Re: Filters for portable ops


John T. Fitzer
 

Paul K3WWP operates exclusively QRP at 5 watts as does the people he operates with. I am unsure if filters would be required with QRP rigs operating on different bands using separate antennas. I did see a segment on Ham Nation during their smoke and solder segment where they discussed band pass filters for use at field day. As I recall they said the filters were so effective that several stations could use the same antenna on different bands and not interfere with each other. They mentioned that the filters are available from DX engineering, but they aint cheap. As you know designing and building a filter with low ripple across an entire ham band while maintaining low SWR at the ports as well as low insertion loss at the pass frequency and very high attenuation at all other frequencies is an engineering headache readymade and available for any brave soul to tackle.  If you are both operating QRP, maybe a far less expensive solution might be a simple tuned circuit in the transmission line coax such as a ZM-2 Z match. They can be adjusted for low swr and provide a parallel resonant circuit to aid attenuation.

 

From: main@4SQRP.groups.io [mailto:main@4SQRP.groups.io] On Behalf Of Paul Smith
Sent: Wednesday, September 19, 2018 11:35 AM
To: main@4SQRP.groups.io
Subject: [4SQRP] Filters for portable ops

 

I was reading in K3WWP's online diary that they operated at Skyview ARC clubhouse. There are several stations set up along long counters. He mentioned that none of the stations interfered with other stations because of band filters!? What would I need to look at buying or building for filters when my sons and I are out and operating in close proximity but on different bands. I may not be explaining what I want but does anyone out there know what I am talking about?  I emailed K3WWP and asked but the guy he usually operates portable with is doing the research and has not shared anything with anyone I know of yet. 
I am looking for ideas, The SSB garble does not bother my CW tx/rx but the boys dont have the time in I have thanks de Paul N0NBD

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