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Date: Wed, 21 Feb 2007 02:08:21 -0500
To: TSCM-L2006_at_googlegroups.com
From: kondrak <kon..._at_phreaker.net>
Subject: Re: [TSCM-L] Re: Wideband (AM) detectors improvement using
filters ?
In-Reply-To: <985848.84288.qm_at_web55504.mail.re4.yahoo.com>
References: <985848.84288.qm_at_web55504.mail.re4.yahoo.com>
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James practically wrote the textbook!
At 22:40 2/19/2007, you wrote:
>Did you go to school for this?
>
>----- Original Message ----
>From: James M. Atkinson <jm..._at_tscm.com>
>To: TSCM-..._at_googlegroups.com
>Sent: Monday, February 19, 2007 4:50:58 PM
>Subject: [TSCM-L] Re: Wideband (AM) detectors improvement using filters ?
>
>In my sweep truck I have a large tool chest with
>heavy duty steel drawers like what you would find
>in a auto shop. Inside this tool chest is an 8
>pole band rejection filter for every single TV
>station in the United State and Canada, plus
>rejection filters for various chucks of the FM
>and, pager band, band pass filters for various
>bands, etc, etc. I also have K&L Microwave
>tunable 5 pole band pass and band reject filters
>that cover up to 3 GHz as well.
>
>All told I have many hundreds of pounds of copper
>brass and silver in the "filter chest" so that I
>can go to pretty where is the US or Canada and
>knock down virtually any signal that might be
>over powering my equipment. If a spy has parked
>his sub-milli watt NFM bug at 97.45 MHz, and
>there is a thunder lizard at 97.30 MHz that is
>located at 800 feet away I can still kill the
>offending lizard and hone in on the bug without saturating my sweep gear.
>
>-jma
>
>
>
>
>At 04:36 PM 2/19/2007, kondrak wrote:
> >Proving once again, theres no such thing as a free lunch :-D.
> >
> >At 15:56 2/19/2007, you wrote:
> >
> >>Check out:
> <http://www.tscm.com/TSCM101noise.html>http://www.tscm.com/TSCM101noise.h=
tml
> >>
> >>Response as follows:
> >>
> >>
> >>
> >>At 09:52 AM 2/15/2007, cont..._at_yahoo.co.uk wrote:
> >>
> >>
> >>>.
> >>>
> >>>
> >>>Wideband (AM) detectors are very popular...because they are easy to
> >>>use
> >>>and relatively cheap.
> >>>
> >>>...the problem is that they are not very sensitive.
> >>>...another problem is that they cant separate signals at different
> >>>frequencies.
> >>>
> >>>
> >>>Question
> >>>--------------
> >>>
> >>>
> >>>-/////////////////////////-
> >>>
> >>>How many times more sensitive would a wideband detector become
> >>>if it had additional filters in the frontend ?
> >>>
> >>>-/////////////////////////-
> >>
> >>
> >>It can be hundreds of thousands, or even millions of times more sensiti=
ve.
> >>
> >>
> >>Fow example, let say you want to build a simple
> >>diode detector that monitors 398.5-400 MHz (1.5
> >>MHz wide), you build a simple 8 pole bandpass
> >>filter that contains 4 high pass, and then 4
> >>low pass filters, or better yet, 8 high pass
> >>cavities, and 8 low pass cavities. This will
> >>knock down even the most powerful FM and TV
> >>broadcast signals so you can pass the signal
> >>to a LNA and then into a diode, and then sum
> >>the voltage that comes out of this diode with a
> >>output of a matching diode (reference
> >>diode/amp), and apply the output of the summing
> >>circuit to another amplifier that drives a
> >>simple 30 dB or larger column of LED's.
> >>
> >>The goal here is to take a hypothetical FM
> >>radio station that is presenting -20 dBm on
> >>site, and to knock it down below -174 dB. This
> >>means that we want to kill everything outside
> >>of the band by 154 dB, but I know some
> >>engineers who use only 40 db, others use 120
> >>dB, and some even use 400 dB as their design
> >>goals for TSCM and SIGINT bandpass filters. An
> >>example is the 60 cycle high pass filters that
> >>I make, they knock down 60 Hz by 400 dB, so you
> >>can plug one end into a 480 volt circuit, and
> >>the other end into the RF input of your
> >>spectrum analyzer or oscilloscope. We als comb
> >>out all the harmonics of the line voltage and
> >>knock down any nastiness that might cause blue smoke to leak out of the=
SA.
