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
...
