CDARC Wednesday Net

At 1900z on Wednesday evenings, the Cambridge and district amateur radio club (CDARC) holds a very informal net on 145.55 MHz FM. Anyone in range is welcome whether a club member or not. Usually there are between 3 and 7 members on. Polarisation is vertical and there is a web SDR if you are having difficulties receiving. I thought the link for this SDR was on the CDARC website, but cannot find it. 

Most people on the net are in the greater Cambridge area (surrounding villages). The net usually lasts for 20-60 minutes, but people come and go as they want. It is rarely technical!

See cdarcvhfrx.hopto.org:8073 for the webSDR.

Matching the earth-electrode antenna in the ground

To allow the auto ATU in the FT-710 to match the earth-electrode antenna on 80m (see the excellent results yesterday) I had to use this transformer.  As you can see, it is not pretty!!  With it, the load presented to the FT-710 was obviously less than 3:1 as it matched well.

12 years ago

Earth-mode experiments in 2011

 
This was my earth-mode signal 4.5km away from home in 2011 at 1.095 kHz using Spectran software on the PC. Strictly speaking, I suppose this is ULF!

It is a long time since I have done any earth-mode experiments, but my health has got in the way. It would be good to do some more experiments.

Sunspots - Wednesday April 12th 2023

Solar flux is 143 and the SSN 103. A=6 and K=1.

70cm activity contest

After copying no stations at all (!) I gave up. I expect the next 70cm FT8 activity contest will be much better!

80m FT8 (Tuesday)

As 6m was so poor, I QSYed to 80m FT8 using the earth-electrode "antenna" in the ground. Although I am receiving spots of my signal from right across Europe, it says I am receiving none. This is rubbish as I can see loads of stations locally. Either there is a delay with uploads from me or, more probably, my spots are not getting to PSKreporter. Shortly I shall do reset to see if this cures it.

UPDATE 1922z:  The reset did the trick with lots of spots on RX. On TX 36 unique station spots of me so far.

UPDATE 2119z:  112 stations have spotted my 10W 80m FT8 TX this evening. Now QRT on all bands.

6m FT8 (Tuesday)

In a word, hopeless. I have been on 6m FT8 for about a hour and have been spotted very strongly by just one station not too far away (50km). On RX absolutely nobody copied.

UPDATE 1708z: Still useless!  Just 2 stations have spotted me and I have spotted nobody! Soon be time to try another band. I might give 80m FT8 a go with the earth-electrode "antenna" in the ground - probably after tea.

Windmill next door - NOT amateur radio

This stunning photo of the windmill next door was taken by a neighbour K. Tingey. 

E-field probes (EFPs)

These are tiny receive only antennas that can work extremely effectively at VLF, LF and MF where external noise is usually the dominant factor. I guess as local external noise is increasingly the dominating factor, these will be as effective as a "big" antenna at even higher frequencies. At LF they can be only a few centimetres long, but be as effective as antennas hundreds of metre long. 

EFP on a mag mount
for 2200m RX

As the signal decreases, so does the external noise! Overall, nothing is lost. There is no advantage by using a large antenna at low frequencies for receive only. For TX efficiency, a large antenna and good earth help! A popular EFP design is that PA0RDT (Google it). I have made versions for LF and VLF with a tuned peak as shown in the circuit.

See https://sites.google.com/view/g3xbm4/home/antennas/137khz-efp-rx-antenna .

Tuesday plans

 Probably 6m FT8 later. Shopping first!