Perhaps Phillip Smith and his wonderful chart should be mentioned. About the highest math required is algebra and a little trig. Plenty of tutorials and explanations are on the web, it just requires a little digging. Don't like to read? Check out YouTube!
Interesting story about Phillip Smith. An engineer I once worked with saw an ad in a technical journal on high quality paper copies of the Smith Chart. He went to the address and bought a ream. It was much later that he realized that the guy selling the copies was Smith himself.
Jim
--------------------------------------------
On Mon, 8/7/17, Michael Hanz <aaf-radio-1 at aafradio.org> wrote:
Subject: Re: [Milsurplus] [ARC5] Smart People: Antenna Matching Mystery
To:
Cc: milsurplus at mailman.qth.net
Date: Monday, August 7, 2017, 1:43 PM
Peter is correct. But what he didn't say was how
easy the
explanation will be, or how long it would take to teach
you, or even
if you would feel any satisfaction at the end. RF
design, and
transmission line and antenna design in particular, is
sort of a
specialty area in EE because so many other factors start
showing up
at different rates with frequency. The differential
equations start
going nuts. They mess up the nice, well behaved lumped
component
view and math that you get in Physics 101. You either
love the
complexity of the specialty, or you don't.
RF engineers have a different frame of mind - a sort of
other-worldly look in their eyes, peering into the
depths of space
as if they can see something several light years away.
Okay, I made
that last sentence up in fun, but from a specialty
choice
standpoint, it does take a slightly different talent
than, say,
circuit design or power distribution. You can get a
whiff of the
problem by reading all the antenna theory battles that
go on
endlessly on the web.
73,
Mike KC4TOS
On 8/7/2017 1:46 PM,
Ray Fantini wrote:
#yiv4021826343
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A
statement like that almost makes me want to say,
Ok so
explain it to people like me who don’t know!
Being of
relatively small mind and limited capabilities
myself am
left to looking at what’s been out there in
the printed
world. Looking at the basic output tank it’s
a straight
forward parallel resonate circuit with T54 also
serving to
match the high impedance of the plate tank to
the low
impedance of the antenna. The kind of thing a
transformer
works best at. L 52 adds inductance to the
output to
compensate for the short electrical length of
the antenna
and that’s about all there is to it. No
suppression of
unwanted harmonics or anything else just a great
example of
fast and expedient engineering.
Like
I said I am not that smart so if I got it wrong
feel free to
correct, most of my knowledge of the inner
workings of the
ARC-5 family beyond my limited experience was
gleamed from
the CQ Surplus conversion Manual or better yet
the $1.50
Command Set compendium published back in 57.
Some of the
later articles in the book outline how to modify
the set for
TVI proof operation but almost all of the
modifications for
Ham use first involved removal of L52 the roller
inductor
and directly connecting to the secondary of
T54
I
know conversion is a dirty word around these
parts but much
can be learned from that book. This is a web
link to it:
http://hilltoparmyradios.com/command_sets.pdf
Would
be real advantageous for one of the smart people
to run a
software model and see just what type of voltage
is
developed across that capacitor and better yet
what RF
current. Assume an output load 50 Ohms and L52
set to 0,
minimum inductance. Think it may be
surprising!
Ray
F/KA3EKH
From:
milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net]
On Behalf Of Peter Gottlieb
Sent: Monday, August 07, 2017 12:54
PM
To: arc5 at ix.netcom.com
Cc: ac2eu at yahoo.com;
arc5 at mailman.qth.net;
milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] [ARC5]
Smart People:
Antenna Matching Mystery
It's not
voodoo, just electrical engineering, and pretty
well
understood.
Peter
On Aug 7, 2017, at 11:50 AM, arc5 at ix.netcom.com
<arc5 at ix.netcom.com>
wrote:
Sent from my Ain't Smart
Phone.
------ Original
message------
From:
J Mcvey
Antenna Matching
Mystery
...The
50 ohm coax at the terminal causes a
host of
reactance and reflection issues by
itself.
Bet
if you added coax length, the
situation would
change to something else, maybe
better, maybe
worse!
RF
is spooky stuff!!
----
You
are so right. I switched the coax
jumper to a
long one, coiled into a big spool
"shield RF
choke." It completely changed
the tuning. RF is
Electronic VooDoo.
73
Dave S.
On
Monday, August 7, 2017 10:13 AM,
Ian Wilson
<ianmwilson73 at gmail.com<
a="">>
wrote:</ianmwilson73 at gmail.com<>
I
have noticed that the
roller coil has
distributed capacitance,
so it
does
not always behave as a
simple
inductance even at lowly
RF.
To
a reasonable
approximation, it could
probably be modelled
as
"a
few" L-C sections.
4 would be a good
starting
point.
73,
ian K3IMW
On
Mon, Aug 7, 2017 at 6:57
AM, David
Stinson <arc5 at ix.netcom.com>
wrote:
OK
y’all-
here’s a mystery
(at least to
me),
Series
circuit,
designed to match
a normally
5-12 Ohm
Aircraft
radio output
to resistive
50
Ohms.
Follow
me
here:
Series
circuit:
PA Tank
coupling link
– Roller
coil
–
120pFd
ceramic cap
mounted at
antenna post
–
50 Ohm
Load = 25 W
out.
PA Tank
coupling coil
– 120pFd
ceramic cap
mounted
at the
input of the
Roller Coil –
Roller Coil
–
50 Ohm
Load = 15W
out.
The
ceramic cap is
near
chassis ground
both ways,
so it’s
not
circulation currents.
The PA
tuning cap
setting does
not
change,
so it’s
not de-tuning
the PA tank.
Why the
difference
between these
two series
circuits?
73 Dave
AB5S
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