Message-ID: <3C9226F6.54590B73@snet.net>
Date: Fri, 15 Mar 2002 11:53:10 -0500
From: "Jay Rusgrove" <advancedreceiver@snet.net>
MIME-Version: 1.0
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Re: If you have downloaded PHD Radio...
References: <3C90AC2B.898F7C6@usa.net> <3C91F52E.8EA7B843@snet.net> <3C921829.BABF01F@usa.net>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Sender: <majordom@post.thorcom.com>

Alberto

Thank you for getting back to me.

I think the Argo "I know that this frequency is xxxx Hz, do your math" .... would be
a good solution if you can implement it. A better solution would be using the spare
audio channel to insert a reference signal, again, if you could implement it. There
is no doubt that future leaps in software improvements will require locking your
receiving setup to GPS, Loran or other source. The equipment to do this is becoming
more reasonably priced - GPS boxes are available all the time now on ebay! The 10 MHz
output (suitably divided down) or the 1 pps perhaps could be used for the reference.
This would result in a completely locked system with both the receiver and sound card
locked to the precision reference. If you do take a look at this, it would be nice to
implement this in Argo, also. Assuming all this is possible...

Thanks again for the great software!

Jay Rusgrove, W1VD

Alberto di Bene wrote:

> Jay Rusgrove wrote:
>
> > Now to my question. What is used as the reference frequency for the BFO and can
> > it be tweaked? I notice that with my GPS referenced receivers a known frequency
> > output  makes the phase meter rotate about 1 revolution every 4 seconds or so.
> > Is there a way to tweak the frequency right on as in Argo?
>
> Jay and the group,
>    thanks for your nice words.
> What is used as the reference frequency for the BFO ?? Guess what ?
> The sampling frequency of the sound card.... which generally is derived from
> a cheap quartz crystal... the BFO is implemented as a  dual-output NCO,
> producing quadrature signals for the half-complex mixers. The rate of updating
> of the phase accumulator for the NCO is directly derived from the rate of
> the callbacks from the MME subsystem of Windows, which in turn depends
> on the hardware interrupts generated from the sound card.
> So I cannot see any possibility to tweak it in hardware.
> A software possibility could be to use the right channel of the Line In
> (the mono input signal is on the left), to input a precise reference,
> from which the software could somehow derive a correction factor...
>
> Or, as in Argo, you could tell to the program "I know that this frequency is
> xxxx Hz, do your math" .... I have to think about this.
>
> Thanks for the feedback.
>
> 73  Alberto  I2PHD