Cheap & simple 500kHz TX by GW3UEP. This design
produces up to 25W and only costs a few pounds.
Loops. Jim's new article on 1m squre receiving loops for 136 and
500kHz. "Band-pass" tuning means no adjustments once set up.
A 500kHz TX
design by Jim Moritz, M0BMU. This is a 10W TX for use under the UK research
A complete DDS LF exciter.
By Murray Greenman ZL1BPU. The LF Exciter described here is in use
around the world, and has been heard trans-Pacific (admittedly with a PA
attached!) It has a DDS synthesizer with 0.3 mHz steps, TCXO precision and
stability, and a built-in programmable beacon with many specialized LF modes
including JASON and Murray's new "CASTLE"
mode. It includes a sweep generator for those tricky antenna and filter
measurements and an incremental power control for the PA. With 1W output from
75 kHz to 300 kHz, it contains a mere 4 ICs and 2 transistors! ($10 firmware
charge, $30 if you want the full source code). The DDS can now reference to a
1pps clock from a GPS receiver.
Calculator for LF
loading coils By M0BMU. An Excel spreadsheet for calculating the coil
and tapping point to resonate and match an LF aerial. To download it rather
than display it in the browser; right-click and choose "save target as" or
"save link as". There is also an explanatory PDF
Transmitting loop for
136kHz By G3YXM. TX loops after the design of Bill Ashlock can give a
good account of themselves when supported by trees. I decided to try one at
GM3YXM at Easter 2006.
The famous ON7YD
LF aerials page is now hosted here as well as at the original QSL.net
LF Tuning meter.
By Jim Moritz, M0BMU. It has 2 meters - one indicates phase, while the
other can be switched between voltage and current to determine the load
resistance. The circuit is slightly more complex than an SWR bridge, using 12
diodes, 3 toroid cores and a few other passive components. It does not require
an external power supply, and is usable with TX power between about 20W and
Experiments with Argo modes. Just how much more effective
is QRSS60 than QRSS10, or QRSS3 than CW, in practice, on a real band, over a
real path? Dave Pick G3YXM asked Alan G3NYK to assist.
An easy LF
receiving loop, tuned in the shack. © Jim Moritz M0BMU. I have
used this system to great effect. Highly recommended. Also check out his
article on "Band-Pass" loops. Here.
vectorscope unit for displaying phase mod. © Jim Moritz M0BMU.
A simple way of displaying phase modulation on an oscilloscope with X and Y
hardware DDS for 136kHz. © Pavel Vachal OK1DX. This DDS uses
74HC series chips to produce full band coverage in 10Hz steps. Can be built in
a day (if you're quick) for £20.
new slow mode for LF DX. This package is written by Alberto I2PHD
and gives keyboard communication at 2.5 chrs/min in 4Hz bandwidth.
Electro-Mechanical RX for VLF Inspired by the recent transmissions
from SAQ, Jim Moritz has built a receiver with no active devices... not even a
bridged FET PA. © Andy Talbot G4JNT. This design uses high
Voltage FETs straight from the mains with no bulky / heavy
variable phase BPSK modulator by M0BMU.Another interesting article
from Jim. He has designed a modulator for BPSK which keeps bandwidth under
Of LF RX loops
and preamps. Some thoughts by G4CNN.
TX protection system. Jim Moritz, M0BMU has written a short article
on the "guard circuit" used to protect the Decca TX.
software-DDS for 136.Dieter Wulff has built a simple DDS for the
band using a AT90S1200-12PC microcontroller chip. Diagram corrected
PA0SE's LF field strength meter. Dick Rollema has full
details on how to build and calibrate the meter.
ON6ND's water analogy of antennas. Werner's LF antenna
is unique. He justifies his choice of antenna with an interesting
DK5PT's compact loading coil on a ferrite core. Dieter
now has this coil working with 300W and 3A antenna current.
My review of the Ropex transmitter. Written for "Radio
Today" magazine and published in the June 1999 edition.
VA7LF. The trans-Pacific tests
2006 By Steve McDonald VE7SL, one of the VA7LF team.
7S6SAJ LF operation from
Karlsborg A vintage LF station fires up on 136.
Guernsey LF DX-pedition, November 2000. A tale of rain and wind and
cold and Loran.
G3XDV's trip to West Wales to work GU. More rain and wind, and
Isle-of-Man trip November 1999. The lighthouse strikes
More articles are welcome, e-mail me at