[R-390] IF sweep alignment

[Stephen M. Murphy]

Y501 on the R-390A is a crystal filter (0.1 KHz.)

-Steve N8NM

On 02/26/2011 06:58 PM, rbethman wrote:
> The R-390 series has NO crystal filters at all.  The R-390s used pure
> circuitry to achieve the end, while the R-390As use the mechanical filters.
>
> Bob - N0DGN
>
> On 2/26/2011 6:43 PM, Bill Hawkins wrote:
>> Haven't seen any mention in this thread of the mechanical filters
>> in the A version.
>>
>> You may recall that there was a hybrid combination of the A and
>> a non-A IF deck (R-725) because the mechanical filters prevented
>> fine direction-finding operation. Ringing mechanical filters,
>> IIRC.
>>
>> There was also at least one thread in the good old days of this
>> list that strongly advised against trying sweep alignment of the
>> IF strip, because the ringing filters distorted the wave form.
>>
>> Perhaps you could use a wide band 455 KC receiver before the
>> filters to see the response curve of the IF transformers before
>> the filters. You can't align the filters anyway. What you do is
>> find the center of the 100 Hz filter (does an A have that crystal
>> filter?) and use that as the base frequency of the sweep generator.
>>
>> Hope this stirs someone's memory.
>>
>> Bill Hawkins
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