Jim
Reception of Alpha signals around 12 kcs are definitely a good guide only 3
kcs away from the frequency of interest 9 kcs, and I agree about the basic
test of DL antenna and real antenna but information from others is scarce. I
am inclined to think few are capable of receiving radio amateur signals
around 9 kcs and especially if the transmitted signals are flea power like
500 kcs.
Noise floor figures and signal over noise would be useful and its not true
to say everyone can copy the Alpha signals and if so what is the signal
above noise like.
Before I start engineering a 9 kcs station I would like to think someone
could copy my signals otherwise its a waste of time and effort.
----- Original Message -----
From: "James Moritz" <[email protected]>
To: <[email protected]>
Sent: Saturday, June 05, 2010 11:29 PM
Subject: LF: Re: 9 kcs
> Dear Mal, LF Group,
>
> G3KEV wrote:
> ...>Information is also scarce in the UK especially about receiving
> capabilities, what is being heard especially alpha signals, strength,
> audibility and general band noise.
>
> If you read previous posts to this reflector on the subject, you will know
> that the receive side of things is fairly straightforward. What is being
> heard on 9kHz is QRN and QRM, except for very short range "induction"
tests,
> where the signals can be audible. If you cannot receive the "Alpha"
beacons
> in the UK, it probably means they are not transmitting, or your RX or
> antenna have stopped working. But, although they may be interesting in
> themselves, they are largely irrelevant as a measure of 9kHz receive
> performance, since they are on a different frequency, are vastly more
> powerful than amateur signals, and for the DX tests that have been done,
> have a much wider bandwidth / shorter duration compared to the amateur
> signals.
>
> A better test of receiver performance at 9kHz is to compare the noise
level
> with and without the antenna. Since the RX or preamp noise level can be
> strongly dependent on the source impedance, it is best to replace the
actual
> antenna with a "dummy antenna" with similar impedance when making this
> comparison. For example, for my loop antenna, I have a change-over switch
> that connects the preamp input to a small choke with about the same
> inductance and resistance as the actual antenna. This enables quick
> comparisons to be made between noise levels at different times and
> locations, and is also a good check on the local QRM level. Obviously, you
> want the antenna noise level to be at least several dB greater than that
> with the dummy antenna, which is usually easily achieved.
Yes agree but on average what is your antenna noise level when you do this
test. With my current antenna I get 10 dB - 15 dB on an average day on 9 kcs
During a thunder storm a lot more. Most days there is static about
especially at this time of year.
I have no preamps, antenna direct to RX and controlled by stepped
attenuator.
I stand a good chance of hearing 9 kcs signals but this is not a band for
flea power.
>
> The general band signal and noise levels are being regularly monitored at
> several locations - you can see the info at http://abelian.org/. But you
> already know that...
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>
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