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AW: Hailing channel and intermodulation suppression

"siegfried jackstien" <siegfried.jackstien@...>
 

These filters are also available as a single bandpass (with several cavities
in a row) ... so ... would that prevent other transmitter signals from
coming down back in the pa??? (isolator would help ... just asking if such a
bandpass would also help??)

Dg9bfc

Sigi

-----Urspr√ľngliche Nachricht-----
Von: UniversalDigitalRadio@...
[mailto:UniversalDigitalRadio@...] Im Auftrag von Tom Hayward
Gesendet: Montag, 24. Juni 2013 16:24
An: UniversalDigitalRadio@...
Betreff: Re: [UniversalDigitalRadio] Hailing channel and intermodulation
suppression



On Sat, Jun 22, 2013 at 10:42 AM, siegfried jackstien
<siegfried.jackstien@... <mailto:siegfried.jackstien%40freenet.de>
wrote:

Repeater builders use a highpass lowpass combination (procom 70/6 or
similar) to transmit and receive on the same antenna ... now my rough
guess
is that you could add such a filter to your antenna input and can
transmit
on one frequency without desensing on the other frequency
Sorry for the delayed response. I was away from Internet all weekend.

The problem is not desense. The UDR56K is half-duplex so I don't need
to worry about desensing the receiver during transmit. And all the
other receivers on the site have bandpass filters so that is not an
issue. The problem I am trying to prevent is signals from nearby
transmitters mixing in the final amplifier of the UDR56K and causing
intermodulation interference. This is accomplished by using an
isolator/circulator to send any signal coming down the antenna into a
dummy load before it reaches the UDR's amplifier. Every
isolator/circulator I am familiar with has a very narrow bandwidth, so
by implementing this technique I would sacrifice the frequency agility
of the UDR56K, the integral feature of "A Hailing Channel for Packet
Radio".

Tom KD7LXL