Optical receiver head completed

481THz optical receiver with 100mm lens

I now have a 100mm lens set-up in some grey drainpipe with 4x sighting scope attached on a tripod together with a "simplified version 3" KA7OEI head (of sorts) with a BPW34 detector. In my version the cascode stage is just followed by a single common emitter stage driving a crystal earpiece, although I intend to add an emitter follower so I can connect to my PC (to use with Spectran/SDR) or a transverter.

A 5mm 20 degree red LEDusing just its own built-in lens was shone out of the stairway window aiming down the street in daylight with 1kHz modulation. It was taking around 20mA. I then walked with the kit to the far end of the street and the signal was solid (S9) in the RX earpiece at a distance of about 0.25km. I now need to find a more distant test range and see how far this can achieve. Depending on results I hope to go looking for GB3CAM next week.

Lightbeam receiver progress

Today I did the part of projects I hate most - drilling holes in aluminum boxes. I can never find the right size drill bits, they are blunt and so on. Despite all this, I managed to get a small metal box complete with BNC socket, phone jack and switch mounted on the end of my optics pipe and carried out some first tentative tests. I am using part of a simplified version 3 KA7OEI optical head based around a BPW34 PIN photo diode. In my case there are no op-amps with discrete transistors used for the amplifiers and buffers following the FET cascode stage.

In the next day or so I want to add the sighting scope and find a way of attaching the whole optical unit onto a stable tripod. At this point and can try some more serious tests for example looking for my own 1kHz beacon at greater distance and, hopefully, GB3CAM at 22km if the system works OK.

The output of the head can feed either a crystal earpiece (to listen to the baseband tones or speech received) or into a PC so that it can be used with an SDR to copy various modes up to around 22kHz.

Winter project list

In this first post of 2012 I thought I'd list the projects that are "on the to-do list" for the coming few months. As always, this is subject to change without notice as my interest and enthusiasm goes through waves:

1. Lightbeam RX. The aim is to detect the GB3CAM 481THz optical beacon at a distance of 22km from my nearest highspot. So far I have breadboarded several good sensitivity optical detector heads and the next stage is to complete the packaging of this into a screened box and attach it to my optics which also need a bit of engineering to complete. Target is this to be completed next week.
2. Light beam transceiver. Following on from (1), this will either be a transceive head with a transverter or an FM transceiver that I can duplicate so I can talk to others who can borrow the second unit.
3. Rebuilt VLF earth mode beacon transmitter. In a few weeks time I will be able to put out a stable signal on 8.97kHz  (the usual VLF test frequency) rather than 8.76kHz. My intention is to rebuild the whole beacon TX so I can run 10wpm CW, QRSS3, 30 and 60 modes as well as WSPR. I may also add a 100W PA option later. With this kit I hope to improve my personal earth mode DX record of 6km.
4. Improved LF loop and E-field probe antennas. I want to erect a more permanent external antenna for VLF and LF grabber work and mount these away from the house. Up to now I have used my 80m square vertical loop on RX but this is currently down.
5. Case up the 137kHz transverter. This has been a rat's nest on a piece of copper laminate for too long!
6. 28MHz WSPR transceiver based on a 14.060MHz crystal doubled in a DSB direct conversion transceiver circuit.

Now, how many of these projects get done is a matter of conjecture, but I hope at least 50% of them will get finished.

Happy New Year

A very happy New Year to all readers of this blog.

2012 should bring us even better HF conditions as we approach the peak of Cycle 24. With luck and hard work we may get a new MF band around 480kHz. As ever, there are challenges from VLF to light beams to be enjoyed and I hope you have as much fun with our hobby as I shall.

My priority once the Christmas holiday is over is to complete my 481THz lightbeam transceivers and test these locally. Further projects will be to improve my VLF earth mode DX and to set up a lower noise VLF grabber in anticipation of more activity in the months ahead. In addition I shall continue with QRP WSPR and QRP operation mainly on 10m and 6m.

