Monday, 7 January 2013

Comparing antennas on RX

I have three HF antennas - and three rigs: The trusty 817, and a couple of shack rigs. I've been "testing" the setup on RX by running three copies of WSPR 2.0 in parallel, on the same band, one connected to each radio (I use SignaLink boxes as interfaces)

The antennas are a couple of long wires, running similar but not identical routes, and an inductively loaded vertical I bought many years ago from sandpiper aerials - it's been lying behind the garage where it was placed when we moved house a few years ago, and everything is seized. I set it up on a fence at the bottom of the garden. It has now grown its own earth stake. I can't tune it for resonance because of the corrosion so the setup I made when it was new is stuck in place. Two or three of the bands - 12,15 and 17 metres - tune reasonably well directly. 40m is a complete no-go, and the others needed tuning.

A few months ago the winner, on most bands, was a LW/earth stake, tuned through an SGC Mac-200 to my Icom 756 ProIII.

Now, things are very different. I have spent the day with this trio, moving down the bands. So far, I've played with 21MHz,14 MHz, 17MHz and 10MHz. The 817 / LW appears to be deaf. It's generally around 12dB down on the winner. The Winner is the corroded Sandpiper which is, as I write, capturing some Stateside stuff on 30m which neither of the others sniff at. The 756 is pretty effective on the LW, generally turning in about 3-6dB down on the vertical

So what has changed? I'm guessing saturated ground probably has a fair bit to do with it. The earth on the vertical must be pretty effective at the moment, since the ground is sodden.

I'm trying to work out why I now find the 817 deaf. I'm sure I remember being pleasantly surprised by it....

I hope to move down to 3.5 and 1.8 this evening. I am confidently predicting that the vertical, with an immense loading coil on it, will not out-perform a long wire. And, of course, on 160m there is no choice.


The situation on 80m is surprisingly even. All three systems perform around the same level - in each case, one is a few dB up or down on the others, and all three have good and bad moments. I'm surprised the Sandpiper does so well. Or, maybe, to put it another way, are the long wires doing badly?

the next step is to rotate the antennas around the rigs

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