How are the resonators tuned? Screws through a soldered-in-place nut do
not make a good solid contact. I've tried it many times at both 1296 and
the H1 line (1420.405 MHz), and the result is unstable. However, if this
were the case, I'd also expect the S11 measurement to be unstable. If this
technique is used, a lock nut is required (which makes proper adjustment
even more 'tricky').
Did you complete and store the full OSLT cal? Are you using the native
NANO instrument or Saver on a PC/lap?top?
Yea, I know. More questions than answers.......??
Dave - W?LEV
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On Tue, Jul 21, 2020 at 8:17 PM Zack Widup <w9sz.zack@...> wrote:
I thought I'd use my NanoVNA H-4 to tweak a 3-pole helical filter for 1296
MHz that I have for a transverter. The helical filter is mounted on a pc
board with SMA input and output. I calibrated the NanoVNA for 1280 to 1320
MHz and connected the filter to it. The NanoVNA displayed s11 as I expected
(a good dip which I could adjust to 1296 MHz). However, the s21 did not
display what I expected. I expected a response that a normal bandpass
filter would have. Instead, I had pretty much a straight line for s21
across the frequency range that fluctuated with each reading.
Is the performance poor at 1296 MHz?
Zack W9SZ
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