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