[R-390] R-390 Digest, Vol 76, Issue 10

[bernie nicholson]

Bill what you are seeing are the actual frequencies of the individual discs 
in the Mechanical filter , and its quiet normal , Regards Bernie Vk2abn
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Sent: Wednesday, August 18, 2010 2:01 AM
Subject: R-390 Digest, Vol 76, Issue 10


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> Today's Topics:
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>   1. R-390A Multiple Signal Peaks (Bill Scurlock)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 17 Aug 2010 10:41:07 -0500
> From: "Bill Scurlock" <k5gcw at sbcglobal.net>
> Subject: [R-390] R-390A Multiple Signal Peaks
> To: <r-390 at mailman.qth.net>
> Message-ID: <B0A40A20846E4804A3590DFB6678F67D at UNIT4>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I obtained my first R-390A a few months ago and have been slowly becoming 
> familiar with it.  There is one operational characteristic that I don't 
> know whether it is normal or not.  As the receiver is tuned across a 
> carrier signal, there are multiple peaks observed on the Carrier Level 
> Meter, and also changes in the audio frequency response resulting in some 
> degree of audio distortion regardless of which signal peak is selected by 
> the tuning knob.  The difference in signal level represented by these 
> "peaks" and "dips" in the carrier level meter are somewhere around 100 
> microvolts or so where I did the testing (at carrier levels of about "40" 
> on the meter).  Visually, the needle on the carrier level meter would 
> swing one or two "needle widths" between signal peaks.  The AGC was on 
> during these tests.
>
> There are 6 identifiable signal peaks across the 16Kc. bandwidth position, 
> spacing varies from 1.1 to 3.2 Kc., and the average spacing is 2.52 Kc. 
> In the 8Kc. bandwidth position, there are also 6 peaks with spacing from 
> 1.2 to 2.5 Kc., and the average spacing is 1.78 Kc.  In the 4Kc. bandwidth 
> position, there are 5 identifiable signal peaks, spacing varies from 0.3 
> to 1.0 Kc., and the average spacing is 750 cycles.  At 2Kc. bandwidth, 
> only 3 peaks can be seen, and they are about 600 cycles apart.  Only one 
> peak can been observed at the 1Kc. and 0.1Kc. bandwidth positions.
>
> I checked the IF tuning, and it is stagger tuned as per instructions. 
> Although I am suspicious that this may be a factor, I wanted to send this 
> email to the group before I started making changes in the IF tuning 
> arrangement.
>
> I have other questions for the group, but wanted to address this one 
> first.
>
> Any assistance you can provide will be appreciated.  Thanks.
>
> 73, Bill, K5GCW
>
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> End of R-390 Digest, Vol 76, Issue 10
> *************************************