[AMRadio] 6BA7 mixer Oscillator Drive


ne1s at securespeed.us ne1s at securespeed.us
Tue Jul 2 11:48:54 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

Hi Byron,

While I don't know the answer to your question, I would guestimate a a few
volts from the local osc. should be sufficient to feed into the 6BA7
mixer.

A good group to answer this type of question is the Glowbugs list - you
may want to join and ask there.

Please let us know how it works out after you try it.

73,
-Larry/NE1S



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