Bouncing Off The Moon

Bdale Garbee

Open Source & Linux CTO

Hewlett-Packard

Direct Reception of Signals from Mars

G3WDG successfully receiving signals from Mars...

Mars Odyssey and Mars Express both heard directly

3m dish, 0.8dB noise figure, 84k system noise temperature

Mars Odyssey, and... Mars Express...

A bit about Ham Radio in general

A gentle introduction to EME

Towards a 100% Open Source EME station

Lots of pictures of progress to date

Yes, this is largely a “Bdale, tell us a story!” talk...

Agenda

Ham Radio

A technical and communications hobby

Licensed radio operators (l33t c4lls1gns!)

Ham Radio

Best known perhaps for use of the "shortwave" bands for international contacts, and continued use of the Morse telegraphy code

Public Service and Technical sub-communities

History of weak signal RF innovation /discovery

ionospheric structure

various scattering modes

radio astronomy

Many facets to the hobby

EME

EME stands for “Earth-Moon-Earth”

Also known as “Moon Bounce”

The basic idea is that you communicate with other people on Earth by bouncing radio signals off the moon.

Why do this? Because it's hard!

Nearly ½ million miles round trip, varies due to elliptical orbit

The moon isn't really very reflective, on the order of 7%

Polarization loss, variations in background “sky noise”

Round trip path loss from 243dB@50Mhz to 289dB@10Ghz

One of the “ultimate challenges” in the hobby...

Path Loss

Source: W3IWI

April 16, 2005 - Announcement of the first QSOs via the moon on 47 GHz.

The team of RW3BP, AD6FP, W5LUA, and VE4MA would like to announce that the first 47 GHz contacts via the moon

have been completed. As you may recall, RW3BP heard the first lunar echoes on 47 GHz back in August of 2004. At

that time he was heard by AD6FP, W5LUA, VE4MA and VE7CLD. Since the receipt of the first 47 GHz echoes via the

moon, numerous tests between RW3BP and AD6FP led to improvements by RW3BP allowing him to copy calls from

the lower power signal of AD6FP in January of 2005.

As of April 16, 2005 the team of AD6FP, W5LUA and VE4MA have each completed a CW QSO via the moon with RW3BP.

The station at RW3BP consists of a 2.4M offset fed dish and 100 plus watts while the station at AD6FP consists of a

1.8M offset fed dish and 30 watts. At W5LUA and VE4MA 2.4M offset fed dishes and 30 watt TWTs were used. Noise

figures of all stations are in the 3.5 to 4.7 dB range.

Since the doppler shift can be as much as 100 + kHz at 47 GHz, one must continuously adjust the receive frequency to

keep the station centered in the passband. Precision frequency control was obtained by using GPS controlled, Rubidium locked, or TV sync controlled phase locked local oscillators. Various techniques were in use to keep the Doppler shifted frequency in the passband of the receivers.

Submitted by RW3BP, AD6FP, W5LUA and VE4MA

First 47 Ghz EME Contacts Last Week!

Why Start at 1296Mhz?

Lowest frequency where circular polarization is the norm

Lowest frequency where a “modest” dish antenna has adequate gain

I already have terrestrial experience on this band, and own some radio gear for 23cm

Kenwood TS-790A with optional band module

80-watt solid state amplifier

low-noise preamp

Enough active stations to make contacts most any day

My older HP network analyzer tops out at 1300 Mhz...

Making Contacts

Modes

Traditionally, EME contacts have mostly used CW

Many experiments with DSP

Joe Taylor, K1JT, applied state of the art digital techniques

Schedules

Many contacts are “scheduled”

Other contacts are “random”, particularly during contests

Format

Operators take turns transmitting and listening according to an agreed-upon contact structure

Audio Clips

A very strong 23cm CW signal from K2UYH

Most stations work with substantially weaker signals...

A sideband (voice!) signal from KB2AH

If you've got a big enough dish, enough power, and good conditions...

Hardware Required

Antenna system (dish and feed)

Antenna pointing system (az / el mount)

Motion control system

Transceiver

Low noise preamp at feed

Transmit power amplifier

High-quality RF feedlines

Software

If you're willing to run Windows, there are a number of excellent programs available.

Nova for Windows

Orbit prediction and success estimation, popular for CW

F1EHN

dish pointing

scheduling

self-survey and receive characterization

WSJT

implements JT65b, a highly optimized digital mode for EME

“echo” mode for system characterization

Linux Software

If you want 100% Open Source, things get tougher!

Dish pointing

lots of pieces, but nothing satisfying, so I'm writing “azeld”

Since CW doesn't excite me...

WSJT internals and core code released!

“Source code is available to illustrate details of exactly how a JT65 message is encoded. Written mostly in Fortran 77, but with a few routines in C, the code can be compiled under Linux to produce a command-line program that will encode any JT65 message into channel symbols, ready for transmission by 64-ary FSK .”

Implementing JT65b with GNU radio using a USRP is my goal!

Linrad, SDR-1000, etc exist and are interesting alternatives

Scheduling and logging

EME Station KB0G... Eventually...

USRP Block Diagram

USRP

What's Next

Complete installation of position indicators and finish work on azeld

Finish fabricating feed and feed mount

Temporarily use TS-790A, 80 watt amp, and Windows PC to start testing JT65b, and perhaps make first contact

Complete and install 500 watt amplifier

Build JT65b implementation on GNU radio and USRP

Design and build a 6-meter-diameter antenna based on an Axially-Displaced Ellipse?

Resources

http://www.gag.com/~bdale/rf/

http://www.nlsa.com/nets/moon-net-help.html

http://pulsar.princeton.edu/~joe/K1JT/

http://www.ettus.com/

http://www.gnu.org/software/gnuradio/

http://www.cpdee.ufmg.br/~fernando/index_e.html

Questions?

Linux is very popular at the edge of the network – web server, file/print server, mail server, firewall, etc.

As Linux has matured, it has gone beyond the network edge and is continuing to make inroads deeper into the data center:

ISVs are standarding their development on Linux

More customers are considering line of business apps on Linux

Linux is going beyond the 1-2 cpu deployments. The 2.6 kernel offers opportunities for greater scalability.

2005-03-09T00:57:06