> >>
> >>
> >>
> >>>For example the detector does 1 Mhz to 3000 Mhz
> >>>
> >>>Now i will devide that into 5 bands...using 5 separate filters :
> >>>
> >>>a) 1-80 Mhz
> >>>b) 80-200 Mhz
> >>>c) 200-520 Mhz
> >>>d) 520-1000 Mhz
> >>>e) 1000-3000 Mhz
> >>>
> >>>
> >>>Ofcourse when using one of above filters... it seems very logical
> >>>that
> >>>the maximal detection range becomes much better then without a filter.
> >>>
> >>>I suppose that is caused by below factors :
> >>
> >>
> >>When not use the wide band detector (3 GHz) to
> >>gate the sampling side of the post filter
> >>detectors. Simply put, when the 3 GHz diode
> >>captures energy on the log scale that exceeds a
> >>certain level (say -50 dB) that it uses to gate
> >>all of the output of the diodes assigned to
> each of the five bands of interest.
> >>
> >>Lets assume (grin) that I have a stack of
> >>Astro-Med Everest analog chart recorders in a
> >>rack. Each chart recorder is capable of 32
> >>analog channels each, and I gang or slave 4 of
> >>them together so that I have 128 virtual
> >>channels. I built a trigger circuit for each
> >>chart recorder that monitors a wide swath of RF
> >>spectrum, so we have the first recorder
> >>listening and reacting to 100 Hz to 1.8 GHz,
> >>the second 1 .5 to 18 GHz, the third from 12
> >>GHz to 30 GHz, and so on. When the broadband
> >>energy at say 500 MHz goes over -50 dB it
> >>triggers the chart recorder to start moving the
> >>paper for 5 seconds, but looking at the chart
> >>you can see which band of the 32 the energy
> >>appears in. The tricky part is that each of the
> >>32 channels have to have thier own filter and
> >>LNA, then diode, and interface for the chart recorder.
> >>
> >>Maximum range requires first maximum
> >>filtration, folwed by maximim amplification,
> >>folwed by the most sensitive detection diodes
> >>you can find, then further amplification to
> >>drive whatever is giong to be your indicator
> >>(LED column, speaker, chart recorder, etc)
> >>
> >>
> >>
> >>>1) The environmental noisefloor is much lower so a signal would stick
> >>>out much easier.
> >>
> >>
> >>Yes, but you have to know the frequency on
> >>which the bugs appear, and this is a tricky
> >>proposition. You have to break the bands into
> >>things like 135-150 MHz, then 150 to 174, 174 to 200 MHz, and so forth.
> >>
> >>
> >>
> >>>2) Bandwidth in the receiver is directly related to noise.
> >>
> >>Yes, it is all part of the KTB formula, with B
> >>being that which we can control the most.
> >>
> >>
> >>
> >>>Offcourse the adantage of filtering would also be that :
> >>>
> >>>1) The wanted signal is not masked (overpowered) by other out of band
> >>>signals
> >>
> >>
> >>Big rule of TSCM is to estimate that which you
> >>should see in the area you will be sweeping,
> >>and then to bring along filters to knock down
> >>things that may be making your measurements
> >>"dirty". Personally, I carry a fixed 8 pole
> >>band reject filter for every TV station
> >>allocation, plus a FM band reject filters (more
> >>then one), and filters to knock out the paging bands.
> >>
> >>You know what your going to need by looking up
> >>FCC allocations for everything within five
> >>miles, but 75 miles for any broadcast (AM, FM,
> >>TV) channels. If I am performing a sweep in
> >>Needham, MA there are huge antenna farms for FM
> >>and TV broadcasting, so every inch of the
> >>office that I am sweep in getting hammered with
> >>high levels of RF. Not only do I have to know
> >>down the main carrier, but even the 15th
> >>harmonic of the main carrier is radiating off
> >>of structural steel and causing massive
> >>headaches. This means that I have to use a
> >>filter that kills not only the main carrier,
> >>but also filters that kill every harmonic out
> >>to the 20th or so carriers that is going to
> tilt or saturate the sweep gear.
> >>
> >>Once you get above 2 GHz you can use one of
> >>more YIG filters to help you do this, but the
> >>low frequencies (below 1 GHz) are going to be quite troublesome.
