PRO-2045 MODS ANY AVAILABLE
tyler
I recently bought the 2045 and am wondering if there are any available mods
before I start my own mods to it. There is no external memory to the
processor chip, so more channels are out. Full 800 Mhz range will be a bear
because I will have to intercept the serial data going to the PLL from the
processor and change that with something. (probably with a basic stamp or
some other microcontroller) I could probably do a discriminator out fairly
easily. What about an signal strength meter? I don't remember seeing an RSSI
signal anywhere.
Any suggestions?
Tyler
Scott Gray
Tyler,
I own a PRO-2045, nice receiver - no cell mods (personally, could care
less).
This "addition" or project will work with just about any FM scanner receiver.
Your mileage may vary................
The following modificaton/project is NOT for the newbie. You should have
expereince with succesful component level debug. I accept NO responsibility if you
blow up your scanner!!
My first concerns with my PRO-2045 was the "anemic" audio output and squelch
tail timing. I have been succesful with the integration of a Motorola "Micor"
series squelch/audio board. The Micor receiver has the famous "smart squelch".
"Smart squelch" was a Motorola's 7909 proprietary chip that would eliminate the
squelch tail on moderate to strong signals, leaving a longer "tail" for weaker
stations and reducing and eliminating "chopping" as in closed squelch. The timing
of the 7909 circuit kept the squelch open during the weaker mobile and HT's
producinga nice quiet "click" at the end of transmision of the stronger signals
(hysterisis timng)...... Much less fatiguing durng long listening periods.
Also the Motorola board took care of the weary audio of the 2045 by giving
better than 10 ~real~ watts with nicely shaped and intelligible audio that could
be heard nearly a block away! Using a GE or Motorola speaker of course. Clarity
was vastly improved over the stock speaker.
Another nice feature was the ability to use the Motorola "PL" decoder, a plug
in option board that was used in almost all of the Micors out there.
The PRO-2045 needs a discriminator out. I used 15k 1/8 watt resistor and a
.1uf cap to pin 9 of IC3, (MC3361) to a RCA type jack. I also added isolated line
for "decoded" PL tones (if your using the RS CTCSS decoder) by using a single
2N3904 switch for isolation to provide to the Micor board.
One drawback is that the Motorola board has excellent AM limiting keeping
imupulse noise to a minimum, thus not passing AM Airband traffc.... So, for AM
listening you have to use the existing volume and squelch on the 2045.
Disconnecting the Micor board (which is housed externally in a small R.S.
project box) does not affect you 2045 for regular use - just enhances the heck out
of its AF/Squelch.
Modification of the Micor AF/Squelch board was relativly simple. Add two
20K ohm Linear pots (squelch and volume) a resistor and a 9.1 volt zener diode.
Some small quality sheilded cable fo interconnect and needed jacks and plugs. Your
power to the Micor box should be about 12 volts at at least 1 amp for best
results.
You can find old Motorola Micor "drawers" for 20 bux and up at most swaps. It
doesn't matter what band they were on. The audio/squelch section unplugs, toss the
rest or scavenge for parts.
I can give details on the Motorola pinouts if you need them.
ANOTHER mod was to reduce or eliminate the background hiss even on the strongest
of signals caused by sysnthesizer (common to the recent Uniden based scan
receivers). Here, you must remove the cover over the synthesizer / front-end.
Then, using a ferrite bead held by tweezers, I placed the bead over and around
some of the synthesizer sections while feeding a strong unmodulated carrier to the
2045. I found a nice spot that gave better than 6db more "quieting" just a few
inches below the 10.85 IF section (there is a small outline or box of unpainted
etch) find the "spot" (Q-15) and secure the bead down wih a dab of hot-glue.
Works! Did the same on my BC-895XLT with similar success!
Also, I added one more 10.85 IF xtal filter in series with the existing one on
the 2045, reducing adjacent channel garbage without sacrificing sensitivity.
Yep, a little "deep" for most folks. DON'T do it unless you have the proper
test equipment and can handle a small soldering iron. Be prepared to do a
"touch-up" alignment on you finished product.
Scott Gray KD6CQ