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Re: LF: Signal bandwidth in Op32 LF

from [Markus Vester] [Permanent Link][Original]
To: [email protected]
Subject: Re: LF: Signal bandwidth in Op32 LF
From: Markus Vester <[email protected]>
Date: Sat, 29 Sep 2018 05:25:41 -0400
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Yes. As Andy says, if you are using a divider it should run continuously to preserve carrier phase. All modulation (either XOR for EbNaut-PSK, or on-off-gating for Opera) should be applied after the divider stage.

Best 73,
Markus


-----Ursprüngliche Mitteilung-----
Von: Andy Talbot <[email protected]>
An: LineOne <[email protected]>
Verschickt: Sa, 29. Sept 2018 10:44
Betreff: Re: LF: Signal bandwidth in Op32 LF

If you stop and start a divider, the phase jumps about randomly.  Each time you start the divider, its output signal starts up in a differnet phase to what it would have been if left running

To achieve phase coherent, you must keep the divider running and gate the OUTPUT separately

This issue is a problem with beacons in general that employ FSK keying for their CW ident.   If they adopted on-off keying, then long term integration cold take place though the keying cycle.  But unfortunately, IARU (or whatever organisation that tries to mandate these things), appear to require FSK keying.  SO most beacon keepers comply.   (I don't, the Bell Hill microwave beacons, GB3SCx all use on-off keying)


On Sat, 29 Sep 2018 at 09:10, VIGILANT Luis Fernández <[email protected]> wrote:
Hi LF

I'm puzzled with the readings of bandwidth at the Op32 correlation detection grabbers

As source I'm using a GPS generated signal, which is coherent in phase and works for EbNaut
So I tested this at 20x frequency to drive an small D class PA and modulated in Opera32
The OOK was achieved by enabling/disabling a divider by 10 just after GPS

Sourprisingly, my decodes at DF6NM and DL0AO varied in width, but always showing width of a non coherent signal
2018-09-24 16:55:09 EA5DOM  1500km 137485.051Hz  71mHz -99.9dBOp  78% 17.6dB
2018-09-24 15:35:10 EA5DOM  1500km 137485.026Hz 114mHz -99.9dBOp 100% 17.3dB 
2018-09-24 14:13:18 EA5DOM  1500km 137485.039Hz 164mHz -37.2dBOp 100% 20.7dB
2018-09-27 19:08:06 EA5DOM  1536km 137485.013Hz 110mHz -38.3dBOp  94% 18.8dB
Last night I tried without PA.  Using just a mosfet driver this time getting
about 1W output. The GPS generates the 10x frequency and the OOK is controlled
by enabling/disabling the divider by 10. Got a couple of decodes at DF6NM
2018-09-29 02:17:39 EA5DOM  1500km 137485.007Hz   5mHz -46.4dBOp  85% 15.4dB
2018-09-29 00:37:50 EA5DOM  1500km 137484.986Hz 112mHz -43.2dBOp 100% 19.6dB
So, 5 and 112mHz, for the same signal. I'm thinking that the problem is caused
by glitches when the signal goes off. A synchronous off would be needed to
cut signal at zero crossing ?
Reports to other stations, like SM2DJK, show just 2 to 3mHz

Any ideas ?

PS: Stefan. Your Op32 correlaton detector is not working actually

73 de Luis
EA5DOM
 
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