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Re: CalAmp DownConverter Info



Hi,

3-4 years ago (when AO-40 was live!) I had placed in my Web page 2 mods for
31732 CalAmp.
The first page is a copy from CalAmp's modification (PTFE tape) by WC0Y, but
unforunatelly
I've lost 1-2 pictures from his page (I remember that, WC0Y's page was
unavailable
after few months).
The URL with this saved copy on my Web is:

http://www.qsl.net/sv1bsx/Ao40/31732/31732.html


I have a second mod with brass shims:

http://www.qsl.net/sv1bsx/Ao40/31732bsx/31732mod_bsx.html

 For your help, as brass shim I've used pieces of gold-plated pin, from PC
extension PCB connector. These pins have about the same width with
CalAmp PCB filter tracks.

73, Mak SV1BSX


----- Original Message -----
From: "Robin Callender" <robin_callender@hotmail.com>
To: <amsat-bb@amsat.org>
Sent: Thursday, June 09, 2005 10:58 PM
Subject: Re: [amsat-bb] CalAmp DownConverter Info


> Hi Roger,
>
> I was wondering if you have any recommended web pages describing how to
use
> brass shims and teflon tape to rework comb filters.
> I too bought one of these units, and am now watching the bb and hoping to
> glean some tech info on it.
>
> 73s
> Robin
> KE7ARL
>
>
> ----- Original Message -----
> From: "Rogerkola" <Rogerkola@aol.com>
> To: "Bill Ress" <bill@hsmicrowave.com>; <amsat-bb@amsat.org>
> Sent: Thursday, June 09, 2005 11:33 AM
> Subject: Re: [amsat-bb] CalAmp DownConverter Info
>
>
> > Hi Bill...
> >
> > Just some ideas reguarding your points:
> >
> >> The biggest problem is the 7 pole combline filter right at the input
> >> covering 2.5 to 2.7 GHz. Tuning it down to 2.4 GHz proved
unsatisfactory
> >> since the tuning screws were already almost touching the resonators.
> >
> > In the past the comb filters have been lengthened with brass shim stock
or
> > capacitivly lowered with teflon tape...could this work here?
> >
> >>To convert the unit to 2401 would require removing (by-passing) the
input
> >>filter, some slight input amplifier matching circuit tweaking, and
> >>conversion of the LO to 2257 Mhz.
> >
> > Would this be necessary if the original IF of 123 MHZ is retained with
the
> > proper receiver?
> >
> >>100 to 350 MHz IF amplifier which has both high pass
> >> and low pass filter elements for the IF band.
> >
> > Did you have a chance to measure the cutoff characteristics of the high
> > pass filter to see if it would pass 121 Mhz without loss? Possibly the
> > high pass filter could be bypassed?
> >
> > I guess the bottom line would be to measure the gain and noise figure in
> > it's current form and to decide if it was worth a conversion.....
> >
> > Just my thoughts outloud...
> >
> > Roger
> > WA1KAT
> >
> >
> >
> > ----- Original Message -----
> > From: "Bill Ress" <bill@hsmicrowave.com>
> > To: <amsat-bb@amsat.org>
> > Sent: Thursday, June 09, 2005 1:24 PM
> > Subject: [amsat-bb] CalAmp DownConverter Info
> >
> >
> >> Since the responses to my post indicated that I should post this
response
> >> for all - here's what I have...
> >>
> >> The unit is for the MMDS/ITFS band which is 2500 to 2690 MHz. This is
the
> >> instructional TV band also used by some wireless pay TV services.
> >>
> >> I purchased the unit for parts: connectors, IC's, transistors, a great
> >> weather protected cast housing, etc., knowing that conversion would be
> >> questionable and I think you'll agree.
> >>
> >> The biggest problem is the 7 pole combline filter right at the input
> >> covering 2.5 to 2.7 GHz. Tuning it down to 2.4 GHz proved
unsatisfactory
> >> since the tuning screws were already almost touching the resonators.
> >>
> >> The LNA uses a device yet to be identified followed by a R37 (believed
> >> this
> >> is a NEC device).
> >>
> >> The mixer uses a pair of Schottky diodes (smd = C2) and a 3 dB branch
> >> line
> >> coupler. This circuit is typically somewhat broadband and should work
at
> >> 2401 MHz.
> >>
> >> This is followed by a 100 to 350 MHz IF amplifier which has both high
> >> pass
> >> and low pass filter elements for the IF band.
> >>
> >> The unit is internally down regulated to 12 volts. Power is applied via
a
> >> bias tee to the type "f" 75 ohm output connector. While the type "f"
> >> connector and output circuit has been designed for 75 ohms, driving 50
> >> ohms
> >> is no problem.
> >>
> >> The LO is a crystal controlled PLL using a 2380 MHz VCO divided by 256
by
> >> a
> >> Fujitsu MB506 (divide by 256) and locked to a crystal at 9.29687 MHz.
> >>
> >> To convert the unit to 2401 would require removing (by-passing) the
input
> >> filter, some slight input amplifier matching circuit tweaking, and
> >> conversion of the LO to 2257 Mhz. This, in my opinion, could only be
done
> >> by
> >> one having the expertise and test equipment. Looking at the 2380 MHz
VCO,
> >> I'm sure it could be pulled down to 2257, but again the right equipment
> >> and
> >> knowledge is needed.
> >>
> >> But I'm happy with the purchase (I got 2) since the N connectors alone
> >> are
> >> worth the price.
> >>
> >> If I can answer any other questions - email me.
> >>
> >> Regards...Bill - N6GHz
> >> ----
> >> Sent via amsat-bb@amsat.org. Opinions expressed are those of the
author.
> >> Not an AMSAT member? Join now to support the amateur satellite program!
> >> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> > ----
> > Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> > Not an AMSAT member? Join now to support the amateur satellite program!
> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> ----
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