Dear LF,
I am sorry that it was not possible to transmit today. Maybe you have heard
about the strong storm that damaged many trees and houses today. It wouldn't
have been a good idea to be on the hill to that time..
A second problem was my DDS VFO. I saw that the duty cycle of the rectangular
output was not 50%. So i had to modify the drivers circuit, adding a CMOS4013
as a f divider and apply 2*f at it's input now.
What i wanted to use as the PA is a prototype of a SMPS that was designed to
operate at abt 50kHz. At 9kHz the ferrite core was already driven in
saturation. By varying the driving f i found, where the saturation occurs. Then
i have known how many primary turns i have to spend at 9kHz. After applying the
new windings everything was right. But the time i had was gone and the wind was
already to strong. So i told Markus to inform you...
Now playing/increasing with the number of output windings of the SMPS
transformer i applied the output voltage by a ordinary loudspeaker cable to the
primary air coil that is inductive coupled to the HV coil. I got 1,6kV rms by
applying 60W at the 12V DC input, really not much :-( But anyway it will be
suitable for a first test if a apply 6dB more power or so.
Lastly i have to get another coil that has more L and Q, so that no parallel C
will be needed. I will try to do that in the next week. Tomorrow i do not have
to work and will spend time improving the PA (trying how much power is possible
until the heat sink gets to warm and so on). Then, if the wind will be not to
strong any more, i will do some tests on the hill, measuring R and C and so
on...
Will keep you informed.
Rik, Pete, anything new dreamers records? Pete, have you increased your power?
If you want i could send you a simple circuit for the PA, if you want.
Dimensioning is really uncritical, switching losses as well, at those low
frequencies. That's one of the advantages ;-)
GN es GL!! 73 de Stefan/DK7FC
PS: Just as 160m is called "Top band" we could call 9kHz the "Dreamers band".
Sounds nice, isn't it? :-)
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