[hpsdr] Preselector PT-8000

[Henry Vredegoor]

Hi All, Pieter,

So we don't need a "reluctance tuned variable flux capacitor" after
all................?

;-)


Henry,


Original message:

Graham,

When you lower the impedance of the load and source, the shape of the series

resonance is much more pronounced. You can get in the order of 20 dB of 
selectivity improvement. This forces you to have better tracking accuracy. i

have been playing with these topologies for about a year and they look 
really promissing. All of the new radios are incorporating some sort of 
tunable preselector based on the same idea. Yaesu tunes the inductor with a 
stepper motor. I have been leaning toward switching the taps on the inductor

and adjusting the caps. The design I use is very similar to the PT8000, but 
it has 2 cores. a T200-2 and a T200-6 for the higher frequencies. I might be

able to get it working with just the T200-2 as in the PT8000 design.

Pieter, N4IP


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