Here's how Russian/Iraqi decode SINCGARS
UB
clik: http://www.aeronautics.ru/news/news002/news071.htm
March 21, 2003
www.aeronautics.ru
The US military is using SINCGARS (Single Channel Ground And Airborne Radio
System) frequency-hopping radios in the field. These radio sets are
categorized as Low Probability of Intercept (LPI) Frequency Hopping Spread
Spectrum (FHSS) transceivers. The FHSS method is not new: it originated from
the Second World War and, simply stated, it employs a narrow band carrier,
shifting frequency in a pattern known only to the transmitter and the
receiver. The frequency can be changed several hundred times per second.
The FHSS military radios are synchronized daily to use the same frequency
modulation algorithm. The synchronization process occurs either through a
direct physical connection of the radio sets to each other or to a special
device known as the programmer. Some radios can also synchronize frequency
modulation algorithms via an encrypted transmission of the frequency
modulation algorithm in a non-frequency-hopping mode, although this method
is generally considered to be less secure.
The military radios in the US armed forces commonly use encryption and the
frequency hopping methods provide an additional layer of security during
transmission of the encrypted signal. An example of a frequency-hopping
field VHF/FM transceiver used by US Special Forces would be the Caracal RPM
4740 manufactured by Thales Communications of France.
The Caracal covers the 30 to 87.975 MHz frequency range. It also has 10
programmable simplex or half-duplex channels out of its repertoire of 2,320.
Hopping in narrowband (6.4 MHz) and wideband (30 to 87.975 MHz) orthogonal
modes, Caracal contains high-grade internal digital encryption and has an
output of 1 W. Insertion of frequency and security codes is accomplished
using the MA 4073B programmer or MA 4083B fill gun. A reset switch on each
radio is used to erase codes rapidly. The synchronization function is
broadcast, requiring about 6 seconds. Other features include receive-only
selective calling, frequency barring and `hailing' by fixed-frequency radios
when in the hopping mode.
However, security afforded by frequency-hopping methods is very dependant on
the strict adherence to protocols for operating such radios. The US troops
and other operators of frequency-hopping radio sets frequently disregard
these protocols. An example would be an artillery unit passing digital
traffic in the frequency-hopping mode, which would enable an unauthorized
listener to determine the frequency-hopping algorithm and eavesdrop on the
transmission.
Even when proper protocols for using frequency-hopping radios are being
adhered to interception and decryption of these signals is still possible.
The frequency-hopping interceptors are special advanced reconnaissance
wideband receivers capable of simultaneously tracking a large number of
frequency-hopping encrypted transmissions even in high background noise
environments.
An example of such a reconnaissance device would be the FH-1
frequency-hopping interceptor manufactured by VIDEOTON-MECHLABOR
Manufacturing and Development Ltd of Hungary. The FH-1 frequency-hopping
interceptor is a modern reconnaissance system based on parallel signal
processing technology.
The equipment has 160 independent receiving channels covering a 4 MHz wide
IF band with 25 kHz channel spacing, 60 dB channel selection and 60 dB
intermodulation suppression. The 4 MHz wide IF band is the IF output of a
special high-speed front-end receiver which has a 20 to 1,000 MHz frequency
range.
The digitized output signals of the channels are multiplexed and fed as 1
Mbits/s data to a fast dedicated signal-processing computer. As the
processing time of the 160 channels is 200 盜 with the front-end receiver 4
MHz frequency setting time, the processing speed of this interceptor is 4
MHz/200 盜 or 20 GHz/s. This high speed makes it possible to process the
complete 30 to 80 MHz ground-to-ground VHF band within a 2.5 ms time slot.
The system's processing algorithm filters out noise spikes and stationary
transmissions and in this way hopping transmissions can be classified either
in the traditional frequency versus amplitude mode or in a waterfall-like
frequency versus time display mode. Optional software modules are available
for direction-finding the FH transmission and for controlling a remote
follower/jammer.
