zin and zout for an rf amp'

hi all, thanks for reading.


i want to ask if somone can please actually measure the input and output impedances of this amp' in above link (no spice models please). it would be used at 28mhz & power in on 20mw. for the entirely professional approach this obviously needs a Large Signal Vector Analyser. its a simple & question but, one of you may have access to facilities to do this. Is there anyone on here or anywhere that could please. if you have any other techniques to measure like a return loss bridge then you you try that and see hat you get for zin & zout please. i accept this last method isnt the full professional treatment but, its just to get a rough estimate.


any help here appreciated & thanks.


i posted this before in another forum but, i think i rambled on too much. i also made a stupid mistake in my previous post by mentioning putting an attenuator in front of a small signal vector network analyser port. i should have said to do this at the output mesurement port of a return loss bridge to do a rough estimate. so anyway i apologise for my silly mistake.

& just one last thing how do i make the image file actually appear in the post rather than just its link to open it.

If you compute the impedances of each part, you can estimate the gain for a given load and output impedance.
Right now it looks like it resonates at 8MHz for highest impedance if a resistance load is applied.

The input bias current will determine the input impedance for this nonlinear design, but it will amplify.

hi sunny

thanks for taking time to reply.

its just a test amp' & not particulary optimised just experimentally derived. i was using it at 27 to 29mhz, mainly 28mhz. i was driving it with my marconi 2019a with 20mw in obtaining about 150 to 200mw ouput. in various test circuits with my source oscillators, driver & then this as the final amp' ive had around 300 & even up to 450mw once i think at 28mhz. thing is this has either had no or very little matching or filtering on input & output. im wanting to obtain zin & zout more precisely. i havent got SA or even a small signal VNA like HP8753 etc, just marconi 2019a & 200mhz analogue c.r.o. & homemade return loss bridge ).

this is just an aknowledgement of your reply firstly. i'll be back on soon though & would like to talk in more about measurements & estimates on it with you if thats ok.

thanks for now

expy...