Hi Stefan and Group
The EU storms were in the UK news today quite amazing. Thanks for the update on the Dreamer's band ...hee.:-))
I have done some measurements on my toroid which if you have time to look at I will send to you direct. Probably late tomorrow busy during the day on other things.
I was going to do a range test with what I have got but the weather here was too miserable to spend time standing on a hill waving a wire in the air and getting soaking wet. 73 es GL petefmt --- On Sun, 28/2/10, Stefan Schäfer <[email protected]> wrote:
From: Stefan Schäfer <[email protected]>
Subject: LF: VLF TX experiments_short report
To: [email protected]
Date: Sunday, 28 February, 2010, 23:08
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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