[R-390] Alignment of the Mechanical Filters and IF with a Spectrum Analyzer

[chuck.rippel at cox.net]

I have a very nice Tektronix 2712 here.  The short answer is yes, you 
can adjust the trimmers to minimize ripple in the passband of the 
mechanical filters.  However, that comes at the cost of an input output 
mismatch @ 455kc and the filter exhibiting some loss.  In the receivers 
I experimented with, the return was barely noticeable and not worth the 
loss.  I stick with injecting exactly 455 kc and peaking each filter and 
T-503 only VIA a VTVM connected to the Diode Load.  The other 2 
transformers accommodate the 16 kc bandwidth for MUX.  As long as they 
have not been diddled with, are usually fine although there is a 
procedure for aligning them.  That alignment is very broad.

A spectrum Analyzer and tracking generator would absolutely be the 
preferred method to align the IF in an R390 or SP-600.

---
No  trees were killed to deliver this message.  However, a large number 
of electrons were terribly inconvenienced.

Chuck Rippel




>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 13 Dec 2012 12:07:17 -0500
> From: Mack McCormick <w4ax.mack at gmail.com>
> To: R-390 Group <R-390 at mailman.qth.net>
> Subject: [R-390] Alignment of the Mechanical Filters and IF with a
> 	Spectrum	Analyzer
> Message-ID:
> 	<CAFzyUt60QdpznMU6EpLP1HPAp1A5XWCGGrcmMxh_QPO5uhsrPg at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> I have a calibrated high quality spectrum analyzer and tracking 
> generator.
> Does anyone have experience with using a spectrum analyzer to:
>
> 1) *Adjust the mechanical filters? *There is some literature that 
> suggests
> just peaking for noise can adversely affect the filter skirts.
>
> 2) *Stagger tune the IF?* My thought is that you could look at the 
> overall
> spectrum of the IF and make optimal adjustments.
>
> I would of course make sure that I don't load the circuit with the 
> spectrum
> analyzer to skew the results.
>
> Does anyone have any experience or suggestions?
>
> -- 
> 73,
>
> Mack de W4AX
> http://w4ax.com