Hi all, there I was playing away on the bench with a new toy....and gosh I
get reports from Jim and an "M" report from Hartmut in Germany !!
The toy was an Adret 201 synth generator 0 to 1.999,999MHz in 0.1Hz steps,
OXCO controlled (or external reference). One nice facility is that the AM
and FM modulation facility have a response down to DC, so I knocked up a
little keyer on vero, hooked on to an external +&-12V PSU (it needs to
swing to -12 to cut the carrier off.)and attached a small square of vero
with a "test amp" on it. This has a BFY50 and a BSX30 in a kind of half
bridge, and is a verson of an aerial test TX on Lyle Kohler's web site. The
keying source is an old 80C85 "notebook", a NEC 8201, with a simple Basic
program using the cassette motor switch (now there is something you dont get
on PCs these days!!) as the keying contacts. The aerial is connected via a
transformer wound on a small (20mm diam) ferrite from an old SMPSU. The
receive aerial loading coil is a 1.25mH solenoid ( 6in long 28swg on 35mm
waste pipe) tuned by stuffing a small fragment of ferrite rod in the end.
The aerial current was measured using a Tek passive current probe P6021.
The "PA" is running 24V at about 100mA and the aerial current is about
200mA, aerial efficiency is about 0.1% so it is about 2.5mW ERP. (Rtot
aerial about 60ohm, and the capacity is about 850pF). This is a power level
that could easily be achieved even in a small garden, or perhaps with a
loop.
I guess most of you thought it would never happen !! I did....I have a
considerable amount to do yet to allow a two-way....I must find some more
cornflakes boxes !! and some choc blocks.
The unit is still running if anyone else wants to look for it. The frequency
is 137.7760kHz. about.0.2Hz hf of a Loran line. The dot length is about
25secs..
Cheers de Alan G3NYK
[email protected]
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