Simon,
I spent 20 years building data circuits using geosynchronous satellites. During that time, my definition of round trip was uplink-dowlink-uplink-downlink or 4 x 150ms (plus or minus a small amount of Doppler).
Yes - you're correct - the loopback delay is 300ms. But if you communicate with another person on Earth, the round trip delay is 600ms.
If you tell someone a joke, you won't hear the laugh until after a 600ms delay. This is only true for a good joke. Tell a bad joke and the delay will be infinite. :O
73 - Paul - W2HRO
On Fri, Feb 8, 2019, 16:09 Simon Brown simon@sdr-radio.com wrote:
Paul,
Unless there's significant latency inside the satellite, I think you're out by a factor of two. Round trip is 2 x 40,000 km (*) = 80,000 km total. Speed of light and radio latency says we're looking at closer to 300 ms.
(*) depending on where you are on the mother planet.
Simon Brown, G4ELI www.sdr-radio.com
-----Original Message----- From: AMSAT-BB amsat-bb-bounces@amsat.org On Behalf Of Paul Andrews Sent: 08 February 2019 19:27 To: Les Rayburn les@highnoonfilm.com Cc: AMSAT BB amsat-bb@amsat.org Subject: Re: [amsat-bb] Geostationary & HEO Satellites
GEOSATs have another interesting characteristic. 600 ms round trip delay due to the longer distance.
Does anyone remember when MCI first started providing a discounted long distance telephone service?
This will make voice QSOs a little unnatural but certainly not impossible.
73 - Paul - W2HRO
On Fri, Feb 8, 2019 at 12:21 PM Les Rayburn les@highnoonfilm.com wrote:
I’m also a newcomer to the birds, but very excited about it. Likewise, I
responded to the survey, but wanted to comment further regarding geostationary and HEO satellites.
In the camp of “Both, please.” The HEO birds would once again offer the
possibility of DXCC and make WAS more realistic—it also offers more operating challenges.
But a geostationary amateur satellite would have many interesting
benefits:
Provide an easier introduction to satellite operation, and attract new
operators.
Excellent tool for emergency communications during a natural disaster. Opportunity to experiment with microwave operations. The ability to enjoy satellite operation any time of the day/night. The
band is always open.
I’m grateful for anyone who incorporates amateur radio into their
satellites, but feel that birds should include either linear, digital, or FM transponders whenever possible. Designers are asking a lot of hams when they solicit our monitoring their telemetry signals, and using amateur spectrum for their purposes without much tangible benefit to us. My opinion only.
It’s wonderful that they asked us. Dialogue is the key to most human
accomplishment.
73,
Les Rayburn, N1LF Maylene, AL EM63nf AMSAT #38965, ARRL Life Member, CVHS Life Member, SVHF Member
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Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb