Re: KD8CEC ‘s SWR senser

Jerry Gaffke
 

Kits and Parts assumes you are using an old school micro-ammeter.  
That would present more of a load than the tens of megaohms presented by the Nano's analog input pin.

The TandemMatch/StocktonBridge circuit has RF going into the diodes that is proportional to the forward and reverse power.
That power can vary from second to second, the 220K resistor discharges the 0.1uF cap when the power decreases.
The value of the resistor is not critical, but without it it might be several seconds before the cap discharges.

Jerry, KE7ER

 

On Sun, Dec 1, 2019 at 01:45 PM, Joel Trenalone wrote:
Also, here are the schematics for both the kitsandparts bridge (I’m using), and the home brew Stockton bridge (that Ian Lee uses in his video and description http://www.hamskey.com/2019/04/installing-swr-and-rf-power-sensor-in.html  )

I see some differences, namely the 220k resistor to ground from the reverse/forward power outputs on the Stockton bridge, but is not on the kitsandparts bridge. Note sure why the difference, and how it affects the operation to the Arduino. 

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