Venturing onto MF - With a Barbed Wire Fence!

Last night, I had one of those 'let's try this!' moments, having started to think about WSPR at MF frequencies.

Now, an effective antenna at MF is something that awaits another lifetime and a property with tens, if not hundreds of acres of land.  A ground dipole is also out of the question, due to very high mineralisation and ground conductivity (in excess of any results I've seen from anywhere in the world.)

For this lifetime, I have to make the most of what's available.

Out came the soldering torch and, within minutes, I had the flying lead connections from a 4:1 balun to...wait for it...a 90m-long barbed wire fence that runs E-W down a 5 degree slope on hugely conductive soil, and an earth stake.  The wire might be 50% longer than this, as it probably continues at 90 degrees at the bottom of the hill.

The fence antenna runs along the stone wall, down slope.

Modelling this arrangement on MMANA-GAL is not easy.  Using modified dipole and sloper files yields low gain values of about -25dBi.  I've no idea whether, in fact, this software works reliably below 1.8MHz.

In any case, here is how my trusty SARK-110 analyser measured things:

A roughly 90m-long fence antenna's curves.

The SARK's output is very interesting!  The SWR remains at low levels throughout the HF, and even the MF spectrum, with many points along the way that yield very good matches.  For example, one of the cursors (M1) lies at 10MHz, with a 1:1.1 match there.  Coax losses are minimal at lower frequencies, but a twin wire feed would probably improve matters.

I would guess that there are quite high losses in this 'antenna' system, and its low height must mean it is a cloud-warmer.


But, listening on WSPR (I have no transmit ability as yet), I was hearing, for example, LA1TN at least 5dB more strongly than any other UK station, which suggests that, whilst it may not be ideal, it is certainly worthwhile experimenting some more.

Running on 10MHz WSPR for a couple of hours shows that the hearing ability is very good, being the only one, or with the only two hearing the US during late morning hours today, and with a signal report between 5dB better and 1dB worse than the other receiving station (both in Scotland.)

On the transmit side, in keeping with its Beverage-type set-up, it's not so good into Europe, being well down by over 10dB on other UK stations.  I'll see what it can do across the Atlantic when the grey line comes over tonight...