On Wed, 28 Apr 2004 22:18:19 GMT, "The other John Smith"
wrote:

Will this work? Your thoughts and advice will be appreciated.

Thanks,
John

Hi John,

The topology is good, however there is work to do to justify your
confidence in the numbers (even if you are willing to discount them to
10 to 15%; which, by the way, is quite optimistic).

I presume you have three 50 Ohm loads, or so I am lead to believe by
the nature of your description. If so, it would do well to rotate
them all through each port and confirm NOTHING changes. This is no
simple expectation. It also pays immensely to have calibrated
mismatch loads on hand to confirm your measurements of an unknown (the
system may fail unbeknownst to you otherwise).

Further, you should also swap the dual coupler input/output and the
side arm ports to confirm it is in fact operating at fixed ratio (this
says nothing of the presumed ratio, but is still a necessary step).
Then repeat the paragraph above concerning the 50 Ohm load rotation.
You can then proceed to confirming the coupling coefficient which may
surprise you (you haven't given the pedigree of this particular
beastie).

I presume you have undamaged leads for your meter (I won't even
presume they are calibrated, but for these purposes, testing should
reveal problems if they are not sufficient to the task).

I presume your source is powerful enough to present at least 1mV of RF
to the meter. I know the meter is more sensitive, but you need head
room to simple measure the return loss (or Z or SWR or any derived
characteristic).

I presume your source is free of spurs and harmonics at that power.
It hardly is worth the effort to measure out of band products.

I presume your source will not pull when presented with a large
mismatch.

I presume your source offers a 50 Ohm output Z. There is nothing like
a mismatched source looking at a mismatched load to increase confusion
by the square.

So, sure, it'll be a snap. ;-)

73's
Richard Clark, KB7QHC