Hi Chong,
I am not exactly sure what the equipment is being used for? Is this a receive amplifier or for transmitters? How much power output do you get with just one signal applied to the amplifier? Will it produce +22dBm with one signal if the input level is increased? What is the gain of the amplifier? How many dB? Are you sure that the amplifier has capability to actually produce +22dBm of signal or is it speced at +22dBm 3rd order intercept point at 1 dB compression? If that is the case you will never see +22dBm out of it as the 3rd order intercept spec is only a theoretical projection point. You mentioned in an earlier post that you had "3 amplifiers in series". Is that still the case? What is the gain of each amplifier by itself? What is the power output capability of each amplifier? Are these receiver preamplifiers? 73 Gary K4FMX _____ From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Kent Chong Sent: Friday, January 11, 2008 3:55 AM To: [email protected] Subject: Re: [Repeater-Builder] Re: Amplifier 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@ <mailto:Repeater-Builder%40yahoogroups.com> 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." _____
