Tenbox 10m AM RX video

It is hard to contain my enthusiasm for simple transceivers and super-regen receivers! This video shows just how well the RX breadboard for the little Tenbox 10m AM transceiver works. 1uV (-107dBm) is a very good signal and it will still detect a well modulated AM signal at -120dBm. Selectivity is not good with this type of receiver, which is the main drawback. However for its intended application - a simple transceiver for local nattering across town - it should be fine. Some people use super-regens as the IF stage of AM receivers. If a filter is added ahead of the super-regen IF this overcomes the selectivity issue but makes the RX design more complicated.

Tenbox 10m AM rig - a bit more

Although I had little time today, I experimented with adding varicap tuning to the Tenbox AM transceiver's RX section. Only problem was I had no varicaps, so tried using a few different diodes and a transistor as a varicap. 1N4148 and a Germanium diode reverse biased hardly produced any change in capacitance going from 2-12V. I know a 1N4007 works quite well but could not find one. Then I used a 2N3904's base-collector junction and got a few pF of change. In the end I just did as I did in the Sixbox and used a fixed capacitor in series with a 365pF polyvaricon tuning capacitor. This moves the RX frequency as much as I need at around 2MHz maximum.

2 countries worked on 500kHz with JT9-1 mode

Well, the JT9-1 test QSO with G3ZJO was a total success and completed in around 10 minutes this evening. Later, I called CQ on JT9-1 and got a reply from OR7T in Belgium who is 334km away. We worked, exchanging reports and 73s but I am not quite "all with it" with the sequencing of reports, R, RRR etc in JT mode exchanges.I am learning, HI.

G3ZJO in QSO with G3XBM this evening on 500kHz

The WSJT digital mode JT9-x is certainly an interesting mode. There are a few bugs in the code still, and more bugs in the operator using it (me!) but I am sure to use this mode more in future on 472kHz and 136kHz.

500kHz JT9-1 test this evening

G3ZJO and I have reported each other's 500kHz WSPR signals and each managed to get reports from close on 1800km away but, despite being only 50km or so apart we have yet to work each other on MF. This evening we are going to attempt a WSJT mode QSO using JT9-1 mode with 1 minute TX periods. I'll report back later how we get on!

More Chromebooks

The new Acer C7 Chromebook on the
www.cnet.com site

A few weeks ago I mentioned the Samsung Series 3 Chromebook which is available in the UK for £229. Now I see there is a new entry, the Acer C7 Chromebook which retails for just £199 here and $199 in the USA. This sports a 320GB hard drive and, like the Samsung, a high resolution 11.6 inch display.

The main drawback (or is it an advantage?) of a Chromebook is that it uses the Chrome OS and depends a lot on cloud based applications, although quite a lot of applications work off-line too these days.

Certainly for a second PC at home and on the move it has to be a good bet.

472kHz WSPR this evening

After the CW QSO and 500kHz WSPR TXing this evening I switched over to 474.2kHz USB dial WSPR receiving, whilst I watched "Homeland" on TV (BTW, this is a truly excellent US drama series - I don't usually like US dramas). Good signals coming through from the usual suspects, HI. The weaker signal at the bottom of the image is DF2JP.

474.2kHz WSPR this evening

It sounds like the first UK access to the 472-479kHz band will be for old 500kHz NoV holders, which includes me, on Jan 1st 2013. It is NOT likely the band will be generally available in the UK at that time, but some time later. Even the 500kHz NoV holder access to the new band is not yet certain on Jan 1st 2013. Watch this space!

CW QSO with M0FMT on 500kHz this evening

After the usual reports from all over the place on my 50mW ERP 500kHz WSPR I took a listen around for some CW stations this evening. G3XIZ was calling CQ and listening on 80m crossband, but then I heard Pete M0FMT not too far away in Hitchin calling CQ. He heard my reply and gave me 529 report. He was about 549 with me deep in the noise that remains on the band. A few days ago this QSO would have been impossible because of the local noise here. The offending noise source (central heating controller SMPSU) is switched off!

Barbados on 10m QRP

8P6BX in Barbados

Whilst looking for QSOs with Lesser Chirpy on 28.060MHz this afternoon I heard Ron 8P6BX in Barbados calling CQ. No go with 70mW so I turned on the FT817 and worked him with 5W getting a 569 report. He was running 3W and was peaking 589 with me. It was a nice, solid 2-way QRP QSO on CW.

Autumn projects - an update

Well, I don't seem to be getting on too well with my autumn project list! The 472kHz transverter got finished, as did the WSPR beacon rig for 10m. I also managed some VLF earth-mode work. However, I've still to get back to the 481THz (lightbeam) over-the-horizon tests using the new higher power Phlatlight 5W LEDs. Neither have I rebuilt my 10m halo or erected a proper RX antenna for LF and MF. Mind you, I've added a new project, the Tenbox 10m AM transceiver, which is progressing quite well so far.  In the end it doesn't matter what gets done and when as long as I'm enjoying the hobby and experimenting with simple ideas.

Burwell Steven's Mill © Copyright Rodney Burton and licensed for reuse under this Creative Commons Licence.

Around the middle of 2013, if things go to plan, we are moving home to a bungalow in the same village which is located on the "hill" (this is a relative term in East Anglia!) next to Burwell windmill and museum. The windmill has just received a National Lottery grant and should be fully restored to full working order with 4 sails. This will be about 20m from our front door! I'll expect to be asked to do a "windmills on the air" weekend, HI. Burwell Museum is really something quite special and well worth a visit.

With what will be a much better VHF and UHF take-off I will be tempted to get much more active DXing on 2m, 70cm and 23cm from the new QTH. This is likely to bring a whole new set of challenges.

Lesser Chirpy spans the Atlantic (10m QRP)

My 28.060MHz ultra-simple QRP transceiver was copied in the USA this afternoon. K3MM (Maryland) reported me on the Reverse Beacon Network as 7dB S/N at 15wpm on 28.060MHz. K3MM is in FM19JH which is 5886km away.

Initially I was unable to hear any stateside stations to call for a QSO. Still, the rig has now been copied across that big ocean! Power out into the halo is around 70mW.

VE2TH was coming through OK with 5W and might have been workable but the band faded out.