Author Archive
Tenner 10m CW transceiver
February 15th, 2015 | 
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The Tenner is a very simple CW rig for 10m. It produces about 500mW output and has worked across the Atlantic on many occasions. Offset RX-TX seems to work out at about right, although no special circuitry is employed. This simple circuit just works. Although I used an “at hand” SBL1, any double balanced mixer is likely to be OK. Although I did not try it, a homebrew DBM would be fine.
Pixie kit from China
My low cost 40m Pixie kit – although G1KQH only paid about 60% of what I paid – is on its way from China but has not yet arrived here. I assume, with free shipping, this comes by sea. I am in no great hurry. As I mentioned before, I very much hope to build this unit as I have not built much in ages because of my brain bleed.
UPDATE 1600z: My kit arrived in the post today. Still to open the package, but judging by the speed this must have come by air. It looks well packed.
Digital experiments
In all my time in amateur radio I have never once experimented with microprocessor programming and I have done very little “digital” design. This seems to be a gap in my knowledge, although I am still not really interested, preferring RF design, especially QRP. I must say I remain very impressed with Wolf’s (W5OLF) tiny WSPR-AXE-CW beacon: this goes to show just how much can be achieved with so little physically. Maybe this is a whole area I should embrace? The trouble is it is impossible to be an expert at lots of things, unless you are very bright. Certainly I do not consider myself a polymath!
Falling sunspots?
Sunspot number today has fallen to 50, the lowest for quite a while and 10m propagation is forecast to be “fair” again.
Yesterday, 10m did open for me to the USA and plenty of stateside stations copied my 500mW beacon in the end after a late start. I suspect today it may be harder going as we seem, on average, to now be on the downward slope towards the next minimum, although this is years away. If predictions of the next maximum are to be believed, a SN of 50 would be considered a decent figure for the next sunspot peak! Of course, the predictions could be wrong, although the predictions have improved a lot and most got cycle 24 pretty accurately.
I have not yet turned on the 10m beacon this morning as we have visitors. It will probably be turned on just before lunch. I am still on MF but there are few active stations in range.
Narrow Band TV (NBTV)
Partly because bandwidths are very low, there has been a revival of interest in NBTV systems similar to the early TV transmissions by Baird in the 1920s and 1930s.
There is even a Televisor kit available for about £40 delivered (in the UK) with a CD with some still and moving images and its own test card generator. I am quite tempted!
The televisor kit is available for £35.94 + shipping from http://www.mindsetsonline.co.uk/Site/Home (search for televisor). This is compatible with the 32 line standard of the NBTV Association. The NBTV Association home page is at http://www.nbtv.wyenet.co.uk/index.htm .
Bandwidths are audio only, so a tape recorder or CD are fine. Over the air transmissions only require audio bandwidths too. Of course, with just 32 lines don’t expect brilliant images!
Motorola for sale?
Is the end in sight for Motorola?
When I was at work (I retired 7 years ago) Motorola was our greatest rival. Since coming into existence in the early years of this century, my own company Sepura has been in profit every year. The demise of Motorola is a salutary lesson never to be complacent. How the mighty have fallen.
VHF AM and the RSGB
Recently, I wrote to the “Last Words” column in Radcom. I very much doubt my letter will be published. The main thrust of the letter is the (very negative) attitude of the RSGB to the AM mode.
My letter (as sent) is reproduced here. I’d be interested to hear your views.
At the present time G6ALB is experimenting with very low cost 70cms AM modules as the heart of a possible short range (3km) voice transceiver. We have had some success already.
“Thank you for publishing the latest Band Plans in the February 2015 RadCom. Although because of my poor voice (stroke) I tend to use digital techniques, I still enjoy the occasional outing using AM. Like many, I have worked transatlantic AMers on 29-29.1MHz with real QRP and simple antennas.
Yet again, one could be forgiven for thinking AM, especially 28MHz and up, is a dirty word at the RSGB. AM gets no mention on 28MHz and 50MHz and gets a (begrudging?) comment as a footnote only in the 144MHz Band Plan when other modes get “centres of activity” mentions. For the avoidance of any doubt, AM is alive and well in the 29-29.1MHz sub-band. AM on the 144MHz (2m) band can be found on and around 144.550MHz. There has been AM on 29-29.1MHz for years and years and years! Yes, this is the all-mode section, but why not say this is the 28MHz (10m) AM sub-band? Also, why are 144MHz AM users asked to “consider adjacent channel activity”? AM should easily fit in 6kHz!!
Sorry, yet again, AM is being treated as a dirty and outdated mode. May I remind readers that ex-PMR AM rigs ripe for use on VHF can be picked up for virtually nothing and that there is room for AM on all bands from 28MHz upwards. AM has its enthusiasts on other bands too, but yet again the RSGB seems hell bent on killing off this mode. Why?
73s
Roger Lapthorn G3XBM”
