[R-390] 0.5-8.0 Low Sensitivity (Long)

[Patrick]

Tod, are u sure that u have the right slug?.....Pat
----- Original Message ----- 
From: "Cecil Acuff" <chacuff at cableone.net>
To: <ToddRoberts2001 at aol.com>; <r-390 at mailman.qth.net>
Sent: Monday, September 11, 2006 11:12 AM
Subject: Re: [R-390] 0.5-8.0 Low Sensitivity (Long)


> Well that's another tip off that there is a resonance problem in that 
> particular tuned circuit.  The slug tuning should never be at it's 
> threaded limit to achieve the peak....(it's actually not the peak because 
> you are at a physical limit prior to reaching the peak)
>
> I've had to add and sometimes even remove fixed capacitance to get within 
> the range of the trimmer.  It's seems to me the inductance value has 
> changed from when the can was manufactured.  Maybe there is fine particles 
> of slug material worn into the coil form.  Maybe the slug has a chunk 
> missing off the bottom of it...who knows.  The factory value of the fixed 
> mica cap is no longer correct and requires custom matching to the current 
> circuit conditions.  I've had to do it several times and sometimes the 
> effect on performance is dramatic because you don't know how far off of 
> the real peak you are until you can achieve two distinct peaks with the 
> trimmer capacitor at different positions in their rotational range.  It's 
> worth the effort....
>
> Cecil...
> ----- Original Message ----- 
> From: <ToddRoberts2001 at aol.com>
> To: <r-390 at mailman.qth.net>
> Sent: Monday, September 11, 2006 9:59 AM
> Subject: Re: [R-390] 0.5-8.0 Low Sensitivity (Long)
>
>
>>
>> All else works fine now and I'm tempted to just leave well enough alone.
>> However, I'm
>> puzzled why fresh trimmers and new micas at spec values cannot get two 
>> peaks
>> during
>> alignment.
>>
>> Got any ideas?
>>
>> Dan
>> WB4GRA
>>
>> Have you tried screwing in the slugs a few more turns? What happens when 
>> you
>> screw in the slugs a few more turns? Does the signal continue to peak or 
>> does
>> it start to fall off? If it starts to fall off then the single peak would
>> appear to be near correct even though you only get one peak when the slug 
>> is
>> maxxed out. I wouldn't worry too much about a single peak if the 
>> sensitivity is
>> back to normal. 73 Todd WD4NGG
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>
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