> >>
> >>
> >>
> >>>2) You have an indication of the frequency-band of the found signal
> >>>
> >>>...etc
> >>
> >>
> >>Simple sample and hold circuit that triggers a flip-flop circuit.
> >>
> >>
> >>
> >>>The mentioned unit lets you either switch to each filter by hand...but
> >>>it can also go into a so called "Scanning-Filter mode"
> >>>
> >>>Filter-scanning mode will switch between filters like this :
> >>>
> >>>Filter 1 >> Filter 2 >> Filter 3 >> Filter 4 >> Filter 5 >> NO-
> >>>Filter ......and over again.
> >>
> >>
> >>Simple six pole mechanical coax switch/relay
> >>with a control circuit. It has been done before
> >>with good results. Basically, you take a six
> >>pole switch, and hand a dedicated filter,
> >>amplifier, and antenna off each of the six input connectors.
> >>
> >>One key is not to apply power to any of the six
> >>amplifiers other then the one you are using at the time.
> >>
> >>
> >>>That NO/filter seems to be a good idea in practice...to also receive
> >>>out of band signals
> >>>not covered by the filters (in this case below 1 mhz and above 3000
> >>>mhz)
> >>>
> >>>The scanning-speed has still to be determined...it depends on the
> >>>shortest duration
> >>>of possible digital signals (pulses) that you want to detect :
> >>>
> >>>...if it is to slow you might miss a short on-time signal (non
> >>>continious bursts)
> >>>...if it is to fast to fast there is no time to validate the signal
> >>>(continious but very-short pulses)
> >>
> >>
> >>
> >>A very effective method of detecting tracking
> >>devices in a vehicle is to use a gang of
> >>generic diode detector such as the CPM-700, add
> >>your own bandpass filters for each of the
> >>"phone to tower" frequencies, and follow it by
> >>a small 20 dB preamplier, or "convert" the RF probes.
> >>
> >>
> >>To convert a probe you unscrew the probe body,
> >>unscrew the antenna, unsolder the screw that
> >>the antenna attached to and install an SMA
> >>female connector. Next visit your local
> >>hardware store and purchase some one inch
> >>tubing and fittings. Mount the SMA/probe
> >>assembly into the end cap, and solder the
> >>ground of the probe to the copper as well. Then
> >>slide the whole thing into a length of copper
> >>tubing that it roughly half the wavelength of
> >>the frequency of interest. The other end of the
> >>copper tube is a Male BNC connector so that you
> >>can merely plug the tube into the BNC connector of the CPM-700
> >>
> >>Next fabricate an antenna out of a length of
> >>copper clad welding wire and terminate it on a
> >>female SMA connector so that you have a high performance dipole antenna=
.
> >>
> >>Inside the copper tubing you will want to add a
> >>small 8 pole bandpass filter and kill off the
> >>tower-to-base and trunking frequencies by at
> >>least 80 dB befoe you go into the probes amplifer.
> >>
> >>The simplest this is to make a standalone box
> >>the size of a carton of cigarettes into which
> >>the phone-to-tower antenna where mounted, then
> >>feed into separate filters for each band (8
> >>poles each), and then take the output and apply
> >>it to dedicated amps all built into the same case.
> >>
> >>The box would best be a brass block that you
> >>drill out with cavities for each of the filter
> >>poles, and then a large cavity for the
> >>amplifiers. You could go with an interdigital
> >>filters for each of the bands, but you really
> >>do not need to displace much heat, and the
> >>physical size of the 800 MHz band will be
> >>unpleasantly large and heavy. I would (and
> >>have) leaned toward a simple LC filters for a
> >>project like this and simply add a lot of pole
> >>to keep the skirts of the filter as sharp as possible.
> >>
> >>Companies that make filters for the cell phones
> >>themselves also make very small duplexer
> >>circuits that you can use in reverse, but they
> >>tend not to knock down the signals by more then
> >>20 ot 30 dB, but it may be a good place for you to start experimenting.
> >>
> >>
> >>
> >>>Forget the scanning speed...lets talk just about sensitivity-
> >>>improvement when using filters.
> >>
> >>
> >>I am a *** BIG *** fan of carefully designed
> >>and built filters, and their use in TSCM.
