Tricky one that Q. Lawrence. 
My first thought in connection with the temp. variable components that you list, it that it will be the coil that is likely to be the main contributor to changing the characteristics of that LC cct. as the temperature changes. So to reduce any such changes, the coil needs to be so constructed to minimize such effects - i.e. standard practice one would adopt for constructing a high stability VFO.
My second thought is that the effect of temperature changes will depend on the type of reaction arrangement that is being used. Where a tickler coil is used to couple the anode back into the grid, then the effect of temperature on that coil needs to be considered as well. How is the degree of reaction to be controlled? By varying the degree of mutual inductance between those coils? By changing the voltage on the screen grid of a pentode? By a variable capacitor: manual adjustment of the amount of reactive current in the feedback coil? Different arrangements will probably have different temperature dependencies.
Overall, for moderate temp. changes, I wouldn't expect the change in sensitivity to be a concern, especially considering that when the main tuning is manually changed, even by a small amount, it is not unusual to then find that the reaction control (or whatever type) needs an adjustment also.
I suppose the only way that you're going to get a definite answer is to follow classic R & D practice: build such a cct., get out a hair dryer - and see what happens!
Al. / Aug. 17, 2013 //
My first thought in connection with the temp. variable components that you list, it that it will be the coil that is likely to be the main contributor to changing the characteristics of that LC cct. as the temperature changes. So to reduce any such changes, the coil needs to be so constructed to minimize such effects - i.e. standard practice one would adopt for constructing a high stability VFO.
My second thought is that the effect of temperature changes will depend on the type of reaction arrangement that is being used. Where a tickler coil is used to couple the anode back into the grid, then the effect of temperature on that coil needs to be considered as well. How is the degree of reaction to be controlled? By varying the degree of mutual inductance between those coils? By changing the voltage on the screen grid of a pentode? By a variable capacitor: manual adjustment of the amount of reactive current in the feedback coil? Different arrangements will probably have different temperature dependencies.
Overall, for moderate temp. changes, I wouldn't expect the change in sensitivity to be a concern, especially considering that when the main tuning is manually changed, even by a small amount, it is not unusual to then find that the reaction control (or whatever type) needs an adjustment also.
I suppose the only way that you're going to get a definite answer is to follow classic R & D practice: build such a cct., get out a hair dryer - and see what happens!
Al. / Aug. 17, 2013 //
