Electronics > RF, Microwave, Ham Radio

CB and Ham Radio Techs Love Their Bird Wattmeters

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Wiring progress for today. I made up female dupont connectors on the ends of some wiring so I will be able to unplug power to the log amps and also unplug the output voltage from either one of them, if needed for testing purposes.

Bends don't look near as bad in this photo.   

Yea I got them to sit a bit better. The bends coming off the coupler are about as tight as I'm comfortable with but I think it's OK.

I think I found the couplers on Ebay in June and started it all from that point, so if I can get this project finished by Dec 31 it'll be seven months.  :phew:

Breadboard eliminated, just a few more components and wires to connect.

I finished the wiring and decided to have headers for all the inputs and outputs so they are removable. However, this decision to use headers made my case now not have enough inside height so I'll have to go back and re-do some 3D printed case parts. Not a large deal but that's how things roll.

The meter seemed to work at first glance. However, upon testing with an rf input of several watts it was obvious that there was a problem with the indicated rf power. I didn't find anything wrong with the wiring I did on the Due proto board. I was certain I didn't muck up the program testing things last time I ran it, but I checked and downloaded the software again to be sure. I proceeded to move down to the log amps because I didn't see any Vout from either one at the A0 or A1 inputs. In fact, the voltage input to analog channel A0 and A1 seemed to be floating though I wasn't sure how that issue could have arisen. Oh no please don't tell me ... no it can't be they're zapped?  :palm:

I opened up the case on the channel one log amp and observed that the center conductor of the Vout cable had pulled away from the solder pad. I then opened up the other log amp and saw that the same thing had happened. Obviously there was a lot more twisting force on the cable than I had anticipated.

I shorted the center conductor to the Vout pad on the log amp with a pin and re-transmitted my test signal. At 146 MHz, the FWD power registered a decent reading, off a bit due to changes needed in all the cal factors, so I'm confident the project will be good to go after I repair the current problem.

What I think I'll do is split the shield into a left and right conductor, and that will anchor it better. It won't be tugged on anymore.

But the bright side is that it appears to be a functional meter from what few tests I've done.


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