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
