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Re: R: 23cm TX converters with 435 MHz IF


I believe that the >432 MHz units designed by N2CEI (Down East) that use a 
28 MHz IF are simply 144 MHz IF devices with an additional 28<-->144 MHz 
converter in them.  In this case the 1212 MHz product isn't a problem, but 
the signal at 144 MHz potentially is if it can be picked up by the 2m radio.

Fred W0FMS

>From: "i8cvs" <domenico.i8cvs@tin.it>
>To: "John P. Toscano" <tosca005@tc.umn.edu>,   "Wayne Estes W9AE" 
><w9ae@earthlink.net>
>CC: "AMSAT-BB" <amsat-bb@AMSAT.Org>
>Subject: R: [amsat-bb] 23cm TX converters with 435 MHz IF
>Date: Tue, 2 Apr 2002 15:41:17 +0200
>
>
>----- Original Message -----
>From: John P. Toscano <tosca005@tc.umn.edu>
>To: Wayne Estes W9AE <w9ae@earthlink.net>
>Cc: <amsat-bb@AMSAT.Org>
>Sent: Tuesday, April 02, 2002 8:24 AM
>Subject: Re: [amsat-bb] 23cm TX converters with 435 MHz IF
>
>
> > Wayne Estes W9AE wrote:
> >
> > > I'm looking for commercially made (or kit) 23cm TX converters that
> > > use a 435 MHz IF.  The only one I can find is the Kuhne MKU13OTX
> > > with the 70IF option . . .
> >
> > That's the only one I've come across in my searching.  I decided to go
> > with a Down East Microwave 1268 transmitting converter with a 28 MHz
> > IF.  Their web site only says it may be a future product, but I spoke
> > with them on the phone recently and they are building one for me, so
> > I guess the future has arrived.
> >
> > The 28 MHz IF will work fine with my FT-847 and not interfere with
> > my MMDS downconverter at 122 MHz (on the 2 meter antenna connector).
> > Of course, if you are using a 2M/70cm only satellite radio, such as
> > one of the Icoms (820, 821, 910), that may not work for you.
> >
> > 73 de KB0ZEV
>
>Hi KB0ZEV,
>
>You must be very careful using 28-30 MHz IF for a transmit converter
>1968 -1970 MHz because the image falls into 1268 - (28 x 2 ) = 1212 MHz
>and unless you have a very sharp interdigital filter after conversion you
>will get a lot of power at 1212 MHz in to the antenna.
>
>1212 MHz is allowed to Aeronautical Navigation Services and it is possible
>to interfere with it.
>
>28-30 MHz IF for 23 cm was widely used in Europe 25 years ago 
>hard-filtering
>the image after convertion but  28 MHz IF was abandoned in favour of
>144 MHz because using such IF the image falls in to 1268-( 144 x 2 )=980 
>MHz
>wich requires less filtering after convertion to reject it from the 
>antenna.
>
>73" de i8CVS Domenico
>
>
> > ----
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> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>
>
>
>
>
>
>
>
>----
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