Modifying an existing radio.

N

Noen

Guest
Hi.

I have an 88-108 fm radio, and want to adjust it to 160 - 180.
I know I probably need to replace the oscillating capacitor, but I dont
know what to change it to. (And where I could locate it.)

Hope anyone can help.
 
In article <doRwb.26538$BD3.5020938@juliett.dax.net>,
not.available@na.no says...

Hi.

I have an 88-108 fm radio, and want to adjust it to 160 - 180.
I know I probably need to replace the oscillating capacitor, but I dont
know what to change it to. (And where I could locate it.)
Click to expand...
The mods you describe would be far more complex than simply
replacing a capacitor. They would involve a complete redesign and
rebuild of the RF section.

Also, remember that a typical FM broadcast receiver's IF section
has a bandwidth of at least 75kHz. This makes them utterly useless for
anything other than -- you guessed it -- FM broadcast reception.

What is it you're really trying to do? Who or what are you trying
to monitor?


--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
Motorola Radio Programming & Service Available -
http://www.bluefeathertech.com/rf.html
"Quando Omni Flunkus Moritati" (Red Green)
 
Dr. Anton Squeegee wrote:
In article <doRwb.26538$BD3.5020938@juliett.dax.net>,
not.available@na.no says...


Hi.

I have an 88-108 fm radio, and want to adjust it to 160 - 180.
I know I probably need to replace the oscillating capacitor, but I dont
know what to change it to. (And where I could locate it.)


The mods you describe would be far more complex than simply
replacing a capacitor. They would involve a complete redesign and
rebuild of the RF section.

Also, remember that a typical FM broadcast receiver's IF section
has a bandwidth of at least 75kHz. This makes them utterly useless for
anything other than -- you guessed it -- FM broadcast reception.

What is it you're really trying to do? Who or what are you trying
to monitor?


Im trying to learn how to monitor radio communication... after Ive
Click to expand...
figured out how make my fm radio to receive on other frequencies, im
thinking of plugging the output into my mic, and start coding programs
for storing communication, filtering noise, squelch etc... Would be fun
for an amatour radio operator (to catch messages while away)...
 
"Dr. Anton Squeegee" wrote:
In article <doRwb.26538$BD3.5020938@juliett.dax.net>,
not.available@na.no says...

Hi.

I have an 88-108 fm radio, and want to adjust it to 160 - 180.
I know I probably need to replace the oscillating capacitor, but I dont
know what to change it to. (And where I could locate it.)

The mods you describe would be far more complex than simply
replacing a capacitor. They would involve a complete redesign and
rebuild of the RF section.

Also, remember that a typical FM broadcast receiver's IF section
has a bandwidth of at least 75kHz. This makes them utterly useless for
anything other than -- you guessed it -- FM broadcast reception.

--
Dr. Anton Squeegee
Click to expand...
That should be ą 75 KHz, for a total of 150 KHz bandwidth. That is
why FM broadcast channels are 200 KHz apart.

--
I say, the boy is so stupid that he tried to make a back up copy of his
hard drive on the Xerox machine!

Michael A. Terrell
Central Florida
 
It is a lot more than changing a cap value. If your set uses a variable cap,
you will also have to change the coils in the RF and oscillator front end.
There will be some re-engineering to get the proper matching.

If you want to listen to UHF communications these bands, it will sound like
a mess full of imaging, and noise. The IF bandwidth in your FM radio is +-
75 kHz, or a total of 150 kHz for FM broadcast listening. You will have to
change all the IF coils to ones with a higher "Q" and re-align the signal
path. You will want to have a 15 kHz total bandwidth for communications
listening.

If your set is a PLL synthesized type, you will have to re-design the PLL to
pre-scale in to the new band that you want. This will also involve
redesigning the firmware that it is working under. The same will go for the
IF amp design, as mentioned above.

You would be best off going out and getting yourself a descent scanner that
was designed to do the job. The reception will be much better than
something you can do at home yourself.

