Quick review of the Kit-Projects AGC board #ubitx

Jim Sheldon

I bought two of these for my 2 uBITX Version 5 radios.  First off, the directions for installing this board are brief but they are easily followed and the boards are easy to install.

Not wanting to drill a hole for the included switch and run a bunch of wires to it, I just wired the common pad to the "fast" pad for always on, Fast AGC.  I found a "Via" hole in the trace between R70 and "Vol HI" and ran a wire from there to the "VOL" pad on the AGC board which worked great.

Even though the "S-meter" output of this AGC system was designed to work with the CEC software, we found it worked with TSW's BITeensio board as well.  We use the A19 analog input on the Teensy 3.6 for the S-meter and this little AGC system drives our S-meter routines just fine.  I fed a 50 microvolt (-73 dBm) signal into the antenna connector and adjusted the software's S-meter routine's division ratio so the touch screen's display read S9 as it should.  The rest of the S units were so close to correct no further tweaking was deemed necessary.

I also found that adjusting the on board RF gain control for max recieved signal was the best way to do it.  As you turn the control counter clockwise, the gain increases and there is a point past which saturation occurs.  This is obvious when listening to a weak signal and you can hear the gain drop past this point.  Adjust it to that point and turn it back to where the signal just peaks.  Best to just leave it there if you want your S-meter to work right.  Once adjusted, this little AGC board keeps the RF input nicely within bounds on strong signals quite well.

ND6T, N8DAH, well done guys, well done!  The kit is certainly worth the price IMO.

Jim Sheldon, W0EB
TSW Project Coordinator

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