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Re: choice of IF frequencies



Yes, it can be done and most of the 1296 MHz transverters in the 1960's and
1970's used a 28 MHz IF. However, they all used fairly large narrowband
interdigital filters built up from sheet metal and tubing. This was required
to get a Q high enough to reject LO and image frequencies. The microstrip
filters used on the DEM transverters cannot acheive a high enough Q to
tolerate a 28 or 50 MHz IF. However, they are much easier to build.

John
KD6OZH

----- Original Message -----
From: "Gary "Joe" Mayfield" <gary_mayfield@hotmail.com>
To: <amsat-bb@AMSAT.Org>
Sent: Friday, 08 December 2000 03:29 UTC
Subject: Re: [amsat-bb] choice of IF frequencies


> I have seen 1269 to 28 MHz boxes so I know it can be done.  With the
> satellite niche market I think 50 MHz would be a great IF frequency.  With
> all of the IC-910 / FT- 847 / TS-2000 supporting 50 MHz out of the box it
> seems like a sensible choice.  No need to run expensive feedline to the
mast
> mounted converter.
>
> Just My thoughts,
> Joe
> ka0yos@amsat.org
>
> ----- Original Message -----
> From: "John Stephensen, KD6OZH" <kd6ozh@gte.net>
> To: "Estes Wayne-W10191" <Wayne_Estes-W10191@email.mot.com>;
> <amsat-bb@AMSAT.Org>
> Sent: Thursday, December 07, 2000 7:46 PM
> Subject: Re: [amsat-bb] choice of IF frequencies
>
>
> > A 435 MHz IF would be a poor choice for a transmit converter as the
third
> > harmonic of the IF would pass right through the printed RF bandpass
> filters
> > on the unit and cause interference to other services. 144 and 222 MHz
are
> > the only viable choices and no one makes 222 MHz transceivers anymore.
So
> > the existing DEM products will limit those with dual-band satellite
> > transceivers to mode LU (AO-13 mode L) and mode US (AO-13 mode S).
> >
> > A 2400 MHz receiving converter with a 435 MHz IF would be the best way
to
> > enable mode LS.
> >
> > John
> > KD6OZH
> >
> > ----- Original Message -----
> > From: "Estes Wayne-W10191" <Wayne_Estes-W10191@email.mot.com>
> > To: <amsat-bb@AMSAT.Org>
> > Sent: Thursday, 07 December 2000 20:23 UTC
> > Subject: [amsat-bb] choice of IF frequencies
> >
> >
> > > Ed Cole wrote:
> > >
> > > I just pre-ordered* my 1269 Tx conv. & 10451 Rx conv. from Steve [DEM]
> > this morning and the schedule sounds about right.  They are holding on
> > production to be sure of which AO-40 modes checkout good, and for some
> > verification of link requirements by actual observation {i.e. if they
make
> a
> > bunch of 10w convertors and you need 20w...they are stuck with unwanted
> > inventory}.
> > >
> > > Wayne Estes replies:
> > >
> > > I notice that DEM's 1269 transmit converter and the 2400 MHz MHz RX
> > converter both have 144 MHz IF's.  Why?
> > >
> > > It seems obvious to me that AO40 transmit and receive converters
should
> > use DIFFERENT IF's.  The logical choice for the transmit IF is 435 MHz.
> > Then the 2400 MHz and 1269 MHz converters would be "plug and play" with
> > EVERY commercially made satellite transceiver, including models that
don't
> > have HF capability.
> > >
> > > This seems even more compelling if AO-40's 435 MHz transmitter really
> > turns out to be dead.  435 MHz would be an "uplink only" band, perfect
as
> > the IF for ALL AO-40 transmit converters.
> > >
> > > Has anybody asked DEM why they don't plan to offer the 1269 MHz
transmit
> > converter with a 430 MHz IF?  Is something wrong with my logic?
> > >
> > > Wayne Estes W9AE
> > > Mundelein, IL, USA
> > >
> > > p.s. I just re-subscribed to AMSAT-BB.  I used to be active on
AMSAT-BB
> in
> > the AO13 days with callsign WD5FFH.
> > >
> > > ----
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> > > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> >
> > ----
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> >
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