Message-ID: <005201c23ec6$2fb47ec0$682565d5@oemcomputer>
From: "Johan Bodin" <sm6lkm.jbeab@swipnet.se>
To: rsgb_lf_group@blacksheep.org
References: <17chZQ-13Oc8eC@fwd05.sul.t-online.com>
Subject: LF: Re: RE off band Jason
Date: Thu, 8 Aug 2002 12:24:59 +0200
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Hi Bernd, Andy

DF8ZR wrote:

> Is number 5 still alive, hi?

No, there are no 5s in the beacon message. The message contains only
one digit, the digit '6' in my callsign. I will not reveal the message content
yet but a clue is that it depends on the local weather here, hi hi...

G4JNT wrote:

> By USB, do you mean the frequency specified is the carrier and the centre  800 
> Hz (or whatever) higher,  or is 7000.003 the centre of the transmission ?   I'm 
> assuming for now you mean the latter, so off to listen throughout the day.

Sorry... I should have been more clear. Yes, 7000003 Hz is the center frequency
and "deltas" add to increase the frequency (unless it it wrapped back by "mod 17').
In other words, the frequency is 7000003 +/- 2.0187 Hz.
Example: Tune the RX to 6999.000 kHz USB and set Jason to USB with 1003 Hz
center frequency.

I hope there is not too much sideband splatter below the band edge :-)

TX line-up is 10 MHz Shera GPS standard -> 74HC74 div-by-2 -> 5 MHz ->
tripler using a few inverters of a 74HC04 and tuned circuits -> 15 MHz ->
ICS501 clock multiplier set to f*8 -> 120 MHz (the board was designed before
AD9851 was available) -> AD9850 -> 40 MHz lowpass filter ->
MAX4012 op-amp -> step attenuator -> two cascaded pi filters with all
X's = 50 ohms @ 7 MHz -> dipole antenna....

A PIC16F628 does the Jason encoding and controls the DDS.

120 MHz DDS clock may seem a bit high for this experiment but I want to
use the DDS as a general purpose signal generator. Worst case error is
only 7.081 mHz on Jason tones 0 and 16, only 8.4% of an FFT bin.

Let me know if you suffer from QRM and I will QSY.

73
Johan SM6LKM