Re: question re performance of bidirectional amplifier (corrected)

Ashhar Farhan <farhan@...>

I dont see the problem at all.
If you inject a 3mv signal, and you get a 20mv signal, the circuit is working just fine.

here is how, you need to check the power gain, not the voltage gain.

Now, a voltage gain of 6.6 translates to 6.6 x 6.6 = 44.4 power gain. (assuming that the input and output impedances are the same). That is smack down 16db as promised.

- farhan

On Mon, 22 Aug 2005, eternalesquire wrote:

1) Checked. These are 10 ohm resistors. I've made 2 stages so far
and had double checked all values of resistors going in.

2) I had been using 0.1 microfarad (value code 104) for all of the
capacitors of these units.

3) On a hunch that this was a bad type of transistor, I substituted a
2N2222A transistor. Gain was acutally worse, X6 rather than X10, so I
put it back.

I strongly suspect that whatever mistake I am making, I am making it

Now, the original schematic specifies 220 Ohm emitter bias resistors
in parallel with the emitter degeneration leg, for 2 of these units.
A 440 Ohm resistor is specified for the unit after the crystal filter.

Were the original values wrong?

Should I make DC voltage readings and show them to you?


The Eternal Squire

--- In BITX20@..., "ajparent1" <kb1gmx@a...> wrote:
Edited. inline comments.

--- In BITX20@..., "eternalesquire" <eternalsquire@c...>
I wired up a second stage and checked it against the schematic as I
was doing it, every trace is accounted for.
Another thought..

One possible is that the 10 ohm emitter resistor (in series with
capacitor) is not 10 ohms! It is sometimes easy to get 100ohm
and 10 ohm by error. Rough calculation suggests that might be the

Another source of error is if any of the capacitors are not
the correct value (too small).

I'd also check the transistors used. Is the gain going TX and RX the
same? It could be possible one transistor is shorted collector to
base internally.

Just thinking out loud.


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