> >>
> >>I am also an even bigger fan of using big-ass
> >>(excuse my French) wide band antennas to suck
> in as much energy as possible.
> >>
> >>
> >>>I know that its a difficult question...but lets say i have to write an
> >>>article or propaganda
> >>>for a unit with those 5 switchable filters...and i have to say how
> >>>many times more sensitive
> >>>a Wideband(AM)-detector with 5 filters like above is...compared to the
> >>>same one without filters
> >>>
> >>>I suppose that the smaller the filter-bandwidth the more "sensitive"
> >>>so lets simplefy the question
> >>>and lets assume that the 5 used filters all have the same bandwidth so
> >>>the whole range is equally
> >>>devided
> >>>
> >>>---------------------------------------------
> ---------------------------------------
> >>>How many times more sensitivity or range would you get ?
> >>>---------------------------------------------
> ---------------------------------------
> >>>
> >>>
> >>>Thanks !
> >>>
> >>>
> >>>Contranl
> >>>
> >>>
> >>>
> >>>Remark...i dont understand why not one single manufacturer of (AM)
> >>>wideband-detectors
> >>> has not incorperated some filters...they are not
> >>>difficult to produce
> >>> and not expensive...but greatly improves them.
> >>>
> >>>
> >>>Please do not respond (in private) to my (old) Yahoo-emailadress...i
> >>>´ve lost the password
> >>>and after weeks of correspondence they dont want to give it...Yahoo
> >>>SUCKS !
> >>
> >>----------------------------------------------
> ------------------------------------------------------
> >> World Class, Professional, Ethical, and Competent Bug Sweeps, and
> >>Wiretap Detection using Sophisticated Laboratory Grade Test Equipment.
> >>----------------------------------------------
> ------------------------------------------------------
> >> James M. Atkinson Phone: (978) 546-3803
> >> Granite Island Group Fax: (978) 546-946=
7
> >> 127 Eastern Avenue
> #291 Web: <http://www.tscm.com/>http://www.tscm.com/
> >> Gloucester, MA 01931-8008 E-mail: mailto:jm..._at_tscm.com
> >>----------------------------------------------
> ------------------------------------------------------
> >> We perform bug sweeps like it's a full
> contact sport, we take no prisoners,
> >>and we give no quarter. Our goal is to simply, and completely stop the =
spy.
> >>----------------------------------------------
> ------------------------------------------------------
> >>
> >>
> >
> >-----------------------------------------------
> -----------------------------------------------------
> > World Class, Professional, Ethical, and Competent Bug Sweeps, and
> >Wiretap Detection using Sophisticated Laboratory Grade Test Equipment.
> >-----------------------------------------------
> -----------------------------------------------------
> > James M. Atkinson Phone: (978) 546-3803
> > Granite Island Group Fax: (978) 546-9467
> > 127 Eastern Avenue
> #291 Web: <http://www.tscm.com/>http://www.tscm.com/
> > Gloucester, MA 01931-8008 E-mail: mailto:jm..._at_tscm.com
> >-----------------------------------------------
> -----------------------------------------------------
> > We perform bug sweeps like it's a full
> contact sport, we take no prisoners,
> >and we give no quarter. Our goal is to simply, and completely stop the s=
py.
> >-----------------------------------------------
> -----------------------------------------------------
> >
>
>
>
>Need a quick answer? Get one in minutes from
>people who know. Ask your question on
><http://answers.yahoo.com/;_ylc=X3oDMTFvbGNhMGE3BF9TAzM5NjU0NTEwOARfcwMz=
OTY1NDUxMDMEc2VjA21haWxfdGFnbGluZQRzbGsDbWFpbF90YWcx>Yahoo!
>Answers.
