Me too curious, about the amplification impedances...
Not only over the entire spectrum, but for diffrent Classes verses VDD too...
On 26/05/2013, Ashhar Farhan <farhanbox@...> wrote:
Giuseppe,
I have been wanting to get someone to test our blocks on N2PK vna. I
just acquired one, but I haven't found time to hook it up. Can you
look at the amplifiers too? Specifically, I want to know the
impedances over the entire spectrum.
- farhan
On 5/26/13, Giuseppe Marullo <giuseppe@...> wrote:
Hello,
I connected two scope probes to my MiniVNA Pro and applied them to the
un-powered BITX20a. Seems interesting.
This is the 11MHz Filter (between C53 and C89):
Center frequency of the filter should be about 11.001703MHz. Not sure
if/how to trust the reported attenuation on the skirt.
I have calibrated the VNA using the probes "against" each
other(transmission mode) and against a 50Ohm dummy load(reflection mode).
I applied the same method on the RF Filter, and I discovered that
probably L4 needs adjustment (1 turn more?) because does not cover up to
half of the 20m band.
This is the flattest response I was able to achieve, too low in
frequency (the markers are the band edges):
Didn't expect too much from the experiment (impedance mismatch at
minimum), but it seems to work, what do you think?
Giuseppe Marullo
IW2JWW - JN45RQ
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