John Galt versus GLONASS: Helping Keep Our RF Environment Clean

Ken Tapping

Example Problems1 559-1 610 MHz: AERONAUTICAL RADIONAVIGATIONRADIONAVIGATION-SATELLITE (space-to-Earth) (space-to-space)

1 610-1 610.6 MHz:MOBILE-SATELLITE (Earth-to-space) AERONAUTICAL RADIONAVIGATIONRADIODETERMINATION SATELLITE (Earth-to-space)

1 610.6-1 613.8 MHz:MOBILE-SATELLITE (Earth-to-space) RADIO ASTRONOMYAERONAUTICAL RADIONAVIGATIONRADIODETERMINATION SATELLITE (Earth-to-space)

1 613.8-1 626.5 MHz: MOBILE-SATELLITE (Earth-to-space) AERONAUTICAL RADIONAVIGATIONRADIODETERMINATION SATELLITE (Earth-to-space)Mobile-satellite (space-to-Earth) Iridium – Another Problem

GLONASS – The Problem

This buffer band is only 0.6 MHz Wide. Not much help.

Glonass Comes On-Stage

GLONASS

• A Russian satellite navigation system.• Uses a spread-spectrum modulation scheme which splatters signal into the

1610.6-1613.8 MHz radio astronomy band. Serious interference from GLONASS is also experienced as far away as the 1 660 1 670 MHz radio ‑astronomy band.

• Satellites already launched could not be modified.• At that time the Russians indicated they were not economically in a position

to redevelop the non-launched systems or those under construction.• In Geneva they said their system related to “safety of life” and is therefore

more important than radio astronomy.• Some improvement was achieved by operational changes, but the problem

is still there.

“Post-Mortem” on GLONASS(Not really a post-mortem because the issue is still alive)

• This issue combines all the elements of observatory spectrum management – local->international.

• Could more vigorous radio astronomer activity at the international level have made a difference?

• What lessons have we learned?• Have we learned enough?

Example Problems1 559-1 610 MHz: AERONAUTICAL RADIONAVIGATIONRADIONAVIGATION-SATELLITE (space-to-Earth) (space-to-space)

1 610-1 610.6 MHz:MOBILE-SATELLITE (Earth-to-space) AERONAUTICAL RADIONAVIGATIONRADIODETERMINATION SATELLITE (Earth-to-space)

1 610.6-1 613.8 MHz:MOBILE-SATELLITE (Earth-to-space) RADIO ASTRONOMYAERONAUTICAL RADIONAVIGATIONRADIODETERMINATION SATELLITE (Earth-to-space)

1 613.8-1 626.5 MHz: MOBILE-SATELLITE (Earth-to-space) AERONAUTICAL RADIONAVIGATIONRADIODETERMINATION SATELLITE (Earth-to-space)Mobile-satellite (space-to-Earth) Iridium – Another Problem

GLONASS – The Problem

This buffer band is only 0.6 MHz Wide. Not much help.

Then Came Iridium• Iridium – a satellite phone system, using the spectrum just

above the 1610-1613 MHz radio astronomy band.• Their modulation and channel use system splattered

interference into the radio astronomy band.• A filter design for suppressing this ended up overweight and

overbudget. So the spacecraft were launched without them.• Iridium representatives visited radio observatories getting

them into individual agreements and to sign non-disclosure agreements that effectively stopped collaborative opposition.

• Canada signed no agreements, but the system got licensed here anyway. Iridium was a better lobbyist than we were.

The Game Had Changed• The diplomacy-driven, collegial system of national and international

spectrum management had gone – replaced by a lobbyist and money-driven system. The politics got dirtier. Being able to prove the numbers no longer worked.

• Those of the radio astronomy community were outmanoeuvred, outsmarted and humiliated. Attending meetings was a horrible experience.

• However, in a backhanded way, Iridium did us a favour. The company made a lot of commercial enemies, and also taught radio astronomers still in the spectrum protection arena how things worked now. So we made allies out of Iridium’s enemies (Alcatel for example). We started making progress again.

