[Hammarlund] HQ-129-X Serial Numbers

[Carl]

Also consider any change in the mechanical alignment of the variables, 
especially the BS as there is very little C to start with.

Carl
KM1H


----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
Cc: <Hammarlund at mailman.qth.net>
Sent: Tuesday, August 14, 2012 6:34 PM
Subject: Re: [Hammarlund] HQ-129-X Serial Numbers


> On 14 Aug 2012 at 15:21, Richard Knoppow wrote:
>
>>      That's what I have.  I checked the LO using a Collins
>> R-388.  I checked _all_ the bands to make sure the LO was on
>> the correct side of the signal.  Just to be clear, its
>> _below_ the signal on the two highest bands and above it on
>> the others.
>
> Excellent. Sounds perfect. :-)
>
>>      Now, about the bandspread.  The bandspread for 80 and
>> 40 turns too far. That is there is a progressive error that
>> reads the frequency low.  That means the bandspread cap must
>> have to turn too far, i.e., must change capacitance more
>> than it should in order to cover the tuning range.  If I
>> arbitrarily set it for a slightly higher frequency than the
>> correct top band edge I can make it read right for
>> _interval_  that is 100 khz points read 100 khz apart.  So,
>> evidently the combined capacitance of the main tuning cap
>> and trimmers is too large meaning the amount the bandspread
>> cap must change to change the frequency by a given amount is
>> too large.  What can cause this?
>
> I don't know for certain, but the manual states that the bandspread cap 
> MUST be set to 200
> on its scale (fully OPEN) when aligning the HFO. If the BS cap is set 
> anywhere else, then the
> main-tuning cap would have to be set at a lower-capacitance setting than 
> it should be to
> compensate, meaning that the BS cap would have to add more to the total 
> capacitance to
> tune where it then should.
>
> Were you careful to set the BS cap fully open, and make certain it stayed 
> there, when you did
> the alignment?
>
> Perhaps that is the problem?
>
> Due to the design of the 9 section BS cap, if it were not set exactly 
> correctly to begin with, it
> MIGHT make a lot less difference on the upper bands than it would on the 
> lower ones, since,
> as I remember it, different sections of the BS cap are used on different 
> bands.
>
> Ken W7EKB
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