Menu

The "Radio Crazy" Well-earned demise of AM IBOC.

Search this Thread

#1

Report Post

Old

July 16th 04, 07:45 AM

Robert Orban

Posts: n/a

Default

In article , says...

In article ,
Mark Roberts wrote:

On a synchronous detector, it sounds worse...like a mosquito buzzing
in the background.

That's because it's in quadrature, which is "invisible" (modulo
transmission artifacts and channel noise) to envelope detectors. Your
sync. detector is only detecting one sideband at a time, so the IBOC
carriers don't cancel out.

You have this exactly wrong. Envelope detectors are not sensitive to
the phase of the carrier, responding instead to the square root of the sum
of the squares of the I and Q components of the modulation:

SQRT(I^2 + Q^2)

(The carrier must be present in order to properly bias the envelope
detector, but, upon demodulation, the carrier simply appears as a DC term.)

A synchronous detector will detect either the I channel or the Q channel (or
some linear sum of the two) depending on the phase of the regenerated
carrier. It can be configured to reject the Q channel entirely by ensuring
that the regenerated carrier is precisely in-phase with the original
carrier.

To detect single sideband, you need two synchronous detectors whose carrier
inputs are in quadrature and whose IF inputs are also in quadrature. A
single synchronous detector will _not_ detect single-sideband.

See any textbook on modulation theory.

Reply With Quote

Reply With Quote

Thread Tools	Search this Thread
Show Printable Version	Search this Thread: Advanced Search
Display Modes
Switch to Linear Mode Hybrid Mode Switch to Threaded Mode

Posting Rules
Smilies are On [IMG] code is On HTML code is Off Trackbacks are On Pingbacks are On Refbacks are On

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Amateur Radio Newslineâ„¢ Report 1412 Â September 3, 2004	Radionews	General	0	September 4th 04 09:35 PM
Amateur Radio Newslineâ„¢ Report 1402 Â June 25, 2004	Radionews	Policy	1	June 26th 04 03:07 AM
Amateur Radio Newsline(tm) Report 1394 - April 30, 2004	Radionews	Broadcasting	0	May 1st 04 12:41 AM
Amateur Radio Newslineâ„¢ Report 1379 â€“ January 16, 2004	Radionews	General	0	January 18th 04 10:34 PM
Amateur Radio NewslineÃ¢â€žÂ¢ Report 1379 Ã¢â‚¬â€œ January 16, 2004	Radionews	Dx	0	January 18th 04 10:34 PM

All times are GMT +1. The time now is 10:03 PM.

About Us

"It's about Radio"

Contact Us RadioBanter forum home Privacy Statement

Copyright © 2017