136khz transverter

I'm getting ideas, and parts, together to allow me to build a small transverter for 136kHz. For the TX low pass filter I'll use either T68-2 or T157-2 (or something on between) toroids as these seem most suitable at up to 30W.  For the RX input tuned circuit I still need to find a suitable inductor, preferably tunable. Any ideas?

Further 136kHz earth electrode tests

Later today I hope to do some more tests on 136kHz using 250mW QRP to the earth electrode "antenna". Last night I went out to look for the QRSS3 signal locally but realised the battery in my E-field probe was flat, so heard and saw nothing!  I expect to see the signal to well beyond 5km.

UPDATE: Well a repeat of the test on July 19th gave less encouraging results. Reasonable copy on QRSS3 at 1.5km but no copy visible at the same spot 4.6km away from the QTH (within 20m). Not sure what has changed as the earth electrodes are the same. Maybe the soil is slightly more damp?

PW author Gordon King G4VFV now silent key

Practical Wireless author Gordon King G4VFV died yesterday from stomach cancer. Gordon wrote many radio and TV related books and contributed regularly to PW. He lived in Brixham, Devon.

Parts from Farnell - good service

For the first time I ordered parts from Farnell on-line yesterday. In the order were some 3C90 toroids (16mm and 42mm) to use in my 136kHz transverter.  I cannot fault the service: parts were here the next morning with free delivery. Just remember the prices on the internet are shown less VAT. For on-line orders there is no minimum order quantity.

4.6kms with earth electrode "antenna" and 250mW on 136kHz

Today I tried some more experiments with my 20m spaced earth electrode "antenna" and small QRP beacon TX on 136kHz. I switched over to QRSS3 and  used the FT817, E-field probe and PC with Spectran to see where copy stopped. 1.5km from home and solid copy on QRSS3 when holding the E-field probe box as high as possible above the car roof. Then I drove on to a spot 4.6km from home and copy was again achieved, albeit not as strongly.  I'm certainly getting a signal radiated beyond the near field.  I'd like to check "antenna" directionality by looking for signal levels with the QRSS3 beacon at all compass points some 4-5kms away from the QTH.

In the meantime, if anyone near Burwell, Cambs wants to look for the QRSS3 signal near 136.93kHz I'll leave it running until about 8pm tonight when I have to switch off as my grandson is sleeping in the shack bedroom. Any reports would be amazing.

Simple 136kHz beacon TX

Francis F6HSI very kindly sent me a "divide by 26" module based on a small micro-controller. With this I've built a small beacon transmitter for 136kHz (QRSS3 or 10wpm CW) by dividing down from 3560kHz, the QRP calling frequency on 80m. At the moment it only puts out 250mW and, with the earth electrode "antenna" used, the ERP probably considerably below 1uW.


Using my 20m spaced earth electrode "antenna" on TX and with a PA0RDT designed active antenna with a 19 inch whip antenna feeding into the (deaf) FT817 I could copy the 10wpm CW at 0.4km across the fields.

New VLF DX record today: 5.6km on 838Hz earth mode

Today I resumed my VLF earth mode tests using 4W into 20m spaced earth electrodes. The aim of the test today was to determine the absolute maximum range possible by utilities assisted earth mode. Best result was 5.6km along Commissioner's Fen to the west of Burwell. Signals were just copied at this distance using the 80cm 30 turn loop and preamp into the PC running Spectran. A test a 6km resulted in no detectable signal.

An amateur solar plane "satellite"?

Recently, Qinetic managed to keep a solar power plane aloft for 7 days using its onboard navigation to keep it over a fixed location and using solar cells to top up batteries to keep it flying at night. Could such solar powered flying devices could be used as "satellites" flying a few miles above the earth to support amateur VHF/UHF repeaters and experiments i.e. a more sophisticated version of balloon experiments?  See http://www.bbc.co.uk/news/science-environment-10664362 .

More 8.97kHz operation from Germany

Just seen this post on the LF reflector from Horst DO1KHS/DI2AN :

"As you know I am planning tests on Dreamers Band from 24. July 2010 on our fieldday at Erpeler Ley, JO30ON.  I will install a 800m earth base. Possibly there is a chance for me to leave the near field. So watch out for my signal.  Beside that there is much space for near field test. So I can compare my vertical antenna with the tv transformer to the big earth base. I will be online there via UMTS so I can give you the details here in the reflector."

So, some further 8.97kHz operation from Germany next week. More details of power, mode etc expected next week but he is expecting to run 100W with QRSS600 and plain carrier.

70MHz, Icom and Yaesu

There are now approaching 40 DXCC countries granting access to the 70MHz (4m) band and further countries are granting access every few months it appears. See  http://www.70mhz.org/bands.htm.  I do hope that some of the commercial "big boys" such as Yaesu and Icom start to make VHF multimode rigs that include 4m in future. It can't be too difficult to add this band. Apart from the latest ChineseWouxun FM handportables (see  www.wouxun.co.uk) and ex-PMR units, only the FT847 has 70MHz coverage. Imagine how operation on 4m SSB/CW would take off if Yaesu's FT817 successor has 4m coverage as well.