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P O L Y T E C H . N U

Icom IC-7100

Until last year I was a “Yaesu man”. Since very good experiences with the IC-7300 I gained interest in other Icom products. I bought a second hand IC-706 and upgraded to a IC-706mkIIG. And since the price of a second hand IC-7100 is rather interesting I upgraded to the “new” IC-7100. And therefore I gathered some information and maybe this is interesting for others to read. The information is shown below.

The Icom IC-7100 is a rather small mobile rig. It’s a new generation “shack in a box” comparable to the Icom IC-706 series or Yaesu FT-857. The main difference is that the IC-7100 is a “software defined” rig. This means that a lot of signal handling is done digital and this results in great filtering capabilities. It’s great that it’s a complete radio for the regular HF bands, 4 m, 6 m, 2 m and 70 cm. Since it’s a mobile rig it’s more simple than a desktop rig. It has a monochrome display and for example no waterfall display. But other than that it’s a rig with a lot of options and rather easy to operate. If the budget is small or if you’re a starting ham radio operator, this is a great radio to start with. This is the next step compared to the Icom IC-706 series radio’s or the Yaesu FT-857/-897.

70 MHz
Compared to Yaesu is the availability of the 70 MHz band a big plus. Yaesu has an IF frequency of 69,45 MHz and that’s too close to 70 MHz which results in the lack of the 70 MHz band. Icom uses other IF frequencies for a long time and therefore more interesting.

detachable front panel
The IC-7100 is a “split radio”. The “remote” front panel is connected by a wire. At first I didn’t liked the design of the radio. But at second thoughts is rather smart. The big plus is that the speaker is built in and the microphone can be connected to the front panel! I owned an Yaesu FT-857 with a remote cable and the “problem” is that next to the data cable also an microphone cable is needed and an external speaker with cable. The FT-7800 is better engineered since the microphone can be connected to the front panel, but the rather new FT-100DR has still the microphone (and speaker) connection at the body of the rig and not at the front panel. I like that the remote front panel is standard and no optional remote kit is needed. I planned to use the rig as a base station and the two part rig has also the benefit is that the footprint of the equipment on the desk is much smaller and the power cables can be shorter since the rig body can be placed next to the power supply under the desk.

The rig is mechanically well built. I like the internal power connection. Instead of soldering two rather big power cables to the circuit board, bolts are used as a mechanical connection (like the Yaesu FT-991 also has). Great improvement!

power amplifier
The HF power amplifier is equipped with two RD70HVF1. The RD70HHF1 would also be logical, but since the rig has also 70 MHz, the frequencies are rather high. The RD70HVF1 are also used in other rigs for V/UHF use. For V/UHF the IC-7100 uses the RD70HUF2 MOSFET. That’s an odd shaped MOSFET which I didn’t knew before. I guess that’s the newest on the market.

I also like that there’s a lot of information available of the IC-7100 (and for other Icom rigs as well). The TX expand information is available and even the service manual is available. Yaesu service manuals are much harder to find. The quality of the documentation is great. Transmit, receive and power signals are indicated by colour which make’s debugging much easier.

IC-7000 comparison / driver design
The IC-7000 has a colour display where the IC-7100 has a black and white display. Unfortunately the IC-7000 plagued with some technical problems. The IC-7000 driver board seems to fail rather fast and the rig tends to get really hot. The IC-7100 seems to be much better engineered. A key difference is a well accessible RD15HVF1 driver for the RF amplifier final stages. For example the IC-7000 has a special driver board under the mainboard which is not easily accessible. (But still even better than the very hard FT-897 driver replacement operations…) Hopefully the driver of the IC-7100 is stable and doesn’t need replacement ever, but more convenient than this it couldn’t get.

ALC modification
There seems to be one design flaw. At SSB the ALC circuit is too fast. The power is by the ALC circuit reduced for every “strong signal”. This results that the output power for SSB is hardly 75 Watts or more. Someone found out that a capacitor and a wire bridge is needed to solve the problem. SMD reworking skills are required! And I don’t like the bulky electrolytic capacitors o I would recommend to use a small SMD capacitor. Peter Schroeder (TRX bench) from Germany shows all the details in this (external) video.

SO-239 antenna connector
What is dislike is that two SO-239 antenna connectors. This connector is for HF fine, but unsuitable for UHF purposes since the losses of the SO-239/PL-259 are significant. Therefore I replaced the original one with a N-type connector. This is almost a drop in replacement since no soldering is needed! The centre connector is clamped onto the circuit board of the radio. The only tools needed is one screwdriver. Yaesu does use the N-type for V/UHF for a long time. It surprise me that Icom still uses the SO-239 ones. Next to the losses it’s also annoying that both connectors are the same and therefore it’s needed to read the markings on the radio which connector is for which frequency range instead of looking to the shape/type of the connector…