Yes, 2.4 GHz was very noisy. AMSAT Eagle was to use a 3.4 GHz high-speed (0.5-1 Mbps) BPSK downlink. BPSK was chosen for maximum efficiency in the PA. WiFi and WiMAX use complex modulation schemes that are optimized for terrestrial applications where the signal is diffused and scattered by nearby objects. This results in a PA DC to RF conversion efficiency of less than 20%.
73,
John KD6OZH
----- Original Message ----- From: "Mark L. Hammond" marklhammond@gmail.com To: "Trevor ." m5aka@yahoo.co.uk Cc: "amsat-bb" amsat-bb@amsat.org Sent: Friday, February 22, 2013 16:20 UTC Subject: [amsat-bb] Re: 2.4GHz broadband router on satellite?
Maybe Drew KO4MA will reply--but I thought he did some "global listening" on 2.4GHz with AO-51 (frequency agile receiver). Seems like he published some plots in The Journal?
Take home from what I recall--it was very noisy!
Mark N8MH
On Fri, Feb 22, 2013 at 10:49 AM, Trevor . m5aka@yahoo.co.uk wrote:
Apart from power budget issues and Doppler the real killer will be the very high noise level on 2.4 GHz.
In urban areas you can expected to receive strong WiFi signals across all of 2402-2450 almost regardless of where you beam.
Any signals from a satellite would need to be strong enough to overcome this interference. 5 GHz is likely to suffer a similar problem in a few years as more use is made of that band for WiFi etc.
73 Trevor M5AKA
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
-- Mark L. Hammond [N8MH] _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb