Message-ID: <158cf60ef68.marcocadeddu@tin.it>
Date: Mon, 5 Dec 2016 15:26:26 +0100 (CET)
From: "marcocadeddu@tin.it" <marcocadeddu@tin.it>
To:  <rsgb_lf_group@blacksheep.org>
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Subject: R: LF: RE: Finally 100 mA on 2.97 kHz
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impressive! :-)
congrats Stefan, really a nice job and a beautiful sunny day in HD!
hope to be able to detect soon the sparks from here ;-)
were is Mr. Frankestein hidden? :-)))
keep on Stefan
Marco IK1HSS
----Messaggio originale----
Da: luis@vigilant.es
Data: 5-dic-2016 11.23
A: "rsgb_lf_group@blacksheep.org"<rsgb_lf_group@blacksheep.org>
Ogg: LF: RE: Finally 100 mA on 2.97 kHz

Congratulations for this great step ahead Stefan !!! :-)

>From your hard work and impressive pictures it is quite clear that ULF 
is veeeeeery hard compared to LF/MF and every Hz down there becomes 
harder and harder
Amazing work and beautiful construction. My best wishes for the results 
in your tests

Please keep posting. May be not many will said anything but we are all 
watching ....mouth wide open ;-)

73 de Luis
EA5DOM

________________________________
De: owner-rsgb_lf_group@blacksheep.org [mailto:owner-
rsgb_lf_group@blacksheep.org] En nombre de DK7FC
Enviado el: domingo, 04 de diciembre de 2016 23:15
Para: rsgb_lf_group@blacksheep.org
Asunto: ULF: Finally 100 mA on 2.97 kHz

ULF,

It was a clear, cold and sunny day again and finally i was testing the 
new large 2.97 kHz coil on the roof: https://dl.dropboxusercontent.com/u/19882028/ULF/20161204_153126.jpg

Not a good idea on MF or LF, but on ULF is can be a good idea to put a 
resistor in series to the coil. I put 500 Ohm in series. This helps to 
attenuate eventual HV transients, makes the resonance curve a bit 
flatter, so the peak is easier to hold.
500 Ohm and 0.1 A, that just a loss of 5W, quite affordable. https://dl.dropboxusercontent.com/u/19882028/ULF/20161204_153113.jpg

Unfortunetely i found that the actual resonance region is adjustable 
from 2993...3130 Hz. So the inductance is still to low :-( I've been 
quite sure that my antenna replacement capacity for resonance tests in 
the shack has the right value. So maybe other effects like an 
additional capacitive load by the things standing arround in the shack? 
Or a different behaviour of the residual antenna +  frozen ground 
capacity on 2970 Hz?
At least it was possible to get 100 mA anyway, just by applying some 
more voltage to the antenna. The PA is now running at 20V and less than 
1A, most of that are PA- and transformer losses. Anyway i have 12 kV on 
the antenna! That's ULF!
I was planning to bring the coil down to the shack anyway, after the 
65km experiment which will start in a few days i think. Then i can add 
more turns to come closer to 2970 Hz.

With 70 uOhm radiation resistance the resulting ERP is now entering the 
microwatt range: 1.2 uW on the 101km band.

A stable carrier at 100 mA was sent from 12:50 UTC to 14:24 UTC.

I tried to measure the antenna current with a true rms digital 
multimeter, shielded by aluminium foil, measuring on high potential. 
But the measurement was wrong anyway. The permanent installed analog 
amperemeter and SpecLab gave a correct measurement. Tomorrow i will 
check the antenna current measurement on high potential with a 
calibrated analog amperemeter.

For the 65km experiment i want to transmit some DFCW-12000 again as 
well as an EbNaut message. The RX site will be in JN39VH :-)

73, Stefan