825 lines
32 KiB
Plaintext
825 lines
32 KiB
Plaintext
X-NEWS: ids alt.radio.pirate: 644
|
|
Path: paperboy.ids.net!uunet!gatekeeper.us.oracle.com!decwrl!nntp.crl.com!acsys!mycal
|
|
From: mycal@NetAcsys.com (Mycal)
|
|
Newsgroups: alt.radio.pirate
|
|
Subject: fm-10 faq
|
|
Message-ID: <753148531.419snx@NetAcsys.com>
|
|
Date: Fri, 12 Nov 93 23:55:31 GMT
|
|
Organization: I Hack.
|
|
Lines: 814
|
|
|
|
|
|
--------------cut-----------
|
|
|
|
Ramsey FM-10 Info
|
|
by
|
|
mycal@netacsys.com
|
|
|
|
9th Edition
|
|
-----------
|
|
Here is a rough compilation of information about the Ramsey FM-10, and
|
|
other BA1404 Stereo FM broadcasters. Some of the modifications may make
|
|
your BA1404 based broadcaster illegal to use on the open airwaves in the
|
|
US and Canada. Also it has been brought up that the stock Ramsey FM-10
|
|
kit may exceed FCC power limits when used with a proper antenna.
|
|
|
|
The information contained in the file is in no way complete, nor do I
|
|
take any responsibility for its accuracy. With that in mind, along
|
|
with the above paragraph I must say :
|
|
|
|
"This file for informational purposes only."
|
|
|
|
|
|
About This File
|
|
---------------
|
|
When I first started hacking on my FM-10, a few of us on alt.radio.pirate
|
|
were exchanging information on mods to improve the range, stability and
|
|
audio quality of the FM-10. After a couple of posts about filters and
|
|
amps, my mailbox was swamped with requests for copies of previously posted
|
|
information and other questions about the FM-10. So rather than drive
|
|
myself crazy with sending a piece of info here and there, I decided to
|
|
dig through my mailbox an notes and compile this file. I hope it helps.
|
|
Also if anyone has more information about the FM-10 or FM transmitters,
|
|
antennas, mixing equipment, programming information, stories about pirates,
|
|
or anything else that falls into this realm, please send it to
|
|
mycal@netacsys.com. I will try to update this file as new information
|
|
becomes available.
|
|
|
|
Also I am working on a some Postscript files that will contain instructions
|
|
on how to build some equipment that is to complex for ASCII art. You
|
|
might want to check the FTPable archives every month or so.
|
|
|
|
I would like to say thanx to all the people that contributed to the
|
|
information in this file. The list has grown quite long, and some
|
|
of the contributors would like to remain anonymous. So for now I am
|
|
going to forgo all the names, if this is not up to your liking please
|
|
let me know.
|
|
|
|
|
|
FM-10 Mailing List
|
|
------------------
|
|
First Things First. There is now a mailing list that deals with the topic
|
|
of the Ramsey FM-10 and other BA1404 based FM Stereo Transmitters. Feel
|
|
free to join up and contribute.
|
|
|
|
To send a message to the mailing list, send your question, reply, comment,
|
|
or contribution to :
|
|
|
|
fm-10@dg-rtp.dg.com
|
|
|
|
To add or delete yourself from the list, send a short message with
|
|
the function (add/delete/change address) along with the relevant e-mail
|
|
address to:
|
|
|
|
fm-10-request@dg-rtp.dg.com
|
|
|
|
|
|
If you have any questions I can be reached at myca@netacsys.com.
|
|
|
|
|
|
FM-10 Archives
|
|
--------------
|
|
Yes it is finally here, message archives of the FM10 mailing list and a
|
|
place to put/find schematics, reviews, stories, etc. related to the FM-10
|
|
and other BA1404 based FM transmitters. Currently a 350mw amp plan,
|
|
800mw amp plans, Radio is my bomb text, slim jim plans/info and
|
|
the BA1404 spec sheet are located there.
|
|
|
|
People can FTP into dg-rtp.dg.com with user "anonymous" and password
|
|
"<your EMail address>". In the fm10 directory you'll currently
|
|
find two sub-directories:
|
|
|
|
incoming
|
|
This is writable by everyone and this is where people should
|
|
upload new stuff.
|
|
|
|
msg-archives
|
|
This directory will have files named according to the date they
|
|
were last "sealed". The file "Current" is a running log of
|
|
all EMail messages from the last "seal" date of the archives.
|
|
|
|
I want to thank Ed Savage and the guys at Data General, NC for
|
|
making the list and the archive possible.
