IC-756Pro II Power Output vs. Frequency Test

Contributed by Paul R."Ray" Vasek W2EC

Figure 1: IC-756Pro2 RF Power Output vs. Frequency. Click to enlarge.
Figure 1: IC-756Pro2 RF Power Output vs. Frequency. Click for larger image.

The purpose of this test was to determine the transmitter RF output Poas a function of frequency in a MARS-modifiedIC-756Pro II.

The test was run with a Bird 43 power meter, using element types 250H (forPo > 100W) and 100H (for Po < 100W).There was a 2ft. 9913 jumper between the IC-756ProII and the Bird, and a 6ft. 9913 jumper between the Bird and a Heath 1Kw "Cantenna" dummy load. 

The measurements were take three times, from 1.6 thru 29.95 MHz, to verify that the power readings reported did indeed occur as shown in Figure 1. There were only a few variances between readings, and no variance was more than 1 watt. Where a variance did occur, the two closest out of of the three power readings were recorded for each frequency. Measurements were taken in CW mode, with the RF POWER control set at maximum.

Note by Adam VA7OJ: It will be observed that Po rolls off sharply in the  5.5 ~ 5.9 MHz and 7.5 ~ 7.9 MHz ranges. The purpose of the 5.5 ~ 5.9 MHz roll-off may be to ensure that the radiated harmonic energy does not exceed the limits specified in FCC Part 97.307(d) when transmitting at the top end of 160m. The reason for the 7.5 ~ 7.9 MHz roll-off is not clear.  The IC-756Pro also exhibits this problem; the IC-756Pro3, which was designed to operate on 60m, does not.
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Last updated: 09/25/2019

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