• Some level of lobbying was important to maintain contacts as well as to actually raise issues.

Canadian Changes • “If radio astronomy is so important to you, why aren’t you in

Ottawa telling us?” Vasilius Mimis (Industry Canada – Ottawa). We had to become lobbyists too.

• We had to exploit our unique advantages: “we are all civil servants”, and we can tell where our numbers come from. “Radio Astronomy for Spectrum Managers”

• We needed to get much more involved in spectrum management at all levels, including regular participation as members of the Canadian Delegation to Geneva.

• We needed to communicate better within our community.• We needed to be able to see what was coming down the tube

before someone deploys it.

Other Big Changes • Emphasis is shifting to networks of low-power, mobile devices

deployed in large numbers (e.g. Mobile Phones).• WiFi everywhere, including in the air.• Smart meters and other networked, low-power, fixed devices.• Collision avoidance radars and other radio devices on cars.• We needed to be able to see what was coming down the tube

before someone deploys it. • The Noise Floor due to large numbers of low-power devices all

operating perfectly legally.• In radio astronomy, increased need to observe (as possible)

outside frequency bands allocated for radio astronomy (e.g. CHIME).

What You Can Pick Up at DRAO(Part of a spectrum monitoring project by John Galt)

A clean radio spectrum in which to observe is as much a national facility

for radio astronomy as is a radio telescope. Unfortunately, that message

is not always getting across, even to radio astronomers.

The Radio Astronomy Problem• Radio astronomical signals are very weak. A cell phone on the Moon

would be the brightest radio source in the sky, and a cell phone on Mars would be detectable using our 26m radio telescope. Almost all manmade signals are stronger than this.

• Although frequency bands are specified in the ITU Radio Regulations for radio astronomical use, untended emissions by radio or other electronic devices may be radiated into radio astronomy bands. This problem may be exacerbated by engineering shortcomings, incorrect installation, deployment in the wrong place or damage (e.g. coffee spilt on it).

• Manufacturer testing may be legal but still inadequate.• The total emission from a lot of devices individually too weak to interfere

significantly to radio astronomy may collectively add up to a problem that may be hard to deal with.

Protecting a Radio Observatory

• Establish threat criteria: what are we looking for?• Establish spectrum monitoring programmes• Establish a stable and consistent staff support• Establish protocols for dealing with external interference• Establish protocols for dealing with self-inflicted interference• Be equipped to meaningfully do these things• Establish working relationships with spectrum managers. Educate them.• Get involved in spectrum management, locally, regionally, nationally and

internationally• The effort must be consistent and on-going.

World Radio Conference - Geneva

The Big Red Book

Extracts from the Radio Regulations

DRAO Radio Protection Zone

a

This zone has been the basis of the spectrum management effort between the Kelowna Office of Industry Canada and the Observatory for more than two decades.

Transportable and Mobile Station

ICOM F2721D UHF Transceiver

Bird Wattmeter and Return Loss Monitor

Transportable Station transmissions are made using the calibrated dipole antenna. Mobile Station transmissions are made using a whip antenna on the van roof.

Transmission Positions are Determined using a GPS Receiver and in the case of the Mobile Transmissions, Logged Automatically on a Laptop PC

Calibrated Dipole Antenna

Observatory Equipment Configuration

Amplifier

Splitter

Directional Coupler

Calibration Signal from Precision Signal Generator (ifr 2023B)

Amplifier

ifr COM-120B Panoramic Receiver/Spectrum Analyzer

Rohde & Schwartz FSP Panoramic Receiver/Spectrum Analyzer

Spectrum Explorer Smart Receiver/Spectrum Monitoring System

Comparison of Calculated and Measured Path Losses for Fixed Locations

Calculated Path Loss (dB) Measured Path Loss (dB)

Location PREDICT Longley Rice Median Std. Dev.

