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Friday, 7 April 2017

I'm about there!


You'll remember last time I started modifying the 13cm PA I had acquired. Well, I think it's about done.

What we have is the modified PA, an Arduino Nano plus some software to monitor:
  • PA Temperature
  • Forward power
  • Reflected power
  • Bias current (driver, Left and Right PA MOSFETs separately)
and trip if anything goes out of bonk.

The Amplifier now looks like this:

I've just to wire up the Analogue inputs in this image. There are three "status" LEDs on the front panel; one for "All OK", one for "It's gone horribly wrong" and a final one for "TX". If you connect the serial cable to the Nano then there is a status line repeatedly output giving the details of all the inputs read and their values.

The connector on the main board of the Amp is configured like this:

and it was therefore a fairly simple case of wiring the various pins to the I/O of the Nano and writing some code. I stole a lot of the ideas for the code from Mike G0MJW - but there are quite a few differences between what I have ended up with and what Mike created a few years ago.

The 9V line to the bias and other bits of the board is permanently on; the 28V line is also enabled all the time but switched bu a FET switch under software control. This switch is the same as the one in the sequencer, it's just altered slightly for 28V:

I've stuck the source code here if anyone is interested.

Time now for some testing.....


A couple of minor software mods (updated on the link above) during testing and all seems to be OK. I am not entirely convinced about the scaling values used to convert from the ADC readings into the value units, but time will tell.

Here's the whole system - there's an IF cable from there to my IC9100 which is used on 70cm as the rig for the transverter: