Re: Getting indication of rf


Neil Smith G4DBN
 

A simple voltmeter works fine Ben, you can pull a milliamp without much impact, but a 20kohm/V movement is fine.  I put the outputs from those at the masthead into a cheap PIC board with multiple analog to digital converters and send the values back over an RS485 link, but other folks use a multicore cable and send back the analogue voltages to the shack end.

If you can borrow a calibrated power meter, you can do a rough calibration of each of the detector outputs as measured by your meter setup.  I have a lookup table in memory to convert the voltages to approx power, but a curve plotted on a bit of graph paper is just as good really.

There are also lots of decent single-rail opamps which will work from rail to rail, but it isn't really worth the effort. A rotary switch, some trimmer potentiometers and a 50 microamp meter would work well.

Neil G4DBN


On 04/06/2020 11:06, militaryoperator via groups.io wrote:
Having several transverts now and a couple of low power amps most have a built in rf o/p indicator, 1 to 3v at the max.

I was thinking of how to meter this, guess putting a simple cheap voltmeter across the pin might just load it too much so was thinking of a 741 opamp say, nice hi z i/p but needing a split rail. 

Plenty of dc to +- units on ebay so should be quite simple/cheap. 

Just wondered what others use?  I know you can use an inline directional couple, costly for a good one, but I was thinking of a unit built into each system. 

Ben G4BXD
_._

Join UKMicrowaves@groups.io to automatically receive all group messages.