[CQ-Contest] Filters

[Tim Duffy K3LR]

Mario:

Just for the record; I used ICE band pass filters when I started multi multi in 1992.
I noticed several things:

I was surprised how much in band loss they had. Measured on a HP 8752A
The near band rejection wasn't very good. Measured on a HP 8752A and verified with
station tests.
The components inside got very hot on 10 and 15 meters when running 85 watts into them

for multi multi service (I need 50 watts (that is what is left after the filter loss)
to drive my amplifier to 1500 watts).

After a blow up or two during a contest with the ICE filters, I called W3NQN on the
phone and asked him to design a better set of filters.
That is what we have today.

I have used W3NQN filters (built by W3NQN with the same parts he described in his
article) in full bore K3LR multi multi efforts on all bands for 8+ years with no
failures or heating what so ever. Perfect operation.

I also used W3NQN filters on Field Days and at the WRTC events running in the low
power category with the exact same results. No problems, low through loss and the best
near band rejection of any LP BP filter.

BTW, I don't consider myself "lucky". These filters are the result of sound
engineering, which is one component of a successful contest station.

73!
Tim K3LR

"Mario, S56A" wrote:

> W0UN: And at no time did any capacitors fail the 200 watt test -- or even
> get very warm.
>
> I guess you were lucky!  I made W3NQN filters with a big VU mica caps for 2
> kV and they all failed on 7 MHz and above.
> Manufacturer sent us new batch for free but they are not tested yet.  DL2NBU
> specifies VAR power ratings required.
>
> Simple ICE filter configuration should survive most abuses but 21/28 MHz
> isolation is not good enough for SO2R.
>
> Please note that BPF info is available in ON4UN book on low bands.
>
> 73 de Mario, S56A
>
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