137kHz QRP transverter (provisional schematic)

Attached is a first draft of the 137kHz QRP transverter schematic. The values are not all correct or optimised on the circuit. Also the RX preamp has still to be added, but this is what I'm proposing to do. The TX is working pretty well (best DX 148km) and produces around 5W from the PA which runs cool and 20uW ERP. An updated version will appear on my website later. It may even get put in a box soon!

500kHz ERP with the vertical loop antenna

Results on 500kHz WSPR with the vertical 80sq m area loop (made from 1mm diameter wire) are very good with signal reports from G3XIZ this evening of +4dB S/N. M0BMU has given me - 4dB S/N. This leads me to believe the ERP of the system is now somewhat higher than with the short Marconi vertical. Based on earlier calculations I think my ERP, in the best direction, must be about 2mW now, some 6dB more than it was.

6th unique WSPR reporter on 137kHz

This autumn is beginning to look a bit like last year when I was taking my first tentative steps on 500kHz WSPR: each week would land me a few new reports from more distant stations. This autumn my challenge is 137kHz WSPR and so far I've been copied by 6 different stations: G6ALB, G3XIZ, G3XVL, G3WCD, G3YXM and, this evening, M0FMT. Best DX remains G3YXM at 148km. Not bad for a true QRP station with less than 5W from the PA and less than 20uW ERP with the transverter just a breadboard on the desk and the ATU sitting on the bedroom table.

Also today I copied G8IMR, Andy Talbot's QRP beacon from Southampton on 137.530kHz.

Sub-9kHz Amateur Radio (Yahoo group) formed

This new group is for anyone interested in amateur radio communications below 9kHz in the so-called "Dreamer's Band".  See http://tech.groups.yahoo.com/group/sub9khz/

VLF DX transmission with earth electrode transmission (49.6km)

DK7FC's 8.97kHz DFCW transmission received at 49.6km

Stefan DK7FC has informed me that he has successfully transmitted the message "CU" in DFCW on 8.97kHz to Michael Oexner at a distance of 49.6km. His TX puts out 250W into a 600m spaced earth electrode pair with a current into the antenna of about 0.5A. This is definitely far field reception. Stefan's earth electrode antenna is capable of further improvement, so he is expecting more successes shortly with it.

Another source of LF/MF and HF interference

This was posted on the LF reflector: we'll have yet another source of LF/MF and HF interference in the years ahead as more people install such systems. Hugh's post got immediate replies from people who'd suffered bad interference from such systems. beware of photocell panels on neighbours' roofs!

"My neighbour informs me that she is intending to have photovoltaic panels installed on her roof, in a scheme where she gets free electricity (all subsidised by the government of course!)

My concern is the possibility of high levels of interference generated by the kW inverters needed to pump electricity back into the National Grid. I would guess that such invertors probably operate kHz and might be expected to interfere with LF and VLF reception. The wiring to all the panels on the roof might act as a
very good aerial!

It also occurs to me that any lack of RF immunity to my transmissions, in the new installation, might have dramatic consequences - I know from studying electrical engineering at college that connecting a generator to the grid with incorrect phase leads to a big bang!

Has anyone any experience of such installations? Perhaps someone has one nearby and could comment on any EMC effects.

Hugh M0WYE"

More sub-9kHz experiments

Just received this from Stefan DK7FC:

Dear LF/VLF,


Today i saw the first time a flag from Norway on my VLF Grabber (http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html). I would be very fascinated if my signal would be copied in LA/SM/OH  (of course, in all countries it would be very fascinating :-) ). Are there any stations, reading the reflector, from there who have the ability to receive on 8.97 kHz (or even 6.47 kHz) with a sensitive and stable RX frequency in DFCW-600 mode?
This would be one of my wishes for this period! One. ;-)
For this weekend i planned the next VLF experiment with the 200m vertical on 8.97 kHz but the wind forecast is not too promising :-( Maybe things look better tomorrow. I have to inform the air traffic control to give out a NOTAM (http://en.wikipedia.org/wiki/NOTAM), 48 hours befor i can start...
I will announce  tmw, if i will carry out the next test, if.
The signal would be once again the strongest i've ever radiated. About 50 mW ERP is the goal.
My planned tests for this year on VLF (kite antenna):
- CW QSO to DF8ZR (16 km distance) on 9 / 137 kHz
- Copying my signal on 8970/6470 Hz in Heidelberg in CW (40.0 km, audio recording and later analysis)
- Beeing visible in DFCW-120 in UK
- Beeing visible on the grabber of Renato Romero on 8970/6470 Hz
- Becoming QRV with the 300 m vertical antenna on 8970/5170 Hz, radiating 100 mW ERP at 8970 Hz
- Beeing visible in Russia and at all interested RX stations :-)
- Maybe a TA contact?
vy 73, Stefan/DK7FC *Dreaming...*

148km on 137.5kHz WSPR!

WSPR reports on 137kHz 21.09.10

Just had a report from G3YXM who gave me -24dB S/N on 137.5kHz when I was running no more than 20uW ERP.  He is now my 5th WSPR report on the band and the best DX by far. This is so thrilling! The transverter is just sat on my desk and the PA isn't even warm.

G3YXM's screen showing my weak signal on 137.471 kHz

Possible progress on a worldwide MF allocation at WARC 2012

Info on the ARRL website suggests the USA authorities are supporting an amateur allocation at MF. See Secondary Amateur Radio Allocation at 461-469 and 471-478 kHz

 

The loop works well on 500kHz TX

Unique reports on 500kHz WSPR this evening

My vertical loop of 1mm diameter wire seems to work very well on 500khz WSPR with some excellent reports this evening, indeed some of these reports are better than I ever received (I think) on the short Marconi vertical last winter. Certainly there will be some directionality, which is the downside of this antenna. Results on 500kHz are SO much easier than on 136kHz where the lower radiation resistance and electrical size make it so much less efficient.