High SWR Meter Value when in RX

Mick W8BE

I have a strange one here. I noticed that our SWR meter on node red was showing a value of 6.5 intermittently on our Node Red dashboard. This is when the radio is in RX mode and it will go between 1 and 6.5 . So first thing I did was look at the subscription stream data and to my surprise I am seeing 6.5 on from the radio. Here is the packet stream data for the SWR meter when it occurs:

I have the data here is displayed as an int. The math I use is:

  var swr1 = msg.payload[2]; // swr1 = 3 in this example

  var swr2 = msg.payload[3]; // swr2 = 68 in this example

  The math is :

  msg.swr = (((swr1*256/128) + (swr2/128));

  msg.swr = parseFloat(msg.swr.toFixed(1));

Which translates to :

(3*256) / 128 ) = 6

(68 / 128) = 0.53 = 0.5

(6 + 0.5) = 6.5

I know there is a bug with the smeters and I wonder could this be bug as well? If the problem was RFI induced, I would expect drop packets. The fact that the value does not change to me indicates this is the actual value the radio is sending in the stream.

Incase any one asks, the meter in question is sub meter 21 (swr).

Regards

Mick W8BE

I hate to say it but the problem was induced by me (argh). I was looking at the swr on my radio (which i use as a test env) and I noticed the same problem there. That was a major red flag for me and I went back and changed how I did the meter subscriptions to what I originally had. I have no idea how setting up subscriptions on different udp ports from the same TCP connection to port 4992 causes such a problem but it does. Lesson learned...let my code soak for a while before I deploy.

Regards