|
|
|
|
|
|
Snail Mail Info Packet (or Pirates Guide to FM Stereo)
|
|
------------------------------------------------------
|
|
The info packet has evolved yet again, it is now 24 pages. It includes
|
|
plans for 4 amps, a 200mw, 350mw, 800mw, and 5watt. Instructions for
|
|
modifying the Ramsey PA-1 for FM broadcast band operation. A section
|
|
on how to design and build your own antenna. Plans for a power meter,
|
|
regulated power supply, and dummy load. A block diagram showing a
|
|
typical station. Spec sheet for the BA1404. FM-10 modifications.
|
|
Sources for parts and info. And a more up to date design of my digitally
|
|
synthesized transmitter. Loaded with schematics, board-layouts and diagrams.
|
|
And now, schematics and construction details of the FRB 5 watt transmitter.
|
|
|
|
The price for this packet is $5 in the US and $8 overseas.
|
|
|
|
Address to send the $$ to is:
|
|
mycal
|
|
PO Box 750381
|
|
Petaluma, CA 94975-0381
|
|
|
|
You can also use this address to send me any info that would be hard
|
|
to send by email. I will trade info packets for hard copy information,
|
|
email me for details.
|
|
|
|
Note : this packet is in a constant state of change, more info could be
|
|
added at any time.
|
|
|
|
Other Places to Look in Cyberspace
|
|
----------------------------------
|
|
alt.radio.pirate is another good forum to find or post information on FM
|
|
radio transmitter. Although you may not have pirate aspirations, many of
|
|
the things talked about can benefit everyone.
|
|
|
|
Other places to scan, sci.electronics and the amateur radio groups.
|
|
|
|
The American Radio Relay League (ARRL) has a useful service -- the ARRL
|
|
Information Mail Server. This is an automated mail server that let's you
|
|
access many of our information files, containing information about various
|
|
facets of Amateur Radio. Some of the information has technical value
|
|
that is related to all radio services.
|
|
|
|
To use it, mail messages to:
|
|
|
|
info@arrl.org
|
|
|
|
With the message :
|
|
|
|
help
|
|
|
|
This will give you all the information you need to use this service.
|
|
|
|
Radio Resistors Bulliten
|
|
------------------------
|
|
A little zine that somtimes discusses pirate/micropower radio along
|
|
with public radio stuph. Send frank a buck to help out with the
|
|
copying and stamps.
|
|
|
|
Frank Haulgren
|
|
RRB
|
|
PO Box 3038
|
|
Bellingham, WA 98227-3038
|
|
|
|
Recommended Test Equipment
|
|
--------------------------
|
|
An SWR/Power meter is a giant help, a CB to 2 meter one will suffice.
|
|
Power readings will not be accurate, but can be useful for peaking.
|
|
The most important part is the SWR meter, this is very important when
|
|
making an antenna.
|
|
|
|
A note on power meters. I recommeded the above power meters because they
|
|
are inexpensive and most people that are interested in hacking a FM-10
|
|
have very limited funds. These are by no means accurate, but they will
|
|
give you some idea what is going on. If you can spend the money you
|
|
can get an accurate power meter that is designed for this band, but the
|
|
cost is 10-15 times more.
|
|
|
|
A rf probe could also be used as a replacement for a powermeter,
|
|
construction details below.
|
|
|
|
A 50ohm non inductive load is also very helpful, for low power applications
|
|
a 50ohm 1/4 or 1/2 watt carbon resistor works well. This can be used to
|
|
tune up your kit and amp without interfearing with anyone. Also note that
|
|
you can run as much power you want, legally, as long is it doesn't radiate.
|
|
|
|
A VOM is also very helpful. High I would put out the extra bucks and
|
|
buy one with a freq counter (if you shop around, about $60-$70). Buy
|
|
the one that covers audio to 20MHz(or more). If you are serious about
|
|
electronics you need one of these!
|
|
|
|
|
|
Dummy load
|
|
----------
|
|
Dummy loads are great for testing, without radiating a signal. In fact
|
|
you can run as much power as you want into one of these things legally!
|
|
|
|
Basically you want to create a non-inductive 50-ohm load. This can be
|
|
done with regular carbon resistors, or by buying pre built Amateur or
|
|
CB radio loads. For low power ( <.5 watt ) an ethernet terminator works
|
|
well (check temp when using if it gets very hot lower input power, if it
|
|
is still cool you may be able to go up to .75 watt.)
|
|
|
|
Most CB loads use a 2-watt carbon 50-ohm resistor.
