Monday, November 11, 2013

More Fun with Iron Donuts Part 3: Bigger is Better?

Is bigger better?
When talking about icecream and chocolate bars, I'm going with yes!
When talking camping gear and portable radio options, I'm thinking no...

Big Happy Iron Donut
I do own 2 QRO radios, only one of which works, the Swan 100-MX. Because I seem to be digging this EFHW design, I decided to up the ante so to speak, and try my hand at making a setup that was a little more robust, capable of handling 100+ watts.  When it comes to Transformers, that means bigger wire and bigger cores. The largest wire I have on hand is 22 gauge, which is big enough to handle 100w, if the match is good, and there's not a lot of core heating. At least I think it is, that's why we give things the ol' trial by fire so to speak. My thoughts were, get it right at QRP levels, and then go QRO.

I wound up the same transformer as The Micro-Matcher, only bigger. it has a 1:9 turns ratio, and is wound on an FT113-43 core. Poking around in the junque baggie of NP0 caps, I found another 150pf cap.

After wiring up the toroid, I hooked up the half wave 20m wire, and got portable. Well, battery powered at least:

OP ready to go, Rig is SW-20+ rated at around 1 watt on battery output.

We have a match!

Since the match looked pretty good, I figured I would go ahead and call CQ a few times to see if I could quickly scare up a QSO. No luck then, but I checked the RBN and there I was!

Notice the one entry from Nov 2? 

I moved the rig back inside, and hooked up to the bench power supply to give me that little extra bit of RF. Life intervened and I had to wait until my wife got home before really testing out the setup from inside the shack. Tuning around 20m I came across a CQ that lead to a QSO. Noticing a hike in the SWR when going through my tuner (even in Bypass mode), I began to suspect either a problem in the tuner or in the antenna switch.  I looked out the window, and discovered my problem. I was a little pressed for time (had to get ready for work) so I apologize for the brevity:

Funniest thing about it was that the SWR was still less than 2:1.

Testing at QRO levels is still ongoing. Things are promising, especially on 20m so far, but the jury is still out, and I need to buy some connectors, coax and PVC to check some things out.

GB Hoyt

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