[ARC5] Converter/front end for Q5-er Sets

[AKLDGUY .]

Hi Leslie

I'm not impressed with the converter stage. It seems over-designed.

There seems to be no need for a bifilar winding at the drain of Q2 (on the
BF-43 core).
A simple RF choke would be OK here since it is followed by the highly
selective tuned
stages of the BC-453. Why complicate things?

The cascode amp/mixer is a strange way to go at HF. I'm suspicious that
high level
LO signal could get coupled via the common Q1 into the antenna circuit, and
because
of the latter's rather broad tuning, there might be substantial LO signal
radiated.

There seems to be no justification for the presence of R1? and R2 (100K) in
the gate
circuit of Q1 since the ferrite rod ensures a ground return at this
location for the gate.
They can be removed since they are doing nothing. R3 (33 ohm) is probably
worth
keeping for stability and should be positioned right at the gate.

The rather high value of Q1's source capacitor (100 nF) may
allow instability at VHF,
since this capacitor will not necessarily adequately decouple VHF and
there's a path
to Q2's gate via the 100K gate resistor. A couple of smaller value caps in
addition
would be advisable here. Suggestions: 1nF and 100pF.

The converter's linearity (think crossmodulation) might benefit from a
raising of the B+,
since something like half the supply voltage gets dropped across each
device.

73 de Neil ZL1ANM


On Mon, Jan 12, 2015 at 6:10 AM, Leslie Smith <vk2bcu at operamail.com> wrote: