From: mycal@netronix.com (Mycal Johnson)
Newsgroups: sci.electronics
Subject: FM-10 FAQ again
Distribution: world
Date: Wed, 14 Oct 92 16:59:33 GMT
Organization: Netronix, Inc.


Ok here is the new Ramsey FM-10 file.

Please check out the info about the FM-10 archives.  There is now a place
we can store postscript or gif schematics, layouts etc.  Also this mailing
list will be archived there.

Once again we have Ed Savage and the guys at Data General, NC for making
yet another giant contribution.


--------------------- cut ------------------------------------------------

                        Ramsey FM-10 Info
                                by
                        mycal@netronix.com

4th Edition
-----------
Here is a rough compilation of information about the Ramsey FM-10, and
BA1404 Stereo FM broadcasters.

It is in no way complete, nor do I take any responsibility for its accuracy.
I know you haven't seen this statement but a 1000 times but here it is :
For informational purposes only.

I have been swamped with requests for information about amps, antennas and
other mods for the FM-10, so I decided to dig through my mailbox and notes
and compile this file.  I hope It helps, and if anyone has more information
about the FM-10 or FM transmitters, please send it to mycal@netronix.com
-or- gallaghe@sonoma.vax.edu.  I will try to update this file as new
information arrives or is found out.  A Postscript version with schematics
and board layouts is also not out of the question.

I would like to acknowledge the following people for the contributions
and support:
                John Brewer -- brewer@anarky.enet.dec.com
                Alan Bryant -- uunet!csn.org!adb
                Greg Thornwall <uunet!wam.umd.edu!thorn>

If I missed anyone, sorry, please drop me a note and remind me.


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@netronix.com.

Once again I want to thank Ed Savage and the guys at Data General, NC for
making this list possible.

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.

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 writeable 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.

Other Places to Look
--------------------
alt.radio.pirate is another good forum to find or post information on these
kits.  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.

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.

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!

                          +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 yealds poorer performance (-5%).

Note that you can lower the resistance of the 220 ohm resistor to
about 200 ohms for more power, but do not do this unless you can
check to see if the transistor has gone into oscillation.

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 R2 that seems to be optimal is 205 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 220 ohms.  If you lower this value below 200
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.

-------
On Wed, 1 Jul 1992 13:16:47 -0600, "Alan D. Bryant" <adb@csn.org> wrote:
> The second stage idea didn't appear to do anything here, but I don't have any
> measuring equipment, so it may have been a small enough improvement that I 
> couldn't detect it.
>
Hmm, very interesting, I haven't tested it in the real world, just with
a HP power meter and spectrum analyzer.  Also note that using a 2n2222a
I could only get 30mw, but when using the mps2222a I got 75mw.  This
was all into a 50 ohm load,  with a mismatched antenna it could actually
degrade performance.  I was kind of amazed when I calculated the optimal
Rl and found it to be 52 ohms for that circuit.
 
> I've been playing around with antennas a little myself.  Made up a weird
> concoction I'll have to describe to you at some point.  No real test results
> from it yet.
I would like to hear about the details of  what you have come up with when
you get it all up and running.  The $19 RS CB power meter would probable
come in handy for doing antenna and power tests, It would be a lot better
than nothing.


ANTENNAS
--------
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.

use the formulas out of your FM-10 manual  234/freq=length of rod.

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:

                                |
                                |
                              // \\

        That is 1 radiator pointing strait up and 4 ground plane
        radials.

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.

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 rivals my di-pole at home and
you can drive to a high, optimal location for your broadcasts.

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.  Do not do this, keep everyone
happy, including yourself, be clean.

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 walk on your neighbors TV, the local fire depart-
ment, or anyone else, you are going to get nailed.  If you are only on
the FM Band, you will hardly be noticed.

...
I have looked into the filter design more, I have come up with these two:
(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    .152uh     .132uh
        -----()()()-----()()()-----()()()-----
          |          |          |          |
<-50ohm   - 33pf     - 68pf     - 68pf     - 33pf  50ohm->
          -          -          -          -
          |          |          |          |
        --------------------------------------
                         |
                        ---
                         -


Filter Design: 5 element Chebyshev
Not as good as above, but thrown in anyway.

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).
I may just make all the coils 3t, and bend them around a little while
watching the analyzer.  Maybe use var-caps too.  Well I will build this
weekend and try Tuesday.  I will let you know how it goes.

mycal


Very simple filter.
-------------------

                      .15uH
from fm10      >------()()()------> to antenna
                  |          |
                  - c1       - c2
                  -          -
                  |          |
                 ---        ---
                  -          -

      88mhz   102mhz     107mhz
c1     62pf     54pf      50pf
c2     62pf     54pf      50pf

its basically a scaled down version of the other filters.
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.

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.

use fixed value parts!

....

I built the 7 element Chebyshev, I substituted .12 uh inducters for
the .132 and .15 uh for the .152.  Also I put 10-50pf var caps in place
of the 33pf's and 10-90pf varcaps for the 68pf's.  After a bit of tweeking
I got -45db on the 2nd harmonic -55db on the 3rd -65 on the 4th, every thing
else was off the scale.  That is much better than -25db,-27db,-30db,-40db...
-40db off the fundamental is required by FCC.
[Actually the fcc says no more than .7mw out on any harmonic when dealing
with VHF equipment, that's on top of the -40db requirement.  But if you
are running 1 watt out -40db is .1mw]

I have found that peeking (buy tuning the var-caps) for maximum power output
into a 50ohm load will give you close to maximum attenuation on the harmonics.

Also the Fc can be raised or lowered quite a bit,  I tried +-10Mhz (of 88Mhz)
and could tune the Fc there.

I am going to stick with the .12uh and .15uh inductors because I can get them
for $.25 apiece at HSC,  But I may try winding my own later on, especially if
I use it on a high power output device.  These molded inductors don't look
like they can handle much power, but I have run 2 watts through them without
problem..  On a side note, I don't think the Q of these inductors is that
high,  I think that if you wound the above mentioned #12 coils you would
have a higher Q, hence, greater performance on the filter.

On a second try I built another filter using variable inductor cans, and
used fixed caps, this one seemed to have better performance than the
last one, it was also much more stable.  Var. caps are not very stable,
so I would recommend using fixed caps.

[Also of intrust is that the FM-10 puts out about 8-9mw and the 2nd harmonic
is -25db off.  The FM-4 Kit by ramsey puts out 130mw and the 2nd harmonic
is only -12db off, which means the 2nd harmonic of the FM-4 is about as
powerful as the FM-10.]

FM-10 Myths
-----------
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 15mw when driven with a 12volt supply.

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.

FM-10 Improvements -
--------------------
(Some from ACE magazine.)

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)
abd 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.

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 yealded 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-empasis/input circut is shown in the July 1992 issue
of "Radio Electronics".  Not only do they use 75K ohm resisters in there
pre-empasis, 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.


==============                  ==============
==============  Other Raw Info  ==============
==============                  ==============


the 2sc2570 is supposedly replaceable with an ecg10.  Also I have used
an MRF901 for a replacement, but it yealds 2.5mw less output.

The MRF239 can be used aas direct replacement for the Ramsey 2 meter PA
kit.  Cost is around $14 bucks.

From: Greg Thornwall <uunet!wam.umd.edu!thorn>
Mycal,
I called the company that produces the BA-1404 chip. The company is the Rohm
Corp. in TN. They sent me some interesting data on the chip: some electrical
characteristic curves, list of distributors & representatives, application
diagram and some similar block diagrams that comes with the FM-10. If you
want any more info just write or call them up and they will send it free! 

