[R-390] IF Alignment Question

[David C. Hallam]

Barry,

The test lead has a .047uF 600V or so capacitor in series to block DC from
getting into the SG attenuator.

Other than that I can't supply much advice.  I am trying, so far
unsuccessfully, to find the source of an oscillation in my R-390 IF.

David
KC2JD

> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Barry
> Sent: Sunday, September 10, 2006 12:27 AM
> To: R-390-List
> Subject: [R-390] IF Alignment Question
>
>
> Gentlemen,
>
> I put the latest project back together today and have begun aligning it.
> Aside from doing something really dumb where I had the PTO tracking from
> 2.55 to 3.55 instead of 2.45 to 3.45, it is going fairly well.
>
> I followed the instructions on pages 115 and 116 of TM 11-8586A
> to align the
> two IF assemblies.  Then I started on the RF coils.  I noticed that when I
> switched slowly from band 0 to band 1, the diode load would increase a bit
> before clicking to the next band and I noticed the rack that was
> moving the
> most at that point was the second IF.
>
> Leaving the radio set to a BC station, I started playing with the slugs in
> the IF and noticed a dramatic improvement in signal strength.  I
> peaked all
> six coils that way and the radio seems to be a lot more sensitive.
>
> Am I doing the alignment a disservice to peak the IF coils this way?  Does
> this set them at an optimal position for one part of the band and
> reception
> will suffer at other portions of the band?  That didn't seem to
> be the case
> but I didn't test it all that much.
>
> When I said I followed the instructions, I don't have the "Test Lead
> CX-2919/U" the instructions call for.  I was just connecting the output of
> the generator directly to the test points and using a minimum signal, did
> the adjustments.  Is this possibly causing the circuit(s) to be loaded
> improperly and detuned?  Does anyone know what's in that Test Lead?
>
> By the way, I'm using a GR-1001A generator with the 50-ohm
> impedence adapter
> and an HP-410B meter.
>
> Thanks in advance for any advice.
>
> Barry - N4BUQ
>
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