This afternoon I warmed up the HP vector network analyzer and tried a few
things.
First I calibrated analyzer port to 50 ohms.
Then I put a 75 ohm load on it and it read 1.5:1 SWR as would be expected.
Next I added a 4 foot and a 10 foot 50 ohm cable between the analyzer and
the 75 ohm load. The analyzer still showed an SWR of 1.5:1 as expected.
Then I hooked up a small Kenwood manual tuner to the analyzer with a 19 inch
cable and placed the 75 ohm load directly at the output of the tuner.
Adjusted the tuner for as near to 1:1 SWR on the analyzer (1.08:1).
Then added the 4 foot cable between the tuner and the analyzer. Then added
the 10 foot cable between the tuner and analyzer.
The SWR remained at 1.08:1 no change in SWR! I did not touch the tuner
tuning.
Then reconnected the tuner to the analyzer with the 19 inch cable and placed
the 10 foot cable between the OUTPUT of the tuner and the 75 ohm load.
Without re-adjusting the tuner the SWR read 1.43:1
Then added the 4 foot cable to the 10 foot one and the SWR was 1.40:1,
almost the same.
I ran this around 30 MHz and then around 26 MHz to move away from a near 1/2
wave length but the results were the same.
The same connectors, cables and adaptors were used with the cables in front
of the tuner as they were in back of the tuner.
Looking at another screen on the network analyzer I could see the resonance
of the tuner shifted in frequency when adding the cable on the output side.
73
Gary K4FMX
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|