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<body>
<font size=3><b>James practically wrote the textbook!<br><br>
</b>At 22:40 2/19/2007, you wrote:<br>
<blockquote type=cite class=cite cite="">Did you go to school for
this?<br><br>
----- Original Message ----<br>
From: James M. Atkinson <j..._at_tscm.com><br>
To: TSCM-..._at_googlegroups.com<br>
Sent: Monday, February 19, 2007 4:50:58 PM<br>
Subject: [TSCM-L] Re: Wideband (AM) detectors improvement using filters
?<br><br>
In my sweep truck I have a large tool chest with <br>
heavy duty steel drawers like what you would find <br>
in a auto shop. Inside this tool chest is an 8 <br>
pole band rejection filter for every single TV <br>
station in the United State and Canada, plus <br>
rejection filters for various chucks of the FM <br>
and, pager band, band pass filters for various <br>
bands, etc, etc. I also have K&L Microwave <br>
tunable 5 pole band pass and band reject filters <br>
that cover up to 3 GHz as well.<br><br>
All told I have many hundreds of pounds of copper <br>
brass and silver in the "filter chest" so that I <br>
can go to pretty where is the US or Canada and <br>
knock down virtually any signal that might be <br>
over powering my equipment. If a spy has parked <br>
his sub-milli watt NFM bug at 97.45 MHz, and <br>
there is a thunder lizard at 97.30 MHz that is <br>
located at 800 feet away I can still kill the <br>
offending lizard and hone in on the bug without saturating my sweep
gear.<br><br>
-jma<br><br>
<br><br>
<br>
At 04:36 PM 2/19/2007, kondrak wrote:<br>
>Proving once again, theres no such thing as a free lunch :-D.<br>
><br>
>At 15:56 2/19/2007, you wrote:<br>
><br>
>>Check out:
<a href="
http://www.tscm.com/TSCM101noise.html">
http://www.tscm.com/TSCM101noise.html</a><br>
>><br>
>>Response as follows:<br>
>><br>
>><br>
>><br>
>>At 09:52 AM 2/15/2007, cont..._at_yahoo.co.uk wrote:<br>
>><br>
>><br>
>>>.<br>
>>><br>
>>><br>
>>>Wideband (AM) detectors are very popular...because they are
easy to<br>
>>>use<br>
>>>and relatively cheap.<br>
>>><br>
>>>...the problem is that they are not very sensitive.<br>
>>>...another problem is that they cant separate signals at
different<br>
>>>frequencies.<br>
>>><br>
>>><br>
>>>Question<br>
>>>--------------<br>
>>><br>
>>><br>
>>>-/////////////////////////-<br>
>>><br>
>>>How many times more sensitive would a wideband detector
become<br>
>>>if it had additional filters in the frontend ?<br>
>>><br>
>>>-/////////////////////////-<br>
>><br>
>><br>
>>It can be hundreds of thousands, or even millions of times more
sensitive.<br>
>><br>
>><br>
>>Fow example, let say you want to build a simple <br>
>>diode detector that monitors 398.5-400 MHz (1.5 <br>
>>MHz wide), you build a simple 8 pole bandpass <br>
>>filter that contains 4 high pass, and then 4 <br>
>>low pass filters, or better yet, 8 high pass <br>
>>cavities, and 8 low pass cavities. This will <br>
>>knock down even the most powerful FM and TV <br>
>>broadcast signals so you can pass the signal <br>
>>to a LNA and then into a diode, and then sum <br>
>>the voltage that comes out of this diode with a <br>
>>output of a matching diode (reference <br>
>>diode/amp), and apply the output of the summing <br>
>>circuit to another amplifier that drives a <br>
>>simple 30 dB or larger column of LED's.<br>
>><br>
>>The goal here is to take a hypothetical FM <br>
>>radio station that is presenting -20 dBm on <br>
>>site, and to knock it down below -174 dB. This <br>
>>means that we want to kill everything outside <br>
>>of the band by 154 dB, but I know some <br>
>>engineers who use only 40 db, others use 120 <br>
>>dB, and some even use 400 dB as their design <br>
>>goals for TSCM and SIGINT bandpass filters. An <br>
>>example is the 60 cycle high pass filters that <br>
>>I make, they knock down 60 Hz by 400 dB, so you <br>
>>can plug one end into a 480 volt circuit, and <br>
>>the other end into the RF input of your <br>
>>spectrum analyzer or oscilloscope. We als comb <br>
>>out all the harmonics of the line voltage and <br>
>>knock down any nastiness that might cause blue smoke to leak out
of the SA.<br>
>><br>
>><br>
>><br>
