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Well there is a cohort of noble men who have set
fire to, window frames, fences, sheds, tuning boxes etc with 136kHz RF over
the years :-)) plus minor infringments like rope guys, and waste-pipe
spreaders .....I think the badge should be the usual symbols of earth, coil, and
aerial but with a couple of small flames licking out of the bottom of the coil
:-)) Yeah well a bit of artistic licence maybe :-))
Alan
G3NYK
----- Original Message -----
Sent: Sunday, October 25, 2015 12:04
AM
Subject: Re: LF: XPQ WSPR15 475/136 and
warm ceramic feed thrus
Thanks Alan - absolutely - and I should have read the tables!
At the beginning of testing I ran the Tx at full throttle for a few
hours at 1.4Kw and measured the heating of components with an IR "laser" and
saw a few degrees in increase but little more than when I measured in okie -
obviously over time something odd happened! Its been running virtually
constant for about a week... Fire in the wire!
Im now going to come in thru a plated out plastic bulkhead as it ended up
last time and direct connect to the bus bars...
Think telephone exchange with a little more kick!
As ever its a learning curve :-)
Cheers
Hi Laurence my book gives Stainless Steel as 8
times resistivity of Brass and 40 times that of pure copper so
maybe you were pushing your luck a bit, though I would have thought the
connections at the ends would be problem. It looks like arcing on the pic
but its obviously not..... the eramoc got so hot is just melted its
way though the plastic and it is cooked plastic on the outer surface. Also
its not bulk resistance at these freqs you have to consider skin effect in
the SS. Still interesting its only one insulator. It might be interesting to
look at it with a milliohm meter if you have such a beast. I would guess you
must have had the equivalent of 0.2 ohm or so to get that
hot....particularly in your climate :-))
Alan
G3NYK
----- Original Message -----
Sent: Saturday, October 24, 2015
11:05 PM
Subject: RE: LF: XPQ WSPR15 475/136
and warm ceramic feed thrus
Thanks Alan - th iono really hadnt cooled off up here from
the continuous heating over the past month or so but it was getting better
so I thought Id better inject a little more heat
The Stainless 5/16th bolt in the feedthru must have had some
imperfections in manufacture and got extremely hot at circa 50-60A :-) it
didnt happen to the other bolt and wasnt at the wire connection points
each side.
I think Ive had it with feed thrus' at this current and
are going to come straight in thru a hole drilled in a hi density cutting
board.
I recall the original brass feed thrus getting a little warm
but this must have got real warm - sufficient to say the Decca kept on
transmitting and didnt see a high SWR at all over the past week...
The Walmart Rubbermaid box was (is) in its 12th year
and Im just going to plate over it... :-)
Laurence KL7L WE2XPQ
From: [email protected]To:
[email protected]Date:
Sat, 24 Oct 2015 22:42:47 +0100 Subject: Re: LF: XPQ WSPR15
475/136
Hi Markus, yes I think that has been
happening, but in Laurence's case the first post did not appear to any of
us so that was probably bounced on theway in, but I have seen cases were
posts have been reflected but not received by the sender. Some ISPs seem
to regard a message sent to self as spam.....I regularly dig out my LF
postings from my webmail spam folder. Marking them as "Not Spam" does not
seem to affect the rules in "Spamguard", the filter used.
I reckon you are due for a few down days
Laurence the CME from the C5 on the 22nd arrived at 1900z. Spaceweather
maked it as arriving unexpectedly early.....I dont see that the interval
was about 62 hours. We only caught the "wash" as it was not pointing at
Earth, and that could account for some of the longer
interval.
Alan
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