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AO-7 SATELLITE USING PAGE




                                  

Useage Guidelines

AO-7 is a tough old bird, but it does have some weaknesses. Those of us who use her respect those weaknesses, and in many ways we feel a special communial bond, much like Leopold's quote. It is important for all who use AO-7 to realize that the greatest risk to successful operation is using excessive power.

Here are some general guidelines that should help you make the most of AO-7:

  • Use efficient antennas with receiver pre-amps. You should be able to hear very weak signals without needing a lot of power. This isn't UO-14 and power will not be an advantage - in fact it will be a disadvantage.
  • Keep your power low. Generally you can work AO-7 on 5 watts or less. You may need to increase power if it is at a distance, but be sure to reduce power as the satellite approaches.
  • Keep your power low, especially in Mode B.  Currently AO-7's mode B uplink is in the middle of the 70cm weak signal band. Excessive power may interfere with other services in that band, and may be considered a spurious out of band emission.
  • Listen for FM from AO-7's transmitter. If you hear your signal FM, you are putting too much power into the bird. Reduce power and the situation should correct itself.
  • Keep to the middle of the passband. The strongest signals are in the middle of the passband and you will need less power to hear your downlink.
  • Adjust for Doppler. We've provided some tips on Doppler to help make things easier. If you adjust your transmitter frequency for a clear reception, others will hear you as well.
  • Use voice if possible. voice strains the power system on AO-7 the least. If you are using CW, be extra vigiliant about the amount of power you are using.

Frequency and Mode Information

Mode-A: Mode-B:
  Type: 2m to 10m non-inverting translator Type: 70 cm to 2m inverting translator
Uplink: 145.850 to 145.950 MHz CW/USB Uplink: 432-125 to 432-175MHz CW/LSB
Downlink: 29.40 to 29.50 mHz CW/USB Downlink: 145.975 to 145.925 MHz CW/USB
Beacon: 29.502 Mhz CW Telemetry Beacon: 145.9775 MHz CW Telemetry
TX: 1W TX: 8W
 
Additional Beacons:
70cm: 435.1, 850hz FSK TTY
17cm 2304.1 - Disabled
 
Additional Modes
Mode C: Low Power (2W) version of Mode B
Mode D: Recharge Mode. Only the 435MHz Beacon is turned on

Doppler

Dealing with Doppler is always an issue, however since AO-7 is higher in altitude than other satellites it is a bit more manageable.

The procedure for dealing with Doppler seems to be a gentleman's agreement. While full doppler tuning is generally the preferred method of dealing with doppler it is very possible to have successful QSOs while manually tuning your transceiver.

The steps to successful operation that I've observed are:

  1. Tune your transmitter frequency away from other signals. This means tuning to 432.160 MHz or 145.840 MHz depending on mode.
  2. Tune your receiver to match the offsets. This means roughly 145.440 MHz or 29.440 MHz.
  3. Transmit a short burst of cw while tuning your receiver. This will allow you to find your uplink offset. Make note of this offset.
  4. Tune your receiver on to another parties transmit signal and tune your transmitter so it matches the offset you noted in step 3.
  5. Listen. When there is a break, transmit your callsign while you are adjusting your transmitter. It helps to say something like "MYCALL - Adjusting, adjusting, adjusting... OK - This is MYCALL on frequency".
  6. Repeat step 5 adjustments each time you transmit though the adjustments should be small unless you haven't transmitted for a while.
  7. Remember, Mode B is inverting - so when making these fine adjustments you will tune your transmitter up to compensate for Doppler, not down like you would for Mode A, which is a non-inverting translator.


 
ALL INFORMATIONS ARE FROM AO-7 AMSAT WEBSITE

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