Their address & number is:

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 BA-1404)
FAX: (615)-641-2022

Also they have:

PO Box 1399
Antioch, TN 37011-1399
                                                --Greg  (KD3SU)

38Khz Crystals....

> > Does anybody have any idea where to find 38KHz crystal (H-18).
> 
>   Don't know what a H-18 is, but you can use a C-2 type quartz crystal
> for 38.000KHz by Epson America, Epson part number C-2 38.000KA-P, which can
> be ordered, for example from Digi-Key Corporation (1-800-DIGI-KEY), Digi-Key
> part No. is SE3314
 

Thanks Andrew, I've got the DK catalog H-18 is a solder welded case and C-2
is a cylinder type.  I don't know if there is any difference in specs between
them.

Aaron B.

...
From: Greg Thornwall <uunet!wam.umd.edu!thorn>
I have some more stuff on another company that sells "pirate"
electrical kits. Panaxis productions, PO Box 130, Paradise, CA
95967-0130 (916)-534-0417 ($1.00 for a catalog). They have a bunch
of FM & AM transmitters from 20mW to 10W! They only sell PLANS for
the high power transmitters here to the US and will sell kits for
export elsewhere. They have a PLL FM oscillator (500mW) for sale in
kit form for $129.00 (better stability!).

From: uunet!toad.horizon.com!kevin (Kevin Criqui)
Sorry for the delay - been super busy at work.  The address I have for
Panaxis Productions is PO Box 130, Paradise, CA  95967-0130.  The phone
number is (916)534-0417.  My catalog has a $1.00 price printed on it,
but I think they're $2 these days (still a bargain).  I'm going to send
my 2 bucks and get a new copy and see what fun stuff has been added.

My little station consists of the "MMC1" Macromod Compander set for 2:1
compression, connected to the "SG" high performance stereo generator
connected to the "FME" PLL FM exciter.  Besides the Panaxis stuff, I
have a homebuilt mixer console and of course, the 1 transistor PA.

Prices from my catalog (which is likely to be out of date) are:

Code    Plans   PCB     P+P     full kit
----    -----   ---     ---     --------
MMC1    12.00   18.00   26.50   87.00
SG      15.00   13.50   26.50   105.00
FME     17.50   15.00   24.50   129.50

While looking for my Panaxis catalog, I ran across a catalog from
Communication Concepts, Inc. that has kits based on some of the AP
Notes in the back of the Motorola RF devices data book (another
must-have).  They have a couple of 300 watt (!) kits that cover the
10-150MHz range (AR305 and AR313).  There's another article (AN1037)
that's a 300W amp specifically for 88-108MHZ FM broadcast use (but CCI
didn't have it in their catalog back when I got my copy).  CCI is
at (513)426-8600 or (513)220-9677.
...
From: gdavis@griffin.uvm.edu (Gary Davis)
 Many responded that they want to know more about the Oregon Comm Sys
line of stereo PLL Fm transmitters.

Here is their address and phone number:
OREGON COM SYSTEMS
1257 Siskiyou Blvd
Suite 132
Ashland,Oregon 97520

TELE: 503-271-3294

Models are stereo, 100mw output,PLL frequency syntehsis.
Some come with audio mixers also.
All are wired and tested.
This would appear an ideal unit for driving a linear amp.
Harmonic output is not specified,however low pass filter designs are
not difficult.
They also stock antennas.
The FM units are rated with an audio response of 10 to 15 kilohertz +/- 2 db.

Frequency coverage: 88-108 mhz
RF output 100 milliwatts
Frequency Stability +/- 100 hertz
Response (audio) 10 hertz to 15 kilohertz +/- 2db
Input level: 500mv
cost: $109.00  Delux stereo models 149.95

------------------
------------------


Well I have more info, but it is not organized enough even for this rough
sheet.  Given time I will polish it an post it.

Once more If you have any info, I stress "ANY", about this subject please
drop me a byte or two.

have fun,

mycal@netronix.com





Newsgroups: sci.electronics