[Amps] High temp magnet wire?

[Jim Thomson]

Date: Fri, 07 Dec 2018 19:21:02 +0000
From: Manfred Mornhinweg <manfred at ludens.cl>
To: amps at contesting.com
Subject: Re: [Amps] High temp magnet wire?

> JI depicts some sky high  Z
> numbers, etc, when he tested that choke  with his VNA.... on all  9 x
>  bands.

<<<Would like to see that. Is it piblished somewhere?

<Manfred

###    https://www.w8ji.com/rf_plate_choke.htm   Excellent writeup.
Scroll to the bottom to see his VNA results.   For choke dissipation 
he is using   RMS  voltage  squared  /    RP.    RMS  RF voltage =  60%  of
loaded  B+. 

##  Note, that  graph at the bottom is NOT the currently produced  choke that
Ameritron uses... which   btw, is the same one sold by RF parts.    Its also the same choke
used in the current crop of alpha amps.   The choke depicted in the graph resonates on 
12.1  mhz  and 15.7 mhz.     The current production choke resonates on 12.5 mhz..and  27.1 mhz. 

##  The graph at the extreme bottom has been cut off.  It was all there  a few years ago. 
What  would be nice, is a higher current version of his choke, doable, but a pita.  Plan B
might be to use  2 of the ameritron chokes in parallel,  which will  reduce the uh  in half.   But at 
least the assy  would handle  double the dc current.   Individual RF and DC currents  would be the
same on each individual choke... at least on paper.  But the chokes  would have to be spaced well
apart from each other.  They would also require bypass caps  at the base of each choke. 

##  On a side note, that  45 uh choke my buddy tried on 160m,  was wound with  18 gauge wire,
not  22 gauge !    The 18 gauge was later removed, and replaced with 22 gauge wire, on the same  1” diam,
solid teflon rod.   That way, the uh could be increased to  70 uh,  using the smaller   gauge wire.
The final config uses  135 uh on a 1 inch diameter solid teflon rod, mounted vertical.  The smaller
70 uh  choke, also wound on 1 inch teflon rod,  Is  L bracketed at right angles to the top of the bigger
choke.   Bypass caps at base of big choke.  More bypass caps  coming off at the junction... to the NO  / hot side
of a spst vac relay.   COM /  Cold end of same vac relay  bonded to chassis.    Cold side of junction caps has  3 megohms
of resistors, between cold side of junction caps... and chassis.     With vac relay de-energized, cold side of junction caps
are DC  grounded.    With vac relay  coil energized, the cold end of the junction caps are  both DC grounded and  rf grounded.
With relay energized, the larger  choke is effectively out of the circuit.   Both chokes used on 160m only.  70 uh choke
used on 80-15m. 

Jim   VE7RF