[600MRG] ANTENNA RF CURRENT METER, GOOD LESSON LEARNED!

[Dwight Blevins]

Okay, can't believe I could be so dumb, but maybe if I tell this little spiel others can learn from my mistakes.

Never used an inline antenna current meter on any station setup before, going all the way back to the 1960's. SWR and power meters, sure, but those are in the shack, not at the antenna feed point.
Signed on 630m cw back in January. Made a couple of contacts with my trusty homebrew 6AG7/1625 low powered transmitter. Of course I've read all the comments about measuring antenna current, but kept right on saying to myself.....too much fuss and trouble and probably won't make any difference anyway. Yeah, right!
Long story short, thoughts about measuring the antenna current kept nagging at me until this morning I decided only one way to find out. Dug around in the junk box for about an hour, found the parts and after months of putting it off, made a junk box RF ammeter in about 20 minutes. Didn't have to buy a single item. 
Hooked the meter between the coax out and the loading coil tap at the base of my old ground mounted Hustler 6BTV, which I have modified for 630m (about 30 ft. tall). Key down and everything looked normal, but no reading at all on the RF current meter. Mmmmmmmm.....must have wired something wrong or found bad parts. But, on a hunch, before starting over again from scratch, I decided to move the input to a different tap on the loading coil. When I first made the loading coil I added several other taps, but ended up using the one that seemed to work the best (wrong!!). Moved the tap two turns from where it was and the RF meter came alive, from zero to PEGGED!
Spent two hours goofing around with different shunt values so as to get the meter in mid range. Otherwise, no way to know which way to go with the inductance for max RF transfer. 
Right now I'm just in the ballpark, with more trimming to do, but thanks to the RF current meter I'm now getting at least TEN TIMES more power into the antenna! When you begin with 20 watts max, that's a real big jump.
Now my plate dip, forward power out, max RF antenna current, and max field strength readings are all occurring at the same time in tuning. Moreover, I'm rockbound, and though I have several 473.5 khz crystals, none of them ever worked until now (old FT-241's). So I was pretty much stuck on either 474.5 or 472.7 khz. So even though the transmitter uses a separate tube for the crystal oscillator, somehow my less than accurate loading of the final, due to antenna mismatch, was reflecting all the way back to the 6AG7 and preventing it from working with some crystals. 
Whole new world down below the broadcast band. The old fly by the seat of your pants, clip and trim, close is good enough, etc.....a sure recipe for failure. Another lesson learned the hard way. Spend an extra 1% of your time doing it right and save yourself months of 99% frustration and mediocre results. Looking back, nothing short of a miracle that I made any cw contacts at all :)
Okay to have a good laugh at my expense. Right now I'm a real happy camper!

Ike, KW7TColorado

  

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