DK8KW Longwave Information
Details of my 136 kHz station

Transmitter DDS VFO II (click here for details) made by S&S Engineering. This VFO has a resolution of 1 Hz and an accuracy in the same range. This DDS VFO type II is a real "overkill" for longwave, as it goes from 0 Hz to 60 MHz. The VFO has an output of about 0.6 Volts p/p at 50 Ohms. 

Top to bottom: PA, TX, Low-Pass Filter, 
T/R Switch and Antenna-Current Meter

The TX contains a 2-stage buffer using one MAV 3 and one single IRFP 450 to get about 1 watt output, resulting in an ERP (according to CCIR curves) of 100 mW. 

PA G0MRF PA with 4 x IRFP 450, now running at full power (approx. 380 W input/280 W output) 

I burned 16 IRFP 450 before finding out that I had a serious cooling problem ...

Pre-Selector I use the pre-selector section of a Teletron LWF45

Receiver MV 62 Selective Level Meter as front-end and converter, 1.7 or 0.1 kHz bandwidth, output IF on 200 kHz 

IC-746 as IF receiver on 200 kHz, equipped with cascaded 250 Hz and 500 Hz CW filter (plus DSP filter, if needed) 

Antenna New setup: My new antenna is a simplified version of what is called in broadcast engineering an "Umbrella-Antenna". It consists of a 18m vertical telescopic fibre glas mast (height depends on the wind condictions), four top-load wires, each about 15 to 20m long at a relatively steep angle (still leaving some room for improvement). 

I use this antenna for transmitting and receiving, the signal strength of DCF39 has improved from -46 dB(75) to -23 dB(75) compared to my previous antenna. 

The picture below shows a commercial umbrella-antenna, also called top-loaded monopole antenna, build for a frequency in the 12 kHz range for the former Omega Navigation system. According to Klawitter and Herold, those antennas had 16 top-load and 16 buried radials. The 425m (!) high tower would roughly compare to a 42m high umbrella-antenna for 136 kHz. 

Previously I used a Marconi type T-antenna, consisting of a 82m long windom antenna for 160 m, u-shaped in a height of 8 to 12 m, soald and shield of coaxial cable connected in my shack. I was copied in the U.K. by G3XDV (707 km) with this relatively simple antenna setup and had a succesful 2-way QSO with HB9ASB (645 km)! 

Antenna Current Meter Russian-type antenna current meter (0-3 A, 50 Hz-7.5 MHz) 

Loading Coil Primary 3.4 mH loading coild 1/3 way up the antenna. This coil improved my ERP signal about 4-5 dB. 

Additional variometer loading coil in my shack, wound approx. 130 m of 0.2 mm Litz wire on 27 cm diameter, 40 cm height plastic bin 

The Piper's Wine-CD gives you an idea 
about the height of the coil: think big!

Detail of the variometer part of the loading coil, tunable approximately between 
0.6 and 4.2 mH

Antenna Switch

Be careful: High Voltage!

I used this antenna switch to switch between longwave and 160/80/40m, as I used the same antenna for all those bands. This explains, why I needed a coule of seconds between transmit and receive when I run crossband QSOs! With the new seperate LF antenna, this should be easier now! I use this monster switch now to ground the umbrella-antenna. 

Ground System One main ground rod about 3 m deep, plus central heating and water pipe system in my old farm house connected, another 2.4m long ground rod at the end of a 20m long buried radial, still two or three more ground radials planned. 
Linear Modes (PSK31, HELL, etc) Since December 2000 I have got a Hagenuk EX 1001 SSB Exciter with LSB/USB option. Late Peter, DJ8WL had told me about this device which produces CW and SSB signals between 100 kHz and 30 MHz in 100 Hz steps.

I use a small buffer amplifier (developed by OM2TW) to increase the signal level from about 20 mW to 4 Watts, sufficient power to drive the G0MRF-PA.

With this setup I am occasionally QRV on 137.500 kHz in PSK31 or 137.400 in HELL and other experimental modes.



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