Simple VLF Receiver

SM6LKM's excellent PC based VLF receiver

In testing my Chirpy 10m transceiver, I used the simple PC based VLF receiver by SM6LKM as a bolt-on SDR. This little VLF receiver works very well as a stand-alone VLF receiver that tunes the 0-22kHz frequency range. Simply by sliding the cursor to any frequency it produces an audible signal just as you would get by tuning a conventional receiver.  Bandwidths are adjustable down to around 300Hz. For my video showing this in action listening to VLF signals (via my loop and small preamp) see http://www.youtube.com/watch?v=TDxRhQYg7lQ. With the SM6LKM VLF receiver you can clearly hear the Omega beacons around 11-14kHz, SAQ when transmitting on 17.2kHz, and various MSK military signals around 18-22kHz. It has also proved useful when carrying out earth-mode (through the ground) VLF communication tests.

A good night on 500kHz WSPR

Not bad for 2mW ERP on 500kHz and a smallish wire loop antenna!

Very good activity levels again this evening on 500kHz WSPR with 13 unique stations reporting my signal in 6 countries. Best DX report was from OH1LSQ at 1733km, the first time this season.

I really must make an effort to get the 137kHz WSPR activity stirring. Maybe if I can get my ERP up this next week I'll swap over to that band for a few nights and see what turns up. Mind you, the WSPR activity on 137kHz is very low currently with most people using QRSS beaconing.

The "Chirpy" 14 parts QRP 10m transceiver video

This is a short video showing "Chirpy" (XBM10-2), my 14 component 28MHz CW transceiver. More details can be found at my website http://sites.google.com/site/g3xbmqrp/Home/xbm10_2.  Best DX is still IT9QAU/QRP but I am hoping for further soon. This is a simple project and, as with all very simple radio projects, it is a compromise between cost, complexity and performance. Nonetheless it DOES work remarkably well for something so simple. AM breakthrough is almost non-existent too, which was a bonus. Couple the audio into a PC rather than a crystal earpiece and  as a bonus you have an SDR receiver capable of copying from about 28.040-28.080kHz. Why the name Chirpy will be evident when you hear the keying!

Elecraft KX3 or FT817 successor?

For some time now we've been expecting the successor to the FT817 to appear on the market as the current offering is now over 10 years old, with just a minor update in this period. Sunspots are rising fast now and I'd expect Yaesu-Vertex to release this within 6 months or miss a big window of opportunity.  The potential sales volumes are very large indeed as a large part of the amateur community owns an FT817 and would aspire to upgrade.

One wonders how Yaesu-Vertex is viewing the Elecraft KX3 and whether any changes to their new product will be made as a result of the KX3 pre-release data. The KX3 does look impressive but its form factor may not appeal to many. It also looks very "square" and Elecrafty! Although it can be used handheld, I understand you have to plug in a local microphone for example - a bit clunky for true handheld portable use, although you need an external mic with the FT817.

It is widely assumed that an FT817 successor will have a Li-Ion battery pack (2hr charge), built-in wide range auto ATU, good DSP features and possibly 70MHz coverage. The form factor is unlikely to be very much different from the current model, but with more inside.

Does anyone have any inside knowledge of Yaesu's release plans? If they don't get a move on the KX3 will steal the show. The KX3 is due to be released at the end of 2011 and order placement is starting very soon.

500kHz humming tonight

WSPR reception at G3XBM tonight - busy on 500kHz!

This evening the 500kHz band is VERY busy with lots of stations on WSPR.  At the moment there are over 20 active stations with 7 stations TXing.  EI0CF and G4WGT are being copied in Russia at over 2500km despite low ERPs.  My own 2mW ERP signal managed to be detected by GM4SLV (896km) and by many others in the UK and Holland.

Another 10m QRP transceiver built

Yesterday I built another simple 10m CW QRP transceiver. This is similar to the Tenner on my website with some improvements. This time the power out is QRO (well 600mW!) and the receiver a direct conversion one built around an SBL1 with passive LP audio filter and 3 stages of audio gain. The VXO, run from a regulated 5V supply, uses a fundamental 28.060MHz crystal which pulls from 28.040-28.070MHz with a sensible RX-TX offset (happens automatically) of around 800-1000Hz. Chirp is better than the simple XBM10-2 as the VXO is better regulated and the PA is a separate stage. Yesterday I worked RZ3QZ before the RX was finished and got reports on the reverse beacon network from W3OA. This morning a full 2-way QSO with UR5IDU (him 579 me 549).

UPDATE 1520z Nov 5th: This rig is working very well with 7 two-way QSOs on 10m CW in the log already since 1140z today. There is a Russian contest and the band is busy with Russian stations. Reports are all 599 of course but no repeats needed so far.

Chirpy (XBM10-2) improvements

28MHz "Chirpy" Transceiver with tuned antenna match

In the last day I  have made some changes to my ultra-simple CW transceiver for 28MHz. Power output now is around 120mW (was 60mW) and the RX sensitivity about 3-4dB better. Both changes are a result of better matching the tank of the oscillator/mixer to 50 ohms using a tuned circuit with a suitable tap rather than a 100uH choke. At the moment the component count is 14 total (excluding crystal earpiece and key). although this could be reduced to 12 if a suitable single component inductor/capacitor with link winding was substituted for the only tuned circuit. The receiver is working and I copied an SV station and K1TG on 28MHz just now. The TX still chirps though. Now I am looking for some further 2-way QSOs (3 so far with best DX IT9QAU/QRP at 1414kms).

500kHz WSPR

Yesterday I fired up the 500kHz WSPR kit (2mW ERP from the loop antenna) for the first time in several months and was pleased with the reports and level of activity. Several people joined in the fun and some new stations are now monitoring and reporting on the band. I want to get my 137kHz WSPR kit sorted this week with around 25W RF and maybe 0.5mW ERP if I am lucky.

Sunspots update

As the days go by this autumn, the sunspot numbers continue to climb progressively and I am beginning to think we may be in for a decent cycle 24 peak after all. Certainly HF conditions have been excellent recently with MUFs up to 40MHz at times.  28MHz has been as good as I ever remember it in the last few weeks.

Have there been any recent revisions of the sunspot predictions for the next 12-24 months? If so, I would expect these to be upwards.

CQWW: update on 10m operation

After a few hours of intermittent QRP operation I've plenty of QSOs in the log, many when using just 500mW pep into my halo antenna. Stations have been worked with QRP in 5 continents on 28MHz SSB already. The band is almost filled with stations in a way that I've not heard since the last sunspot peak. If you want to work some QRP SSB DX on the HF bands, especially on 10m, then this weekend is your opportunity.