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.

Loop antenna on 500kHz

My vertical loop antenna (about 80sq m area) made with 1mm diameter wire (tuned with a capacitance decade box) performs quite well on 500kHz judging by reports. Yesterday I lowered the bottom wire to run along the ground, increasing the loop area from about 70 to 80sq m.  Reports from M0LMH (223km) and M0BMU (69km) are pretty good with my 1mW ERP signal at M0BMU up to -5dB S/N on WSPR, which is as good as I've ever had and he's not in the best direction for the loop. Also, PA3EGO was up to -2dB S/N on receive. Results on 500kHz are much easier to obtain than on 137kHz although this is explainable by the much lower ERP (probably 20dB less than on 500kHz).

Increasing interest in 137kHz WSPR

WSPR LF activity lunchtime Sept 19th

In the last week there seems to have been an increase in 137kHz WSPR activity. The attached image shows the stations active on 137 and 500kHz this lunchtime.  G8IMR was the call being used by Andy G4JNT for his WSPR beacon before it died.

Why NOT to use QRO on 136kHz

Andy G4JNT was testing a 600W RF WSPR beacon on 137kHz today when he noticed burning from the plastic shed used to house the ATU. When he opened the door he saw the plastic shed and shelf melting and flames everywhere which he quickly extinguished.  LF at high power can be dangerous stuff and one reason why I've restricted my activity to QRP.

New all-band SDR from Funk Amateur

SDR transceiver PCB assembly

http://www.dh1tw.de/first-pictures-of-allband-software-defined-radio-fa-sdr-trx

The German magazine Funk Amateur has a new all-band 1W SDR transceiver kit in the October edition. This will sell for around $170 US and looks a very interesting project. More details from the link above.

137.5kHz WSPR - best DX now 61km with less than 20uW ERP

137.5kHz WSPR reports so far today - with <20uW ERP!

Just got a -27dB S/N report on 137.5kHz WSPR from G3XVL near Ipswich at 61km. This is particularly good as this is more or less in the null of my TX loop antenna: in the better direction the signal could be some 6-10dB stronger!