Netherlands on 500kHz and 70MHz

Some good news: amateurs in The Netherlands now have access to the 500kHz band (again) and 70-70.5MHz (4m).  Countries permitting 4m operation are growing every few months. Let's hope one of the major equipment manufacturers includes the band in multimode HF-6m rigs. Adding 4m cannot be too hard.

Elecraft KX3 can now be ordered

On Dec 27th 2011 Elecraft announced that their new QRP radio can now be ordered with deliveries starting in about 8-9 weeks time. As a QRP radio the KX3 is likely to be "best in class" with some excellent features, but it is not low cost when loaded with options and imported into the UK after VAT and any duty is paid. See the KX3 page for more details.

The basic KX3 includes:

   * 10 watts output typical (13.8V) on 160-6 meters. (Up to 5W using internal batteries)
   * All modes (SSB, CW, Data, FM, AM)
   * Many features from the Elecraft K3, including the same full-size LCD
   * Advanced DSP features, including PSK31 and RTTY text display, noise reduction, auto-notch
   * Built-in 8-AA-cell battery holder
   * USB serial cable for firmware upgrades and for use with logging/contesting software

Available options include:

   * KXPD3 precision attached keyer paddle
   * KXFL3 dual-bandwidth roofing filter module for SSB/CW/Data modes
   * KXAT3 internal wide-range automatic antenna tuner
   * KXBC3 internal NiMH battery charger
   * MH3 hand mic with UP/DN VFO controls
   * RS232 control cable (optional replacement for supplied USB cable)

Although I certainly covet this little radio, I have not decided if I can justify the purchase, or indeed afford it!

Happy Christmas

To everyone that reads this blog from time to time, may I wish you and your friends and families a very happy and peaceful Christmas. It is a time to both give and receive love and kindness - enjoy it.

Shortwave broadcast QSLs

Talking about QSL cards makes me think of my very first QSL cards received back in the 1960s. In those days I used the ISWL QSL bureau which handled broadcast band QSLs (I think it still does) and well remember the thrill when I got my very first cards. The first ever QSL was from Radio Nederland and it was an exciting moment. Somewhere I still have that red card with a windmill on!

In the subsequent years I did a fair bit of QSLing when using just my shortwave crystal set and got a few cards back from these reports. I heard stations all over the globe using that simple crystal set with best DX being Radio Havana Cuba, All India Radio and even Radio Australia, all direct and not via any relays. Not bad for just a tuned circuit, a diode a resistor and a crystal earpiece. I must have another go at a shortwave crystal set just for fun, especially as HF conditions are so good now, but these days shortwave broadcasting is not what it was. Using a decent toroid and a bridge detector it should be possible to arrive at a sensitive design with quite good selectivity.

WSPR QSL cards?

Just been having an interesting debate on Facebook about someone requesting an eQSL for an exchange of WSPR reports. Some would argue that, simply exchanging reports via the WSPR database does not constitute a "real" QSO, so a QSL is not appropriate. Indeed, some would say the WSPR database report is itself a confirmation of the report (which it is) so what is the point of a QSL card? On HF contests it is VERY common for only one callsign to be heard in reports such as, "G3XBM 599233 TU" yet such exchanges are used for DXCC credits if a QSL card is sent following such a "contact".

Personally I would eQSL a full 2-way exchange of WSPR data if done within, say 10 minutes, on any given band and consider this valid. I will only do this in response to one received. Others may violently disagree!

Quartz crystal suppliers in the UK

Recently I wanted to buy a couple of non-standard crystals for a VLF project with the crystal divided down using a 4060 divider. After asking other people for advice it looks like Quartslab can provide the service.  Individual crystals range from around £12-14 depending on frequency and type.

This is not cheap, but at least they can offer the low quantity service. There is a minimum order charge of £22.29,  so I will probably order a couple of crystals for 4.59264MHz to give me a stable signal on 8.970kHz when divided by 512.  The company contact is Dave Hayes G4AKY 020 7100 6357.