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Technology Stocks : Teligent -- Ignore unavailable to you. Want to Upgrade?

To: jtel who wrote (79)	3/8/1998 8:12:00 PM
From: Bernard Levy	Read Replies (1) \| Respond to of 270

Dear jtel: Some time back, I posted a message on the CVUS thread which compared the bandwidths available to TGNT at 24GHz, LMDS bidders at 28GHz, and WCII at 38GHz. The starting point is that all these frequencies are impacted in a similar manner by rain fade and LOS requirements. For LOS transmission, the received power varies like the inverse squared frequency. This means that since 38GHz is roughly 1.5 times 24GHz. the received power is smaller by a factor (1.5)^2 at 38GHz. In dB's, this amounts to about 3.5dB. The smaller power is compensated by the use of a higher bandwidth. On the CVUS thread, I did a rough computation based on FM modulation. For a more typical digital QPSK modulation scheme, the main way of overcoming a smaller signal to noise ratio is to employ forward error correction. For a code at rate 3/4 (one out of 4 bits is redundant) a coding gain of almost 4 dBs can be easily achieved. My guess is therefore that you need about 25% more bandwidth (4/3 would be 33%) at 38Ghz to achieve the same bit probability of error for equal transmitted power. In other words, 80Mhz at 24GHz = 100MHz at 38GHz. The argument that TGNT needed 400MHz at 24GHz to compensate its 100MHz at 18GHz is totally bogus. This is a smokescreen used to hide some very shady manipulations by the FCC which may have been related to contributions to Clinton's reelection campaign. Both WCII and current LMDS bidders have good reasons to be suspicious of the way TGNT received its spectrum. I hope that Senator McCain will be successful in finding out what happened. Best wishes for your TGNT investment, but keep an eye on Congressional scrutiny of the FCC. Bernard Levy