I once heard of a term called Gain Bandwidth Product where the greater the bandwidth - lower the gain. FM commercial broadcast uses extremely wide bandwidth to support 15 Khz audio and good s/n. Business once used +/- 15 kHz transmitter deviation to support 300 to 3000 Hz, then +/- 5 kHz, and now +/- 2.5 kHz.
I have had it explained that DSTAR has better s/n because of it's narrow bandwidth. My own observations in 460 mHz trunked radio, repeaters and systems, is there is not much noticeable difference in analog FM radios whether they are running 2.5 or 5 kHz transmitter deviation. Every one has told me that the s/n will be somewhat worse on 2.5 but I have not noticed it. This all considers the receiving station is intended to receive the bandwidth being transmitted. As far as the antenna goes - within reason bandwidth is not an issue - kinda like how bright is the light bulb in terms of power applied to the antenna - the bandwidth should not matter unless you get out of the design bandwidth of the antenna. Maybe some graduate engineering student has a thesis on this topic? Steve NU5D (tired old bench technician) Kris Kirby wrote: > I've been milling a few things over in my head and one thing that has > struck my mind and resonated is power versus modulation -- our 900MHz > repeaters typically use a +/-2.5KHz average deviation, which is smaller > than the VHF norm of +/-4.5KHz. At almost half the deviation, it would > seem that one would obverse an apparent increase in signal power of a > little less than three decibels. > > Here's where I'm getting confused: Does 50W RMS at 950MHz over +/-2.5KHz > deviation mean the wideband (+/-4.5KHz) rating would be 25W? Does the > antenna manufacturer even bother to take deviation into consideration > when factoring power specifications? How does this factor in terms of > power wasted as heat (in the unlikely case that I'll attempt to put too > much power into an insufficently-sized radiator)? > > -- > Kris Kirby, KE4AHR <[EMAIL PROTECTED]> > * WAR IS PEACE * FREEDOM IS SLAVERY * > * IGNORANCE IS STRENGTH * KETCHUP IS * > * A VEGETABLE * > > > > -- Ham Radio Spoken Here !!! NU5D EM11 http://www.qrz.com/callsign/NU5D Nickel Under 5 Dollars
