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Date: Wed, 13 Apr 1994 13:45:49 -0700
From: Stephen Dunifer <frbspd@crl.com>
Message-Id: <199404132045.AA16487@crl.crl.com>
To: mycal@netacsys.com (Mycal)
Subject: Re: I'll be in Europe in May
Newsgroups: alt.radio.pirate
Organization: CRL Dialup Internet Access (415) 705-6060 [login: guest]
X-Newsreader: TIN [version 1.2 PL2]
In article <766263680.606snx@NetAcsys.com> you wrote:
: I'll be in Europe in May, hanging out in Germany and taking many
: trips around. I would like to visit some Euro-casters, and
: I could possibly bring FRB and/or Ramsey kits for people.
Mycal,
Enclosed is the PLL information. I have a contact list for
anarchist and other groups in Germany which I can send to you. There are
a number of infoshops in Germany that would be really cool to visit. Let
me know if you would like this list. I have some friends who could give
some contacts as well.
take care
Stephen
-----------------------
From DAVEFORBES@delphi.com Wed Apr 13 13:02:42 1994
Date: Sun, 10 Apr 1994 22:27:24 -0400 (EDT)
From: DAVEFORBES@delphi.com
To: frbspd@crl.com
Subject: PLL stuff
Steve,
Here's the sedign notes and schematic of
the loop filter that I made. Works from 50Hz up.
The Problem
An FM radio station wishes to frequency-modulate a 95.5-MHz carrier
with a 5O Hz sine wave so that the peak frequency deviation is 75 kHz.
That is,
wi = 2pi(95.5MHz) = 600 Mrad/s (operating freq),
wm = 2pi(50 Hz) = 314 rad/s (lowest audio freq), and
delta wo = 2pi(75 kHz) cos wm t = (471 krad/s) cos wm t (maximum
deviation).
To get good programmability from a readily available reference
frequency, we use a 20KHz loop frequency, and divide by N=4775. Using
a large divide-by-N number worsens spurious modulation; we reduce this
below with an extra low-pass filter element.
To satisfy the FM modulator design rule
K <= 2piBm1
where Bm1 is the low-freq. 3dB audio response: 50Hz
with the highest K possible, let
K = 314 rad/s.
Calculating Loop Gain
Our VCO has Ko = 6 Mrad/s/V (1 MHz/V).
To determine the Ko of your VCO, hook it up to a pot and measure the
voltage on the pot wiper and the frequency of the VCO, and calculate
the ratio over the center half of the supply voltage.
The voltage necessary to produce the modulation
delta wo = 2pi(75 kHz) cos wm t
is
m(t) = delta wo/Ko = (80 mV) cos wm t.
The MC145152's two-output phase detector uses CMOS outputs
with VH = 5 V and VL = 0 V.
So the maximum correction voltage out of the phase detector
Vdm = VH Q VL = 5 V
and the gain of the phase detector is
Kd = Vdm/2piN = 5/(4775*2pi) = 160 uV/rad
To realize the bandwidth K, we need a loop filter gain
Kh = K/KdKo = 314/(160 u x 6 M) = 0.33
To minimize pullin time, we pick w2 as large as possible:
w2 = K/4 = 78 rad/s.
To reduce the spurious modulation, we place a pole at
w3 = 4 K = 1256 rad/s
by adding an additional passive low-pass filter to the input
of the loop filter.
The Loop Filter
I used an active loop filter with two poles. These are w2 and
w3, which set the response time and the spurious modulation
as per above. The goal here is to barely pass the lowest bass
notes by setting w2 to K/4, where K is the lowest nagular
velocity we want to pass (the 3db low-end audio cutoff freq).
The loop filter gain Kh we calculated above is set by the
loop filter feedback ratio R2/R1:
Kh = R2/R1 = 56K/164K = 0.34
where R1 is op-amp input resistor and R2 is feedback
resistor.
The active loop filter comprises a low-pass filter whose time
constant is set by R2 and C:
w2 = 1/(R2*C) = 1/(56K*.22uF) = 80 rad/s
desired w2 = K/4 = 78 rad/s which is with 2%.
where C is feedback cap.
Next, we need to add another low-pass filter to the input of the op-amp
set to w3. This reduces spurious modulation by reducing the loop-
frequency component of the error signal fed back to the VCO.
