[AMRadio] 6BA7 mixer Oscillator Drive
Byron Tatum
bjtatum1 at att.net
Mon Jul 1 08:52:49 EDT 2013
Hello-
In a homebrew dual conversion tube receiver I am building I must resort to a solid state osc to supply a 2.155 Mhz signal for the 6BA7 second mixer, which is converting 1.700 Mhz to 455 KHz. I just cannot support another miniature tube on my small power transformer, even a 0.15 amp such as 6BH6.
I have chosen a 2N5484 osc circuit that is very similar to the tube-type tuned-grid/tuned plate osc circuit. There will be a resonant circuit at the crystal freq of 2.155 Mhz in the drain (output) of the 2N5484. My question is: Am I going to have the proper osc drive to the 6BA7 from this single transistor osc? The output (from the drain/ tuned circuit) of the osc circuit I chose shows a 10 pF coupling capacitor. I noticed on the Collins 75A-4 circuit for both 6BA7 mixers there are 100 pF capacitors coupling the crystal osc or the VFO. I am thinking that I should build a buffer amplifier but thought I would ask first.
Thanks, Byron WA5THJ
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