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Re: LF: TXing on VLF again, A fan in series to the antenna?! :-)

To: [email protected]
Subject: Re: LF: TXing on VLF again, A fan in series to the antenna?! :-)
From: DK7FC <[email protected]>
Date: Fri, 15 Apr 2016 11:32:46 +0200
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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 EMRP).

73, Stefan

Am 15.04.2016 09:15, schrieb Markus Vester:
Hi Stefan,
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,

-----Ursprüngliche Mitteilung-----
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. 
73, Stefan 
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 
>> --  

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