Re: LPF frequency curves #lpf

Paul Jorgenson KE7HR
 

Wes,

The antenna analyzer is only looking at the SWR (reflection) and will not give you an accurate indication of the transmission characteristics. Since you have a good test set, use the tracking generator in the HP 8935 and look at the transmission.

I normally use my MiniVNA or an Array Solutions VNA-2180 to look at the "as built" filters. For higher frequencies, I have an older HP spectrum analyzer that is good to 3 GHz (nice when setting up my UHF repeater filters).

If I did not have those available to me, I have used an oscilloscope with a 50 ohm load. Feed the filter with a steady (or at least, known) signal level and record the voltage to the load into a spreadsheet. Do the math in the spreadsheet and generate a graph. Much more time consuming than setting up your instrument and doing a direct measurement...

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Paul KE7HR

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