Very interesting! Much easier than dragging equipment to antenna feed point. I wouldn't have thought of this technique. Thank you!
@oschonrock
3 жыл бұрын
Great stuff. Might start using this straight away. Was there a reason you used a 75Ohm Dummy load rather than one which matched the impedance of the system?
@wardharriman8965
3 жыл бұрын
It is important that there be an impedance mismatch so that you see the rotation on the chart. It is probably easier to do 25 ohms (two 50 ohm terminations in parallel) but any impedance will do. An SWR of around 2 to 1 is probably optimal.
@oschonrock
3 жыл бұрын
@@wardharriman8965 Thanks. That was obvious really, if I had thought about it a bit more ;-) Think I will just use an all female SO239 T piece and 2 x 25W 50Ohm dummy loads to make a 25Ohm mismatch. The little T-piece shouldn't affect the reference plane too much at HF.
@wardharriman8965
3 жыл бұрын
@@oschonrock I expect I used 75 ohms 'cuz I had a 75 ohm termination plug in the drawer and found it before I found a 'T' and two 50s. :-)
@oschonrock
3 жыл бұрын
@@wardharriman8965 It just occurred to me that the "tweaking" to reverse model and thus find the params of the TX line, could be an application for the V18.0+ optimisers, similar to here: kzitem.info/news/bejne/l4JuvZx9nH-Sfqg except that the "optimising function" will need to take into account something like "maximum radius of the full swept frequency paths" . I didn't know how to express that in code within SimSmith.
@wardharriman8965
3 жыл бұрын
@@oschonrock There is a way to get a list of all the frequencies an impedance file contains. Check the Anvil manual for ‘GetParamSweepInfo()’.
@dallasshell6455
3 жыл бұрын
Thanks for sharing all your hard work. N5FEE
@troy3456789
2 жыл бұрын
There are no videos that simply explain "feed point impedance", and show what they mean. I see a lot of questions on this on the extra test. I don't know what it means. I think a ham should make a video about it, and show their work. I do not know what what your drawings are. Many of these hams that make these videos assume their audience is composed of seasoned experts.
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