Yes,
Mike is right. Zooming the spectrogram on Luis' signal did not
show any central carrier, so subsequent dashes seem to have random
phase. An additional problem could be the temperature drift of the master
crystal oscillator (neither the common 125 MHz-clocked AD9850 modules nor the
Si570 source are very stable).
Regarding a new transmitter, I
would recommend starting with a stable continuous signal from an OCXO or TCXO,
and applying the keying only directly before the PA, after any divider stages.
As far as I can see, this is done right in the W1VD design, where the flipflop
runs through and keying is applied to the FET drivers.
All the
best,
Markus (DF6NM)
-----Ursprüngliche Mitteilung-----
Von:
Mike Dennison <
[email protected]>
An: rsgb_lf_group
<
[email protected]>
Verschickt: Do, 8 Sept 2016 12:12
pm
Betreff: LF: OPDS bandwidth (was EA5DOM LF tests)
The wider
bandwidth seen on OPDS may be key clicks but I have found
it can be caused
by a non-coherent signal, ie the 'oscillator' is not
continuously running.
I found this, for instance, when keying a
divider chip on my GW3UEP 472kHz
rig, and it was cured by keying the
PA instead.
Mike,
G3XDV
============
On 7 Sep 2016 at 11:20, DK7FC wrote:
>
date time call distance frequency bandwidth snr
> correlation
>
> 2016-09-07 04:35:08 EA5DOM 1398km 137519.960Hz 97mHz -37.7dBOp
100%
> 20.2dB 2016-09-07 03:35:08 EA5DOM 1398km 137519.910Hz
112mHz
> -48.5dBOp 100% 19.8dB 2016-09-07 02:35:09 EA5DOM 1398km
137519.928Hz
> 75mHz -42.0dBOp 46% 16.6dB 2016-09-07 01:35:07 EA5DOM
1398km
> 137519.926Hz 71mHz -99.9dBOp 77% 16.6dB
>
>
> Somehow the bandwidth values are quite high. Normally it is arround
<
> 10 mHz. Anyway, a nice
result.
