Welcome back 10m "big time"

Today 10m sounded like the good old days with good strong contest signals from the USA and Canada as well as South America and Africa earlier in the day. I managed to work several stations in Texas, Alabama, Tennessee and Louisiana when running QRP SSB to the Homebase10 wire halo. This is the first time in around 5 years that I've heard the band like this. Welcome back good old 10m!

14.9km on 136kHz QRP (earth electrode antenna)

This morning I did some more tests using my little 136.93kHz 2W QRSS3 beacon feeding into the 20m spaced earth electrodes. The TX end was unchanged, but this time on receive I used my 30t 80cm loop resonated with about 700pF and fed straight into the high impedance input of my E-field probe. Results were as follows:

• At 2.4km good copy by ear (12wpm CW would have been very solid)
• At 8.6km good copy using Spectran
• At 14.9km clear copy of my callsign and locator in QRSS3 with Spectran on the Gog Megog Hills near Cambridge (see screenshot)

All these locations are more or less in the line of the earth electrodes that run NE-SW from the home QTH (JO02dg).  Another RX test some 11km to the south of the QTH  resulted in no visible trace, suggesting the TX earth electrodes are behaving as a loop antenna with some directionality. This was not the case when the same earth electrodes were used at 0.838kHz some weeks ago and when the mode was mainly conduction through buried utilities. Remember, this is ultra simple stuff:

• 2W out crystal controlled QRP 136kHz beacon TX on a 5 x 5cm board (see picture)
• Invisible ground "antenna" that can't be seen, even when a few metres away from it.
• No attempt to match the TX to the earth electrodes.
  
• Simple loop + FET impedance matching circuit and deaf FT817 at the receiver end.

It would be interesting to work out what the ERP must be and interesting to speculate what would happen with such a system at 73kHz. Pity there is no allocation there today.

Kanga Products kits

The well known range of QRP kits from Kanga are now available again in the UK. These include the FOXX3 transceiver and the Sudden receiver. See the Kanga Products UK website.

6m Es

Only had a brief chance to operate today as I was busy in the garden then out at a BBQ in the hot sunshine, but managed to work some 6m QRP Es this afternoon. Although I worked some DX last week when out pedestrian portable, this was the first 6m Es QSO this season from home. In the coming weeks we can expect 6m to be open for DX most days.

G3RJV QRP lecture on the BATC streaming site

A talk called "QRP Why and How" by G3RJV is available now on the BATC website. Go to http://www.batc.tv/ and click on the 'Film Archive' icon and select "G3RJV QRP Lecture" from the drop-down list on the left hand side. The BATC site has a wide choice of videos available to view on-line as well as streamed outputs of amateur TV stations and repeaters.

Simple LF/MF QRP transmitter

VE7SL has a neat little LF/MF TX circuit on his website which is suitable for QRP 136 or 500kHz operation. Its original application was for 160-190kHz part 15 "lowfer" beacons in the USA. I used the same PA arrangement in my first 500kHz transverter and I can confirm it is very reliable and robust.

Sixbox video added

As promised, I've put a small video about the Sixbox 6m AM transceiver on my YouTube channel. You will recall that the Sixbox was a small 40mW AM transceiver derived from the 2m Fredbox. This version is built "ugly style" in a diecast box and has a tunable receiver covering about 5MHz around 49-54MHz. The Sixbox is described in SPRAT 140 and also in the German magazine QRP-Report. It is also described on my website.

500kHz ATU video

Just put a short video of my tiny ATU for 500kHz onto YouTube.

New G3XBM videos on YouTube

Today I've added a couple more videos to my G3XBM YouTube Channel. They are of the Fredbox 2m AM transceiver and of the FETer 80m CW transceiver. The latter uses just 14 parts but works remarkably well. I hope to add more videos about my projects in the next few weeks.

500kHz transverter video

There is now a short video clip on YouTube describing my 500kHz QRP transverter. Sorry the quality is not brilliant but I had problems holding the camera, pointing the pointer and deciding what to say! Still, it gives you some idea what is inside the box.

See http://www.youtube.com/watch?v=86K19chQ06Q

40m CW with the Elecraft K1

This evening, for a change, I fired up my little Elecraft K1 4 band QRP CW transceiver that I built a few years ago. Not much doing on 20m or 30m so I went on 40m CW and worked a few stations around Europe. Worst report was 559 and the best 599. It was a change from 500kHz WSPR.

10m - the return of the good days?