|
|
|
|
You can build your own, as wimpy or as studly as you want by running
|
|
resistors in parallel to create 50-ohms. ie, 2 100 ohm 1/4 watt resistors
|
|
will create a 1/2 watt 50 ohm load...
|
|
|
|
Do not use 50 ohm wire wound resistors, they are not 50 ohms at radio
|
|
frequencies.
|
|
|
|
-----
|
|
---------\ Sample Dummy Load where -****- = 50 ohm
|
|
---|--****-- / mounted in UHF connector. carbon
|
|
--------- resistor
|
|
-----
|
|
|
|
RF Probe
|
|
--------
|
|
For those of you (like me) who are in constant Starving Student
|
|
mode, and DONT have a good Scope, you can use a good DMM for RF power
|
|
calcualtions. All you need to do is build a RF probe. Here's the
|
|
schematic: (Yes, taken from 1989 ARRL Handbook)
|
|
|
|
--probe tip-----||-----/\/\/\-------to center of 50 ohm coax.
|
|
.01uf | 4.7M -------to braid
|
|
__ |
|
|
\/ |
|
|
---- |
|
|
| |
|
|
cliplead for gnd--------------------
|
|
|
|
Anyway, the Diode ( arrow-points to ground) should ideally be
|
|
a Schottky diode (low rf capacitance). Although a 1n914 will work.
|
|
To use, just hook up to your digital Meter, set on DC voltage.
|
|
You will get very close to RMS RF Voltage. (this probe was specified for a
|
|
10Meg Ohm meter).
|
|
|
|
To calculate power into a KNOWN purely resistive load (a.k.a. a dummy)
|
|
use:
|
|
e^2/R
|
|
where e is the RMS RF voltage, R is resistance :-)
|
|
|
|
This is also useful for checking inputs and outputs of low
|
|
power RF units, since the inexpensive power meters don't seem to do real
|
|
well below 1watt.
|
|
jsawyer@crash.cts.com
|
|
|
|
Paranoid?
|
|
---------
|
|
I've been talking to a few ppl that are worried about there "voice" being
|
|
on the air, since they are afraid of being recognized.
|
|
|
|
So I dusted off the old stacks of Radio-Electronics and found two articles
|
|
that may be of intrest.
|
|
|
|
In the January 1993 issue they have a "build your own digital voice
|
|
changer" using a simple Real time digital signal processor. I think that
|
|
this design is very simalar to the voice changing telephones. It basically
|
|
raises or lowers your voice pitch. A place called LNS Technologies @ 1-800
|
|
-886-7150 sells the kits for $59.
|
|
|
|
In there September 1992 issues they have a "build this dsp voice-effects
|
|
board" using a little more complex, programmable, real time digital signal
|
|
processor. The software they include contains a harmonizer, echo, reverb,
|
|
and pitch. The kit is sold by American Disributors Inc for $105 @
|
|
1-800-877-0510. You can also write your won software but the programmer
|
|
is several hundred $$.
|
|
|
|
DC electronics has a Robot Voice Kit for $15. I don't know how well this
|
|
works or what it sounds like, but it clames to be adjustable for many
|
|
different effects.
|
|
|
|
Ramsey's Address
|
|
----------------
|
|
If your looking to purchase a FM-10 kit and can't find one locally try :
|
|
|
|
Ramsey Electronics, Inc.
|
|
793 Canning Parkway
|
|
Victor, New York 14564
|
|
Phone (716) 924-4560
|
|
FAX (716) 924-4555
|
|
|
|
|
|
Ramsey FM-10 70mw output amplifier
|
|
----------------------------------
|
|
Provides almost 9db gain to bring the output power of the Ramsey FM-10 Stereo
|
|
transmitter from 8mw to 70mw. Not the best design, but all parts can be
|
|
found at Radio Shack! Much better designs are available at the archive
|
|
site.
|
|
|
|
+12v
|
|
|
|
|
/
|
|
\ R1 *220 ohms(1/2 watt)
|
|
/
|
|
\
|
|
R2 9k | C2
|
|
-/\/\/\/-----------||-----> output
|
|
| /
|
|
| /
|
|
| | /
|
|
C1 | |/ <----------MPS2222A (276-2009)
|
|
in --||------|\ -or- 2N4401
|
|
^ | -> --
|
|
| |
|
|
| GND
|
|
currently on board
|
|
|
|
* you can also use 2 440 ohm 1/4 watt resistors run in parallel
|
|
|
|
I built this thing right on the underside of the FM-10 kit, C1 is the
|
|
cap that currently goes to the RCA ant jack, the 9k and the 220 ohm
|
|
resistor have to be bought, note that if you cannot find 220 ohms you
|
|
can make one by using 2 440 ohm resistors in parallel, and that a 10k
|
|
will work in place of the 9k but yields poorer performance (-5%).
