2696km on 10GHz - new record

A new DX record for terrestrial (non EME) communication has been set with a QSO between D44 and CT on July 10th over an incredible 2696km. See http://www.hyperatlantica.ch/ for more information.

136kHz with QRP and earth electrode antenna

Today I increased the power from my QRSS3 136.93kHz beacon to 2W out of the PA into the 20m spaced earth electrodes. Another "ride about" test locally with the deaf FT817 and E-field probe RX antenna gave the following results:

At 2.4km good copy on the Spectran display

At 4.6km clear copy on the Spectran display.

At 8.6km the signal was detectable, but weak (see picture attached from Spectran screen).

These reports are roughly "end on" to the electrodes and I've yet to try other directions such as orthogonal to them. No attempt was made to match the PA output to the impedance presented by the earth electrodes which are around 40-60 ohms below 10kHz; I've not measured it at 136kHz yet.

Even with true QRP it looks like a range of at least 10km should be possible on QRSS3 (and probably WSPR) with a half decent receiver (better than my crude set-up) using just a 20m earth electrode TX antenna on 136kHz.  I'll leave the QRSS3 beacon running over the weekend on 136.93kHz from my QTH in Burwell, Cambs (JO02dg) and any reports and screen shots would be much appreciated.

Class E MOSFET PA for 136kHz

I'm trying to optimise an IRF510 MOSFET PA for use in the 136kHz beacon and later transverter design. Alan Melia G3NYK has a very useful page on practical approaches to class E designs for 136kHz at his page http://www.alan.melia.btinternet.co.uk/classepa.htm together with a useful Excel worksheet to come up with practical values for the output network. Class E using square wave drive on the input can produce very good efficiencies, thereby reducing heatsink requirements.

136kHz PA progress

Today I started to modify my 136kHz QRP beacon to increase the power from 250mW to around 5W using an IRF510 MOSFET PA. I've still work to do to optimise the design but hope to complete this tomorrow.

More on time travel

A rather long, but fascinating article on the possibilities and issues with time travel is on Wikipedia.

Quantum time machine?

Researchers at MIT may have come up with a way of travelling through time (and space) using quantum closed timeline curves or CTCs. It has always fascinated me that in quantum mechanics one can describe things as wave functions that have existed in all space and all time, past present and future. It takes a leap of imagination to consider the possibilities. For an explanation see http://www.telegraph.co.uk/science/7904712/Quantum-time-machine-allows-paradox-free-time-travel.html

This is the abstract of the original MIT paper:

"This paper discusses the quantum mechanics of closed timelike curves (CTC) and of other potential methods for time travel. We analyze a specific proposal for such quantum time travel, the quantum description of CTCs based on post-selected teleportation (P-CTCs). We compare the theory of P-CTCs to previously proposed quantum theories of time travel: the theory is physically inequivalent to Deutsch's theory of CTCs, but it is consistent with path-integral approaches (which are the best suited for analyzing quantum field theory in curved spacetime). We derive the dynamical equations that a chronology-respecting system interacting with a CTC will experience. We discuss the possibility of time travel in the absence of general relativistic closed timelike curves, and investigate the implications of P-CTCs for enhancing the power of computation."

Simple ??? See http://arxiv.org/abs/1007.2615

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.