Clear air forward scatter optical kit

The schematics below are of the RX and TX used in the recent "over the horizon" NLOS 481THz optical tests. As you can see, not too much complexity involved considering the useful science that results. All parts are inexpensive and readily available. Nothing critical apart from the PIN photodiode and the 280000mcd red LED which I got from Hong Kong via eBay. 100mm optics used at the TX and RX ends.

The 481THz receiver

The 481THz beacon transmitter

Reverse beacon Network

7MHz QRP RBN spots this evening

The Reverse Beacon Network is an extremely useful resource. This evening, in addition to several QRP QSOs on CW, I got quite a few RBN "spots" proving just where my signal was reaching and at what strength. This is a bit like the WSPR database but for CW. As such signals have to be stronger to be copied than for WSPR but it is helpful.

More books on eBay

A couple more books have been listed on eBay this afternoon which may be of interest to readers. They are the RSGB's latest VHF/UHF handbook and the Backscatter Technical Compendium with articles from Backscatter (UK Microwave Group) from 2004-2008. The auction ends next weekend.

I have an almost complete set of SPRATs from the early 1980s to today that may be listed soon: as I have the CD, the paper copies are taking up shelf space. Paper copies are easier to thumb through though, so I may decide to keep these. We'll see.

There are a few other books and some baby clothes too if you, or your XYL, are interested. My aim is to declutter the shack as much as I can before the house move. The other books include some on disability related subjects, psychology and the Galapagos Islands (the latter is a very nice BBC book).

Last week's auction was very successful with all the books (and the fireplace surround!) finding new homes.

eBay is quite fun in small doses: I don't like to do this all the time - too much trouble packaging and labelling things and making the trip to the post office to send them off, but from time to time it is fun, especially watching the last minute rushes!

More books, including a few more obscure non radio related ones, will be listed next month.

More K1 fun

http://www.elecraft.com

Since getting my Elecraft K1 out of "hibernation" a few days ago I've had some lovely contacts with it on 40 and 20m as well as plenty of reverse beacon reports on 40, 30, 20 and 15m CW. I'd forgotten quite what a gem the K1 really is. No great DX - all the QSOs have been around Europe - but all at 5W with just the fairly basic Par 10/20/40 end-fed antenna. The receiver is lovely with signals just appearing nice and clearly, even QRP signals, out of the quiet background. This is not a synthesised rig and it sounds more like my old FT7 which had an excellent receiver.  Sensitivity is pretty good, and certainly fine for working other QRP stations around 7.030 and 14.060MHz, the QRP centres of activity.

FT817ND prices at Waters and Stanton

Looking on the Waters and Stanton website I notice they have increased the price of the FT817ND by around £30 to £565.95, despite the Yen exchange rate improving (in W&S's favour) by around 10%. I was rather hoping that the revised price might be nearer £499 i.e. downwards.

Would W&S care to comment on why the price has gone up suddenly by so much?

Perhaps there is a very good reason. To help everyone understand what I mean, see the BBC currency graph for the Yen over the last 12 months.

http://www.bbc.co.uk/news/business/

Looks to me like the UK pound buys a LOT more yen than in the summer of last year. Come on W&S, tell us what's going on.

UPDATE: I am being told the price in the USA has risen by $50 recently so maybe the rise is being driven by Yaesu? If so then they could be in trouble: falling handheld sales as a result of Chinese competition may be forcing them to squeeze for profits elsewhere? The slippery slope to niche markets and ...?

What happened to Wireless World?

When I was younger, and that was a LONG time ago back in the 1960s, Wireless World was an amazing monthly magazine: it was around 10mm thick and packed with articles and information. My old girlfriend's dad had a WW collection going back to the late 1940s and I used the excuse of looking through these to go to see her during summer holidays. Not that much reading took place on those visits!

My question was what happened to Wireless World? It was still around a few years ago in a rather sad state about one third as thick as the editions I recall in the 1960s and earlier. I presumed it has died a death as I'd not seen copies for some time in the shops.  A little more searching shows that Wireless World is now known as Electronics World and this April marks the 100th anniversary of its foundation as Wireless World back in 1913.  Can't say I've noticed copies in W.H.Smith.

Phasing direct conversion receivers

What I think is quite an old paper turned up in my browsing today: http://www.norcalqrp.org/files/austinnc2030presentation.pdf . In it, Dan Tayloe N7VE describes how a direct conversion design with phasing to cancel out the unwanted sideband can be a truly excellent receiver. I have never tried this approach myself, but think it would be worth it for, for example, a WSPR receiver where the phase accuracy has only to be maintained over a 200Hz audio bandwidth. Over such a small audio bandwidth a very simple phase shift network would work.The same applies on TX where a very simple final frequency phasing TX could produce quite good sideband suppression with very few parts.

The current G3XBM (operating) shack

G3XBM QRP shack in a bedroom corner

Thought readers might like to see what the G3XBM station consists of currently.  In the photo I have annotated most pieces. The little silvery box to the right of the SignaLink interface was a VX2 programmer (software for which crashed my PC a year ago), but this box  is to be used to house my WISPY 10m WSPR beacon transceiver. The K1 was last used yesterday and the FT817 gets almost daily use, with the very nice audio speech processor underneath. Not shown are the lightbeam kit or the LF and MF tranverters for 136 and 472kHz which are housed elsewhere close the the earth-electrode antenna feed. There are also several homebrew rigs in drawers that get brought out from time to time. For the time being, the Elecraft K1 is not being sold.

The maximum power I can run currently is around 7W from the K1 and about 12W out on 472kHz from the transverter (about 5-10mW ERP) and 30W from the 136kHz transverter (about 50uW ERP). I have no great desire to run much more power. The FT817 is only used at 2.5W or less.  

RaspberryPi WSPR TX

This means little to my software incapable brain, but may be of interest to some readers: a Raspberry Pi mini-computer used as a basic 10mW WSPR TX up to 250MHz with a suitable low pass filter on the output. I know my old colleague Bob G3WKW has done something similar. I am impressed.

See https://github.com/threeme3/WsprryPi

KW Vanguard

Alan's KW Vanguard

Memories of when first licenced were stirred this evening with an email from Alan McWhirter near Edinburgh who is restoring an old KW Vanguard (CW and AM transmitter) to working order. My first ever outings on HF were with my old G8 callsign operating under the supervision of Bill G4PJ. On a Sunday morning he would let me loose with the Vanguard and we'd work several locals on 80m and some Europeans on 40 and 20m, all on AM in 1967.

A reminder to Alan and others that most 10m AM activity is between 29 - 29.1MHz. In recent months there has been plenty of activity on AM when the band has been open across the Atlantic. Great fun.