|
|
|
|
The MPS2222A is from Radio Shack part number 276-2009, use this part! if
|
|
you substitute it for a 2N2222A you will get only half the gain. Be
|
|
very careful to get the leads in the correct orientation!
|
|
|
|
I have found that a 2N4401 can be used in place of the MPS2222A with a
|
|
little better performance, about 5mw more. I think the 2N4401 can be
|
|
found at Radio Shack too.
|
|
|
|
C2 is of the same value of C1, I took the one that goes to the on board
|
|
antenna pad.
|
|
|
|
Important! the value for R1 that seems to be optimal is 220 ohms, but it
|
|
is very close to the sat point, If the amp. seems noisy (interferes with the
|
|
TV etc.) back this value off to 240 ohms. If you lower this value below 205
|
|
ohms the power meter may read higher power but this will not be true, the
|
|
transistor will be spewing all kinds of junk and the power meter will
|
|
mistake this for higher output (in reality the signal we want will drop
|
|
considerably.)
|
|
|
|
Well that's it, effective range with a good antenna should be a little
|
|
over double.
|
|
|
|
|
|
Ramsey PA-1 2-meter to 3-meter conversion mod
|
|
---------------------------------------------
|
|
The Ramsey 2-meter amp (PA-1) can be converted for use on the FM broadcast
|
|
band. The inductors L1 and L2 need to be changed to the following:
|
|
|
|
L1 - Should be replaced with a 1-turn 1/4" diameter coil, Identical to
|
|
the stock L2 shown in the PA-1 manual.
|
|
|
|
L2 - Should be replaced with a 2 turn 1/4" diameter coil, one more turn
|
|
than the above coil.
|
|
|
|
Tune up should be the same as in the PA-1 Manual. Note that a FM-10 kit
|
|
cannot be used to drive a PA-1 kit alone. The FM-10 kit doesn't put out
|
|
enough power to turn on the PA-1 kit running class-c. So you have two
|
|
options. One, you can do the "biased on" (newer kits may call this class-b)
|
|
modification shown in the PA-1 manual. Doing this you can drive the PA-1
|
|
with a stock FM-10, yielding about 200-300mw of output power. Or two, you
|
|
can drive the PA-1 with the output of the 70mw amp shown above and get close
|
|
to a watt of output power.
|
|
|
|
It should be noted here that running the PA-1 "biased on" (or class-b)
|
|
produces a much cleaner output signal than running the PA-1 class-c. Also
|
|
that you can run the PA-1 "biased on" while driving it with the 70mw amp,
|
|
but you will show slightly less gain than in class-c.
|
|
|
|
|
|
ANTENNAS -- read, read, read, read, most important!
|
|
--------
|
|
Also Do you have a good antenna? I think that is the most important
|
|
thing that you can do for extended range. I built a 1/4 wave ground plane
|
|
using a UHF connector and 5 lengths of copper plated brazing rod (found at
|
|
the local welding shop). Works great and only cost $3 dollars to make.
|
|
Remember good antenna will improve you range much further than a good amp
|
|
into a bad antenna. So this should be your 1st project to increase your
|
|
range.
|
|
|
|
use the formulas out of your FM-10 manual 234/freq=length of rod.
|
|
|
|
Example : 234/88Mhz = 2.66 feet * 12 in/feet = 31.9" -or-
|
|
234/108Mhz= 2.17 feet * 12 in/feet = 26"
|
|
|
|
insert the 4 ground plane rods in the 4 holes of the UHF connector, stick
|
|
them through about 1/4 inch and solder. Solder the radiator in the top
|
|
of the UHF connector (you may have to grind it a bit to fit.) Then bend
|
|
the ground plane rods to a 45 degree angle to the radiator. There you
|
|
have it a very effective antenna, just connect with a 50 ohm CB cable
|
|
to your amplified Ramsey, stick the antenna in a tree or in another high
|
|
place and you should have 1 miles of solid coverage (when using the
|
|
above amp.).
|
|
|
|
Also If you have an SWR meter you can cut the rods a little longer and start
|
|
clipping the ends off a little until you get the best SWR reading.
