Bandfilters for PA6Z made by PA9M,
designed byW3NQN.
Foreword:
For a multi multi station the real challenge is working as many possible bands at the same time.
In order to accomplishe this there was a need for filters with an outstanding performance.
Marcel PA9M pulled the trick and he build filters according to the W3NQN design.
They have been under a real test, PA6Z took
them to Luxembourg where they shown their worth, with great results.
Marcel tnx for loaning the filters, the whole PA6Z crew.
Year 2004
When you are a growing contest station with enthusiastic members you make plans and goals.
We decided to do contesting in
a multi-multi section. We don't have a permanent contest location but each time we build up a station at a different location in the neighborhood.
In a room from about 12M2 we settled the multi-multi station.
Each member brings his own TRX and other stuff.
So I decide to make band filters. For each station one in-line.
First some questions to answer:
Where do we place the filter?
1.Between Tx and PA
2.Between PA and antenna
Ad 1:
* not more than 200 watt trough the filter.
* using standard, readily available components.
Ad 2:
* more than 1500 watt trough the filter.
* using components for high voltages.
* components difficult to get and expensive.
So I decide to built the filter between TX and PA.
For each contest band one filter and I made also a box with inside the filters for all contest bands.
First filter design is from N1AL. The documentation for these filter is on the internet published by
DL3KDV member of RRDXA www.qsl.net/rrdxa/filter.html.
If you look at the pictures below you can see that I made the box of PCB. (nice working material).
I did the first testing with my antenna analyzer from MFJ. A friend ( PA5R) off mine made a plot from the filters( see
pictures below).
We are using this filter for our multiplier station. Switching is easy.
If
you are interesting in sources of interference, required stop bands you must read the article published in CQ contest February 1996 by Thomas Moliere
And now band filters from W3NQN, Ed Wetherhold.
He is the man who designed these filters especially for mult-multi contest stations. Each contest band one filter inline between TX and PA.
There are some articles in the internet you must read.
First:
Clean up your signals with band pass filters – Part one QST may 1998
Clean up your signals with band pass filters – Part two QST june 1998
Both articles from Ed Wetherhold W3NQN
Second:
100 watt Band pass filter after W3NQN by Peter Pfann, DL2NBU this article you find on the BCC site. www.bavarian-contest-club.de/projects/index.html
Some practical comments:
it's a three resonated bandpass filter
- boxes made from PCB , W 16.5cm H 5.2cm D 8.0cm
- all the coils are wounded on separeted toroidal coils ( T130-6, T130-17, T130-0, T106-0)
- capacitors are silver mica > 500v
- tested with dummyload and the antenneanalyser from MFJ. Second test by PA5R de Jelmer with a real analyser. (plots below)
- several evenings, weekends of soldering, winding, testing
- Below you see some pictures of my filters.
These filters are using every contest, expeditions (LX) etc. Each time when there is a multi-multi happening.
PA9M
Marcel
PA9M@home.nl
Several plots:
