I seem to remember taking out the feedthrus and rods down in Okie - but I think they were copper/brass and still got warm.
Odd stuff this RF... I measured the DC resistance of the 5/16th SS and it was 14.4 milliohm at DC; as the other rod was "ok" Im thinking I had something else going on that side of the feed - the good thing is the Loop is floating relative to Earth so it could have been worse.
So Ive plated out the hole and run thru new cable and connectors to the bus bars and its back to how it was in Okie, save I dont have multiple loop conductors and that 1dB "gain" but I have to be realistic with the trees here.
Back up and running on WSPR 15 and IR Laser showing air temp +38F, toriod at 54F (15 mins at 800W), and caps generally around 40-42F so looks benign. The loop conductor is a few degrees warmer in free air with the current running thru it -
Im sure stainless hardware is generally fine but avoid it if its in the RF path - thanks for the story John -
Sure was a great melt down - Ive binned the ceramic feed thru as the glazing had become sintered or breached with some form of chemical reaction from the plastics vapor Im guessing - probably Cyanide :-(
Thanks for all the feed back - this isnt the first RF hot component this enclosure has had in its LF/MF life - probably wont be the last either... come home to a real fire
Laurence KL7L WE2XPQ -
From:
[email protected]Date: Sat, 24 Oct 2015 20:13:25 -0400
To:
[email protected]Subject: Re: LF: XPQ WSPR15 475/136 and warm ceramic feed thrus
I remember a graveyard maintenance shift many years ago, when my boss observed that a braid wire connection clipped onto a coil in a MF power divider was looking kind of shabby. Not being able to find a piece of flat copper, he tried length of stainless steel "Wraplock", which started out nice and shiny. After a few minutes of operation, it got very warm, and turned black. We quickly located some copper.
John, W1TAG