|
|
|
|
|
|
|
| | | = brazing rod
|
|
| | |
|
|
| |
|
|
----- ----- ----- = UHF connector
|
|
| - | / - \ -
|
|
| | / \
|
|
| | / \
|
|
|
|
|
|
The final antenna should look like this:
|
|
|
|
| ^
|
|
| |
|
|
// \\ sky ground --horizon--
|
|
|
|
|
v
|
|
|
|
That is 1 radiator pointing strait up and 4 ground plane
|
|
radials. (sorry for this extreme description, but there
|
|
has been some confusion.)
|
|
|
|
Be careful when you bend the brazing rod, don't break the connector. Grab
|
|
the rod right below the connector with a pair of vice-grips (or the likes)
|
|
and bend the brazing rod at that point.
|
|
|
|
Try not to have anything metal near the radiator, this will effect
|
|
the radiation pattern. The radiation pattern should look a lot like
|
|
a doughnut surrounding the radiator, though deformed a bit.
|
|
|
|
I have been told that you can shorten the radiator and make the ground
|
|
radials longer to lower your radiation angle, but I haven't tried this, nor
|
|
do I know what this would do to the antenna impedance.
|
|
|
|
|
|
On The Road
|
|
-----------
|
|
Old magnet mount CB antennas can make great mobile antennas, just take all
|
|
of the base load out of them and cut the radiator to 1/4 wave length.
|
|
If you need a longer radiator than the one that comes with the antenna
|
|
use the above mentioned brazing rod.
|
|
|
|
I've tried this antenna and it works great! It is better than my di-pole at
|
|
home and you can drive to a high, optimal location for your broadcasts.
|
|
Also with this setup you need very little coax cable. Line loss using
|
|
RU-58u can be killer @ 100MHz.
|
|
|
|
You could also try a 5/8 wave length antenna, this would give you 2+db gain,
|
|
or almost 2x power gain on transmit.
|
|
|
|
|
|
Filter design for FM Radio Transmitters.
|
|
----------------------------------------
|
|
It is very important to have a clean signal, the way 99% of all people
|
|
who get busted for illegal transmitting is that the people that live
|
|
around them complain about interference. Most of this interference
|
|
is caused by harmonics. Filters cut down these nasties. So don't
|
|
draw attention to yourself, keep everyone happy, including yourself,
|
|
be clean, use a filter.
|
|
|
|
When you amplify a signal, you get unwanted byproducts these are called
|
|
harmonics. The show up at multiples of your starting frequency. For
|
|
example if you amplify a 50MHz signal you may get echo's on 100MHz, 150MHz
|
|
200MHz, 250MHz... If you interfear with your neighbors TV, the local fire
|
|
department, or anyone else, you are just asking for trouble. If you are
|
|
only on the FM Band, you will hardly be noticed.
|
|
|
|
...
|
|
Filter Designs
|
|
--------------
|
|
(basically scaled from the charts in the ARRL handbook).
|
|
|
|
Filter Design: 7 element Chebyshev
|
|
I run @ 88.1 so my 1st harmonic is 176.2
|
|
This filter seems ideal.
|
|
|
|
Fc 3db 20db 40db
|
|
85.8MHz 95.9MHz 116MHz 148MHz
|
|
|
|
.132uh .150uh .132uh
|
|
-----()()()-----()()()-----()()()-----
|
|
| | | |
|
|
<-50ohm - 33pF - 68pF - 68pF - 33pF 50ohm->
|
|
- - - -
|
|
| | | |
|
|
--------------------------------------
|
|
|
|
|
---
|
|
-
|
|
|
|
lowering the 33pF caps to 30pF and the 68pF caps to 62pF would make
|
|
this filter sutible for higher frequencies like 100MHz.
|
|
|
|
|
|
Filter Design: 5 element Chebyshev
|
|
Not as good as above.
|
|
|
|
Fc 3db 20db 40db
|
|
81.8MHz 105MHz 147MHz 222MHz
|
|
|
|
.128uh .128uh
|
|
-----()()()-----()()()-----
|
|
| | |
|
|
<-50ohm - 30pF - 62pF - 30pF 50ohm->
|
|
- - -
|
|
| | |
|
|
---------------------------
|
|
|
|
|
---
|
|
-
|
|
|
|
The tuff part in the above is winding the coils. 3t of #12 wire 1/2" diam
|
|
should be about .12 uh. 4t is .17 uh. (but ugh, #12 wire is big stuff).
|
|
You could just use molded inductors, I have found these work well. Try
|
|
to use fixed value caps, or fixed value with small 5pF trimmers. The
|
|
latter works well when you have a spectrum analizer to tune there babies.
|
|
|
|
I just pulled a program of a BBS that tells you how to wind inductors.