L3 208 187 160 3

L4 215 190 171 2

L5 184 165 154 3

L6 200 165 129 3

L7 208 172 145 3

L8 196 170 149 4

L9 191 175 160 4

L10 191 180 168 3

L11 176 170 153 5

Revised Zone

The Quinn Machine: A Pathfinder Project

• A sofware-defined-radio based system that can be tuned over a wide range (70 MHz – 6 GHz).

• Variable bandwidth (up to only 5 MHz unfortunately).• Can record and display power levels and spectra.• Can be set up to demodulate most signal types, in order to

identify interference sources.• Can run automatically for long periods.

Quinn Machine

The Aether Sniffer

Who’s Going to Win?OTHER SPECTRUM USERSRADIO SPECTRUM MANAGEMENT IS DONE BY EXPERTS WHO MELD YEARS OF EXPERIENCE WITH A CURIOUS BLEND OF REGULATIONS, ELECTRONICS, POLITICS AND NOT A LITTLE BIT OF LARCENY. THEY JUSTIFY REQUIREMENTS, HORSE-TRADE, COERCE, BLUFF AND GAMBLE WITH AN INTUITION THAT CANNOT BE TAUGHT OTHER THAN BY LONG EXPERIENCE.Vice-Admiral Jon L. Boyes, U.S. NAVY

RADIO ASTRONOMERSI’M GLAD SOMEONE IS DOING IT, BUT I AM TOO BUSY DOING MY SCIENCE.One of only two identical replies when I sought guidance from the Canadian astronomical community before heading to an international spectrum management meeting. The scientists in question shall remain anonymous.

Touching the Tar Baby

END SLIDE

The Issues

• New radio services are being implemented. They require spectrum space in which to operate, and are likely to produce unwanted radio emissions that may cause problems for radio astronomers, as well as other spectrum users.

• The sheer number of radio devices in everyday use is rocketing, meaning that low, legal levels of interference from individual devices may add up to a significant interference problem due to the aggregate emission from many devices.

• Radio astronomical instrumentation is changing, from (radio-quiet) analogue systems to predominantly digital (radio-noisy) ones.

• Spectrum politics is becoming much more aggressive, requiring more radio astronomers to participate in this process, taking them away from science and instrumentation development.

• Many astronomers and observatory managers still don’t appreciate the magnitude of the problem or the need to invest in addressing it. Even here at DRAO protecting the observatory’s function through spectrum monitoring and management has been patchy, mainly based on the action of dedicated individuals, and we’re among the better observatories in this regard.

Protecting DRAO’s Key Asset

• Electromagnetic Hygiene starts at home. How much of our interference is caused by us? What can be done about it?

• How do we identify sources of interference when they arise.• Working with local, regional and national spectrum managers,

and our part in international spectrum management.• The DRAO Radio Quiet Zone

DRAO Issues• DRAO’s main asset is its low interference site.• This quality has to be available over as much as possible of

the spectrum of interest to radio astronomers.• We need to identify any issues occurring in bands allocated

in the ITU Radio Regulations for radio astronomy .• We need to know what other parts of the radio spectrum

might be available for opportunistic observing.• We need to know what is changing in that environment and

to assess the threat potential of any new deployments.

DRAO Measures• To have on-site spectrum monitoring programmes

covering the full frequency range of astronomical interest.

• To have the means to demodulate or decode interfering signals to a point where they can be identified.

• To monitor background noise levels over the spectrum – monitoring possible degradation.

• To liaise with Industry Canada regarding protection requirements, problem identification and assessment of problem potential for new proposed deployments.

• To help maintain the DRAO Protection Zone

Electromagnetic Hygiene Begins at Home

Checking The Zone

• The original DRAO Protection Zone had been in place for at least two decades.

• In that area, spectrum demands have increased.• Are the current restrictions too restrictive, and could be relaxed

without impacting us while making room for others? Or not?• A recent joint project was conducted in collaboration with

Industry Canada to evaluate the zone and to redefine it.• The study was done in the 406-410 MHz band, since this one is

shared with other services (not purely radio astronomy), so the interference potential is much higher. These other services operate under the restriction that they do not interfere with radio astronomy.

