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The Ilmari-2007 is the first flight (series) of a balloon borne radio amateur payload project, which started back in 2003. This is one of longer series of Ilmari-balloons that have only this name in common.

Lento / Flight

Ilmari-2007a 2007-08-11 07:00 UTC

More on separate Ilmari-2007a page.

Ilmari-2007b 2007-09-02 06:00 UTC ?

A flight in planning: more on page Ilmari-2007b (finnish only) On 2007-09-02 at 06:00 UTC, or soon after that..

It didn't happen, next flight not in planning.

Operation instructions

How to properly work via Ilmari-2007 ?

Ilmari-2007 can be worked with any SSB/CW radio combination you have handy for 144 MHz and 437 MHz. The uplink band, the band you must transmit in, is 144 MHz and the downlink band, the band you receive in, is 437 MHz. One thing you must take into account is that the transponder is inverting. This means that if you tune your transmit frequency upwards, your downlink receive frequency will go downwards. Also, your sideband will be inverted, i.e. your default SSB uplink mode (should be LSB on 144 MHz) will be returned to you by the Ilmari transponder as a 70 cm band USB signal. This is because it is designed as a low orbit satellite (high Doppler shift) transponder allowing some cancellation of Doppler.

In theory following settings on a rig with "satellite mode" will set you right:

  • SAT-mode, TRK-REV
  • Tx frequency: 144.305, SSB LSB
  • Rx frequency: 437.386, SSB USB
f(Tx) = 581.691 - f(Rx)

In practice the transponder oscillators have fairly severe temperature dependency and the frequency may change as much as 5 kHz!

When working Ilmari-2007, you should always first locate the transponder downlink before transmitting. If the balloon is above the radio horizon for you observation point, you should have no problem whatsoever copying the downlink CW beacon that is close to the ‘passband’, the approximately 38 kHz band that is fully usable by SSB/CW and compatible modes.

You should then note the peak level of the beacon on your receiver S meter. After this, select a spot free of traffic in the passband (you might be able to hear the passband noise in your receiver too) and tune your transmitter to the corresponding uplink frequency calculated from the frequency plan.

Strong recommendation is that you use single dipole or a GP antenna for transmit with minimal amount of power that your VHF transmitted can do, and use Yagis only for receivers on 70cm UHF band!
People have surprising amount of difficulties to produce QRP powers, and this does need such!

Starting with very low power to start with (absolutely no linear amplifiers allowed here !), you can try transmitting a steady carrier like CW and tuning your receiver around a few kilohertz. You should have absolutely no problem hearing your downlink after you have found the correct frequency. Set your transmit power so that your downlink signal is one (1) S unit, i.e. approx. 6 dB below the observed beacon peak level. This is very important so as to avoid causing distortion to everybody else on the transponder.

Please remember that this transponder is very sensitive indeed and the output power is quite sufficient to be copied whenever the transponder is above your horizon. This transponder has been designed to specifications of a low earth orbit satellite !

Yagis are not recommended for transmit antenna, consider using single dipole! (or magnetic car rooftop whip) Place it on wrong side of your house if you still use too much transmit power and have already minimized outgoing power! If you have to use Yagis, at least point them enough offset to reduce 144 MHz gain towards Ilmari-2007.

If you use too much power, the command team will at first try to tell you to reduce the power, or if that does not help, they may have to turn off the transponder for some moments.

And a final note: FM is absolutely forbidden on the Ilmari-2007 2m/70cm transponder. (This is linear transponder and the pass-band is only 40 kHz wide!)

For non-licenced enthusiasts, Ilmari-2007 offers many interesting signals for licence-free reception, like the transponder traffic itself, the 1.3 GHz amateur FM television transmission (you can use a regular TV satellite receiver and preamp with suitable aerial for reception), 70 cm packet telemetry for observing onboard flight data and GPS location information with the same data available in CW over the 70 cm and 80 m beacons.

Michael Fletcher, OH2AUE & OH2FM
Ilmari-2007 Payload Manager
AMSAT-OH Chairman


  1. Linear Transponder: (f(up)+f(down) = 581.691 MHz)
    1. Rx/Uplink: 144.305-144.345 MHz (LSB, CW) 40 kHz
    2. Tx/Downlink: 437.346-437.386 MHz (USB, CW)
  2. Beacon: 3579.5 kHz CW
  3. Beacon: 437.725 MHz CW
  4. Beacon: 437.850 MHz FM APRS (or AX.25 packet)
  5. Beacon: 1282 MHz FM-ATV
    1. ATV Subcarriers: 6.0 MHz, 6.5 MHz, no pre-emphasis
  6. Flight ops announcements: 3690 kHz LSB ± QRM (±USB)

APRS callsign


However as altitude data is broken in that packet, a virtual balloon OH2SIX-12 flies with fixes altitude data.

APRS-AzEl "gunnery-calculator"

This UNIX-tool calculates target azimuth and elevation which enables directing your own antenna to for example for the ATV-signal reception. (You might be able to run this on windows, it is written in Perl.)

This tool attaches itself into APRS-IS -network, meaning that user must have live internet connection or then have private internal APRS-IS instance which is fed ARPS packets from locally attached radio.

This tool was made to calculate directions for a 4m fully steerable antenna to be used to downlink balloon's 1.3 GHz FM ATV signal.

Downloadable at: