[600MRG] Checking SWR

[John Langridge]

Thanks Murray,

I can agree that an SWR meter can tell something about the health of a
station.  I use the scope match and measure antenna current in real
time to accomplish that here at my station.  My monitor sensors
transverters have SWR meters on them but I rarely look at them.

Full disclosure:  I am heavily biased against SWR meters because they
don't tell the user much information about their system, only that
there may or may not be a problem.

And maybe the bigger point:  In and of themselves SWR meters are not
very useful for someone developing a station as a meter is condensing
two independent variables, R and X, down to a single measurement
ratio.  R may be at the characteristic impedance of the line while X
may be through the roof and visa versa but the SWR is still high.  Ive
seen this happen at Field Day where guys didn't know how to use their
analyzers as analyzers (R+X), instead only looking at the SWR values
and subsequently chasing their tails all afternoon.

So maybe that's an important point to make:  If you are building a
station, and an antenna in particular,  there is a high probability
that you will need to actually have the values of R and X (or a
graphical representation as displayed with scope match) unless you hit
the jack pot through dumb luck.  Not many people are that lucky.

73/GM!

John



On 3/17/19, Murray Greenman <denwood at orcon.net.nz> wrote:
> Hi,
> If anyone is interested, I can supply details for the SWR Bridge / Power
> Meter incorporated in the Southern Avionics SC1000 USCG transmitter.
>
> The beauty of this device is that it uses no ferrite, just two simple
> coils wound on 20 mm plastic formers. It is a Breune coupler type, so is
> flat with frequency. It's designed for 1 kW output, but works fine at
> 100 W. I've used it on 2200 m and 630 m.
>
> Since I know you'll be impatient, I've attached the schematic, and
> here's a small photo of the board:
>
>
> Each of the coils has a two-turn primary on top of a 10-turn (or
> thereabouts) secondary, with a decent layer of insulation between.
>
> 73,
> Murray ZL1BPU
>
>
>