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IIRC some early German RF cables and test equipment impedance was nominally 60 Ohms for that reason.? The book "Transmision-Line Theory" by Prof. RWP King analyses this and many other transmission

I just emailed you the service manual so check your email. I also have the manuals for the PM3065 and 3067. Sam W3OHM

I have used a PM3050 quite a while ago, there may be a switch on the rear panel for the channel, but mor likely there is something in the soft menu about configuration, or channel select. Do check

So I don't know if any one as this issue, I bought a used PM3070 scope and the 2chs are summed together and I cannot figure out how to clear that to make them independent.? I went threw the menus and

Great discussion, very informative. I just want to point out that a good portion of the article describes the counterpoise and ground part of the system. In my opinion, this is the main difference

Thanks for the clue, Alan. I dug up the links to the article so I could see the schematic. https://www.pa3fwm.nl/projects/miniwhip/ looks pretty good; I believe that is what the missing link in your

The original design has a very unusual source, an Australian Government Sigintel agency. This is a very unusual source of information and may be subject to? unusual conditions that have been not

Assuming this comment is directed at me, years ago I did the IMD tests for Roelof's Mini-Whip before he had that capability. His original Mini-Whip with the jfet front end and bipolar output measured

Thanks to Robin for the detailed comments. I built the Aussie active whip today, testing it on the bench. I used a plastic J310 with no heat sinking. The use of just a 39 ohm resistor plus whatever

Many thanks to Robin, G8DQX and Martin, G8JNJ for your insightful comments - I'm glad that others have had a chance to read Martinsen's paper in more detail than I have yet had. I fear that my

The design is now dated as more modern devices have become available and our understanding of active antennas has also improved. The choice of coax is not that important from the perspective of loss,

Jeff and others, the need for a well defined output impedance from the active antenna/aerial is explained on pp22-24. The graph in figure 2.16 shows the variation of gain with frequency when around 2

Ed Breya <edbreya@...> added the album Ed's Q meter project ( /g/Test-Equipment-Design-Construction/album?id=285303 ) : building the box, heading toward final design --- The

I just quick-looked at this, and don't see any particular problems. Here are some comments: The document is dated 2018 - it is likely not some ancient work, although the principles and components have

Mike, Thanks for the reading on the article. I’ve read over it but not studied it. I agree with what you said about the devices but one point there. The characteristics of these devices are very

Mike, Thanks for the reading on the article. I’ve read over it but not studied it. ?I agree with what you said about the devices but one point there. The characteristics of these devices are very

It is curious that the document is undated. The design and construction photo makes it look like it is from the last millenium. Impedance matching does help as he describes in that paper as far as

Correction to my previous post - the JFET front end in Mr. Martinsen's active antenna design is the U310 - typing glitch! Mike, K8CN ________________________________ Sent: Wednesday, March 22, 2023

Thanks, Jeff, for posting your questions and the link to the paper (and to another poster who gave a viable link). I only quickly scanned Mr. Martinsen's paper and will return to a more careful

Thank you, that worked.? I will read it and see what I make of it.? However, I am not an expert? Mostly just lurk here?Sent from my Galaxy