|
|
Give it the value and wire size you have and it will tell you how many turns
|
|
and what size. Way cool. More on this later.
|
|
|
|
|
|
Very simple Chebyshev filter.
|
|
------------------------------
|
|
|
|
.15uH
|
|
from FM10 >------()()()------> to antenna
|
|
| |
|
|
- c1 - c2
|
|
- -
|
|
| |
|
|
--- ---
|
|
- -
|
|
|
|
88MHz 102MHz 107MHz
|
|
c1 62pF 54pF 50pF
|
|
c2 62pF 54pF 50pF
|
|
|
|
It won't knock the harmonics down as much as the other two designs but
|
|
the good thing about this one is that it uses standard off the shelf
|
|
parts. The inductor is one of those molded jobbies that looks like
|
|
a resistor so you can make this very small. You may stack these things
|
|
to make a better filter. Each stage will knock the 1st harmonic down
|
|
about 15db.
|
|
|
|
Use the above cap values depending on which freq range you want to operate
|
|
at. ie. if you run 87-90 use the 88MHz vals, 90-103 use 102MHz vals,
|
|
and above that use 107MHz vals.
|
|
|
|
[Also of interest is that the FM-10 puts out about 8-9mw and the 2nd harmonic
|
|
is -25db off the fundamental (frequency we are broadcasting on). The FM-4
|
|
Kit by Ramsey puts out 130mw and the 2nd harmonic is only -12db off the
|
|
fundamental, which means the 2nd harmonic of the FM-4 is about as
|
|
powerful as the FM-10. db is log10, ie 3db is 2 times 6db is 4 times...]
|
|
|
|
|
|
FM-10 Myths
|
|
-----------
|
|
There have been several myths about the FM-10 kit, the most prevalent are :
|
|
|
|
1) The FM-10 puts out 100mw of power. This is not true, or at least not
|
|
true for the Ramsey FM-10's that I have tested. They put out between
|
|
8 and 12mw when driven with a 12volt supply. (note: there has been several
|
|
revisions of the FM-10, it is possible that the original version put out
|
|
more power, but I find even that highly unlikely since it would require
|
|
another amplifier stage.) Also the FM-10 is the only low cost kit, that
|
|
I have seen, with an amplifier stage. Most others have power outputs
|
|
in the fraction of a mw area.
|
|
|
|
2) The FM-10's output can be cranked up by reducing the value of R9. This
|
|
like the above is not true. R9 and R10 are optimized for maximum output
|
|
and greatest harmonic suppression at 12volts. There are much better ways
|
|
of getting more output power than to mess with this output stage. Lowering
|
|
the value of R9 will most likely degrade the FM-10's performance and cause
|
|
lots of interference.
|
|
|
|
=============================================================================
|
|
|
|
FM-10 Improvements -
|
|
--------------------
|
|
Note : I sent this file and a list of other modifications to John Ramsey.
|
|
Low and behold 4 monthes later the FM-10a is released. The new FM-10a
|
|
incorporates all of these following mods.
|
|
|
|
Stereo Pilot Mod
|
|
----------------
|
|
One of the first problems experienced with the FM-10 is difficulty
|
|
in getting the stereo pilot to operate correctly. One solution is to
|
|
replace C7 and C8 with a 38KHz crystal, this works the best and is
|
|
recommended. If you cannot find a 38KHz crystal, you can make your life
|
|
a whole lot easier with a couple part changes. As indicated on the
|
|
Ramsey schematic, about 110pF is necessary to tune the oscillator. The
|
|
components supplied to achieve this are a small fixed value capacitor (C7)
|
|
and a slightly larger value trimmer (C8). Since proper setting of the
|
|
trimmer occurs within a very small 'window' (about 5% of the trimmers
|
|
range), it can bet difficult or impossible to adjust the pilot to 19KHz
|
|
and have it stay put. This can be cured by increasing the value of c7 to
|
|
100pF and replacing c8 with a 6-50pF trimmer (Radio Shack #272-1340);
|
|
a 5-30pF trimmer will do the trick. The RS trimmer will not fit the holes
|
|
in the pc board; one needs to cut the leads off a spare resistor and
|
|
solder them to the legs of the trimmer (just use bits of wire) to mount
|
|
it on the component side of the board.
|
|
|
|
On a 2nd note: I replaced c7 with a 68pF cap and found it much easyer to
|
|
tune a rock solid 19KHz at the test point.
