[TowerTalk] Loading Coils

[Steve Harrison]

On 8/4/2025 7:44 AM, Brian Beezley wrote:
> Q is not easy to accurately measure for big coils like those sold by 
> QCoil. The fields may extend quite a distance and interact with nearby 
> objects, such as the instrument enclosure or even your body.

I am continually amazed with the placement of air-wound pi net inductors 
just an inch or less from the side walls of final amp compartments, and 
in other examples such as antenna tuners. Even Ameritron amplifiers 
occasionally show such mounting. My Elmer taught me long ago that to 
minimize the effect of such surfaces upon tuned circuits, always keep 
the inductor at least a coil-diameter away from a solid surface. That 
advice has stood me in good stead through the years. When I've had 
access to reliable Q-meters, experiments with large coils and solid 
nearby surfaces has always shown some detrimental effect upon the coil's 
Q by the surface.

Steve, K0XP