
5 Mar 2010
More 10m antennas

500kHz TXing using the 10m halo
Having taken down the 500kHz antenna and put 28MHz wire halo back up I tried TXing on 500kHz with it. I strapped the coax feeder inner and outer together and fed it via the ferrite rod ATU with a bit more inductance. First report was from M0LMH some 223kms away at -20dB S/N , so I still get out OK on 500kHz with now <1mW ERP. Also getting reports from G6AVK at 78kms. At 8pm I also got a report from PA1GSJ, so the 28MHz halo and feeder makes quite a respectable 500kHz antenna!
10m halo re-erected

Labels:
10m,
halo,
homebase10,
wspr
10m tropo?

USB powered direct conversion RX

Labels:
15m direct conversion,
receiver,
sdr,
SignaLink USB,
simple
4 Mar 2010
UK on-line VLF Receiver
There is an on-line VLF receiver on which you can hear natural emissions such as sferics, tweeks and whistlers located at Todmorden in the north of England. As well as a real-time audio stream, it has an interesting way of plotting received signals so you can see the direction of arrival of sferics.
3 Mar 2010
Fivehead QRP SSB transceiver kit
1 Mar 2010
Warm sunshine and G3XBM up a tree
Today the sun has been shining and it's quite warm so I've been up the neighbour's tree lopping branches so that they don't obstruct the light. It is a field maple and it grows so fast. I took down branches about 4 metres long and these have grown in the last 3-4years. There is also a method in my madness: there's a sturdy branch just the right height to act as a support for the end of my longwire. It's twice as high as the original on the clothes line support. So, when the job is done I'll string out some black PVC covered wire. Also, for the first time this year I managed a cup of tea on the patio: maybe spring really is almost here at long last.
28 Feb 2010
11th country on 500kHz
Just had a 500kHz WSPR report from MW0CVT 250kms to the west of me. This is now my 11th country from which I've had reports on the band. This is also my 83rd unique report on the band.
Amateur DXing below 9kHz (VLF)
Some recent discussion on the LF Reflector is suggesting that distances of >100kms should be workable with amateur stations below 9kHz, albeit running QRO exciters. This would be possible with optimised stations and antennas and very slow QRSS modes. As an example, see the email posted this evening by RA9MB:
I was wonder if it is posible to use a loop on 9 kHz. Serious problem to radiate 9 kHz is high voltage we saw. Loop has that advantage that voltage is not too high. Then i do some estimations. Let's assume vertical loop 15m x 50 m with 20 mm diameter coper tube as a wire. Then effectivity of such a loop on 9 kHz is about -65 dB. It is adequate to radiate 1 mW
on 9kHz (I=250A, TX power about 4 kW). We saw such a radiation should give abt 100 km distance in QRSS. Besides such a loop is well suited for 136 kHz. On 136 kHz it effectivity should be about -25 dB. Not too bad: 1 W radiation with 400 W TX :-)
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