mounted on the ground. The land was nice, heavy clay and the location was close to the beach (Middleton On Sea, near Bognor). The excellent ground plane was the key to the success of this installation.
I had similar success with a mobile whip mounted on a balcony railing while based in Hong Kong in the 1980s but in that case the VS6 callsign probably contributed an additional 6dB to my signal strength The ground plane wire run back into the apartment under the carpet probably helped.
Both of these installations were practically useless for local (i.e. within 500km) working. Low angle radiation is no use at all for NVIS.
Re NVIS, the trick is to use a frequency that is LOW enough to be reflected more or less straight back down from the F2 layer (i.e. as close as you can get to F0F2, the F2 critical frequency) and at the same time HIGH enough to avoid being absorbed in the lower D layer. Recently, during daylight hours F0F2 has been below 7MHz and absorption has been killing 3.5MHz, hence no NVIS joy for those of us without access to 5MHz. When conditions are right, use a low-slung horizontal antenna to persuade your signal to go straight up.
As Andrew points out, you wonât see F0F2 approaching 14MHz (or even 10MHz) at this stage of the solar cycle so you can forget that band for NVIS work. Groundwave will be absorbed very quickly so again no joy there unless you plan to run QRO⌠Probably not from a Summit, Iâm guessing. Only solution - get the EU activators down on 7MHz (or 5MHz if you have it) when NVIS conditions apply, then youâll work them out to 600km or so easily enough.
Hi Bernard,
Thanks for the reply, confirming what others have said. Of course the issue at the moment is that many continental Europe SOTA activators are using 20m SSB as their main band as the get a good number of contacts and some exotic ones from time to time (canât blame them for that). They either donât have a 40m antenna or donât have the time to switch, or simply donât need to go to 40m (no 30m SSB or 60m anything here in Germany). Let me be clear though, there are those activators who cover 20m and 40m (myself being one) but itâs the activators choice which bands they use.
I am talking about my home QTH antenna at the moment and the ground makes a big difference - being located above the largest aquifier in Australia while in Woy Woy, Iâm sure helped the antenna there! Out of every 10 spots that come up (filtered to SSB only on the HF bands) I can hear perhaps one or two. Being located as I am in the Centre of continental Europe, so many of the stations are simply too close for 20m SSB. In the UK, there can be stations on 40m that I wish would go to 20m for the opposite reason!
It sounds to me that all I can do is improve the horizontal loop by perhaps adding a groundplane under it. Going to a vertical antenna wont help me as the loop (at 9m agl) is already acting as a DX antenna on 20m and since NVIS is not an option on 20m during the current phase of the solar cycle, lowering it to an NVIS height isnât going to help.
9m is still (just) less than a quarter wave on 40m, so itâs acting as an NVIS antenna there already.
73 Ed.
Additional info - hereâs a map of the summits 20m skip distance (estimated) stop me from contacting on 20m - quite a few as you can see âŚ
This is based on being able to contact up to 175 Miles (~300km) by ground wave on 20m and hoping that I can also contact stations greater than 500 miles (~800 kms) away. The mapping project tool only goes out to 500 miles maximum in any case. This would seem to correspond to what I am actually finding in any case.
The only answer I know of for extending range without ionospheric reflection is to have the lowest possible angle of radiation, so that there is the most possible signal as close to the horizon as possible. Random scatter always happens but if you have stronger signals at the furthest distance, you will increase your odds of working longer distances without ionospheric reflection. The usual methods for that are increasing the height of horizontal antennas or using vertical antennas with excellent ground systems.
There is probably also an optimum height for some purposes that does not suit others so well. For certain distances, a radiation angle of 20 degrees might be better than 10 degrees, though few of us have antennas with a narrow enough beamwidth that tuning the elevation (by raising and lowering the antenna) has any effect. I would guess that at least 5 elements would be required of a yagi to get the 3db beamwidth down below âfairly wideâ.
Also, while simple wire antennas are described as having maximum radiation at a certain angle, the radiation at 10 degrees might only be a few db below that at 45 degrees. eg. the oft-cited radiation pattern of a low dipole shows the peak at 90 degrees (straight up) but at angles down to 30 degrees, there is not a lot of reduction, which is why those antennas are quite ok for general use. The pattern looks like a mushroom, not a skyscraper. As I have commented before, we are not dealing with lasers.
There is a relevant article in the October QST which arrived here this week. All about dispelling myths. Some good reading about grey line propagation.
Re the cw option, I think signals that are in your âimpossibleâ zone are there, but are just too weak to copy in the presence of noise and QRM. CW might make it more feasible even at low signal levels, but there will still be some that are too weak to work. I have that problem here sometimes with VK1 activations out to the east of Canberra, they are less than 100km away but are sometimes just too weak to copy in the presence of QRM or local noise. I would like to compare their signals on horizontal and vertical antennas at their end. But few activators take two antennas for one band.
Hi Andrew,
Thanks, as usual for a very valuable and informative reply.
So really I would need at least two antennas I think - one optimised for maximum distance ground wave, and one for DX via Ionespheric reflections. I had thought about whether a method to lower and raise my wire antenna might help in this area, being surrounded by houses here however once Iâm below 8m the ground wave signal will simply be hitting those house walls. Itâs interesting that you say a vertical with a good ground system might be an option. I might be able to get a vertical high enough but getting a really good ground system in my small garden is going to be a challenge.
Increasing output power is possible (maximum 750w output allowed here) but I need to improve the receive side more, so an antenna improvement is a better solution bring improved receive and transmit as it does. I have tried a 2 element mini-tribander-beam and was disappointed with itâs performance. There is no way I could get even a single band full-sized or 3 element beam installed here.
