Thursday, Nov. 21, 2019 — The MFJ 986 Differential T tuner I obtained from eBay arrived a couple of days ago, and as is always the case when buying an antenna tuner, I took time to remove the cover and take a look “under the hood.”
The tuner look mint — with one exception.
MFJ’s AirCore roller inductor — with its “self-resonance killer” looked a little worse for wear. Actually, the only issue I found was that the “killer” — which is nothing more than a switch that shorts the unused part of the inductor to ground once the roller gets about 5/8th the way down — was apparently “switched” back and forth at significant power.
The “switch” itself was blackened from arcing, as was the top parts of the roller coil wire where the “switch” touches the coil. From the looks of things, a previous owner was adjusting the roller while applying significant power — a no-no with ANY roller inductor tuner.
One of the reasons I opened the tuner was to determine if the roller was an actual roller inductor or the AirCore version. This tuner was a fairly early model without a “B” or “C” suffix, but it wasn’t early enough to have a real inductor.
So now I’m left with figuring out if I wish to disassemble the blasted coil and clean it to insure good contact with the roller, or just leaving it be. I’m thinking of making the “resonance killer” switch inoperable, which is easy to do — all you have to do is to flip the switch up so there’s not arm to trip when the roller passes its position.
A little research indicates that the biggest issue with the AirCore roller is the grease that’s used. Most recommendations are to remove the grease and to use something like 3-in-1 or other light oil to lubricate the roller.
But I haven’t put the tuner in the shack lineup yet; I want to give it a go, as I’ve read some decent reviews about the tuner for balanced feedlines.
IMPROVED 80 CW CONDITIONS. Last night I checked in on my Georgia CW net after a week or more of attempts at doing so. The NCS as a rule is generally a little low in signal strength, but often times the band noise has been such that its been damned near impossible to copy him.
CW nets are so formatted that you can sometimes get by with checking in with only having an intermittent copy on the NCS; but the danger there is if you are asked a questions or sent traffic, you’ll probably never have solid enough copy to do so.
But Thursday night, the NCS was Q5, and the band noise was low enough to make all the check-ins good copy. It was nice to hear the band conditions much improved.
73 es CUL … de KY4Z … SK SK … dit dit …