>>>For example the detector does 1 Mhz to 3000 Mhz<br>
>>><br>
>>>Now i will devide that into 5 bands...using 5 separate
filters :<br>
>>><br>
>>>a) 1-80 Mhz<br>
>>>b) 80-200 Mhz<br>
>>>c) 200-520 Mhz<br>
>>>d) 520-1000 Mhz<br>
>>>e) 1000-3000 Mhz<br>
>>><br>
>>><br>
>>>Ofcourse when using one of above filters... it seems very
logical<br>
>>>that<br>
>>>the maximal detection range becomes much better then without
a filter.<br>
>>><br>
>>>I suppose that is caused by below factors :<br>
>><br>
>><br>
>>When not use the wide band detector (3 GHz) to <br>
>>gate the sampling side of the post filter <br>
>>detectors. Simply put, when the 3 GHz diode <br>
>>captures energy on the log scale that exceeds a <br>
>>certain level (say -50 dB) that it uses to gate <br>
>>all of the output of the diodes assigned to each of the five
bands of interest.<br>
>><br>
>>Lets assume (grin) that I have a stack of <br>
>>Astro-Med Everest analog chart recorders in a <br>
>>rack. Each chart recorder is capable of 32 <br>
>>analog channels each, and I gang or slave 4 of <br>
>>them together so that I have 128 virtual <br>
>>channels. I built a trigger circuit for each <br>
>>chart recorder that monitors a wide swath of RF <br>
>>spectrum, so we have the first recorder <br>
>>listening and reacting to 100 Hz to 1.8 GHz, <br>
>>the second 1 .5 to 18 GHz, the third from 12 <br>
>>GHz to 30 GHz, and so on. When the broadband <br>
>>energy at say 500 MHz goes over -50 dB it <br>
>>triggers the chart recorder to start moving the <br>
>>paper for 5 seconds, but looking at the chart <br>
>>you can see which band of the 32 the energy <br>
>>appears in. The tricky part is that each of the <br>
>>32 channels have to have thier own filter and <br>
>>LNA, then diode, and interface for the chart recorder.<br>
>><br>
>>Maximum range requires first maximum <br>
>>filtration, folwed by maximim amplification, <br>
>>folwed by the most sensitive detection diodes <br>
>>you can find, then further amplification to <br>
>>drive whatever is giong to be your indicator <br>
>>(LED column, speaker, chart recorder, etc)<br>
>><br>
>><br>
>><br>
>>>1) The environmental noisefloor is much lower so a signal
would stick<br>
>>>out much easier.<br>
>><br>
>><br>
>>Yes, but you have to know the frequency on <br>
>>which the bugs appear, and this is a tricky <br>
>>proposition. You have to break the bands into <br>
>>things like 135-150 MHz, then 150 to 174, 174 to 200 MHz, and so
forth.<br>
>><br>
>><br>
>><br>
>>>2) Bandwidth in the receiver is directly related to
noise.<br>
>><br>
>>Yes, it is all part of the KTB formula, with B <br>
>>being that which we can control the most.<br>
>><br>
>><br>
>><br>
>>>Offcourse the adantage of filtering would also be that :<br>
>>><br>
>>>1) The wanted signal is not masked (overpowered) by other out
of band<br>
>>>signals<br>
>><br>
>><br>
>>Big rule of TSCM is to estimate that which you <br>
>>should see in the area you will be sweeping, <br>
>>and then to bring along filters to knock down <br>
>>things that may be making your measurements <br>
>>"dirty". Personally, I carry a fixed 8 pole <br>
>>band reject filter for every TV station <br>
>>allocation, plus a FM band reject filters (more <br>
>>then one), and filters to knock out the paging bands.<br>
>><br>
>>You know what your going to need by looking up <br>
>>FCC allocations for everything within five <br>
>>miles, but 75 miles for any broadcast (AM, FM, <br>
>>TV) channels. If I am performing a sweep in <br>
>>Needham, MA there are huge antenna farms for FM <br>
>>and TV broadcasting, so every inch of the <br>
>>office that I am sweep in getting hammered with <br>
>>high levels of RF. Not only do I have to know <br>
>>down the main carrier, but even the 15th <br>
>>harmonic of the main carrier is radiating off <br>
>>of structural steel and causing massive <br>
>>headaches. This means that I have to use a <br>
>>filter that kills not only the main carrier, <br>
>>but also filters that kill every harmonic out <br>
>>to the 20th or so carriers that is going to tilt or saturate the
sweep gear.<br>
>><br>
>>Once you get above 2 GHz you can use one of <br>
