[TenTec] Omni VI XTAL OSC problem

[Bob McGraw - K4TAX]

Good going Steve!

73
Bob, K4TAX


----- Original Message ----- 
From: "Steve Hunt" <steve at karinya.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Monday, January 07, 2008 9:02 AM
Subject: Re: [TenTec] Omni VI XTAL OSC problem


> Did a bit more work on the Omni VI today, and I'm pretty happy with the 
> results.
> 
> The line carrying the RF output from the Xtal Osc board to the Logic 
> board phase comparator also returns the DC control voltage to the Xtal 
> Osc varactor diode. So looking at this complex waveform with a DVM to 
> measure the loop control voltage was probably not very sensible :) 
> Looking at it with a 'scope makes it much easier to see what is going on.
> 
> I've now pretty much centred the DC component between Gnd and +5v , and 
> all the oscillators are now stable and under the control of the loop - 
> i.e. you can make a small adjustment to the inductor and the frequency 
> stays the same! The loop time constant is very slow - presumably so as 
> not to damage the Crystal Oscillator phase noise performance - so when 
> you tweak the inductor you have to allow half a second or so for 
> everything to re-stabilise.
> 
> Yes, in the process I managed to damage one of the inductor cores. 
> Fortunately I was able to remove the coil, get at the core from the 
> other end, and re-use it "upside down". You need a very steady hand to 
> remove the coils - they're only held to the PCB by the thin entammelled 
> wire used for the winding !!
> 
> I've asked Ten Tec Service if they have a recommended setting-up 
> procedure for the board. If not I'm pretty happy with it as it is.
> 
> 73,
> Steve G3TXQ
> 
> 
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