Hi Markus, |
Yes, you're right. I had the wrong value in my mind, downscaled 0.82
Ohm radiation resistance to VLF but that was for a 100m (kite)
vertical. So the signal is another 6 dB weaker, maybe 35 uW ERP (not
Am 15.04.2016 09:15, schrieb Markus Vester:
I looked for your carrier in the 478 uHz grabber window, but
nothing significant due to the high QRN background. I hope to be able
to catch a daytime transmission as soon as the weather improves.
150 uW ERP at 0.2 amps (corresponding to Rrad ~ 2 milliohms
or heff ~ 40 meters) sounds a bit optimistic, especially considering
surrounding buildings etc. I think Dex had similar estimated ERP
during his legendary EbNaut TA crossing.
All the best,
Von: DK7FC <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Fr, 15 Apr 2016 12:34 am
Betreff: Re: LF: TXing on VLF again, A fan in series to the antenna?!
BTW the calculated ERP is 150 uW. Quite low :-( But i will be able to
run it permanently...
The transmission is now stopped and was running from 20:45...22:30 UTC.
Am 14.04.2016 23:01, schrieb DK7FC:
> Hi VLF,
> Since 22:45 i'm running 200 mA on 8270.0050 Hz into my antenna again.
> 200 mA is the limitation of this compact yoghurt-coil. The overall
> system loss is about 1 kOhm, so i just need 40W to run the system at
> 100%. Or, in other words, power is not the limiting factor :-) There
> are holes into the single yoghurt cups so there can be an air flow in
> the cups. And this will be helpful/necessary in summer / daytime.
> 200 mA is about the current consumption of a 12V fan used in PC power
> supplies. So i've constructed a plate with a fan mounted on that,
> improvong the air flow. Later, a tube must be used to form a curve on
> the top of the arrangement to prevent water from flowing between the
> coils. Then, a forced air flow becomes necessary, normal thermal
> convection could be to small.
> A normal bridge rectifier with UF4007 diodes, then 2 ZD15 Z-diodes, a
> single UF4007 diode (to reduce the voltage a bit) and a 100nF C,
> that's all. It works very well and automatically :-)
> 73, Stefan
> Am 13.04.2016 23:28, schrieb Paul Nicholson:
>> Sorry Stefan, nothing showing for 20:14,+30m in
>> 555uHz. The noise floor there is 0.2 fT probably
>> due to all the thunderstorms in Europe tonight.
>> I expect your signal is down below 0.1 fT.
>> Also checked 20:14,+60m in 278 uHz in case you ran
>> for a full hour, but nothing.
>> Let's try again when the background is lower.
>> Paul Nicholson