In the recent past the squelch appears to have been set fairly high. As
witnessed by the repeated signals being essentially noise free.
It is now much easier to track the correct uplink on 2m as the doppler shift
is small compared to the 12.5kHz or so (a guess) bandwidth of the ISS
receivers IF filter.
Unfortunately, I believe the D800 is unable to operate with the squelch open
due to overheating problems. Not that anyone is complaining, this ARISS
operation is great!
But the D800 is not a purpose built satellite repeater. Given a choice, a
SO50 type approach would give easier access for operators while saving power /
heating and RF pollution. A CTCSS detector that initiated a timer, or perhaps
a system that simply allowed the repeater to stay open for 10 or 15 seconds
after loss of the tone would allow people to 'net' onto the correct uplink
frequency, or hear when their signal had a fade or collision with another
I suppose the ARISS equipment will be upgraded at some point in the future
and maybe some dedicated hardware with simple to operate controls for the crew
(and remote commanding from the ground) will overcome these minor problems
with an otherwise very successful system.
Still, 5 Watts downlink is quite amazing and unlike any conventional
satellite we have. Where's my 2m amp......
In a message dated 06/01/2009 10:07:23 GMT Standard Time, rogerkola(a)aol.com
An interesting thought...could they have the squelch engaged while also
requiring tone? I personally haven't been able to get in on 80 degree passes
over New England with 25 watts and an omni at 5:30 AM local time.
Reception is just fine, but there are a lot of "empty" spaces in between
contacts that could be collisions I guess...