Contact author.	Contact author:
George Tuck - G4RNI

Many people have complained that the IC-7100’s SSB output on HF is abysmally low. I decided to investigate further.

Note: I accept NO RESPONSIBILITY for the outcome, should you decide to go ahead with this. YOU DO SO AT YOUR OWN RISK.

A WORD OF ADVICE: DESPITE WHAT SOME WILL TELL YOU, DO NOT INCREASE THE TRANSMITTER POWER SETTINGS OF THE IC-7100.

Whilst I would agree that the output transistors are run well below specifications, with a huge safety margin, the issue is NOT that PEP can’t be achieved. More that the transmitter severly limits the  average output available.

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Looking at the IC-7100 service manual, in order to set the TX gain it says to set up the test equipment as follows:

Connect the AG and millivoltmeter to

[MIC], and then set it as;

Frequency: 1.5 kHz

Level: 30 mV RMS

Connect a power meter to [ANT1].

Looking at the service manual for the IC-7410 it gives the following instructions:

 Connect an AG and millivoltmeter

to [MIC], and then set it as;

Frequency: 1.5 kHz

Level: 1 mV

Connect a power meter to [ANT1].
Both manuals then continue with instructions to adjust the output from the transmitter to give 50 watts PEP.

I also noted that the IC-9100 and the IC-7600 both suggest mic levels of 1mV and to adjust the TX output for 50 Watts.

As Icom mics are interchangeable and therefore have similar outputs, there is surely an anomaly here? The IC-7100 requires 30mV of mic to develop 50 Watts whereas the IC-7410 requires only 1mV. Note that the IC-7100 specifies RMS whereas the IC-7410 does not.

I decided to “suck it and see”.

Instead of applying 30mV to the IC-7100 and adjusting for 50 watts RF out, I applied just 10mV. The difference was immediately obvious. I had a much louder SSB signal but NO(!) I wasn’t peaking over 100 Watts.

Further examination of the waveform on my spectrum analyser showed no flat topping, no nasty spurrii, no harmonics that weren’t there before “tweaking”.

I then restarted the alignment procedure and applied approximately 3.5mV of audio. Once again the difference was amazing.

I finally applied 1mV, the same as other Icom radios require and the output was virtually indiscernible from my IC-7410, my IC-7600 and my IC-9100. I used an on air comparison between my two IC-7100’s (one adjusted and the other original) using the same SM-8 mic, the same Hustler 6BTV antenna and the same frequency (20 metres), contacting a friend some 10km away using the remnants of my ground wave. He reported S7-8 signals on the “adjusted” IC-7100 and COULDN’T HEAR the unadjusted one.

I compared the adjusted IC-7100 against my IC-7410 and IC-7600. The results were “the same”. I reconnected the unadjusted IC-7100 and again, he couldn’t hear it.

I then was asked to carry out the same work to two IC-7100’s belonging to two friends. They both reported that it was like having a new radio or that it was like giving it a new life.

You will need to run the full HF TX alignment procedure on page 4-5 of the service manual.

Note that for the SWR meter alignment you will need either a 100 Ohm or a 25 Ohm dummy load although it is possible to terminate the alignment procedure before carrying out that adjustment.

Once again, I accept NO RESPONSIBILITY for the outcome, should you decide to go ahead with this.

YOU DO SO AT YOUR OWN RISK.