Wednesday, August 15, 2012

Radio-Kits Digital SWR/power meter kit review

Ross, VK1UN (and several others) writes: G'dday Peter,

Yesterday afternoon, I finally got the Digital SWR/power meter kit from Radio-Kits in the UK and built it last evening.

A very straight forward build as all the parts came in separate zip-top bags wit a component list in each. Instructions for building are down-loadable from the above site and are quite complete.

I added all the resistors first, capacitors, diodes, transistor and then the op-amp IC. The PIC was socket mountable so that remained out until the "smoke test!"

There are two boards, firstly the main meter and control board and the detector board, both can be built concurrently as there are resistors, caps and diodes on the detector, as well as the toroids and sockets.

It passed the "smoke test" - a check of DC resistance (using diode setting on the meter to make sure semiconductors did) and then I connected the 9V battery. Display lit up and no pops, bangs or smoke!
I then adjusted the display contrast pot and the display showed all the right screens so all appeared to be working OK and first time, no diagnosis needed at all!!

I waited until morning to test on RF as the WSPR station was in use all night.

Morning, put the device in line between the SGC MAC-200 tuner and the transceiver and got readings that I was able to play with. The SWR showed 1.72:1 so I was a bit suspicious, however a dummy load showed 1.0:1- good! I then QSYed from 40m I was using for the initial test to 17m and the SWR dropped to 1.29:1, better but not wonderful. I do realise that the MAC-200 is not designed to auto-tune at low powers, so maybe I was a bit unfair.

I then calibrated the power readings using my coffee can dummy load with diode inside to measure the peak voltage across the dummy load. It calibrated nicely.

Finally, I thought I would insert the LDG Z11ProII inline and got a nice low reading on 17m of 1.04:1 - much better. The LDG is much happier tuning at very low powers.

I've attached some photos of the device on the test bench with a ruler lying beside, so one can see the dimensions clearly. My only criticism is that the only case available tom R-K with the kit, is way too big - I could probably fit a couple of Ensemble RxTxes in with it!

Very happy with the kit as with the built-in 9V battery it is entirely stand-alone.



Thanks Ross!

1 comment:

Anonymous said...

Good to see your review. I just saw this kit online and wondered if I should order it.

Looks like a good purchase.