It is even worse using the same short ant, say that I am using on 29 at 800 w. I would say a power reduction of several db would be required and added to your calculated signal reduction when going from 29 to 9 kHz-Bob
From:
[email protected]To:
[email protected]Date: Thu, 6 Mar 2014 00:08:04 +0100
Subject: Re: LF: Re: VLF 29501, signal?
Johan,
unfortunately the difference between "upper and
lower" VLF will be much larger than that. Operating a small electric
antenna at the same voltage limit, radiated power scales with the
fourth power of frequency. A current limited TX loop would scale the same way.
Thus going from 29.5 to 8.27 kHz will reduce the fieldstrength by 22
dB. In addition, background noise from distant static tends
to peak around 9
kHz, which may easily make another 10 dB SNR
deterioration.
But well, challenges are there
for us to meet them ;-)
Best 73,
Markus
Sent: Wednesday, March 05, 2014 11:48 PM
Subject: Re: LF: Re: VLF 29501, signal?
Yes, an impressive
achievement indeed, congratulations to all involved!
Wow is the word! The
24dB S/N ratio on Dex' signal exceeded all my
expectations! 24 dB S/N is
"armchair copy". It would be interesting to
actually listen to a spectrally
shifted and time compressed version of
the signal. Can you do that on your
Linux box Paul? Not for scientific
purposes but for pure sheer joy
:-)
Given 24dB S/N headroom at 29.5kHz, sub 9 kHz TA is probably not too
far
away! The TX antenna would be no more than ~10dB down compared to
30k.
73
Johan SM6LKM
...