Would phased verticals give better ground wave propagation than my horizontal wire loop at 8 metres high?
OK on the article in QST, unfortunately I decided not to renew my ARRL membership, I could not justify the cost, so I no longer have access to the online QST magazine.
I do have a couple of books on antennas here, however their data is often related to someone having a farm field sized garden to install into, not a postage stamp sized one as I have!
For what I have here, the hoorizontal loop antenna performs quite well, but we all, always want to improve things if we can. Now I wonder how far apart is the wooden flag pole and one of the squiddies? Perhaps itâs about the right distance for a phased (also non-visible) 20m vertical configuration âŚ
Mark has it right. In Australia the telescopic fibreglass poles that we like to use as antenna supports in SOTA are called Squid poles - poles meant to be used for fishing for squid (I presume). âSquiddieâ is simply slang for squid pole.
Ed.
I do love your determination to defeat them pesky laws of physics!
If we could use easily extend the ground wave range on 14MHz where antennas are moderate in size why do we faff about on 7MHz where antennas are twice the size and the D layer comes along to put the kibosh on much of what we want to do?
I can hear RAF Volmet (WX service info) on 11MHz at a range of 230km most days. I know itâs there and it is a constant strength. Constant strength suggests no sky wave component. It is transmitted from RAF Inskip (now DCSA Inskip) and this wiki article has a picture of the transmit masts. RNAS Inskip (HMS Nightjar) - Wikipedia I canât corroborate the info I was told but the transmitters for Volmet on 5MHz and 11MHz are in the â10kW rangeâ. If we scale the antennas and powers to SOTA levels you should now see that you are not going to hear 14MHz SOTA activations by ground wave at 450km or so. Sorry, but thatâs how things are.
You need to move further away, move nearer, or persuade the activator to use lower bands, or persaude the activator to use a small Yagi on 2m SSB and use one yourself.
Online only subscription is the answer. Itâs a fraction of the cost of the European subscription for a paper QST. You can print the only magazine to PDF (about 70MB) and then view that at your leisure, you donât need to be online to read it. I have the last 18 issues on my Android tablet.
Squid: a cephalopod thatâs nice when freshly cooked with some garlic.
Squid pole: a VK term for what is known as a Roach pole in UK fishing circles.
Roach pole: known to Anglophone radio amateurs as a telescopic fishing pole and used by many SOTA devotees.
Donât confuse Squid Pole with Squid Proxy, the latter is a web proxy cache server application that is used to speed up web access, itâs no use on a summit.
By âexcellent ground systemsâ I meant a system of wires simulating perfect ground, usually three or four radials are used and recent experience suggests that elevated radials work very well, due (I think) to providing a low loss path for the âground currentsâ to flow in as an alternative to the higher resistance path through other materials. If the magnetic and electrostatic field around the antenna has a low loss path through real wire, that low loss path is the one where most of the âgroundâ current will flow, rather than the lossy path through real earth, grass, vegetables, chicken coops, concrete, garden gnomes and other decorative features of suburban back yards.
So getting the ground radials up in the air and possibly using them as the first 5m of the guys (for the 20m band) for the mast, then a 5m vertical as the main radiator, is an efficient antenna that provides good dx operation. However even that antenna cannot be guaranteed to provide a reliable tropo path out to 300 km. It improves slightly with more height and less obstructions. If your house, and/or the neighboursâ houses are multiple storey buildings they provide more obstruction in the direction of the horizon. And you are still at the mercy of the relatively low 20m antenna used by most activators. It is the height above ground in the first few wavelengths that determines the primary angle of radiation, though as discussed earlier, there is always some radiation at low angles, it is just not as strong as the main lobe.
With these complications for close-in 20m contacts I suspect the best answer will be to take up Andyâs suggestion of VHF for those activators. Establish a good 2m SSB station, with a substantial antenna, over 5 elements and up to 10 would be even better. Low loss coax, a rotator (which can be at the base of your mast, as per my field setup) and youâd be workable out to 300km with even ordinary vhf conditions, on ssb. But you still need the activators to take a 2m ssb station. Having them know there were a number of chasers wanting them on 2m ssb would be a key factor to make that happen.
Good luck with all that, hope you can find a way to make those contacts.
Unfortunately raised radials (possibly running down guy ropes) are not an option in my small garden, due to the WAF (Wife acceptance factor) and the fact that we have a dog who would possibly run into or chew through the ropes (even nylon ones!).
As far as possible any additional antenna needs to be âstelthâ or at least not a glaringly visible installation.
The two story plus loft houses around here means anything below 8 metres is going to be shielded and using 10m or 12.5m squiddies without guying gets somewhat dangerous in the high winds that we get.
OK on the 2m option - presumably with a crossed yagi for FM and SSB or vertical for just FM contacts. That would be an option for stations on the lowlands up to the alps (or at this side of the mountains) but with their 2500-3000m height they can cause somewhat of a barrier on VHF as Iâm not that far away from them (Iâm at 750m ASL here)!
My target here is to try to optimise what I can do with the space and other restrictions that I have so that I have a chance of receiving as many SOTA activators as possible. As I cannot ask them to move away another 300 km or even to change from 20m to 40m or 2m (as the activator decides themselves beforehand which band they want to (or can) operate on).
This is all good discussion but as Andy (I think) put it, we canât change the laws of physics - there will always be stations that I canât hear from this location. Itâs the problem of being so centrally located when activators are using 20m (or any band where NVIS wont work).
The ground plane wire run back into the apartment under the carpet probably helped.
