stacysound Posted October 2, 2014 Report Share Posted October 2, 2014 Hey Larry - How long is a wavelength for a block 21 system? In your white papers on Comparing Diversity Reception Techniques. "The Audio Switching design illustrated here follows the logic that if one antenna has a multipath problem, the other antenna is not likely to have a problem at the same time. This requires that the antennas be separated by at least a half wavelength of the operating frequency (preferably even more)." How would one figure that out? Looking forward to another outstanding lesson in RF... http://www.lectrosonics.com/Support/Wireless/comparing-diversity-reception-techniques.html Quote Link to comment Share on other sites More sharing options...
LarryF Posted October 2, 2014 Report Share Posted October 2, 2014 wavelength = velocity divided by frequency. The velocity of light (RF) is 186,000 miles per second (Stacy is in Texas) or within a few percent of a billion feet per second. So if you like doing things in your head the wavelength of a 1 GHz signal (1000 MHz) is very close to one foot. Then 300 MHz would be 3.3 times longer or 3.3 feet. Then 500 MHz is a frequency half of 1000 MHz or twice as long a wavelength or 2 feet. So just do 1000/MHz or 1000 divided by MHz. Just remember lower frequencies are longer as a reality check on doing inverses in your head. For our frequencies, a wavelength is always greater than a single foot. Remember this is a full wavelength. A half wavelength at 1000 MHz is a half foot. At 500 MHz it is one half of 1000/500 or one foot. For users not in the anti-metric USA, use 300 MHz as a 1 meter wavelength and go from there. Then 600 MHz is half a meter and so forth. All this is in vacuum or air. RF is slower in coax so wavelengths are about 60% to 80% of open air, i.e., 1 GHz is 0.7 feet long. Best Regards, Larry Fisher Lectrosonics Quote Link to comment Share on other sites More sharing options...
studiomprd Posted October 2, 2014 Report Share Posted October 2, 2014 another rough measurement is to figure 1/2 wavelength is twice the length of 2 x 1/4 wave whips. and Lectro also makes a handy guide for this: emblazoned on the elements of an SNA Quote Link to comment Share on other sites More sharing options...
bralleput Posted October 2, 2014 Report Share Posted October 2, 2014 Wow.I think I just want my SMV's to work,and not have to worry about the above (though interesting)! Quote Link to comment Share on other sites More sharing options...
studiomprd Posted October 2, 2014 Report Share Posted October 2, 2014 the diversity benefits are enhanced when antennae (sic) are more separated. Quote Link to comment Share on other sites More sharing options...
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