[CQ-Contest] Bandpass filters for M/S or M/M environment

[jukka.klemola at nokia.com]

> -----Original Message-----
> From: cq-contest-bounces at contesting.com
> [mailto:cq-contest-bounces at contesting.com]On Behalf Of ext David
> Hachadorian
...
> has a pair of ICE filters, and they also work well for
> him, with his closely spaced antennas and 1500 watts. He has had a few
> problems with his though. On initial delivery, one of his boxes had a
> problem with the received signal intermittently dropping out. That
> unit was replaced by the manufacturer. He has also blown a few
> capacitors in the ICE units, even with 100 watts of drive. The caps
> actually change value, rather than blow, but the swr goes sky high.
> The manufacturer has provided replacements, but we get them a lot
> faster from a commercial source (Mouser). It is fairly easy to change
> the caps. He now has two low-drive amplifiers, which has solved that
> problem for him, at least in the high-power contests. The ICE units
> come with a manual DC switch that picks up the internal relays. The
> ICE units use +12vdc switching. There is no provision for ground-type
> switching.
> 
> Dave Hachadorian, K6LL
> Yuma, AZ
> 


My challenge is what I expected to see someone would challenge my
earlier message:


The filters can take 200W with good SWR or 100W with poorer SWR
on the fundamental pass-frequency.

The power handling capability is poorer at the disturbing signal.
This is 40m filter can take 100W easily on 40 but much less if
you feed 20m, 80m or any other band signal into it.

You can blow a filter very easily if you transmit into it
-directly on wrong band
-indirectly via poor isolation somewhere, like between antennas


Power levels to cause for this filter breaking are in order of a
couple of tens of watts at most.
I have not seen any specification on the subject, but would like
to see some test results if anyone has buts to start to break
the units.

Measuring power is difficult as the impedance is not even close to
match with 50 ohms.
Maybe voltage would be the right measurable.


To summarize:
the decision if a filter is good or bad or 'good enough', should
also depend on the stop band power handling capability.


For the great majority of us, the performance of 
post amplifier stubs + ICE BPFs should be enough.


73,
Jukka OH6LI