I recently bought a second hand Icom IC-7100 HF radio for a reasonable price. This radio is known for a very conservative approach to internal ALC on the power output. This causes the output power to not go above approx 75-80W (PEP) as measured on my LPA-100 wattmeter in PEP mode with 14,5V DC input. Of course, there is no need to overdrive any linear amplifier, however Icom engineers have probably overdone it a bit on the conservative side on this radio (?).
There are two published mods that are possible on this radio. I did only one of the mods that involves a jumper from C1509 to ground, because the other mod that involves a 10uF capacitor is reported to cause modulation issues on FM and AM.
The PEP output power increased from 75-80W PEP to approx 140-145W PEP (14,5V DC input). Note: PEP, not average. On a sidenote the peak to average ratio also improved. There is no need to have PEP output of more than 100-110W PEP by the way.
The mod is easy:
- Unplug the radio DC lead and all other leads incl. the antenna connector
- Use an antistatic mat and handlead
- Remove the back cover
- Locate the C1509 and the ground lug
- Solder a small jumper from the C1509 to the ground lug
- Check carefully that you didn’t spill any solder residue on the PCB
- Blow with compressed air to remove any residue
- Close the radio
I did also upgrade the firmware to :
- CPU 1.11
- DSP 1.03
The firmware upgrade did have a small but insignificant effect on the PEP output power according to what I found. The hardware mod, did have a signficant impact as the DSP is led to believe that the output power is lower than it is.
- All mods are done on your own risk!
- You may void the warranty of your radio if carrying out this mod
- I will not be held responsible for any problems, malfunctions, defects, indirect consequences or any other issues caused by the mod
- Do at all times follow the license regulations of your country
- Check that your bandwidth is not excessive
- Check that your harmonic content is well below maximum allowed