Ultra-simple WSPR

G3XIZ has been having a lot of success on 40m WSPR recently using a 100mW DSB transmitter to generate a WSPR signal. All that is needed is an audio source (for the baseband WSPR signal), a balanced mixer and a PA. Of course, with this arrangement 3dB of power is lost in the "other" sideband which will appear outside of the WSPR sub-band. At some point - when I've got my lightbeam kit finished in January - I hope to try this arrangement on 28MHz WSPR. A very inexpensive 14.060MHz QRP frequency crystal will double to 28.120-28.130MHz so will be ideal to generate a 28MHz DSB WSPR signal at 28.1246MHz. Of course one could convert the TX into a phasing exciter and null out the other unwanted sideband. This should not be too difficult either as the phasing has only got to be good over just a 200Hz wide audio band, unlike speech which needs good phase balance over the full 300-2.4kHz band.

15kW HF PA - definitely not for a QRP man!

A friend sent me this link http://www.dc9dz.de/en/index.html which shows the design and construction of a 15kW HF PA circuit for the amateur bands based around the Eimac 4CX10000D valve. Although I have no real interest in very high power and I do not expect to hear this on the air (please no!), it is a rather elegant piece of radio engineering.

EU bureacracy threat to ham radio kit building?

The excellent Southgate Amateur Radio News site has some information which should concern amateurs who build kits. They recommend writing to your local MEP to make you views known.

"Thilo DL9KCE, reports a threat to amateur radio kits and modified equipment arising from changes to the EMC directive.  Currently amateur radio kits and modified equipment are specifically excluded from the directive but under the proposed changes they would be fully subjected to the EMC directive. The resulting high compliance costs could make it uneconomic to develop and sell kits so killing off the kit market. If radio amateurs wished to modify equipment it appears they would also incur additional costs and bureaucratic hassle."

The aim of the EU as a common market for trade is sensible but, like many here in the UK, I abhor it when the bureaucrats in Brussels start to interfere and try to fix things that are not broken. I don't want to get into a debate here about the merits of the Euro, but do feel that 2012 will be a year in which the citizens of Europe, and that includes the UK, will face some very tough decisions.

Waters and Stanton - wake up guys!

Today, having still received no feedback from Waters and Stanton about my emailed question on the FT-450D TX hum (has Yaesu fixed it yet?), I decided to ring them up, check prices and ask the question directly. To my amazement the sales person said, "I have never heard of the TX hum problem". Well, he can't be too well in touch with the market and customers then.

I also asked what was the best price for the rig ("same as in the magazines, no deals") and then asked if they still had the 3 year warranty running. "What 3 year warranty? I've never heard of that." I pointed him in the direction of several recent RadCom and Practical Wireless adverts.

In summary, I was NOT impressed with the responses, or rather lack of them, from this well known UK supplier. At a time when business near Christmas is tight surely it is important that sales staff  know about the product and can answer questions as simple as "what is the length of the warranty?".

Unless this supplier wakes up a bit I think I will defer my decision about purchasing the FT-450D.

Incidentally, they did say that Yaesu would be at Hockley this weekend for the W&S open day. I expect people going will ask about the TX hum question directly. And I wonder if there will be any news about the FT817's replacement?

Simple speech processing

Recently Peter Thornton G6NGR sent me a number of example circuits for speech processors, some dating back to the 1960s. Anyone who operates QRP SSB on HF or VHF will appreciate how important "punchy audio" is when running low power. One circuit I remember working extremely well was one based on an idea by John Hay G3TDZ. Back in the 1970s I was using 100mW AM on 2m and wanted to be heard across Cambridgeshire. My audio stage consisted of a couple of pre-emphasis stages followed by a hard audio clipper and a low pass active filter. The result was an amazingly punchy signal with barely any change in audio level when talking. The 12dB/octave pre-emphasis helped to ensure that clipping of LF signals did not result in many artifacts within the audio passband. The LPF was essential because the heavy clipping  results in many audio harmonics which would otherwise result in a broadened signal. With just 100mW and a dipole the QRP AM signal was excellent copy across the county. I keep meaning to try the same circuit (if I can remember it) with the FT817. It would produce a mighty punchy QRP signal!

KX3 release date

The Elecraft KX3 10W QRP transceiver is edging slowly towards formal release for orders. There is an enormous pent up demand for this 0.1- 10W QRP full featured HF/6m radio. Elecraft are still expecting to be able to announce that orders can be placed by the end of December with first products reaching customers in Feb 2012. I am still unsure if this is a possible candidate for my replacement to the IC703.

FT-450D hum?

Although usually/mostly a QRP operator, I've been considering an update to my main station transceiver since selling my 10W IC703 to a local friend. One possible candidate rig is the 5-100W Yaesu FT-450D. It is getting very good reviews with excellent comments on its  receiver features. For a "full feature" HF/6m radio it is good value for money.

But, I am bothered about one thing: many reviews and comments on the FT-450D Yahoo group confirm a design issue with TX hum, believed to eminate from the poor grounding of the display unit. Nothing I've seen or heard has convinced me this widely reported issue has yet been properly fixed by Yaesu. This is not a problem with the display set to its brightest setting, but should one pay around £800 for a radio with a fundamental design issue not solved in a recent upgrade? No.  A question to Waters and Stanton asking if Yaesu has fixed it has not received a reply yet after 2 days: I suspect they don't want to say "no". I have said that if it hums it would be returned.  So, until I hear the problem has been resolved my "buy" decision is on hold. I am in no great hurry.

More optical comms tests

A few days ago I received some 10000mcd 5mm "high brightness" Toshiba TLSH180P LEDs from Maplins.  Today I did some tests without optics using these. Still using just my NE555 1kHz oscillator output directly driving the LED the signal is considerably brighter. It should be some 10dB better than the high brightness LED used before. Using the Toshiba LED both as TX and (unbiased) RX detector the signal could be detected over a range of around 20m in daylight. The beamwidth of the LEDs is narrower (8 degrees) so aiming is quite critical. Further may well be possible with very careful beam alignment.

So, with 100mm lenses at each end (24dB minimum gain each) 5km should be possible and maybe up to 20km.  Progress on the full FM/SSB systems has slowed as Christmas approaches with other activities taking priorities in the family, but the 481THz work is my main priority ham radio-wise.

You Kits SSB transceivers

For some reason I have missed the news that YouKits are producing (or about to) 2 band and 4 band HF SSB/CW transceiver kits at very reasonable prices. See http://www.youkits.com/ . One is a backpack and one a handheld. Quite interesting. See TJ2A and TJ4A code numbers on their website.

Micropower generation/power harvesting

Linear Technology lists the LTC3108, an Ultralow Voltage Step-Up Converter and Power Manager than runs with an input of just 20mV producing a 5V output to power things such as low power wireless devices and processors. Surely there must be an application for such a device in ultra-QRP portable equipment? Imagine, where can you find 20-500mV of noise from? 50Hz crud in the ground, a thermo electric sensor, solar cells etc. I wonder who will be the first person to make a QRPp uW beacon powered using the 50/60Hz buzz available between a couple of earth electrodes in the ground?