Hello Stefan,
To
have "smoked" (satelized would be the real term for some MOS) many
MOSFET is overheating, or by cross conduction effect, I decided to
build "solid" ...
This kind of radiator was originally intended
for a linear amplifier over 160m (although for 99.99% CW use). Since
I had to buy a bar 1m long, so why not continue for LF amps?
This
is one of the reasons for this fabrication.
At
first the diet was linear, but I quickly gave up (the CW first!).
Indeed
the geographical position is very important in LF, I made some tests on
160m since the edge of the beach (a simple quarter wave always with the
kite) but now it is no longer possible to use this material for even
one full night.
The
public domain is monitored and we spend our time trying to explain that
we are not a terrorist (to be simple, if you understand what I mean ...
Poor current situation ...)
I
could see about 6 to 10dB better than from the mainland, which is for
us amateur a dream!
You
really have to love Radio now!
I would like to place me in a bog or marsh but my friend does
not agree, he likes his motorhome, already that his YL is not too happy
when he returns to his QRA all a little dirty with mud!
(LF is winter and winter there is also "humidity" ... To put it
simply!)
Water castles like lighthouses can not be used either
...
I even try to use a bridge (in the area there are some very
high with "humidity down", but also categorical refusal.We do not have
an easy hobby and I do not like stamp
collections ...;-)
I did not know
exactly the maximum power of the final stage, but I think that it will
be appropriate for our amateur application, the important thing is to
have a reliable machine not to risk to ruin an expedition in the nature
for some MOS which return to the wild life! ;-)
I am interested in all your
maneuvering on frequencies lower and lower, it's beautiful! But
I'm not there yet ... At the speed of things in 2000 years maybe?
For
the ULF with the capricious amp, the good old method is often the best,
it's like the "old formulas": 
, it still works in
2018, no? :-P
I like your
"style", like Ed RU6LA, all shots are allowed as long as you have fun!
Have a nice evening and see you soon!
VY 73's: Jeff
PS:
Now, I'm all alone to do LF (and no more young), so it goes
slower ...
But you have enough time, right?
The wise man said: Life is a great master, the misfortune is
that he kills his students!
Bye!
Le 13/07/2018 à 14:11, DK7FC a écrit :
Hello Jeff,
Am 13.07.2018 15:37, schrieb F6CWN:
Nice. The first time i saw a photo of F5WK. I know him from some years
back but now he is not so much active on this reflector. He detected me
many times on LF and VLF.
The
difficulty of the kite is especially the takeoff in order to capture as
soon as possible the good windy zone (not always easy in the middle of
June!), But after that it goes ...
I
do not speak also of the difficulties to pick up the wire when it falls
with the kite in a field of corn! (You have to
love the RADIO!)
I think i know exactly what you mean :-)
Now, I'm all alone to do LF (and no more young), so it goes
slower ...
But you have enough time, right?
The
main difficulty here (I am in Normandy, near the sea, where there is
wind!) Is to find charitable souls able to share my tastes for
"curious" things like the LF / VLF. It's
long and you have to make concessions, but over time ... It's starting
to become concrete!
Oh and when you are close to the sea, your ground losses will be very
low too.
Just stay in contact here with the list. It is not only the antenna
that must be tuned to resonance. It is also your mind and the mind of
some people 'on the other side', the RX side! This must be tuned to a
certain resonance as well, hoping for some Q :-)
I
have several fields to grow antennas beverage, K9AY, and of course
kite! But
to this is added some difficulties such as energy and housing that are
about to be resolved. Camping
in the middle of winter is a bit hard for my old bones ...
On
the power stage side, I'm thinking of a power MOS-based amplifier with
IXYS IXFH94N30 at liquid-cooled IXYS (water + glycol), with the primary
cooler out and the heat up (winter is good sometimes).
Is it a linear mode design? For a switch mode design you will not need
such a heavy cooling. Looks fine for 2 kW +
The
transformers are mounted on welder station ferrites (nominal frequency
~ 100 KHz, a good choice of manufacturers, thanks!) The "high voltage"
power supply provided by two 51V 57 A server power supplies (HP EPS120)
compatible with a capricious generator! (I think
he's allergic to CW!)
Sounds solid.
I've done some CW on 8.97 kHz in 2011, using a weak generator that was
able to produce 350W ('key-down') at that time. In CW the regulation
has gone mad and the average power dropped. The PA was running at 320V
DC (230V AC rectified, H-bridge using 4x IRFP460). But a parallel pack
of 10x 6000 uF/350V solved the problem. For a short moment, like a
'dit' i got up to 1.8 A antenna current into my 300m vertical wire.
Good luck with the build up of your LF station and i'm looking forward
to your big signal.
73, Stefan