Venik
Harris
> These radio sets are
> categorized as Low Probability of Intercept (LPI) Frequency Hopping Spread
> Spectrum (FHSS) transceivers. The FHSS method is not new: it originated from
> the Second World War and, simply stated, it employs a narrow band carrier,
> shifting frequency in a pattern known only to the transmitter and the
> receiver. The frequency can be changed several hundred times per second.
An the frequency hopping scheme was invented by none other than actress
Hedy Lamarr!
See:
http://www.inventions.org/culture/female/lamarr.html
Art Harris N2AH
Tom2000
Thanks, Art. I knew that she had invented something fundamental to
military communications, but I'd forgotten just what her contribution
had been.
Very 73,
Tom
M. J. Powell
<tom...@mindspring.com> writes
Plus the radio-controlled torpedo!
Mike
--
M.J.Powell
Ross Archer
"Harris" <aha...@bookworm.suffolk.lib.ny.us> wrote in message
news:yW1ga.6858$io.2...@iad-read.news.verio.net...
> In rec.radio.shortwave UB <ubu...@yahoo.com> wrote:
>
> > These radio sets are
> > categorized as Low Probability of Intercept (LPI) Frequency Hopping Spread
> > Spectrum (FHSS) transceivers.
Actually, I'd prefer direct sequence digital phase shift keying to FHSS for
security, especially if you're just hopping a conventional AM or FM voice
signal. If you've got a receiver that receives broadbandedly across the whole
stepping range, and you're close enough to the source, you might decode the
signal with a conventional demodulator!
At least with DS, the signal is digital and mangulated with the sequence code,
so it requires a knowledge of the spreading sequence as well as the
encryption/encoding method to intercept and decode the signal.
Comments?
P.S.: Yeah, that Hedy Lamarr story below is true. At least, they printed up
quite a story in the local newspaper about her and her idea to guide torpedos
using this technique.
Eric F. Richards
>
> "Harris" <aha...@bookworm.suffolk.lib.ny.us> wrote in message
> news:yW1ga.6858$io.2...@iad-read.news.verio.net...
> > In rec.radio.shortwave UB <ubu...@yahoo.com> wrote:
> >
> > > These radio sets are
> > > categorized as Low Probability of Intercept (LPI) Frequency Hopping Spread
> > > Spectrum (FHSS) transceivers.
>
> Actually, I'd prefer direct sequence digital phase shift keying to FHSS for
> security, especially if you're just hopping a conventional AM or FM voice
> signal. If you've got a receiver that receives broadbandedly across the whole
> stepping range, and you're close enough to the source, you might decode the
> signal with a conventional demodulator!
>
> At least with DS, the signal is digital and mangulated with the sequence code,
> so it requires a knowledge of the spreading sequence as well as the
> encryption/encoding method to intercept and decode the signal.
>
> Comments?
>
> P.S.: Yeah, that Hedy Lamarr story below is true. At least, they printed up
> quite a story in the local newspaper about her and her idea to guide torpedos
> using this technique.
>
Yes, and the IEEE gave her an award a couple years back; her response
was, "It's about time!" She also played the "dumb-blonde" hanging on
the arm of German generals and passed intelligence back to the allies.
Tough cookie, that lady.
> > The FHSS method is not new: it originated from
> > > the Second World War and, simply stated, it employs a narrow band carrier,
> > > shifting frequency in a pattern known only to the transmitter and the
> > > receiver. The frequency can be changed several hundred times per second.
> >
> > An the frequency hopping scheme was invented by none other than actress
> > Hedy Lamarr!
> >
> > See:
> > http://www.inventions.org/culture/female/lamarr.html
> >
> > Art Harris N2AH
> >
> >
>
--
Eric F. Richards, efr...@dim.com
"Don't destroy the Earth! That's where I keep all of my stuff!"
- Squidd on www.fark.com