Autofocus Correction of Phase Distortion Effects on SHARAD Echoes
Mars high resolution Shallow Radar (SHARAD) for the MRO 2005 mission
SHARAD design and operation
SHARAD, a shallow radar sounder to investigate the red planet
Subsurface Radar Sounding of the Jovian Moon Ganymede
SolarSystem2012: The Planetary Science Decadal Survey
The SHAllow RADar (SHARAD) Onboard the NASA MRO Mission
Mars Express Scientific Overview After One Martian Year in Orbit
The SHAllow RADar (SHARAD) Experiment, a subsurface sounding radar for MRO
Analysis of spacecraft antenna systems: Implications for STEREO/WAVES
MARSIS Calibration Plan
Calibration of the SHARAD Instrument
MARSIS, a radar for the study of the Martian subsurface in the Mars Express mission
Analysis of spacecraft antenna systems: Implications for STEREO/WAVES
RHEOMETRY: calibration of spacecraft via scale model
Cassini model rheometry
Radar Sounding of Mars with MARSIS
An exploratory survey of the attenuation of radio signals by the ionosphere of Mars
In-flight calibration of the Cassini-Radio and Plasma Wave Science (RPWS) antenna system for direction-finding and polarization measurements
Wire-grid modeling of Cassini spacecraft for the determination of effective antenna length vectors of the RPWS antennas
Analysis of sounding antennas of the Mars express MARSIS experiment
Simulation of a surface-penetrating radar for Mars exploration
Radio Wave Propagation Handbook for Communication on and Around Mars
A simple inversion model for the estimation of subsurface features of Mars poles
Applying non-iterative phase errors compensation method to restore radar subsurface image
Fast radar signal simulator for SAR ground penetrating applications
GLRT-detection performance in subsurface sounding
GPR Missions on Mars
Mars ionosphere data inversion by MARSIS surface and subsurface signals analysis
Mars surface models and subsurface detection performance in MARSIS
Radar Soundings of the Subsurface of Mars
Radar subsurface sounding over the putative frozen sea in Cerberus Palus, Mars
Subsurface sounding of Mars: multi-pulse detection of water-related interfaces
Surface echo reduction by clutter simulation, application to the Marsis data
Surface echo reduction by clutter simulation, Application to the Marsis data
Subsurface Investigations by MARSIS in Mars Express Mission
Subsurface imaging method (SSIM) based on phase compensation of radar echoes
Structure of the basal unit of the North Polar Plateau of Mars, from MARSIS
The subsurface investigation by Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS)
Radio-Transparent Deposits in the Elysium Region of Mars as Observed by MARSIS and SHARAD Radar Sounders
The Lightweight Deployable Antenna for the MARSIS Experiment on the Mars Express Spacecraft
Analysis of Sounding Antennas of the Mars Express MARSIS Experiment
Analysis of the Lenticular Jointed MARSIS Antenna Deployment
MARSIS antenna flight deployment anomaly and resolution.
MARSIS antenna deployment testing and analysis
Various methods of calibration of the STEREO/WAVES antennas
Numerical Computation of Radar Echoes Measured by MARSIS During Phobos Flybys
MARSIS: Mars Advanced Radar for Subsurface and Ionosphere Sounding (SP-1240)
The System and Implementation aspects of MARSIS
Probing the Subsurface of Mars with MARSIS on Mars Express
Surface εr reconstruction of Phobos
MARSIS at Phobos: Real Data Processing Compared with Simulations Results
MARS EXPRESS AND MARSIS
Mars Express Science Overview
An Inflatable L-band Microstrip SAR Array
RECENT ADVANCES IN RADAR TECHNOLOGY AND TECHNIQUES FOR AFFORDABLE PLANETARY REMOTE SENSING
Numerical Computation of Radar Echoes Measured by MARSIS During Phobos Flybys
Various methods of calibration of the STEREO/WAVES antennas
MARSIS expected results
Radar signal simulation: Surface modeling with the Facet Method
Mars and Venus the Express Way
THE DIGITAL ELECTRONIC SUBSYSTEM OF MARSIS
An exploratory survey of the attenuation of radio signals by the ionosphere of Mars
An Imaging HF GPR Using Stationary Antennas:
Areas of enhanced ionization in the deep nightside ionosphere of Mars
Attenuation of radio signals by the ionosphere of Mars (withers)
Comparison between MARSIS & SHARAD results
Dayside ionosphere of Mars: Empirical model based on data from the MARSIS instrument
Doppler analysis for data inversion and image processing in the MARSIS experiment
Doppler analysis for data inversion and image processing in the MARSIS experiment
Dual-spacecraft observation of large-scale magnetic flux ropes in the Martian ionosphere
Electromagnetic Features of Ground Penetrating Radars for the Exploration of Martian Subsurface
EMI in orbiting sounding radar from ripple in solar arrays
Exploring the Martian subsurface of Athabasca using MARSIS radar data
GPR Missions on Mars
In situ observations of the ionized environment of Mars: the antenna impedance measurements
Ionosphere compensation and stepped frequency processing in the MARSIS experiment
Mars Express: The Scientific Payload
Mars Ionosphere preliminary impact analysis on SHARAD radar signal
MARSIS Data Inversion Approach
MARSIS data inversion approach: Preliminary results
MARSIS Radar Signal Simulation
Modeling the Configuration of HF Electrical Antennas for Deep Bistatic Subsurface Sounding
Nightside ionosphere of Mars: Radar soundings by the Mars Express spacecraft
Overlapping ionospheric and surface echoes observed by the Mars Express radar sounder near the Martian terminator
Radar subsurface sounding over the putative frozen sea in Cerberus Palus, Mars
Sharad Design and Operation
Sounding Data with SHARAD & MARSIS
Subsurface sounding in Northern hemisphere for Mars by MARSIS: Mars express mission
The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS): concept and performance
The Mars express MARSIS sounder instrument
Transterminator ion flow in the Martian ionosphere
Electron densities in the upper ionosphere of Mars from the excitation of electron plasma oscillations
Dayside Induced (akalin)
Radar Absorption due to a corotating interaction region encounter with Mars detected by MARSIS
An Overview of Radar Sounding of the Martian ionosphere from the Mars Express spacecraft
The vacation grounds of upstate New York, particularly the Adirondack area suffer from poor cellular service. Recent fatal accidents have left the public blaming the lack of cell phone coverage for slow emergency response. There are a few things professional users (including volunteer emergency services) and prosumers can do to improve in-car cellular service.
