Hi,
I have here to same set ups.
RTL-SDR >> 4.5 meter coax 75 Ohm >> LNA >> Antenna
I disconnected the RTL-SDR from the coax an antenna set up and connected the Nano VNA to both set ups and yes I can measure SWR, Logmag and get a Smith circle.
Compared the values of both and they are different which is absolutely clear for me as Yesterday we optimized one antenna to get a better signal at 174 310 000 and mine was not optimized.
So I guess I spent the bucks for the DC Blocks for nothing but does not matter. It is leanring material and perhaps one day I can use them somewhere else :-)
Both set ups are running pointing at the same transmitter 960 km away from here and later in the afternoon we will compare data of Meteor scatter.
Thanks everybody for the comments which made me analyze everything more.
One interesting thing is that now having measured with the LNA in the line the good SWR value did move to a higher frequency compared to optimizing without the LNA.
I am talking about a DIY 4 element YAGI antenna for 174 310 kHz. you can see my meteor scatter data in the rmob.org under Rainer Ehlert in Mexico San Luis Potosi. The second set up is still under testing and will be in the same city on the roof of a friend about 4.5 km away from my site to the Northeast.
Lots of things still to learn. Radio waves are magic :-)
Rainer
