Late Swallow - faulty GPS?

Had a change from ham radio today when I went birdwatching on the Wash in North Norfolk with our University of the Third Age group in Cambridge. Conditions were good but the wind very strong. Some decent birds about on the tidal mudflats and lagoons including black tailed godwits, mergansers, goldeneye, golden plovers and thousands of shelduck. No snow buntings seen although there were a few about. Apparently there was still a swallow up there last week, which is very late for the UK. Someone suggested it had a faulty GPS so didn't know which way to fly!

See http://www.rspb.org.uk/reserves/guide/s/snettisham/ .

Backscatter - microwave compendium

Last week G4BAO showed me a copy of a new book running to nearly 400 pages called "Backscatter" which has been created from articles previously published in the microwave newsletter "Scatterpoint". The book is available for £14 and, if you are into microwaves from 1.3GHz upwards this is a very useful reference book.

It was fascinating to read about something called rainscatter which allows 10GHz stations to work each other by scattering signals off rain clouds/drops up to distances of 600-700kms. This mode allows narrowband uWave stations to work great distances, even from less than perfect home locations. Small 45cm dishes and about 1W RF seems all that is required at 10GHz to use this mode, which works even with NBFM. Signals sound like aurora as they get spread by the scattering process.

I can't see myself getting on 10GHz in a hurry but I can understand the fascination with such intriguing propagation modes to be explored.

Another sked with the FETer rig (unsuccessful)

Tried a sked on 3560 this morning with Richard G4ICP in Braintree when using the FETer micro-transceiver with 18mW and the single FET RX. Although he was quite a reasonable signal with me, as was G3LUB in Aylesbury, Richard could not hear me. This all suggests that for the 1 FET transceiver to be more useful it needs more power on TX. Probably 500mW is needed to stand a reasonable chance of random QSOs - I need to experiment some more to get the TX power up.

I am still keen to do further local tests to see what the limit of daylight range is. At night there will be too much activity on 3560 to stand a chance.

Miracle Whip Yahoo Group

Back in 2002 I started the Miracle Whip Yahoo group for those interested in the Miracle Whip antenna and similar homebrew versions. Today the membership topped 1000 people for the first time making it one of the largest Yahoo ham groups. If you are interested in this and similar compact multi-band portable antennas feel free to join. Sometimes the topics can get quite heated.

Talk at the Huntingdonshire Club

This week I was fortunate to be asked along to the Huntingdonshire Amateur Radio Society to give my talk on Kitchen Sink Minimalist Radio. The club was excellent with lots of people attending and a real sense of "buzz" about the place. If you live in the Cambridge, Huntingdon, Ely or Peterborough area I'm sure you'll receive as warm a welcome as I did.

For those who attended and wanted copies of the presentation slides, they're now on my main www.g3xbm.co.uk website.

PS I've noticed I put up not quite the final version- I will change to the correct version when I get access to my WinXP PC.

Publish Post

uu80b micro-transceiver now on main website

www.g3xbm.co.uk now has the information on the 12 parts only micro-transceiver for 80m. I have also corrected the link to the DX cluster's new URL.

uu80b 80m Micro-transceiver - measured performance figures

Following a 2-way QSO this evening with M0BXT 2 miles away using the uu80b micro-transceiver on 3.560MHz CW I went across to his shack to measure the performance figures on a decent calibrated signal generator and spectrum analyser.

These are the results:

MDS -93dBm (comfortably copy 10uV signal)
TX Power out +28dBm (>600mW)
TX harmonics 2nd -6dBc, 3rd -15dBc i.e. poor without LPF!
TX/RX offset 400Hz (without 22pF cap fitted)

Overall, not bad for something this ultra simple.

However, it needs more TX/RX offset and needs a low pass filter. The RX is also too insensitive for serious use as it would not hear weak QRP stations on the same frequency. Nonetheless, it will allow some QSOs over very decent distances to stations >10uV in level. This evening it was copying stations in PA0, DL, YL, F and G without too much effort.

Even simpler 80m micro-transceiver!

Just finishing off breadboarding a 12 parts QRP transceiver (plus hi-Z earpiece, xtal and key) for 80m CW. The name is the uu80b.

It is crystal controlled on both RX and TX and the inspiration was the Curumim rig from PY2OHH (see earlier post). TX output is 450mW. The xtal controlled regen RX seems to be quite sensitive too. Unlike my FETer, this rig is full break-in and needs no multi-way TX/RX switching. I have already seen and heard the TX part on the on-line Twente University SDR which is 150 miles away from here in Holland. The rig uses just two 2N3904 transistors and a handful of standard parts.

Currently it is on 3.579MHz but this will be moved to 3.560 as soon as I get another crystal next week. Skeds welcomed!

Isn't ultra-simple QRP construction magic!

500kHz - OR7T in Belgium

OR7T was a new country for my SWLing on 500kHz this evening. He was calling CQ and was called by G3KEV but no QSO resulted (that I heard). Also heard tonight was M0FMT. All stations were on normal speed CW.

Is this the world's simplest transceiver?

My attention has been drawn to this circuit which is, as far as I am aware, the simplest transceiver I have ever seen that is likely to be capable of serious use. It looks like an even simpler version of the well known Pixie circuit but replacing the oscillator and PA with just an oscillator used as the TX and the mixer in a direct conversion RX.

For more information visit PY2OHH's website:
http://py2ohh.w2c.com.br/trx/curumim/curumim.htm