[Lowfer] MP's captures

[Stewart Nelson]

Hi Eric and all,

Yes, I did attempt to measure the frequency and write it on the
datasheet.  But I thought that it was written down to the
nearest Hz, e.g. 12.800030 or 12.800003 .  So if it says 12.80003,
then I messed up, and that may not be what was measured.
And I also failed to keep a backup record.  My apologies.

But it should not be too hard to accurately determine the frequency.
Just turn off the final, set the DDS to output something near WWVB or
a strong LORAN line, and compare with ARGO.

There is a manual adjustment that you could use to set the oscillator
very close to 12.800000 MHz.  With some patience, you can get within
1 or 2 Hz.  Be warned that the total range is something like +/- 250 Hz,
so you can make things much worse if you're not careful.  If you get
way off, you can set your DDS so that a harmonic lands on e.g. 10 MHz,
and zero beat it with WWV.

73,

Stewart


----- Original Message ----- 
From: "Eric Smith" <eric@willow.nutstreet.net>
To: <lowfer@mailman.qth.net>
Sent: Sunday, October 05, 2003 7:15 AM
Subject: Re: [Lowfer] MP's captures


> Hi, Bill,
> 
> > Eric, I'll lower my osc to .3000 or mybe a bit lower in a few minutes.
> 
> No need, I moved up near WE (I think heh see below).  Thanks, though.
> 
> > How do you know you are at .3003?
> 
> Unfortunately, I don't.  As you know, I don't have the gear to find out :(
> I'm using the ZL1BPU dds exciter and I used one of the 12.8 MHz TCXOs 
> Stewart Nelson made available early this year.  The paperwork (in Chinese) 
> that came with it had handwritten "12.80003" in pen -- I've always thought 
> Stewart wrote this.
> 
> ok -- bear with me ...
> 
> The exciter is adjustable NOT in 1 Hz steps -- it's resolution depends on 
> the xtal frequency.  The resolution relationship is:
> 
> Fcrystal / (9 x 2^24) Hz
> 
> So, for me that works out to 0.084 Hz steps (or .08477107021543714735 Hz 
> steps, really :)
> 
> Anyway, I have a spreadsheet (from Lyle) that makes working this out easy 
> so that I know what to plug into the exciter for a given frequency.  It is 
> programmed with a number to be multiplied by the resolution to achieve the 
> desired frequency.
> 
> Since the steps are some odd number, it works out that my frequency should 
> be 185.30201.
> 
> But that all hinges on what the TCXO frequency really is.  If it is 10 Hz 
> higher, my frequency would be off from where I think I have it programmed 
> ... it would be 185.30216.  If it is 50 Hz high, I would be at 185.30274.
> 
> So, unfortunately, I'm only hoping for the best, and won't really know 
> until someone can get a capture for me.
> 
> Does that make any sense?
> 
> Regards,
> Eric