Re: [loopantennas] Questions for Chris Trask
- Had to think about this a bit.
> After trying several options (gain, bandwidth, stability - pick any two
> I've decided to build the amplifier described in your articlestage.
> The problem is I don't have the binocular cores made of 61 material, only
> made of 43 material. I understand this will kill the performance of T3,
> because it is loaded with the very low input impedance of the second
>Yes, you can probably get away with that. I made T3 and T6 identical so
> Question 1: Can 43 material still be used for T6? Its loading impedance is
> 50 Ohm.
as to reduce that number of different parts. 43 material performs poorly in
low-impedance circuitry so I use either 61 or 73.
>Transformer T3 gives you a current gain factor of 2 (6dB of power gain).
> Question 2: If I omit T3 altogether and couple the stages directly (with
> the necessary bias circuit modifications), how much gain would I lose?
> My naive opinion is that in the end, voltage gain of the whole amplifier
> is the ratio of 50 Ohm to the input impedance. I don't see how interstage
> and output transformers can increase it. T6 is still nice to have for
> balanced to unbalanced connection and for splitting/combining the power
> and the signal.
It also provides second-order IMD immunity from even-order products from the
first amplifier stage. So, you'll lose 6dB of gain plus the OIP2 will
N7ZWY / WDX3HLB
Senior Member IEEE