[TowerTalk] ICE 419A Combination Bandpass Filter 10M Section Blown

[David Hachadorian]

----- Original Message ----- 
From: "Keith Dutson" <kjdutson at earthlink.net>
To: "TowerTalk" <towertalk at contesting.com>
Sent: Friday, December 10, 2004 12:39 PM
Subject: [TowerTalk] ICE 419A Combination Bandpass 
Filter 10M Section Blown


> Subject says it all.  VSWR went to 5 at some point 
> during operation of
> VP8WWW.  The filter box was set to 10 meters and 
> connected to a trapped
> vertical and Kenwood 480HX.  Transceiver was set to 
> 200 watts CW on 10
> meters.  We were using two boxes and switched them. 
> About an hour later the
> second box did the same thing.
>
> I read the manual.  It states the unit is rated at 
> 200 watts.  I am guessing
> that is for SSB rather than CW.  Anyone else 
> experience this problem?
>
> Each filter section apparently consists of a simple 
> coil and two caps in T
> configuration.  This is only an observation as I do 
> not have a schematic.  I
> would like to beef up the capacity and assume this 
> might be done with higher
> voltage caps.
>
> Keith NM5G
-------------------------------

A friend of mine has the ICE filters, and I have helped 
him change bad 10 meter capacitors twice now. At least 
one other person has publicly complained of the same 
thing. The factory guys say they have never heard of 
such a problem. They did supply the replacement caps 
for free, but it took a few weeks to get them, and by 
then we had already purchased the replacement caps from 
Mouser. The cap that failed both times was in the leg 
that runs to ground on the rig side, not the antenna 
side. This leg is a parallel combinaton of two caps. 
The cap did not blow completely, rather it just made a 
significant change in value.  If you separate them you 
can use an impedance measuring device, such as an 
antenna analyzer, to figure out which one has changed. 
The capacitor values are all different for the various 
bands, but a typical Mouser part number would be 
5982-19-500V270 for the 270 pF. The Mouser catalog does 
have some 1000V micas, but the selection of values is 
quite limited. You could switch to a parallel/series 
combination of four 500V caps, at least in this leg.

Another thing I don't like about the ICE Filters is 
that the signal path goes through 12 normally-closed 
relay contacts. In my friend's units, he experiences 
occasional signal dropout on receive. As soon as he 
sends one 50 watt "dit" through the filter, the film on 
the relay contacts is penetrated, and the receive 
signals reappear. The factory guys say they have never 
heard of that one, either.

Just pull the cover off the filter, and you will see 
how it is built. At least it is easy to work on. We've 
had the covers off my friend's unit so much that now we 
just have to whistle, and the screws unscrew 
themselves. After you change the caps, just squeeze the 
10 meter coil/bend cap leads for min swr. We keep a 
rubber glove handy for this purpose, to avoid rf burns, 
and to avoid affecting the swr. Make final adjustment 
with the cover on as far as you can get it, and still 
be able to reach in. We can change these caps in about 
ten minutes now. It looks like a Wood brothers' pit 
stop.


Dave Hachadorian, K6LL
Yuma, AZ