In the older days with the tube type FM radios, with some work done by
someone that really knew what he was doing, it was possible to modify the
radio to receive the aircraft bands that were in use in those days. The
detector had to be changed to an AM type, and the IF amp stages had to be
modified to have the required 15 kHz bandwidth. In most cases it still
worked out cheaper and better to buy a hobby type aircraft receiver, which
was engineered from its base design to do this.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Noen" <not.available@na.no> wrote in message
news:doRwb.26538$BD3.5020938@juliett.dax.net...
Hi.

I have an 88-108 fm radio, and want to adjust it to 160 - 180.
I know I probably need to replace the oscillating capacitor, but I dont
know what to change it to. (And where I could locate it.)

Hope anyone can help.
 
In article <doRwb.26538$BD3.5020938@juliett.dax.net>,
not.available@na.no mentioned...
Hi.

I have an 88-108 fm radio, and want to adjust it to 160 - 180.
I know I probably need to replace the oscillating capacitor, but I dont
know what to change it to. (And where I could locate it.)

Hope anyone can help.
Click to expand...
You could move it maybe 10 percent in that direction, but doubling the
freq will probably not work because the transistors and other
components would need to be replaced. You can remove a leaf from the
variable capacitor, and turns from the coil, but once you do that, the
alignment will suffer greatly, and you will have to realign it.

And another major problem is that almost all of the stations you would
pick up in those frequencies are narrow band FM. They are 1/15 the
bandwidth of the normal FM broadcast station. This means that you
will receive several stations at the same time, which is a real
problem when you're in a city with a lot of activity in those bands.
And adjusting the dial to a single station is nearly impossible
because just moving it a slight amount will change it dozens of
channels. I have an old Rat Shack Patrolman-5 radio that has similar
bands and does something similar, and it is nearly useless when it is
tuned to the VHF and UHF bands. I found out the hard way, I bought
the radio thinking I could use it like a scanner. When I found out
how bad it was, I went out and bought a real scanner.

Good luck; you're going to need it.
--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
In article <MPG.1a2e8ea7ef44455e989b32@192.168.42.131>,
SpammersAreVermin@DevNull mentioned...
In article <doRwb.26538$BD3.5020938@juliett.dax.net>,
not.available@na.no says...

Hi.

I have an 88-108 fm radio, and want to adjust it to 160 - 180.
I know I probably need to replace the oscillating capacitor, but I dont
know what to change it to. (And where I could locate it.)

The mods you describe would be far more complex than simply
replacing a capacitor. They would involve a complete redesign and
rebuild of the RF section.

Also, remember that a typical FM broadcast receiver's IF section
has a bandwidth of at least 75kHz. This makes them utterly useless for
anything other than -- you guessed it -- FM broadcast reception.
Click to expand...
Well, not totally useless. But nearly so, especially in a crowded
band with many active stations. If you were out in the sticks with
very few stations, you might be able to hear just one. But nowadays,
this is very rare. And you're right, I do _not_ recommend that anyone
try to mod a radio like this, it's a waste of time.


What is it you're really trying to do? Who or what are you trying
to monitor?
Click to expand...

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
In article <doRwb.26538$BD3.5020938@juliett.dax.net>,
Noen <not.available@na.no> wrote:
Hi.

I have an 88-108 fm radio, and want to adjust it to 160 - 180.
I know I probably need to replace the oscillating capacitor, but I dont
know what to change it to. (And where I could locate it.)
Click to expand...
I did that to a 1970 vintage stereo hi-fi tuner. That type and era
radio is easy to work on because they're big, have air variable capacitor
tuning and leaded discrete components, but modern enough to use ceramic
IF filters and MOSFET front ends. I was trying to get the weather
satellites at 137 MHz and managed to get the top end above 148 MHz,
(the two meter ham band), by rewinding the oscillator coil with one less
turn and tweeking the RF trimmer caps and coil adjustments. It worked
fine for monitoring the local 2 meter repeater.

But if you don't know what to change, you'll need to get the service
data for the radio, or (if it's newer than a couple of decades old) the
datasheet for the integrated circuit that the radio uses. The two most
common radio chip manufacturers that I see are Philips and Telefunken ->
Temic -> Atmel. Alas, (last I checked) Atmel seems to have taken the
older Telefunken chips off their german web site.

Mark Zenier mzenier@eskimo.com Washington State resident
 
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