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Date: Tue, 09 May 2017 15:09:39 +0200
From: DK7FC <selberdenken@posteo.de>
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Subject: Re: LF: NA VLF
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Status: RO

Hi Joe,

Maybe you can provide some informations for us, to get a clear 
impression of what you're doing:

-A picture of the coil in its current location (when transmitting).
- A picture of the antenna, along with some data like, length, height 
above ground, sourrounding trees, antenna capacity.
- Measured coil DC resistance
- Which antenna current at which RF power?
- What is the antenna wire diameter?
- A picture of the isolators which hold the wire.

With SpecLab you can measure and monitor the antenna current, you can 
transmit carriers and e.g. EbNaut. You can program (or get mine) a 
safety function which stops the transmission in case that the current 
drops under a certain level. This can prevent from a fire when there 
should be a flash over across the coil or somewhere else.
And another important function: The phase of the radiated signal is 
constant even when the antenna becomes detuned due to temperature 
changes or rain. This is realised by a capacitive feedback pickup probe 
applied to the soundcard input (a tool by DF6NM). The phase is compared 
with the phase of a SL internal signal generator and variations are 
corrected. So it is a PLL function.
So all you need is a cheap GPS module, all other components are already 
in your shack...

73, Stefan


Am 09.05.2017 14:48, schrieb jcraig@mun.ca:
> Your efforts are greatly appreciated, Paul, along with the kind words
> and motivation from Stefan DK7FC Markus DF6NM Marco IK1HSS and Luis 
> EA5DOM.
>
> The TX has been QRV since Sunday afternoon and is still going.
> The drift is interesting -- but not desirable.  It is time to look
> at Spectrum lab again and explore some ideas to increase the ERP.
>
> Joe VO1NA
>
> On Tue, 9 May 2017, Paul Nicholson wrote:
>
>>
>> I can't detect any signal from Joe last night
>> 8th/9th 22:00 to 04:00, not a trace - perhaps
>> the tx has gone off.
>>
>> After sweeping for optimum settings, I couldn't get
>> much improvement.
>>
>> Daytime reception, S/N = 13.5 dB in 23.148 uHz:
>>
>> http://abelian.org/vlf/tmp/170509a.png
>>
>> Some of the energy is in adjacent bins on this 12
>> hour integration, the frequency probably drifted
>> a little, losing a dB or so.
>>
>> Nighttime, S/N = 14.3 dB in 46.296 uHz:
>>
>> http://abelian.org/vlf/tmp/170509b.png
>>
>> Tried an EbNaut 'decode' of the 6 hour nighttime
>> signal.  Unmodulated carrier is a valid message which
>> decodes to a string of '*' characters. Because of the
>> linearity of the coding, the performance is representative
>> of any other message with the same settings.
>>
>> 4 chars 16K25A CRC=12 Symbols = 22 seconds, duration 05:52:00
>> gives
>>
>> rank 946 ber 42.2% '****'
>>
>> carrier Eb/N0: -0.1 dB
>> carrier S/N: 13.53 dB in 47.3 uHz,
>>             -29.72 dB in 1Hz,
>>             -63.70 dB in 2.5kHz
>>
>> The snag is, this 'decode' is only possible because I could
>> see the signal and measure its frequency.  A real EbNaut
>> message is invisible and if the frequency is out by more than
>> about 5uHz it will not decode.
>>
>> 5 chars should just be possible but I could not get it to
>> decode.
>> -- 
>> Paul Nicholson
>> -- 
>>
>>
>