On 2/1/2011 6:20 PM, DGB wrote:
> .... and I repeat .... is it acceptable to enclose it in a
> non-conductive enclosure, on a multiband antenna, say resonant on 160 or
> 80, especially at high power (1500w)?
>
> 73 Dwight NS9I
If you want to make some estimates:
I used this paper before to make some rough guesses at thermal dissipation for
enclosed electronics
http://www.hoffmanonline.com/stream_document.aspx?rRID=233311&pRID=162534
<http://www.hoffmanonline.com/stream_document.aspx?rRID=233311&pRID=162534>
Assume you need to dissipate 30W or so. You can derate that by some duty cycle
(assuming you listen sometimes? :)
It's all about the total surface area of the box and it's material. Just
because
it's enclosed, doesn't mean it doesn't dissipate.
Plus: a little breeze and you've got airflow on the surface.
The biggest heat rise will actually be from the sun, I believe. (see evaluation
of solar heat gain)
Look at those charts and think about the black baluns you've seen.
White is right!
I was also going to comment on how I used 16 awg silver plated teflon for my
bifilar windings so I could fit enough turns but still get substantial turn to
turn spacing.
Also, I've not seen enough agreement on the sources of stray capacitance..from
what I read, the winding to core substantial capacitance...I wrapped my core
with two layers of the yellow gas teflon tape (easier to handle than the thin
white stuff). I've seen some stuff showing that tight winding of enamelled wire
has more stray capacitance than insulated wire (which gets the wire up off the
core). Thoughts?
But then I figured I'd keep my mouth shut, because Jim will probably say
parallel #12 THHN has lower impedance than my #16 parallel insulated. I suspect
they're both about same though.
-kevin
ad6z
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