|
|
|
|
Crystal Mod
|
|
-----------
|
|
old set up new setup
|
|
c8 c1 xtl where c1=10pF and xtl=38KHz
|
|
|-||-| |-||-|\|-|
|
|
| c7 | | | v8=var cap
|
|
|-||-| | | c7=cap
|
|
| | | |
|
|
|
|
Remove C7 and C8, replace with 38KHz crystal and 10pF cap. Note that
|
|
the 10pF cap and the crystal are running series and the old cap setup
|
|
is running in parallel.
|
|
|
|
Note: there have been good and bad reports on using the Epson crystal
|
|
from digi-key. From what I have heard the crystal is quite delicate,
|
|
and in at least one case the experimenter destroyed the crystal.
|
|
In one of the positive case C1's 10pF cap was replaced by 2 22pF caps
|
|
run in parallel, this yielded a rock solid stereo.
|
|
|
|
|
|
Treble Boost Mod
|
|
----------------
|
|
Treble boost (pre-emphasis) improvement. The FM-10 appears to have
|
|
been designed by someone outside the United States since it operates
|
|
at the European audio standard of 50 microseconds. Receivers in the
|
|
US are set up for 75 microsecond de-emphasis. R3 and R6 determine the
|
|
time constant for the pre-emphasis curve. Replacing them with 75K ohm
|
|
resistors (standard value 68K ohm is close enough) will result in
|
|
improved audio response.
|
|
|
|
A much better pre-emphasis/input circuit is shown in the July 1992 issue
|
|
of "Radio Electronics". Not only do they use 75K ohm resisters in there
|
|
pre-emphasis, but they filter stray RF signals by inserting a .001 cap
|
|
between pin 1 (of the BA1404) and ground, and pin 18 and ground.
|
|
|
|
It has been noted that the above mod may actually cause distortion on
|
|
cheaper stereo receivers, since they were mass produced for the world market,
|
|
they were designed for the European audio standard, which Japan and other
|
|
Asian nations use too. Try it out, let me know what works for you.
|
|
|
|
|
|
Anti-Drift Mod
|
|
--------------
|
|
There has been quite a bit of discussion on the FM-10's frequency stability.
|
|
Complaints that digital receivers cannot lock onto the FM-10's signal for
|
|
any great length of time. I have used the below mod with good results
|
|
(I used an N750 negative temperature compensated disc), but I have been
|
|
told that Mylar or Polystyrene caps are even better.
|
|
|
|
The FM-10 was designed to be inexpensive and cost-saving measures with
|
|
components are inevitable. Disc ceramic capacitors are less expensive than
|
|
silver-mica caps, and also much less stable. Simply replace c16 with a
|
|
silver-mica, tantalum or negative temperature compensated disc (say anywhere
|
|
from N150 to N750) cap of the same value.
|
|
|
|
============================================================================
|
|
|
|
Sources
|
|
-------
|
|
The following is a list of sources for items used for modifications,
|
|
replacement parts, or other kits and equipment used in FM radio
|
|
transmitting:
|
|
|
|
--
|
|
BA1404s and other FM Broadcaster kits can be found at :
|
|
|
|
D.C. Electronics
|
|
phone: 1-800-467-7736 & 1-800-423-0070
|
|
fax:1-602-994-1707
|
|
|
|
They sell BA1404s for $2 a piece, seems to be the best deal going.
|
|
Also they Sell 38KHz crystals for $5.99, which is also a fair deal, the
|
|
crystals are tiny ones like the digi-key ones, but a different brand and
|
|
work without problems or the Digi-Key ones.
|
|
--
|
|
--
|
|
38KHz Crystals can be obtained by calling :
|
|
|
|
Digi-Key at 1-800-DIGI-KEY.
|
|
|
|
38.000 KHz by Epson America, Digi-Key part No. is SE3314
|
|
(see notes on crystal mod on using this crystal, also note that
|
|
this is a cylinder type crystal and kinda delicate. you are probably
|
|
better off getting the 38KHz crystals from D.C. Electronics.)
|
|
--
|
|
--
|
|
Mouser Electronics
|
|
(800)346-6873
|
|
(817)483-9384 fax
|
|
Giant Catalog! 239pages of parts!
|
|
Just about everything.
|
|
No min order for north america.
|
|
$100 min for overseas.
|
|
--
|
|
--
|
|
RF Parts (transistors)
|
|
1320-16 Grand Ave
|
|
San Marcos, CA 92061
|
|
Just about any RF transistor!
|
|
--
|
|
--
|
|
Dalbani
|
|
2733 Carrier Ave.
|
|
Los Angeles, CA 90040
|
|
(800)325-2264 USA
|
|
(213)727-0054 WORLD
|
|
(213)727-6032 FAX
|
|
RF transistors and other
|
|
semiconductors + more catalog=
|
|
178pgs $20 min order
|
|
--
|
|
--
|
|
Panaxis Productions makes some very high quality FM transmitters. The
|
|
last word in Transmitting, tons of kits.
