I recently performed several IP3 and dynamic-range measurements on the IC-756Pro III. Here are the final results:
14 MHz, CW, 500 Hz filter selected, Preamp off, AGC off
|Close-in crystal oscillator frequencies kHz|
|Test Setup 1||Test Setup 2|
|f1 = 14205.67||f1 = 14252.11|
|f2 = 14209.52||f2 = 14256.52|
|Test offset inside 15 kHz roofing filter ( f2 - f1) kHz|
|IMD3 Product Frequencies kHz|
|2f2 - f1 = 14213.37||2f2 - f1 = 14260.93|
|2f1 - f2 = 14201.82||2f1 - f2 = 14247.70|
|IMD3 Bandwidth kHz|
|Test band centre kHz|
|Wide-spaced crystal oscillator frequencies kHz|
|f1 = 14209.52, f2 = 14256.52|
|Test offset ( f2 - f1) kHz|
The 2 crystal oscillators, each with -50 dBm signal power output, were first checked on the selective voltmeter, then connected to the IC-756Pro III input via the combiner. The combiner insertion loss is included in the stated test signal levels. For close-spaced IMD measurement, test signal power = (source output - combiner insertion loss). Example: If source output = -50 dBm per tone and combiner loss = 3 dB, test signal power = (-50-3) = -53 dbm per tone, or -47 dBm 2-signal (composite).
The AC voltmeter was connected to the PHONES jack to measure the 3 dB rise in noise floor due to IMD.
MDS = -131 dBm ( noise + 3dB); thus, noise floor is -134 dBm.
IMD3 Dynamic Range is the difference between MDS and the power level of either of 2 equal test signals applied to the receiver input which yields IMD3 products 3 dB above the noise floor.
2f1 - f2: Power level of either of 2 equal test signals to raise IMD products 3dB over the noise = -24 dBm
IP3 = + 29.5 dBm
IMD3 Dynamic Range = 107 dB
2f2 - f1: Power level of either of 2 equal test signals to raise IMD products 3dB over the noise = -22 dBm
IP3 = +32.5 dBm
IMD3 Dynamic Range = 109 dB
2f1 - f2: Power level of either of 2 equal test signals to raise IMD products 3dB over the noise = - 53 dBm
IP3 = -15.5 dBm
IMD3 Dynamic Range = 78 dB
2f2 - f1: Power level of either of 2 equal test signals to raise IMD products 3dB over the noise = -50 dBm
IP3 = - 9.5 dBm
IMD3 Dynamic Range= 81 dB
I calculated IMD3 Dynamic Range using -131 dBm MDS as the lower reference.
Contents copyright © 2005 P. Odone I1ODP.
Page created & edited by A. Farson VA7OJ/AB4OJ. Last updated: 09/25/2019