Ian Jackson wrote:

In message , Michael A.
Terrell writes



Do you know that the channel combiners in a CATV head end
were wired in odd and even banks, on separate groups to prevent IMD
caused in the passive mixing?

It might have depended on whose combiners you were using.

I hadn't heard about this so, one day (it must have been back in the
80s), I decided to do a quick test to see if it was true. To be honest,
I don't think I saw much difference whichever way I grouped the
channels. From what I remember, with the modulators putting each out
60dBmV, all the intermod products were at least 85dB down, and were
rather difficult to measure quickly. Such low levels of intermod would
have had a negligible impact on the overall system performance.


How many channels and at what signal levels did you try it on? We
had seven six port combiners in two groups of eight for a 36 channel
headend. The six outputs were combined in the seventh unit and
amplified before leaving the building. It did help in some
installations, where HSP were used for off air processing and for
stations who would push their character generators to over 100%
modulation from affecting other channels.


--
You can't have a sense of humor, if you have no sense.