Well, I considered that too. However, after further study of isolators (and
discussing my situation with a manufacturer of isolators) I discovered that
a VHF isolator will not stop signals in the 800MHz range from passing
through it. An isolator should work great if I was dealing with several VHF
transmitters at the same level on the tower.
I'm wondering if the IMD is being generated somewhere on the tower,
antenna(s), etc.? A bandpass cavity on the tx drops the 800MHz signal
levels (as seen at the tx port) from -40dBm to -75dBm. I would think levels
of -75dBm "shouldn't" be a problem for the 2m tx? The harmonic filter in
the tx should drop the -75 to nearly nothing - right? That's why I'm
thinking perhaps the IMD is being generated somewhere else. Although, it
does only occur when the 2m tx is on.
tnx
Richard
> -----Original Message-----
> From: Charles Miller
>
> Richard,
>
> You said that the IMD is only there when YOUR TX in on. If this
> is the case
> you may need an Isolator for your TX. I had a site that was getting eat
> alive with IMD at 150 MHz only when the TX was on. Found out that the IMD
> was being generated in the transmitter. Put an isolator on the
> thing and no
> more IMD.
>
> Just a thought 8-)
>
> Charles Miller
>
> ----- Original Message -----
>
> [snip]
> > I can see carriers appear and disappear on the rx side when the
> tx is on.
> [snip]
>
>
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