Thought this item from TV Technology might interest this group...
Enjoy!
Eric W3DQ
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>From TV Technology
Doug Lung's RF Report
1/16/2015
List of Experimental Licenses Reveals Interesting HF Data Comm Experiments
Ham radio operators have been using the shortwave ("high-frequency" or HF)
bands for data communications for over 50 years, but the data rates are
much less than those available with dial-up modems. HF communications have
the advantage that they don't depend on vulnerable satellites, don't
require line-of-sight, and can cover huge distances under the right
conditions.
The FCC recently granted two companies experimental licenses to use HF
bands for data communications at far greater bandwidths and data rates than
have been used by amateur radio operators. While these communication
systems are being developed for the military, it's possible some of the
techniques developed could be used for digital broadcasting in the AM band,
or more likely for shortwave broadcasting where sky wave propagation is
important.
According to the commission's Office of Engineering and Technology
Experimental Licensing Branch's list of experimental applications between
10/1/14 to 10/31/14, license WH2XCI was granted to The MITRE Corporation to
operate in the 2505.00 - 4100.00, 4210.00 - 4995.00, 5005.00 - 6210.00,
6320.0 - 8250.00, 8450.00 - 9995.00, 10005.00 - 12200.00, 13500.00 -
14990.00 and 15010.00 - 16000.00 kHz bands to test HF communications at
fixed locations in Bedford and Worcester in Massachusetts and Oneida and
Rome in New York.
MITRE's application states, "While satellite communication provides high
data rate connectivity, there are vulnerabilities that include degradation
and disruption of service. HF radio communication generally are limited to
narrower bandwidths and lower data rates than satellite communications. To
ensure critical communications are maintained, we are investigating the
capability of higher bandwidth and higher data rate communications in the
HF band applying polarization diversity MIMO concepts."
The goal, according to the application, is to obtain reliable
communications at a data rate between 1 and 4 bits/Hz/s. MITRE said it will
develop a 100 kHz bandwidth waveform that can achieve approximately 256
kbps with forward error correction (FEC) coding. MITRE will attempt to use
both X and O modes to carry independent communications channels. PA0SIM has
an excellent description of the X and O modes at XO propagation web page.
In addition to the 100 kHz bandwidth, MITRE's license allows bandwidths up
to 1 MHz. MITRE states, "A stretch goal is to extend to wider bandwidth
waveforms, up to 1 MHz." The researchers' note: "we understand that this
wideband waveform may run up against other users and possibly cause
interference. We plan to transmit at as low a power as possible and on a
not-to-interfere basis."
According to the license, MITRE will use emissions with the designators
5K00Q3N, 500KD7D, 500Q3N, 500W7D, 1M00D7D, 1M00Q3N and 1M00D7W. These
designators imply maximum bandwidths of 5 kHz, 500 kHz and 1 MHz. The
authorized effective radiated power ranges from 6 W to 122 W, depending on
frequency and bandwidth. The license includes a condition stating "Licensee
should be aware that other stations may be licensed on these frequencies
and if any interference occurs, the licensee of this authorization will be
subject to immediate shut down." MITRE application shows the equipment
being used includes nine Ettus N210 software defined radios, six
Minicircuits ZHL-5W-1 and six BAE Australia "TBD - 50 W unit". Apparently
these are the power amplifiers.
MITRE's application describes the antennas - crossed dipoles and verticals
- that will be used in testing to isolate the X and O propagation modes.
You find the application, associated exhibits, and the grant using the
Experimental Licensing System Call Sign Search and entering callsign
WH2XCI. MITRE will be using
Another interesting grant is WG2XZF to TrellisWare Technologies, Inc.. It
is an experimental license to operate between 1.800 and 12.00 MHz "to
implement and field test the design of an advanced hf waveform" mobile in
Julian, CA. The application shows the emission type as 30K0D7D,
significantly narrower than the MITRE filing, utilizing QPSK to 64QAM
modulation. I did not find any data rate specification.
Even if these communications technologies never find their way to AM or
shortwave broadcasting, it is encouraging to see how HF communications is
continuing to evolve.
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