>>more YIG filters to help you do this, but the <br>
>>low frequencies (below 1 GHz) are going to be quite
troublesome.<br>
>><br>
>><br>
>><br>
>>>2) You have an indication of the frequency-band of the found
signal<br>
>>><br>
>>>...etc<br>
>><br>
>><br>
>>Simple sample and hold circuit that triggers a flip-flop
circuit.<br>
>><br>
>><br>
>><br>
>>>The mentioned unit lets you either switch to each filter by
hand...but<br>
>>>it can also go into a so called "Scanning-Filter
mode"<br>
>>><br>
>>>Filter-scanning mode will switch between filters like this
:<br>
>>><br>
>>>Filter 1 >> Filter 2 >> Filter
3 >> Filter 4 >> Filter 5 >> NO-<br>
>>>Filter ......and over again.<br>
>><br>
>><br>
>>Simple six pole mechanical coax switch/relay <br>
>>with a control circuit. It has been done before <br>
>>with good results. Basically, you take a six <br>
>>pole switch, and hand a dedicated filter, <br>
>>amplifier, and antenna off each of the six input connectors.<br>
>><br>
>>One key is not to apply power to any of the six <br>
>>amplifiers other then the one you are using at the time.<br>
>><br>
>><br>
>>>That NO/filter seems to be a good idea in practice...to also
receive<br>
>>>out of band signals<br>
>>>not covered by the filters (in this case below 1 mhz and
above 3000<br>
>>>mhz)<br>
>>><br>
>>>The scanning-speed has still to be determined...it depends on
the<br>
>>>shortest duration<br>
>>>of possible digital signals (pulses) that you want to detect
:<br>
>>><br>
>>>...if it is to slow you might miss a short on-time
signal (non<br>
>>>continious bursts)<br>
>>>...if it is to fast to fast there is no time to validate the
signal<br>
>>>(continious but very-short pulses)<br>
>><br>
>><br>
>><br>
>>A very effective method of detecting tracking <br>
>>devices in a vehicle is to use a gang of <br>
>>generic diode detector such as the CPM-700, add <br>
>>your own bandpass filters for each of the <br>
>>"phone to tower" frequencies, and follow it by <br>
>>a small 20 dB preamplier, or "convert" the RF
probes.<br>
>><br>
>><br>
>>To convert a probe you unscrew the probe body, <br>
>>unscrew the antenna, unsolder the screw that <br>
>>the antenna attached to and install an SMA <br>
>>female connector. Next visit your local <br>
>>hardware store and purchase some one inch <br>
>>tubing and fittings. Mount the SMA/probe <br>
>>assembly into the end cap, and solder the <br>
>>ground of the probe to the copper as well. Then <br>
>>slide the whole thing into a length of copper <br>
>>tubing that it roughly half the wavelength of <br>
>>the frequency of interest. The other end of the <br>
>>copper tube is a Male BNC connector so that you <br>
>>can merely plug the tube into the BNC connector of the
CPM-700<br>
>><br>
>>Next fabricate an antenna out of a length of <br>
>>copper clad welding wire and terminate it on a <br>
>>female SMA connector so that you have a high performance dipole
antenna.<br>
>><br>
>>Inside the copper tubing you will want to add a <br>
>>small 8 pole bandpass filter and kill off the <br>
>>tower-to-base and trunking frequencies by at <br>
>>least 80 dB befoe you go into the probes amplifer.<br>
>><br>
>>The simplest this is to make a standalone box <br>
>>the size of a carton of cigarettes into which <br>
>>the phone-to-tower antenna where mounted, then <br>
>>feed into separate filters for each band (8 <br>
>>poles each), and then take the output and apply <br>
>>it to dedicated amps all built into the same case.<br>
>><br>
>>The box would best be a brass block that you <br>
>>drill out with cavities for each of the filter <br>
>>poles, and then a large cavity for the <br>
>>amplifiers. You could go with an interdigital <br>
>>filters for each of the bands, but you really <br>
>>do not need to displace much heat, and the <br>
>>physical size of the 800 MHz band will be <br>
>>unpleasantly large and heavy. I would (and <br>
>>have) leaned toward a simple LC filters for a <br>
>>project like this and simply add a lot of pole <br>
>>to keep the skirts of the filter as sharp as possible.<br>
>><br>
>>Companies that make filters for the cell phones <br>
>>themselves also make very small duplexer <br>
