Dear Gary, Thanks for the calculations. As we are using a +22dBm amplifier, the output per channel shall work out as -2dBm (+22dBm - 24dB, and +22dBm is 1dB compression point). However, the measurement shows that it is -24dBm per channel. Anything we have missed out?
Best Regards, Chong Kwan Meng ----- Original Message ---- From: Gary Schafer <[EMAIL PROTECTED]> To: [email protected] Sent: Friday, 11 January 2008 2:28:09 Subject: RE: [Repeater-Builder] Re: Amplifier If you want each signal, of the 16 signals, to be 0 dBm (1 mW) output capable then the amplifier has to be capable of 16 squared times 1 mW or 256 milliwatts. This is the peak envelope power that can be present at any one time in the amplifier with 16 signals present. So the amplifier would need to be able to handle a little over +24dBm with a single signal (256mW) With only 2 signals of 1 mW each the peak envelope power would be 2 squared (2x2) or 4 mW that the amplifier would need to handle or +6dBm. It is the number of signals squared times the power of one of the signals assuming that all the signal levels are the same. This is exactly the same thing as if it was an SSB linear amplifier and you were testing it with multiple tones. 73 Gary K4FMX From: Repeater-Builder@ yahoogroups. com [mailto:Repeater- [EMAIL PROTECTED] ups.com] On Behalf Of Kent Chong Sent: Thursday, January 10, 2008 8:46 PM To: Repeater-Builder@ yahoogroups. com Subject: Re: [Repeater-Builder] Re: Amplifier Dear NJ902, Thanks for your advise. In this case, what is the amplifier power rating for us to obtain 0dBm output power for 16 channels? Best Regards, Chong Kwan Meng ----- Original Message ---- From: nj902 <[EMAIL PROTECTED] net> To: Repeater-Builder@ yahoogroups. com Sent: Friday, 11 January 2008 12:23:19 Subject: [Repeater-Builder] Re: Amplifier It appears that your amplifier is doing what you should expect. An amplifier's power handling capability, compression point, etc. are rated based on amplification of a single sinusoid. When multiple signals are present at the amplifier input, the total output power of the amplifier does not change, hence the power available per channel decreases as the number of input signals increases. Also, since multiple independent signals will combine randomly, crest factor issues further decrease the available power per channel in order to keep the amplifier output below clipping. This is a common issue in the design of signal enhancement products such as BDA's used to provide coverage extension for trunking and cellular radio systems. ------------ --------- --------- --------- --------- --------- - --- In Repeater-Builder@ yahoogroups. com, Kent Chong <kentchongkm@ ...> wrote: "All three amplifiers are connected in series. I shall correct my statement: in the lab, we get 0dBm output on the last stage of amplifier. However, when we are at the site, it max at -24dBm (it is - ve, sorry). There is no difference in the configuration but number of channel." Tired of visiting multiple sites for showtimes? Yahoo! Movies is all you need ______________________________________________________________________ Search, browse and book your hotels and flights through Yahoo! Travel. http://sg.travel.yahoo.com
