Silicon Investor (SI) -- The First Internet Community

STOCKTALK

We've detected that you're using an ad content blocking browser plug-in or feature. Ads provide a critical source of revenue to the continued operation of Silicon Investor. We ask that you disable ad blocking while on Silicon Investor in the best interests of our community. If you are not using an ad blocker but are still receiving this message, make sure your browser's tracking protection is set to the 'standard' level.

Microcap & Penny Stocks : Globalstar Telecommunications Limited GSAT -- Ignore unavailable to you. Want to Upgrade?

To: djane who wrote (2815)	2/7/1999 11:12:00 PM
From: djane	Read Replies (1) \| Respond to of 29987

Response to Jack Morgan technical questions about G/I (thanks to kaband on the IRIDF yahoo thread) Top:Business and Finance:Stocks:Services:Communications Services:IRIDF (Iridium World Comm. Ltd.) To Jack Morgan/djane-SI by: kaband 8090 of 8090 re: www4.techstocks.com a "techie" responds: You asked about bands - Iridium uses ~1621-1626.5MHz up/downlinks in a TDMA fashion - it has the biggest problem with radio astronomy because it downlinks on frequencies close to radio astronomy bands at about ~1610MHz. Globalstar downlinks are at 2400MHz so the satellites don't radiate down into radio astronomy sites. The only concern is with G* handsets getting too close to a site - this can be mitigated by control of geographic-frequency assignment. G* did/does still have an issue with Glonass (like GPS) use just below 1610MHz. G's out-of-band emissions are enough to potentially cause harm to aircraft landing under some pretty limited circumstances. This was a long-standing problem with FAA but there is a plan to gradually phase in tighter radio emission controls to solve it. As far as 2400MHz being a trash band - it is globally allocated for MSS but is adjacent to a widely used ISM band - where microwave ovens, etc. operate. As long as your oven is not leaking (cooking you), it is probably OK but there is increasing use of the band for unlicensed datacom devices - this may be more of an interference source eventually. Finally - link margin. Way overrated as Iridium's 16dB link margin is for clear-sky directly overhead. Most of Iridium (and G) time is with satellites at low elevation angles. This results in blockage (beyond margin) and multipath. Worst part about multipath is that margin does you no good - performance is set by signal-to-interference ratio, not signal-to-noise. Globalstar's CDMA waveform helps with this, as multipath is more easily rejected (and can be processed by the groundstation, unlike Iridium). But don't believe G* early claims that they will do diversity combining - I believe that it is only diversity selection and does not buy as much as combining does in terrestrial cellular (G* is limited by some geometry problems dealing with combining multiple gateways). Best solution - high elevation angles (either tons of satellites or higher orbits like MEO) Feel free to forward post to SI. Posted: Feb 7 1999 7:46PM EST as a reply to: Msg 1 by YahooFinance