...i stopped the transmission and will restart with 30 seconds
symbol length at 20:30 UTC. All other parameters are unchanged.
I can also run plain carriers later, if of interest. But EbNaut
messages are more interesting i find.
73, Stefan
Am 16.10.2017 21:30, schrieb DK7FC:
Hello
Paul, VLF,
Thanks for the results. The message '73' is correct! Well, i was unable
to hold the antenna current constant on both frequencies, see
attachment.
Let's say the average current on 6510 was just 190 mA. Relative to 200
mA that's -0.45 dB. But on 6510, the radiation resistance is higher,
giving a gain, relative to 6430 Hz of +0.1 dB. All in all that's still
quite negiligible.
But the difference of the Eb/N0 of both transmissions is > 3 dB.
Quite a difference. Do you exclude local QRM of the individual
frequencies?
Our distance is 881 km.
6510 Hz has a wavelength of 46.08 km, so our distance is at 19.1
lambda.
6430 Hz has a wavelength of 46.66 km, so our distance is at 18.9
lambda.
A difference of lambda/5, quite close to lambda/4...
This applies at least for the groundwave.
Does it help us in any way, the result we saw now?
On 2970 Hz, this could make a much bigger difference but due to the
weaker signal, we can't check is quickly in < 3 hours...
Meanwhile the night has started between us.
I will repeat the same experiment starting 20 UTC.
Maybe we will get more impressions...
73, Stefan
Am 16.10.2017 19:05, schrieb Paul Nicholson:
Stefan wrote:
> f1 = 6430.005000 Hz
> f2 = 6510.005000 Hz
> Start time: 16.October.2017 13:00:00 UTC
> Symbol period: 15 s
> Characters: 2
> CRC bits: 6
> Coding 16K21A
> Duration: 2h32min
H-field only:
6430.005000 copied '51' at -1.8 dB and 'ZV' at -1.1 dB;
6510.005000 copied '73' at +3.0 dB;
--
Paul Nicholson
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