|
|
|
|
Panaxis Productions
|
|
PO Box 130 (right next to my old place of study
|
|
Paradise, CA 95967-0130. Chico State! )
|
|
(916)534-0417
|
|
|
|
Catalogs are $2, well worth it, a must have item.
|
|
|
|
A little taste of there catalog :
|
|
|
|
MMC1 Macromod Compander for 2:1 compression
|
|
Plans $12, PCB $18, P+P 26.50, Full kit $87
|
|
|
|
SG High performance stereo generator
|
|
Plans $15, PCB $13.5, P+P 26.50, Full kit $105
|
|
|
|
FME PLL FM exciter
|
|
Plans $17.5, PCB $15, P+P 24.50, Full kit $129
|
|
|
|
More expensive than a FM-10 but much higher performance.
|
|
--
|
|
--
|
|
A company called Progressive Concepts sells plans for a 88MHz to 108MHz
|
|
amp. The power curves show that 12mw in will yield 2.5 watts, but can
|
|
be driven harder for up to 12 watts. (I have not seen these plans)
|
|
|
|
Plans only in U.S., $16 (a bit spendy, ouch!)
|
|
Progressive Concepts
|
|
1313 N. Grand Ave. #291
|
|
Walnut, CA. 91789
|
|
--
|
|
--
|
|
If your looking to purchase a FM-10 kit (or a PA-1 kit) and can't find one
|
|
locally try :
|
|
|
|
Ramsey Electronics, Inc.
|
|
793 Canning Parkway
|
|
Victor, New York 14564
|
|
Phone (716) 924-4560
|
|
FAX (716) 924-4555
|
|
|
|
Should be $29
|
|
--
|
|
--
|
|
The makers of the infamous BA1404 :
|
|
|
|
Rohm Corporation
|
|
Rohm Electronics Division
|
|
3034 Owen DR
|
|
Jackson Business Park
|
|
Antioch, TN 37013
|
|
|
|
PH: (615)-641-2020 (ask for someone who deals with the BA1404)
|
|
FAX: (615)-641-2022
|
|
|
|
Also they have:
|
|
|
|
PO Box 1399
|
|
Antioch, TN 37011-1399
|
|
|
|
|
|
=============================================================================
|
|
--
|
|
|
|
============== ==============
|
|
============== Other Raw Info ==============
|
|
============== ==============
|
|
|
|
the 2SC2570 is supposedly replaceable with an ECG10. Also I have used
|
|
an MRF901 for a replacement, though tough to mount, try bottom of the
|
|
pc board and connecting the whip antenna pad to ground plane. MPS901s
|
|
seem to replace the 2SC2570 directly, same case too, check the pinouts
|
|
though. I have also been told that MPS918s work well also.
|
|
|
|
The MRF239 can be used as direct replacement for the Ramsey 2 meter PA-1
|
|
kit. Cost is around $14 bucks.
|
|
|
|
Newark also has the 38KHz crystals for $2.90 ( I don't know Newark's address,
|
|
this was sent to me in the mail, will try to find it though.)
|
|
|
|
------------------
|
|
|
|
|
|
Once more If you have any info, I stress "ANY", about this subject please
|
|
drop me a byte or two.
|
|
|
|
have fun,
|
|
|
|
mycal@netacsys.com
|
|
|
|
my public key is as follows:
|
|
-----BEGIN PGP MESSAGE-----
|
|
Version: 2.1
|
|
|
|
owEBmABn/4kAlQIFACsiwof0ygCBjeci2QEB3XkEALLCAgpRyo9jEfq6TmyNr3q/
|
|
13k6+OEBEMWh70HzS6cyTXyD2EpUWlNLIndQN9fDNC5HZq8YgES2vrxpiZBiLiv4
|
|
ZaqFE1REtDvAHO0owW75mcZW0dczngzI2tzqaANL/05DrWezeMLGGRLzeQNeaaK0
|
|
VSxyQYX0xE736qRo3SEh
|
|
=J2FX
|
|
-----END PGP MESSAGE-----
|
|
|
|
|
|
|
|
--
|
|
----------------------------------------------------------------------------
|
|
If Micro Power Radio sounds too politically correct of a term for pirate
|
|
radio, be easy on us, its just that we've been listening to too much NPR.
|
|
mycal@netacsys.com
|
|
|