Readily available technology yields:
There isn’t any fundamental difference in radio waves between two-way radio and cellular. The ubiquitous handheld cell phones with internal antennas suffer several dB disadvantage vs. older handheld phones with external antennas. Add several more dB penalty for handheld cell phone used in car or building. Cellular coverage can be significantly augmented by using bidirectional amplifiers in the home, office or vehicle. However, terrain in mountainous areas precludes 100% coverage.
Automobile-installed cellular phone repeaters and amplifiers can yield up to 3 Watts output power from your car back to the tower, just like traditional bag phones. The bidirectional amplifier costs about $200-$300, the phone adapter another $20, and the install probably $100-$200. This could be a life-saver or at least a time-saver in remote areas. The cellular signal is attenuated by more than 10 dB in both directions with a handheld phone in the car compared to an external antenna. However, in mountainous terrain, oftentimes the problem is simply terrain blockage, so sometimes no amount of hardware will help. This is where emergency services use their own VHF/UHF repeater towers to fill the cellular gaps via radio.
Burning Man 2007 saw the debut of standalone cellular service via USRP OpenBTS. OpenBTS can cover remote worksites and campgrounds with cellular, when the provider’s network doesn’t yield coverage.
Bidirectional amplifiers can have 20-80 dB of gain depending on the model. The lower gain (< 40 dB) models assume the phone is within about 10 meters of the amplifier–and that with a good signal at the donor amplifier. If the phone already does not have an adequate signal, then a high-gain donor antenna placed up high is required. To cover outdoor areas with bidirectional amplifier, free-space loss and antenna pattern analysis shows that the isolation distance required is large enough to require fiber optic interconnection to be practical. This translates to significant expense, probably excessive for a large number of campgrounds and remote outdoor worksites.
Telephone and data coverage to campsites and remote outdoor worksites can consist of two-way radio with interconnect along with outdoor WiFi APs. Outdoor WiFi AP coverage can be over 100 meters outside when placed at 5-10 meter height.
Two-way radio callboxes are available for < $500, and if a campsite / remote worksite has only one security guard on duty at night on patrol, their walkie-talkie can communicate with the callbox and on the same (or different) channel dial the telephone for half-duplex communications with emergency services over the radio channel. A callbox per bloc of cabins or periodically throughout the worksite may suffice.
For long-range staff cordless telephones, multiple base stations and dozens of handsets are possible. It is possible to get over 100 meter range from the base station when it’s placed in a high, clear view location.
Reference: Bidirectional amplifier white paper
The Kenwood TS-2000 has a strong birdie (false signal) at 436.800MHz. This is the 28th harmonic of X400, the 15.6 MHz TCXO.
Symptoms: the 436.8 MHz TS-2000 birdie interferes with the first third of AO-27 and SO-50 passes, as the 436.795 MHz downlink of these satellites is well within the ± 7.5 kHz bandwidth of the TS-2000 FM receiver. The maximum 436 MHz Doppler shift for these LEO satellites is about ± 9 kHz. Thus near AOS of a given pass, AO-27 or SO-50 apparent center frequency is as high as 436.804 MHz. It’s not until the satellite is reaching maximum elevation that the Doppler shift makes the apparent center frequency low enough (say 463.796 MHz) so that Narrow FM (bandwidth ± 3.75 kHz) and tuning away from the birdie can help greatly.
Aside from hacking the circuitry around X400, the easy fix is simple to use a 436 → 29 MHz downconvertor that completely eliminates the birdie concern.
Kenwood TS-2000 internal TNC UNDOCUMENTED COMMANDS:
PASSALL ON
SOFTDCD ONThe effectiveness of SOFTDCD doesn’t match a “real” external TNC–the TNC still relies on the hardware squelch.
