[HBR] Fw: Building a HB-65.... (sort of)

[Hugo W. Catta]

...snip....

> The only thing that might be an issue is the change of mixers.   A
> 6U8 will certainly work as a mixer but has much lower gain than a
> 7360 or other beam deflection tube.  Looking at the HB-65 diagram,
> you have two mixers, one IF stage of modest gain (6BA6),

....snip....

....TWO I.F. stages.

a no-gain
> 2nd detector (solid state diodes) and a moderate gain AF amp.
> That's probably not really enough gain if using a pentode instead of a
> beam deflection 1st mixer -- you may not have enough volume or
> decent AGC action.  I'd consider using a 6BA6 RF stage between
> the two front end coils

....snip...

> A second issue is that a beam deflection tube provides better
> isolation between the VFO and the signal path than does a pentode.
> You might want to consider using a 6C4 as the VFO and making the
> triode of the 6U8 1st mixer into a buffer.   Otherwise, voice signal
> peaks will tend to pull the oscillator off frequency and cause
> distortion.

Unfortunately the limitations imposed by the lack of space and transformer
power don't leave room for such alternatives. Also the 20-15-10 M converter
is out. 40 and 80 only. And on these bands I am concerned more about strong
signal handling rather than conversion gain. I guess an RF stage will
further "soften" the 6U8.

BTW; the cabinet is from an old National NC-60.

....snip....

> The HBR2K project has been shelved the last few weeks due to
> outside work, a family wedding, and other such trivial non-homebrew
> activities;  I'll be back to it shortly.

Is there a site where to see pictures/diagrams/circuits of the HBR2K ?

Thanks
Hugo
AA1XV