[AMPS] ICE Filters - A final note

[Jon Ogden]

Hi all,

I finally have resolution to my satisfaction regarding my problems with 
my VHF bandpass filters from ICE.

First of all, I must say that ICE has done a great job at promptly 
looking into the problem and being responsive.  They do have good 
customer service.  

It turns out that what I was doing was stressing the filters beyond their 
rated limits.  The units are spec'd for 250 Watts Power ICS for the 6M 
filter and 200 W ICS for the 2M filter.  This power number is really a 
PEP number and not a carrier power number.  What I mean is that, they 
will easily handle 200 Watts SSB or CW in the "typical" amateur duty 
cycles of those modes (the instruction manual mentions 1 minute on, 30 
seconds off).  Under those conditions, the filters will work and work 
fine.  Also, they would probably work in packet radio type applications 
at the 200 Watt level.  Where they will not work is in constant carrier 
applications at the 200 Watt level.  So one were to transmit FM, RTTY, 
etc. the units would fail.  I was testing them under this sort of 
environment.  For constant carrier use, the rating is really 100 Watts.

As a result of this, ICE is going to be changing their literature and the 
way that they spec the parts.  Also, they are considering designing a set 
of higher power VHF filters.

Please note that I am only speaking here of ICE's 6M and 2M filters.  
According to ICE, their HF bandpass filters are capable of the 200 Watt 
rating under constant carrier conditions.  The design topology is 
different between the HF and VHF units.

Also, thanks everyone for the comments, opinions regarding where to put 
the filters.  I have determined that putting the filters between radio 
and amp will work fine.  In order to meet FCC specs, the amplifiers 
already must have their harmonics in the mud, so if a clean signal is put 
into the amp, a clean signal should be output.  The amplifier's matching 
circuits also act as filters.  As for receive, having the filter in 
between the amp and rig should work as well.  I thought that the preamp 
in the amp might get overloaded by a strong out of band signal, but the 
preamp has matching circuits as well which tend to filter those signals 
anyhow.

I am still considering the idea of using a 1/4 wave stub after the 
amplifiers to knock down the second harmonic should one be there at all.

My very first filters from ICE definitely had something wrong with them 
as they failed right upon keydown.  They've admitted a problem and fixed 
it.

I have kept my ICE filters and plan on using them.  I would also go back 
to them for other products as well.  Their HF Lowpass filters are really 
nice and their prices are good.

Thanks for the ramblings......

73,

Jon
KE9NA


--------------------------------------------------------------------------
The Second Amendment is NOT about duck hunting!


Jon Ogden

jono@enteract.com
www.qsl.net/ke9na

"A life lived in fear is a life half lived."


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