Quick review of the Kit-Projects AGC board

Jim W0EB, TSW Project Coordinator,  bought two of these kits for his 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, he just wired the common pad to the “fast” pad for always on, Fast AGC.  A “Via” hole was identified in the trace between R70 and “Vol HI” and Jim ran a wire from there to the “VOL” pad on the AGC board. This 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.

The BITeensio uses the A19 analog input on the Teensy 3.6 for the S-meter. This little AGC system drives the S-meter routines just fine on the BITeensio.

A 50 microvolt (-73 dBm) signal was fed into the antenna connector and Jim adjusted the software’s S-meter routine’s division ratio so the touch screen’s display read S9 as it should with a 50µV input. The rest of the S units were so close to correct that no further tweaking was deemed necessary.

He also found that adjusting the on board RF gain control for max recieved signal was the best way to adjust the level control. 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. Simply adjust the gain to that point and turn it back to where the signal is just peaking.  It is 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.

Jim calls out ND6T and N8DAH and says “Well done guys, well done! The kit is certainly worth the price IMO”.

Reference

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