The CQWW SSB contest has livened things up on 10m this weekend, but the sunspots are also showing signs of activity again and the band generally has been in good shape. In the last 24 hours I have heard DX from 4 continents and confidently expect it to open to the USA this afternoon. Good signals from 9J2B0 on CW and ZS9X on SSB today as well as wall-to-wall Europeans from 28.38-28.62MHz at times. Could this be a sign of the good times to come? Let's hope so as 10m is one of the best allocations we have on HF and a great band for QRP DXing when conditions really improve.

AA1TJ's Voice Powered DSB TX (El Silbo)

Mike has done it again - a superb piece of QRP creativity. This is from his email today:

"AA1MY and W1PID met with me on 3686kHz this afternoon. I was operating a new, DSB version of my "El Silbo," voice-powered transmitter. Both Seab and Jim successfully copied my/their calls and signal reports. Jim commented later that I would have been hard pressed to pick a worse day for the attempt. The propagation was producing severe QSB fading and the QRN was all over the place (peaking at S-7 to S-9 at times). I came away nearly dumbfounded that these two operators could pull enough of my 5mW DSB signal out of the mess, at distances of 100 and 67miles, to complete the QSOs."

Sound powered transmitters

A few people are currently experimenting with sound powered RF transmitters, generating the DC power to run a microwatt level oscillator from the human voice or morse key activation. There have been a few such ideas published. What appeals to me is a sound powered TX coupled with a crystal set RX. Such a system might get a mile or two as long as the station at the far end was running a few watts of AM or MCW. This would be the ultimate in QRPp!

There is a patent for this sort of sound powered transmitter - see United States Patent US2981833 dating from 1955 which has some schematics. This is available to view at http://www.freepatentsonline.com/2981833.pdf

ERP estimates on 500kHz

Just got this letter from M0BMU who has estimated my ERP on 500kHz currently .

Dear Roger, LF Group,

It is interesting to make an estimate of what G3XBM's ERP might be...

The noise level at M0BMU during relatively quiet daytime conditions I estimate to be of the order of 3uV/m in the 2.5kHz WSPR reference bandwidth. The reported SNR gets up to about -25dB, making the signal level from G3XBM about 0.18uV/m.

ERP = (Ed)^2 / 49; with E = 0.18 x 10e-6, d = 69000m , ERP is about 3uW with only "geometric spreading" propagation losses. But there is some additional reduction in field strength due to ground wave propagation losses, perhaps 3dB with "good" ground, so the ERP would then become about 6uW. Diffraction losses due to the curvature of the earth are negligible at this distance.

Obviously, this could be +/- several dB due to various uncertainties, but should be of the right order of magnitude. Plenty of potential for improvement then!

Cheers, Jim Moritz
73 de M0BMU

160m WSPR

On 160m I have an almost useless antenna by accepted standards: just 15m of low wire down the garden and a central heating ground. Not only that, but my Elecraft auto-ATU cannot find a match on 160m. So, I get around this crudely by putting a 1dB pad between the antenna and the auto-ATU and it then manages to find a match. OK, I lose another 1dB but that is a fraction of an S-point.

Now, even with this crude set-up I have had reports from G, GM and PA0 on WSPR running 5W (less 1dB) into the antenna, proving that a piece of wet string is very nearly all you need to get out. Clearly, with a bit of effort I could make at least 10-20dB improvement on my signal - adding loading coils in the antenna, running out more wire and higher up, improving the ground system etc. I shall need to all of these if my efforts on 500kHz are to come to anything.

Another SixBox QSO

This afternoon I worked G3PTQ in Bottisham, 6kms away with the 50mW Sixbox AM transceiver. Report was RS41 (weak, but 80% readable). Then Terry mentioned he was using a low horizontal dipole, so signals could easily have been some 10-20dB (2-3 S points) stronger had he had a vertical antenna. This little transceiver is definitely proving useful for local 6m contacts.

6m AM and noise

Two local tests with stations on 6m AM have shown just how noisy the band can be when using this mode. M1KTA was 18kms away and M1MAJ around 15kms yet both were not strong on the vertical V2000 antenna on 6m AM even when they were using FT817 rigs at 2W AM. We were going to try the SixBox but signals would have been too weak. Switching to USB made a lot of difference (better) unsurprisingly, as the noise level reduces with the bandwidth.

This goes to show how AM signals do need to be strong to overcome the band noise: when signals are a decent level AM is a fine mode, but it can be hard work when they are very marginal with lots of noise in the background.