[Drake] Drake Xtal Eliminator - Spurs anyone?

[Bob Camp]

Hi

I have not built the same box you did but have done some similar stuff. 
Based on that here are a couple of guesses:

If you are getting extra beat notes to either side of the signal that's 
generally an indication of phase modulation of your VCO.  I would check 
the parts in the filter between the phase detector and the VCO to be 
sure they are all the right value and working properly. Since the spurs 
are phase modulation changing the size of the coupling cap may not help 
things much.

Since you square up the reference oscillator as soon as it goes into 
the PLL chip it's harmonics will be running around everywhere. They 
almost immediately get on the power and ground lines to the digital 
section of the PLL. Makes listening to WWV a bit tough.

	Take Care!

		Bob Camp
		KB8TQ



On Aug 10, 2004, at 12:18 AM, Tom Hammond wrote:

> Hi Folks:
>
> Has anyone else managed to get their (Hageman) Drake Xtal Eliminator 
> build and installed?
>
> If so, how bad are the spurs you're hearing?
>
> I'm hearing a number of relatively low-level spurs, almost ALL within 
> the bottom 50 kHz of each ham band (right in the middle of the CW 
> section).
>
> For the most part, the spurs are low enough in level that they don't 
> significantly effect received signals which are S-1 or stronger, but 
> they're still there, and do make copy a bit more difficult... and less 
> enjoyable.
>
> I have noted that, on 20M at least, when I'm copying a strong signal, 
> I hear additional beat notes on either side of the main signal. I'm 
> wondering if this might indicate excessive injection... anyone care to 
> comment upon this? I've not yet tried reducing the coupling cap, but 
> that will be something I'll try.
>
> I also noted that the 10MHz oscillator has some pretty strong 
> harmonics, even though the oscillator's enclosed. I guess the signals 
> are sneaking out via some of the other signal paths.
>
> It's a good thing that I changed R100 (originally 47 Ohms 3W) to a 5W 
> resistor... even at 5W dissipation, that resistor gets plenty 'warm', 
> as does the aluminum box to which all three Vregs are physically 
> attached for heatsinking. They'd BURN UP if they weren't screwed to 
> the box.
>
> If you HAVE gotten your project built and installed and found that the 
> frequency was off by about 5-8kHz, try replacing the 10MHz master 
> oscillator xtal (Y1) with a 10MHz SERIES-resonant (18pF load) xtal. I 
> think the xtal I received from FAR circuits may have either been 
> mis-cut or was a parallel-resonant xtal instead of series-resonant. 
> Replacing it with a series-resonant xtal eliminated my off-freq 
> readings.
>
> I'd really like to hear from anyone else who might have completed 
> their Xtal Eliminator and have it installed... at least HOOKED UP, if 
> not completely 'installed'.
>
> 73,
>
> Tom Hammond    N0SS
>
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