[sci.electronics] monimatch?

bks@ucbarpa.Berkeley.EDU (Brian K. Shiratsuki) (07/13/88)

i'm interested in building an swr meter to use on amateur hf
frequencies.  a chapter of the 1962 edition of the Radio Amateur's
Handbook features an antenna tuner which includes a foward/reflected
power meter, which is driven off something called a ``monimatch.''
since they give instructions on how to construct this device (it
looks like a four inch length of small copper tube, flanked by two
wires, with two strips of copper outside the wires.  the rf signal
passes through the copper tube), is it reasonable to assume these
weren't available commercially?

the meter itself is driven from a diodes attached to either of the
two wires, depending on whether you want to read forward or reflected
power.

are there better ways of making an swr meter 26 years later?  is
there a place to buy items like the ``monimatch?''

				brian

res1@mhuxu.UUCP (Rick Stealey) (07/14/88)

> 
> are there better ways of making an swr meter 26 years later?  is
> there a place to buy items like the ``monimatch?''

Today the monimatch type of swr bridge has pretty much given way to 
the toroid transformer type of detector.  The transmission line
goes through the core of a small donut, and the two small windings are
used for detecting the forward and reverse current, and detected with 
diodes the same way as the monimatch.  There are two advantages:
:the mechanical arrangement is simpler
the outputs are not dependent on frequency (well, not as much) so that
you get an output that you can calibrate as a power meter.  
I built one and the mail problem with it is balancing it so that
reverse current is not detected by the forward meter and vice versa.
GL with it.   73 de KT2Q
-- 
Rick Stealey
{ihnp4}!mhuxu!res1

abostick@gethen.UUCP (Alan Bostick) (07/18/88)

In article <25048@ucbvax.BERKELEY.EDU> bks@ucbarpa.Berkeley.EDU (Brian K. Shiratsuki) writes:
>i'm interested in building an swr meter to use on amateur hf
>frequencies.  a chapter of the 1962 edition of the Radio Amateur's
>Handbook features an antenna tuner which includes a foward/reflected
>power meter, which is driven off something called a ``monimatch.''
>since they give instructions on how to construct this device (it
>looks like a four inch length of small copper tube, flanked by two
>wires, with two strips of copper outside the wires.  the rf signal
>passes through the copper tube), is it reasonable to assume these
>weren't available commercially?
>
>the meter itself is driven from a diodes attached to either of the
>two wires, depending on whether you want to read forward or reflected
>power.
>
>are there better ways of making an swr meter 26 years later?  is
>there a place to buy items like the ``monimatch?''
>
>				brian


Why bother constructing such a thing when you can buy them, or at least
the parts that go into them, ready-made?

Minicircuits, a manufacturer of LOTS of nifty RF and microwave devices,
has a line of "directional couplers"  little (about 1 inch on a side)
boxes with three BNC connectors on them.  Signals going in one direction
go from one port to the second, and signals travelling in the other
direction go from the second to the third port.  They are truly clever
devices, based on diodes.  I am told that they are similar in design to
stuff which appears in  ARRL handbooks, and may in fact be what you are
talking about.

Sorry, I don't have Minicircuits ordering or catalogue info on hand.
Check with a serious electronics supply store, or the catalogue shelf of
just about any good electronics lab that works a lot with RF.

				Alan Bostick
				ucbvax!unisoft!gethen!abostick

WALT@MAINE.BITNET (Walter G Horbert) (07/20/88)

> >are there better ways of making an swr meter 26 years later?  is
> >there a place to buy items like the ``monimatch?''
> >
> >                                brian
>
>
> Why bother constructing such a thing when you can buy them, or at least
> the parts that go into them, ready-made?
>

Once upon a time, in a land far away, this is what much of Ham Radio
was all about...
                    W.

res1@mhuxu.UUCP (Rick Stealey) (07/22/88)

> 
> Minicircuits, a manufacturer of LOTS of nifty RF and microwave devices,
> has a line of "directional couplers"  little (about 1 inch on a side)
> boxes with three BNC connectors on them.  Signals going in one direction
> go from one port to the second, and signals travelling in the other
> direction go from the second to the third port.  They are truly clever
> devices, based on diodes.  

Chances are the Minicircuits things cannot handle transmitter power.
Also, from your description, it sounds like the directional coupler
is a circulator.  
But to answer your question as to why someone would build something
when he could buy it, the best reason I can think of is that it is
the best way to LEARN something, and it is extremely rewarding to
accomplish something !


-- 
Rick Stealey
{ihnp4}!mhuxu!res1