ISS cross-band repeater
(doppler).
Many stations do not correct their fequency with the
doppler
effect that's the reason you hear often much QRM.
If you do not correct your doppler please STOP operating
on the ISS cross-band repeater!!!
The ISS is traveling with an speed of 7km per second.
When the ISS is comming to you the RF signals (from
the ISS) will be pushed (it means the ISS freq. will be increase).
When the ISS is leaveing, the ISS RF signals will be pulled it
means the ISS frequency will be decrease, this is
what we call doppler effect.
A good example of doppler effect is a raceing motor-cycle.
When it comes to you (with high speed) the sound is high, and when it is
leaving the sound is low.
Example: 10 Minutes (high elevation pass).
435.791TX--------------435.800TX-----------435.809TX
ISS-> -------->---->----QTH--->---->---->--ISS->
145.803RX-------------145.800RX------------145.797RX
You can see the
doppler effect is 3 times more on 70cm in -
comparing with the 2 meter band!!!!
Example: 5 Minutes (low elevation pass).
If you compare the 5 minutes
pass to the 10 minutes pass
you will see that the 5 minutes pass requeres less frequency
correction.
When there is a short 1 minute (low elevation) pass, I do not
change the frequencies!
Do you have a transceiver (ts-790, ts-2000, ft-847...) with -
a MAIN and SUB frequency display?
You can display 437Mhz on the MAIN-display, and
145Mhz on the SUB-display.
Turn the audio off at the MAIN unit, and turn it on at the
SUB unit (do not use the squelch!).
Use a headphone so you can concentrate much better at
weak signals in the noise.
During the ISS pass you have to jump a few times to your SUB
display to correct 145Mhz receiving frequency.
When your transceiver can not make 1 Khz steps on the FM mode,
you can select the 5 Khz steps (DO NOT USE 10 or 12,5Khz steps!!!).
For some simple transceivers it is better to program some
doppler frequencies in the memorie channels.
When you have two single band transceiver one for 2m. and
one for 70cm it is easy to tune each transceiver separate!
Always operate full duplex so you can listen direct on
the ISS downlink frequency (even when you are TX'ing!).
Keep tunning your TX-VFO button (watch at your tracking software).
If you have a tranceiver with CAT interface it is possible
to correct the doppler automaticly with your computer (-:
Nice freeware software is hamradio de luxe:
http://www.hb9drv.ch/
Even when you do not have a computer controlled rig it
is recommed to take a look at Hamradio De Luxe so you can
learn the doppler behaviour!
ISS APRS/PACKET (doppler correction).
10 minutes high elevation pass.
145.987TX--------------145.990TX-----------145.993TX
ISS-> -------->---->----QTH--->---->---->--ISS->
145.803RX-------------145.800RX------------145.797RX
For transceivers with 5khz steps:
145.985TX--------------145.990TX-----------145.995TX
ISS-> -------->---->----QTH--->---->---->--ISS->
145.805RX-------------145.800RX------------145.795RX
For a few minutes pass (low elevation) it requeres less frequency -
correction in comparing with a long (high elevation) pass.
ISS CREW chat (doppler correction).
10 minutes high elevation pass.
Always be prepared for a CQ call from the ISS crew!!!
The crew are eating at 12:00UTC and when they are warming
up their food it is possible that they come in voice, their hamradio
transceiver is in the same room!
Remember in the weekends the crew have more spare time.
It is wise to program some frequencies in your memorie channels.
Region 1 = Europe * Middle East * Africa * North-Asia
145.197TX--------------145.200TX-----------145.203TX
ISS-> -------->---->----QTH--->---->---->--ISS->
145.803RX-------------145.800RX------------145.797RX
For transceivers with 5khz steps:
145.195TX--------------145.200TX-----------145.205TX
ISS-> -------->---->----QTH--->---->---->--ISS->
145.805RX-------------145.800RX------------145.795RX
Region 2 = North and South America * Caribbean * Greenland
Region 3 = South Asia * Australia * New Zealand * Oceania
145.487TX--------------144.490TX-----------144.493TX
ISS-> -------->---->----QTH--->---->---->--ISS->
145.803RX-------------145.800RX------------145.797RX
For transceivers with 5khz steps:
145.485TX--------------145.490TX-----------145.495TX
ISS-> -------->---->----QTH--->---->---->--ISS->
145.803RX-------------145.800RX------------145.797RX
For a few minutes pass (low elevation) it requeres less frequency -
correction in comparing with a long (high elevation) pass.
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