Re: [amsat-bb] 2 meter uplink interference on 70 cm downlink

[Roy Welch <rdwelch@xxxxxxxxxx>]

Hi Erik,

Erik Smith wrote:
> 
> Hello,
> 
> When I am using FO20 or FO29 in JA mode I cannot copy myself on the 70 cm
> downlink because of havy interference. When using CW I can copy my signal,
> so I know that I have downlink signal. For SSB I can not copy my downlink
> signal. Looking at some documents about amateur satellite they are talking
> about a mode J filter.
> 
> But what is the best way? Making a filter for my 70 cm pre amp or making a
> filter for my 2 meter up-link?

I found the 70cm filter to be best.
 
> Or is my uplink signal too much for my first stage of my 70 cm receiver? Or
> is a 3rd harmonic of my 2 mtr spoiling my 70 cm receiver?

In my radio, the 2M signal was generating the 3rd harmonic in my 70cm radio
front end, therefore the 70cm filter.
 
> Is a part of a duplexer a good way to filter and has some one an easy to
> build filter for qrp power (like something which can be put in serie with
> the arrow antenna)?

In past ARRL hand books in the section on Interference there were several
strip line filters. built in small Bud Miniboxes.  A small cavity is
sharper, but too narrow for the entire 435-437 range.  The Bud box type are
just about right.  They are cheap and easy to build.  I have not seen these
filters in the more recent Handbooks.

 
> 73's
> 
> Erik
> 
> ON1DAG
> 
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-- 
73, Roy

Internet: w0sl@amsat.org
Home Page: http://home.swbell.net/rdwelch
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