Re: LF: 630m WSPR this evening

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Hi Stefan,

It is on our local "hill" on the 20m contour, so is a better VHF, UHF, uW QTH but the garden shape/size is less ideal for LF and MF.

The loop, at present, is 1mm diameter wire running along a 2m high fence, for about 10m, then along another fence at 2m at right angles for about 5m, then a wire back along the top of the grass to the shack. I estimate loop area as around 60-80m sq, but it is far from vertical. TX power into the loop is around 12W and the measured antenna current 0.9A. My aim is to get an efficient LF/MF antenna that is not noticeable by the neighbours, HI. The earth-electrode system fully meets this criterion, but is not good enough at this QTH.  If tests tonight are encouraging I will raise the loop height (and increase loop area) in the coming weeks.  BTW, you were a very good signal last night on the earth-electrode antenna with signals close to 0dB S/N at times.

I am being tempted onto 23cms and 10GHz by locals here and have further red light and IR "over the horizon" scatter tests to try, so progress on LF/MF may be interrupted.

73s

Roger G3XBM

On 12 September 2013 19:35, Stefan Schäfer <Stefan.Schaefer@iup.uni-heidelberg.de> wrote:

Hi Roger,

Some more details please. What is the loop's cross section area. What type of wire did you use? What TX power? Will you some day try to get an antenna efficiency that is as good as possible for the given QTH?
Did you actually move to a QTH with even more restricted antenna possibilities???
I'm watching!

73, Stefan/DK7FC

Am 12.09.2013 20:15, schrieb Roger Lapthorn:

'Recently I moved 350m east (!) to a new QTH and I've been experimenting with 630m WSPR.

My initial tests were with the transverter on my website feeding a pair of earth-electrodes but with a shorter baseline than was possible at the old QTH (about 12m separation). Although I managed to get reports from G, ON and PA, it was clear that results were nowhere near as good as I obtained at the old QTH. I am speculating that this is due to the effective spacing between earth rods being much shorter and due to buried wires and pipes criss-crossing the lawn. On RX it is working very well though and I have copied most of the nearer Europeans on 630m WSPR.

This afternoon I converted the earth-electrode antenna to an "in the air" loop by disconnecting the earth rods and joining the wire ends with a wire running along the top of the lawn (in the grass). The loop DC resistance is 0.9 ohms and it tunes sharply with about 1.7nF. Matching is via a 3C90 step-down toroid.

Initial encouraging reports include first spots from M0PPP, who had failed to copy me before from this QTH, as well as PA3ABK/2 and G8HUH.

If anyone else can look for me this evening I'd appreciate it. The loop is not very high and can be further improved if results this evening are encouraging.

73s
Roger G3XBM

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http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
https://sites.google.com/site/sub9khz/
http://qss2.blogspot.com/
http://www.youtube.com/user/g3xbm