[ARC5] GF-11/12 frequency lowering

[WA5CAB at cs.com]

OK.  My error on saying receiver instead of transmitter.  You did write 
"GF".

I would have said that my comments would apply equally to the transmitter 
coil sets, but I take it you want to get it to go lower than the frequency 
marked on the coil set.  The manuals give the capacitor maximum values.  From 
that and the lowest rated frequency you should be able to calculate the 
approximate coil inductance.  And from those two, calculate roughly how much 
additional capacitance is required to get 5% lower.  I would do the padding in 
the coil set.

In a message dated 08/23/2011 12:59:21 PM Central Daylight Time, 
dennis.monticelli at gmail.com writes: 
> Thanks for the inputs.  Actually, I was referring to the transmitter, not 
> the receiver.  The transmitter has a much less complicated coil set.  I 
> was thinking about padding down the VFO tank and the PA tank.  I didn't think 
> there was enough range in the screw adjustments to swing 5%.  Any thoughts 
> regarding the transmitter?
>   
>  
> 
>  
>  On Tue, Aug 23, 2011 at 9:31 AM, <WA5CAB at cs.com> wrote:
> >> I haven't, and don't recall anyone else ever mentioning it.  But the 
>> coils are match-marked to a specific serial number receiver.  I don't know, 
>> and the manuals don't say, whether the tweaking was done in the receivers 
>> or the coils, but logic says it must have been the coils.  If what you are 
>> trying to do is to get the frequency to match the tuning chart, I see no 
>> real "collector" reason not to tweak the coils.  So long as you edit 
>> somehow the serial number on the coil to match the receiver it now belongs to.  
>> The odds of anyone ever again matching the coil up to its original 
>> receiver are quite small.
>> 
>> I'll add (although I have never looked carefully at the coil sets to 
>> prove it) that there is probably some way in which to adjust the coils, as 
>> well as maybe "select on assembly" padder capacitors. 
>> 
>> 
>> In a message dated 08/23/2011 02:46:41 AM Central Daylight Time, 
>> dennis.monticelli at gmail.com writes: 
>> >>> Has anyone tried capacitively padding a GF-11/12 to bring the freq 
>>> down
>>> slightly (about 5%)?   I would like to do it in a gentle way such that 
>>> the
>>> caps could be easily unsoldered to restore originality.  Of course 
>>> another
>>> way to do this is to locate and acquire a different coil set.
>> 
>> 
>> 
> 
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480