[Hallicrafters] anyone got May 69 QST& tech query

[wb8jkr at juno.com]

  Glenn,

 I think it mainly depends on the circuitry the xtal
is connected to and the shunt capacitance it shows 
to the xtal. Usually in transistor gear the capacitor is
placed in series with the xtal because the circuit 
capacitance is somewhat high, in a tube circuit
the capacitance is typically lower so the capacitor
is placed in parallel. Placing capacitance in parallel
won't "block" the xtal UNLESS too much capacitance
is used any more or less than a series capacitance would
"block" the crystal if too little capacitance is used.
 Also, when reactance (Xc or Xl) is placed in series
with the crystal the result is a rise in frequency, when
its placed in parallel it will result in a decrease in 
frequency. For an example of crystal frequency
"fudging" see my article in the Feb. 2003 QST 
"Optimizing the Heath HW/SB transceivers" on
page 77. The pictorials are located on the ARRL
website, the entire article may be as well.

73,  Mark  WB8JKR


> Also, I have a question for the tech experts., specifically, some 
> xtal 
> controlled transmitters have trimmers in parallel with the xtal and 
> others in series 
> with the xtal. Both ways claim to rubberize the xtal a bit for 
> getting it on 
> frequency. My question is why are some trimmers in parallel and 
> others in 
> series with the xtal? It would seem to me that parallel is the only 
> way. Putting a 
> cap in series would block the xtal output altogether. Whatdoyathink?
> 
> 73s, Glenn  


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