The Procedure

• To make transmissions at 408 MHz at a known power, with an antenna of known properties, from various positions in the Southern Okanagan and elsewhere, and measuring the strength of the received signal at DRAO.

• Compare the measured path loss with the loss calculated using terrain data and two propagation models: Predict and Longley-Rice.

• Use these data to redefine the Protection Zone.

Basic Measurement Procedures

“This is Industry Canada testing… testing…This is Industry Canada testing… testing… This is …”

Two Modes

Transportable Base Mode using the mounted folded dipole as shown (more precise but takes longer), and Mobile Mode, using the whip antenna on the van roof (less precise but easy to get lots of data)

Signals received by both calibrated dipole and log periodic antennas

Folded Dipole

Whip

Relocatable Station Measurement Procedure

0

1

2

3

4Tent Peg

Dipole phase centre 3m above ground and vertical (using plumb line – antenna is not vertical in this shot)

Slight null in antenna beam pattern is always pointed south.

0

1

2

3

4

1 m

North

Process repeated for low (4.5 W), medium (24 W) and high (42 W) transmitter power at 406.9875 MHz. Transmission BW = 15 kHz.

This 5-point measuring procedure is recommended by the ITU-R for fixed-point measurements.

GPS Receiver and Thermometer

q

Comparison of Calculated and Measured Path Losses for Mobile Transmissions

Segment PREDICT Calculated path loss (dB)

Longley Rice Calculated path loss (dB)

Preliminary* Measured path loss (dB)

S1 195 176 168 S2 195 179 162 S3 206 189 162 S4 208 185 175 S5 208 191 176 S6 209 191 175

Note that for the terrain local to DRAO, the models dramatically and consistently overestimate the path loss.

Conclusions

• The propagation models always overestimate the path loss, so they cannot be used alone without generous margins (30dB for Predict, 20dB for Longley-Rice).

• Even so it did look as though there were places were the restrictions could be relaxed a little without affecting DRAO.

Quinn Machine

Broadband Antenna

Directional Coupler

Noise Source

Broadband Amplifier

Ettus B200 sdr Module

USB/Fibre Converter

USB/Fibre Converter

Linux PC Running GNU Radio Software plus some additional modules

In Box on Roof

ITU Involvements

• World Radio Conference• Study Group 7 (Science Services)• Working Party 7C (Space Passive)• Working Party 7D (Radio Astronomy)• Task Group 1/5 (Compatibility Studies)• Task Group 1/7 (More Compatibility Studies)• Task Group 1/8 (Ultra Wideband Technologies)• Task Group 1/9 (Yet More Compatibility Studies)

Member of Canadian Delegation to:

Other Committee Involvements:• Inter-Union Committee for the Allocation of

Frequencies – IUCAF (International) - a creature of the International Council of Scientific Unions (ICSU)

• Committee on Radioastronomy Frequencies – CORF (A US National Committee under the NSF)

• CASCA Radio Astronomy Committee

At the ITU In Geneva

The international radio astronomy crew + a Russian

INTERFERENCE MONITORCosmic radio emissions are far weaker than almost all

manmade radio signals. Therefore we need the most sensitive radio technology to observe them, and we need a low-interference environment. Many radio devices in everyday use can severely interfere with our ability to observe the cosmos..

Receiver

Antenna

Interference Display Oscilloscope

Roll Up! TRY YOUR LUCK! Are you an interferer?GIVE IT A TRY!

If the display on the oscilloscope screen changes at all, the device you’re operating will degrade radio observations of cosmic radio waves, because the sensitivity of the radio telescopes to interference is more than a million times greater than the device in this demonstration.

We can’t imagine modern life without these gadgets, and many others that use radio technology. The only solution is to make sure the devices and the radio telescopes are as far apart as feasible.