Do this by adding an RC filter to each leg of the op-amp inputs by
splitting R1 into two resistors each R1/2 and letting
w3 = 4/(R1*C3) = 4/(164K*.022uF) = 1108 rad/s
desired w3 = 4 K = 1256 rad/s which is within 14%.
where R1 is the sum of the input and output resistors of the
input filter, and C3 is the capacitor to ground.
Summary of component values for Ko=1MHz/volt VCO:
R1/2 = 82K ohm
R2 = 56K ohm
C = 0.22 uF
C3 = 0.022 uF
Experimental conmfirmation gives -3dB response at 50Hz.
VCO output spectrum is down 40dB at +/-500 Hz with unshielded VCO.
From DAVEFORBES@delphi.com Wed Apr 13 13:03:01 1994
Date: Sun, 10 Apr 1994 22:29:28 -0400 (EDT)
From: DAVEFORBES@delphi.com
To: frbspd@crl.com
Subject: PLL part 2
Programming the FS
I used a div by 64/65 prescaler. This gives good range for future UHF
work and makes it easy to calculate the programming of the FS.
Using a 5.12 MHz crystal, set the RA2:0 bits to 011 to select /256 mode
for a 20 KHz loop frequency. This makes the reference whine inaudible.
Now the A bits and the N bits form a binary number which is
the desired freq. over 20KHz. The form is NNNNNNNNNNAAAAAA.
Just divide your freq. by 20 KHz and convert to binary. Add a
jumper for a 0 and remove a jumper for a 1.
Example: 105.1 MHz / 20 KHz = 5255. = 0x1487
Convert to binary: 0001 0100 1000 0111
Install jumpers for 0 bits:
pin 2111 1111 1112 2222
0987 6543 2105 4213
bit NNNN NNNN NNAA AAAA
9876 5432 1054 3210
value 0001 0100 1000 0111
For FM band use only, the five bits N9:5 may be tied permanently to the
value 00010. This allows coverage of the freq. range 81.92 to 122.86 MHz.
The Circuit
0.22
R2 | |
+--/\/\/\---| |-+
MC145152 | | | |
| | | \ C |
| 8 R1/2 R1/2 | 2 | \ |
phi V|---/\/\/\-*------/\/\/\-*---|- \ 6 |
| 7 82K | 82K 3 | LF356 >---*----O Vc
phi R|---/\/\/\-+----*-/\/\/\-*---|+ / Kvco =
| R1/2 | | R1/2 | | / -1MHz/Volt
| | | | | / C
Fpd=20KHz C3 --- --- C3 | | |
--- --- +--/\/\/\---| |-+
|.022| R2 | | |
| | 0.22 |
ground> --- --- ---
- - -
I hope you like it.
From DAVEFORBES@delphi.com Wed Apr 13 13:29:25 1994
Date: Tue, 12 Apr 1994 04:16:25 -0400 (EDT)
From: DAVEFORBES@delphi.com
To: frbspd@crl.com
Subject: PLL circuit change
Steve,
I have discovered a problem with the circuit I sent yesterday.
The VCO constant Ko is -1MHz/volt. It turns out that
the ECG612 varactor I was using is packaged backwards form a
Motorola MV2104, which part number I saw faintly under the ECG612
label. I used the Motorola data sheet, which caused me to
forward-bias the varactor, getting a different (but functional)
capacitance characteristic.
To correct the circuit for a correctly-installed varactor,
just swap pins 7 and 8 of the MC145152.
I have also hooked up a BA1404 to get stereo modulation. It works well.
In fact, the stereo carrier is cleaner than the one coming out of
KUAT-FM, the local university classical station!!
I can't wait to get this thing into production. It's real well-behaved.
Gotta go now.
--David
--------------------------
TAKE BACK THE AIRWAVES - THE SPRING & SUMMER OFFENSIVE
Free Radio Berkeley / Free Communications Coalition
First, we would like to thank everyone for their support of micro power
liberation broadcasting and their extreme degree of patience as we get
our act together on ramping up for full scale production of kits.
