Re: question re performance of bidirectional amplifier (corrected)

ajparent1 <kb1gmx@...>

--- In BITX20@..., "eternalesquire" <eternalsquire@c...>

No, I intend this to be used as 20M. I just use a colorburst crystal
oscillator for signal tracing, and I used a scope to compare the
incoming and outgoing signals to measure gain.
Ok, just curious.

Either those are very poor quality versions of MPS2222 (defective
lot?) or something is very wrong. Could it be measurement error?

I wired up a second stage and checked it against the schematic as I
was doing it, every trace is accounted for.

I had used ground-plane component support construction. Could that
technique reduce the gain?
That works well you unless you use really long leads.
I do groundplane AKA "dead bug", Ugly or Manhattan style mostly
as I can fabricate faster than creating a PCB first. Also ground
loops are unheard of with deadbug. I've used this method to
frequencies up to 1296mhz!


--- In BITX20@..., "ajparent1" <kb1gmx@a...> wrote:
Inline and edited.

--- In BITX20@..., "eternalesquire" <eternalsquire@c...>
Next question: I have now finished building the first bidirectional
amplifier after the preselector. I injected a 3 mV signal at
3579 KhZ in each direction, and got out a 20mV phase-inverted
copy of the same signal when power in the correct direction was
applied. The fidelity is good, but the gain stages are not
even a factor of 10. Is this the expected performance?
This is very low gain. The expected should be far higher in the
order of of around 16DB. I would expect to see around 100mv
for 3mv in.

I'm curious why 3.579nmhz? IS thise going to be 80M version?
If so I'd suggest using T50-2(red) ferrite rings for the bandpass
filter or the required turns will be very high.

I am using all parts as specified, for transistors I am using
MPS2222 and for switching diodes I am using 1N4148.

I know these are probably not the best of transistors, but I
want to attempt to duplicate the results per the web article.
Those should be more than adaquate at 4mhz. However, I'd suggest
rechecking your wiring. Make sure the capacitors are in the correct


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