This means that the internal TNC may miss packets from mobile/portable devices with fluttering signals common to VHF/UHF.
try “S-meter Squelch (menu #19A)” to enable you to transmit when the received signal is strong and transmits constantly (such as packet satellites like GO-32).
This is ONLY effective when the station you desire to communicate with can receive while transmitting. You must manually turn up the squelch for an instant, then turn it back down so that the TS-2000 can receive the other station after the TS-2000 sends its data.
The Kenwood TS-2000 with internal TNC is capable of ARISS packet operations. The performance of the internal TNC can be a little frustrating on receive.
The satellite TRACE feature of the TS-2000 is ONLY useful in conjunction with computer tuning, since it does not account for Doppler shift magnitude increasing relative to frequency.
That is, 1:1 frequency tuning of TRACE is OK for quick adjustments in a satellite linear transponder passband, but computer frequency tracking is necessary to account for Doppler shift during the satellite pass.
For example, a -1.0 kHz Doppler shift on 146 MHz will be about -2.99 kHz on 436 MHz, and so on.
The VX-7 and other Yaesu VX series are noted for low microphone audio. It is generally a bad idea to blindly increase the deviation through the service menu. If maximium deviation is set beyond 5kHz total, “talk-off” may be experienced for loud audio through the repeater/receiving radio. The transmit bandwidth becomes excessive and falsely closes the repeater squelch on loud audio.
I had read that piercing the microphone diaphragm (on the front cover, NOT on the mic element itself!) would improve the microphone sensitivity. I pierced the thin diaphragm, and noted increased microphone sensitivity. Wind noise is frequently a problem in internal mics, and it did raise this issue slightly. However, I now can talk about 12 cm from the microphone in most cases and be well heard–before it was more like 4 cm from the microphone! Of course, I left the TX deviation adjustment as from the factory.
You should keep in mind that you are now inviting dust and water into the microphone element. I plan to put a small piece of Motorola speaker felt into the cavity, to prevent most impurities from entering. I would not recommend just leaving the hole open.
I was pleasantly surprised upon some informal empirical testing with the Maldol MH-209SMA vs. the SMA503. The SMA503 has about 18 cm of radiating length while the MH-209SMA appears to have only about 5 cm. When used in conjunction with the Yaesu MH-57 speaker-mic, about 2cm of the 5cm is blocked.
As compared to an SMA503 with no speaker-mic, the loss seems to be no worse than 5 dB or so (both receive and transmit). This is true on both 2 meters and 440. I didn’t test it on 6 m or 220 MHz, because the SMA503 is not rated for those bands. Shortwave and MW band performance is much BETTER with the MH-209 than with the SMA503, which seems counterintuitive unless you consider that the feedpoint method of the SMA503 may be presenting a very bad impedance far from the desired bands. FM broadcast was a little worse, but very usable. 800 MHz seemed a little worse too.
The antenna is very flexible and seems like it won’t be prone to the breakage and kinking the SMA503 is known for. I would recommend the MH-209 antenna to people where range is not the overriding concern, but who need small size while maintaining adequate performance.
The Yaesu VX-7, while overall an excellent amateur transceiver, suffers from a problem it shares with certain commercial handheld radios, that is of losing receive audio intermittently. The loss of audio stems from the flexible tensioned metal tangs that make contact to tin patches on the VX-7 internal speaker. I bent the speaker tension tangs outward resulting in about 1.5 mm more outward protrusion, thus reenacting a secure connection to the internal speaker.
Overbending these tangs could cause them to break, or worse, weaken them so they break later, shorting out internal components of the VX-7. I recommend you take this radio to a qualified repairperson to perform this repair.
It appears the VX-7 speaker model number is “Pryme 32N-A9906”; 8 Ω, 0.5 W
Nextel iDEN tethering to a laptop phone connection was at about 10 kbps speeds. Less than the average home 30-40 kbps modem connection but not much worse considering the wide Nextel coverage area. Typical bandwidth is 0.5-1 Mbps depending on the time of day. Dynamic browser sensing for three tiers of content presentation for mobile/desktop web could work like:
Essential mobile 2G Java browsing. 2-3 small images max, simple table, list.
Full mobile: For Blackberry / Opera class browsers on 3G. 3-4 small images, pretty table, list, forms. HTML+CSS+images < 150kB ~ 6 seconds render time.
Full desktop: often not rendered properly on the mobile browser.
Heavily loaded LTR trunked radio systems with too many users homed on the same repeater may have a problem with radios randomly failing to transmit. Monitoring for LTR trunked radio system overloading may be viewable via controller statistics. With LTR if too many groups are homed on one repeater, the chance of two people keying up before the repeater can make its first response goes up. Then, either neither party can transmit if the overlap is early (no clear-to-talk), or both will transmit. In the first case, out-of-range tone is given. In the second case, clear to talk is given but the transmissions are uselessly garbled (or maybe, one signal dominates).
Solving LTR trunked radio system overloading involves reprogramming every radio in the system, so plan first. Distribute home channels for different groups that talk at the same time. If the system needs an “all call”, have a small dispatch console that can key multiple radios simultaneously–if not, you’ll need to implement one. This solution is fairly unique to LTR.