FRB and the Peoples' FCC invite you to take part in reclaiming the
airwaves. This can be done in many ways, it is not necessary for you and
your community to put a station on the air if you feel that is too great
of a risk. A lot of public education needs to happen around this issue
so folks understand that is a matter of free speech, constituitional and
human rights. We urge you to consider conducting public forums and
presentations on this in your community. Printed materials, videos, etc.
can be provided for this type of activity.
Further, if you are technically inclined and would like to provide
assistance as a mentor to those whose technical abilities are vastly
exceeded by their enthusiasm, we would like to hear from so we can refer
folks needing assistance to someone in their area.
If your are good at teaching and presenting technical matters in an
understable manner, please consider leading a workhsop in your
community. We can supply materials for this including a how to video
that is in production.
We need any information on what happening in your community as it regards
micro power broadcasting, especially regarding any actions taken by the FCC.
Micro power broadcasting will be part of the Lolapalooza tour this
summer. A transmitter will accompying some foks who are part of the tour
and we have been invited to have a table at each concert site. If you
live anywhere close to the concert sites (most major urban areas) and can
volunteer to run an info table, pleaes contact us. We will see that
passes are arranged and send you the materials to be distributed along
with materials you might wish to add. That would be a good time to
organize a local meeting/public forum or workshop on micro power
broadcasting and reclaiming the airwaves. All in all, the Lolapalooza
tour was attended by 2 million people last year, a great opportunity for
outreach.
Let us know if there is any way we can help you, many of us here are rather
experienced community activists and organizers. We have legal support
available through the National Lawyers Guild and can send legal info to
supportive attorneys in your area to bring them up to speed on this issue.
If you can, come to the Bay Area for the weeekend of April 30 and May 1
and the following week. On Saturday, April 30 Food Not Bombs is putting
on Soupstock 94 with lots of good bands including MDC, Mudwimmin, Clan
Dyken, etc. It will be held at the Golden Gate Park Bandshell near the
DeYoung Museum and starts at 12 noon. San Francisco Liberation Radio
will be broadcasting it live at 93.7 FM with a possible higher power AM
simulcast. On Sunday, May 1 the 25th anniversary of Peoples' Park will
be celebrated with a big party and concert at Peoples' Park in Berkeley.
This event will be broadcast live by Free Radio Berkeley at 88.1 FM. A
whole series of workshops on media, computers, broadcasting, etc. will be
held that week in both SF and Berkeley. A public forum on micro power
broadcasting and radical art will be held on Thursday evening, May 5 at
the Capp Street Gallery in SF. A micropower broadcasting workshop will
held on Wednesday, May 4 in Berkeley and on Saturday, May 6 at the Capp
Street Gallery in SF.
More article are coming out on mirco power broadcasting. The most recent
issue of Option had a very good article. The May issue of Spin will
feature an article as well. It is possible that Rolling Stone might be
interested in this issue. Hopefully, you can get the local media in your
area to do the same.
Richard Edmondson with San Francisco Liberation Radio and Food Not Bombs
Radio Network is now producing a weekly show for Radio For Peace
International, a shortwave station operating from Costa Rica. It is a
half hour show on the best of micro power broadcasting in the US with
segments from air tapes of various stations that are currently on the
air. If you are on the air send us air tapes so they can be incorporated
into the show.
We are setting up to record program materials onto hard disk with a DSP
card in one our PCs. These will be compressed with a program from Xing
and loaded into our FTP site for distribution. This will begin on May
1. If you are interested in this project, let us know
We have decided to make a major push for next 6 months to create a
national movement to take back the airwaves and break the
coporate/government stranglehold on the free flow and exchange of ideas,
information, news, music, culture and artistic expression. If we do this
in an organized, concerted way we can take back the airwaves and show
what real democracy is all about. It involves taking risks and a
lot of hard work but if worth the effort if one values free speech, human
rights, liberty and self determination.
Thanks again.
Stephen Dunifer
Doug Forbes
Richard Edmondson
Keith McHenry
Captain Fred
JS
Universal Radio
and many others who wish to remain unknown at this time
Contact:
Free Radio Berkeley / Free Communications Coalition
1442 A Walnut St. #406
Berkeley, CA
94709
(510) 464-3041 - voice mail
email - frbspd@crl.com
ftp site: crl.com - directory: /ftp/users/ro/frbspd
Send us any program material you might have.