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

[W0UN -- John Brosnahan]

Mihail--

ICE and Dunestar use capacitive top-coupling between the two
parallel-tuned stages.   W3NQN uses a series-tuned circuit between
the two parallel-tuned stages.   This results in the NQN filter having
significantly better shape factor.  The NQN filters provides much
better ejection of the adjacent ham bands.

I have not power-tested the ICE and Dunestar filters but have
blown some in contests with 100 watts.   I personally tested
the NQN filters with 200 watts of carrier for 30 minutes straight
and measured the temperature rise.  So my experience is that
the NQN filters will be very reliable at 100-200 watts.  But I do
not have that confidence in the Dunestar and ICE filters.

The NQN filters were described in detail in QST a few years ago.
So it is possible to duplicate that design for much less money--
assuming you have access to the components and the test
equipment.

In the interest of a full disclosure I did this testing at the request of
W3NQN (as did K3LR) as mentioned in the QST article.  My interest
was in helping W3NQN make some better filters than what were then
available.  I have no financial interest in any of the companies mentioned.

73--John   WØUN


At 11:03 AM 6/9/2004, you wrote:

>Hello,
>
>We are in the process of upgrading the YR7M site from SO capable to M/S.
>That means, among other, a second workplace equipped with transceiver and
>linear amplifier. We expect to need bandpass filters at each workplace.
>
>We have identified three manufacturers for such filters (homebrew is
>excluded since we have barely enough free time to set-up antennas):
>
>ICE via WX0B: model 419A, $228
>W3NQN via WX0B: set of 6 filters, $525 plus FM-6 switch, $165
>Dunestar model 600, $339
>All models are 200W capable.
>
>This is a large price variation for essentially the same product, so there
>must be a catch. Please let us know your experience with these products as
>well as your recommendation. Many thanks.
>
>73 from YR7M team,
>Mike, YO3CTK
>
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>
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