>>circuits that you can use in reverse, but they <br>
>>tend not to knock down the signals by more then <br>
>>20 ot 30 dB, but it may be a good place for you to start
experimenting.<br>
>><br>
>><br>
>><br>
>>>Forget the scanning speed...lets talk just about
sensitivity-<br>
>>>improvement when using filters.<br>
>><br>
>><br>
>>I am a *** BIG *** fan of carefully designed <br>
>>and built filters, and their use in TSCM.<br>
>><br>
>>I am also an even bigger fan of using big-ass <br>
>>(excuse my French) wide band antennas to suck in as much energy
as possible.<br>
>><br>
>><br>
>>>I know that its a difficult question...but lets say i have to
write an<br>
>>>article or propaganda<br>
>>>for a unit with those 5 switchable filters...and i have to
say how<br>
>>>many times more sensitive<br>
>>>a Wideband(AM)-detector with 5 filters like above
is...compared to the<br>
>>>same one without filters<br>
>>><br>
>>>I suppose that the smaller the filter-bandwidth the more
"sensitive"<br>
>>>so lets simplefy the question<br>
>>>and lets assume that the 5 used filters all have the same
bandwidth so<br>
>>>the whole range is equally<br>
>>>devided<br>
>>><br>
>>>---------------------------------------------------------------=
---------------------<br>
>>>How many times more sensitivity or range would you get ?<br>
>>>---------------------------------------------------------------=
---------------------<br>
>>><br>
>>><br>
>>>Thanks !<br>
>>><br>
>>><br>
>>>Contranl<br>
>>><br>
>>><br>
>>><br>
>>>Remark...i dont understand why not one single manufacturer of
(AM)<br>
>>>wideband-detectors<br>
>>> &nb=
sp;
has not incorperated some filters...they are not<br>
>>>difficult to produce<br>
>>> &nb=
sp;
and not expensive...but greatly improves them.<br>
>>><br>
>>><br>
>>>Please do not respond (in private) to my (old)
Yahoo-emailadress...i<br>
>>>´ve lost the password<br>
>>>and after weeks of correspondence they dont want to give
it...Yahoo<br>
>>>SUCKS !<br>
>><br>
>>-------------------------------------------------------------------=
---------------------------------<br>
>> World Class, Professional, Ethical, and Competent
Bug Sweeps, and<br>
>>Wiretap Detection using Sophisticated Laboratory Grade Test
Equipment.<br>
>>-------------------------------------------------------------------=
---------------------------------<br>
>> James M.
Atkinson &=
nbsp; &nbs=
p;
Phone: (978) 546-3803<br>
>> Granite Island
Group &nbs=
p; &=
nbsp;
Fax: (978) 546-9467<br>
>> 127 Eastern Avenue
#291  =
;
Web:
<a href="
http://www.tscm.com/">
http://www.tscm.com/</a><br>
>> Gloucester, MA
01931-8008  =
;
E-mail: mailto:jm..._at_tscm.com<br>
>>-------------------------------------------------------------------=
---------------------------------<br>
>> We perform bug sweeps like it's a full contact sport, we
take no prisoners,<br>
>>and we give no quarter. Our goal is to simply, and completely
stop the spy.<br>
>>-------------------------------------------------------------------=
---------------------------------<br>
>><br>
>><br>
><br>
>-----------------------------------------------------------------------=
-----------------------------<br>
> World Class, Professional, Ethical, and Competent Bug
Sweeps, and<br>
>Wiretap Detection using Sophisticated Laboratory Grade Test
Equipment.<br>
>-----------------------------------------------------------------------=
-----------------------------<br>
> James M.
Atkinson &=
nbsp; &nbs=
p;
Phone: (978) 546-3803<br>
> Granite Island
Group &nbs=
p; &=
nbsp;
Fax: (978) 546-9467<br>
> 127 Eastern Avenue
#291  =
;
Web:
<a href="
http://www.tscm.com/">
http://www.tscm.com/</a><br>
> Gloucester, MA
01931-8008  =
;
E-mail: mailto:jm..._at_tscm.com<br>
>-----------------------------------------------------------------------=
-----------------------------<br>
> We perform bug sweeps like it's a full contact sport, we take
no prisoners,<br>
>and we give no quarter. Our goal is to simply, and completely stop
the spy.<br>
>-----------------------------------------------------------------------=
-----------------------------<br>
><br><br>
<br>
<br>
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