Re: VLF: 4th VLF experiment by DK7FC/p

[Gary - G4WGT <g4wgt@tiscali.co.uk>]

Hi Stefan, LF,

I will be monitoring your frequency using a M0BMU type 30 turn 0.8M square loop and 9kHz pre-amp into my PC sound card, software is SpecLab running Marcus's "9kHz_4mHz" configuration. This loop system has increased my reception of the Alpha signals by about 10db giving up to 25db SNR. Thanks to Jim for a great design.

Stefan, can you tell me the QTH locator for your Tx site please.

Good luck with the 4th test.

73

Gary - G4WGT.

2010/4/2 Stefan Schäfer <schaefer@hst.tu-darmstadt.de>

Dear group,

After a break of one week i plan to transmit again on VLF / 8,97 kHz. If the wind will be enough i will come up on saturday, 3. April, at arround 10 UTC.

The DFCW-600 mode was a good choice in the last experiment, so i will keep this mode.

If Markus/DF6NM has time to make QSP on the mobile phone to the reflector (Markus ?) we could arrange various tests. I will also call other local stations for reception reports during the transmission.

There will be some new components to test:

Today i started building up the 600W class D PA (at least 600W) that is directly fed out of the 230V (rectified) of the generator. PTT and VFO input is realised by fiber optic cables. The DC capacitor is 2000µF/350V and can be put on voltage without a NTC or charging resistor due to the relatively high output impedance of the small generator (tested). This works very fine now. Tomorrow i will apply the FETs and the big ferrite core and it's windings. Then i will do a test on a dummy load at home. If the signal will be 3dB stronger, we could theoretically change to DFCW-300 compared to the last experiment. But there are many OMs writing private mails to me and prepare to be QRV on this next test. Some of them are using E-Field antennas and/or are more than 860km away, that' why i want to stay in QRSS-600 first. So there might come a new distance record? In any case it will be exciting to me watching the new system running :-) Also it will be interesting to see if the E-field antenna will get the signal!

The primary winding of the TX coil is increased from 9 to 13 turns due to the higher power that will be applied. Otherwise the current will become to high.

I will mount the amperemeter (analog, 1A) into the coil. That makes it easier to adjust to resonance and watch the stability and maximum and average (estimation) current.

Finally i will try to apply some copper rods into the earth and will look how the antenna current is changing.

The goal is to radiate 4mW ERP. Another goal is to reach as many stations as possible. So i would be pleased if YOU would be one of them. :-)

Since the QRM/QRN comes up in the late afternoon and transmitting for 4...5 hours i will close at about 15 UTC. So the planned LF activity is not affected :-). Sorry, but i cannot participate on the LF acty later since the VLF coil takes all the place in my car ;-)

I looking forward to this experiment and wish you good luck and fun by receiving  :-)

73 es gl, Stefan/DK7FC

PS: Could you give me a short feedback if you plan to be RX?