Richard L. King wrote:
> At 09:25 PM 11/19/97 -0600, you wrote:
> Hi Jon. Does you scope have a "B-Gate" pulse port? It is sometimes on the
> side or the back of the scope. If you do, then you can use the B-gate pulse
> as a TDR wavefront and by comparing the termination using delayed sweep, it
> is possible to check that the two antennas are in phase. That is how I used
> to do it.
Yes, but I've never thought of trying that... are you looking at the
reflected wave to see that the apparent "lengths" are the same, or something
By the way, I should've said that the coax lengths should be similar to
start with, lest the phasing be correct on one band and wrong on others.
What I described should work OK to compensate for driven elements being
in offset positions, though (I'm ignoring the complications if one tribander
has a single driven element and the other has more than one, complicating
the issue-- I'd still compare them and see).
> Could an MFJ259 create enough reference signal?
I doubt you'd be able to get enough signal from an MFJ259 because...
> Do you just connect the probe to the coax termination and see the sine
> wave at the frequency the system is for? Do you use dual sweep to compare
> the two directly?
... yes, that is what I do. The old Tek 454 is a 150 MHz scope and they're
fairly cheap and plentiful. Fortunately, N5XT lives less than a mile away
and can give me a reference signal using 100W into his KT34A, and I can
see nice signals using 10:1 probes at the coax terminations. Before N5XT,
I set up a dipole at a relative's house something over a mile away and
remotely keyed the transmitter.
Oh, BTW, and the BIP/BOP references in my previous post is only applicable
to monoband applications, or to swap the phase one a single band of a triband
Jon A. Barclay N5JA (ex-AA5BL)
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