An older offering from Icom, this is a great little radio. For us UK hams we get HF/2m/70cm including 5MHz and 70MHz. It's architecture is the older IF DSP design so it's hackable to include IF / RF taps if you want to add a panadapter. KV5R has done a great write up on IF tapping the radio. The IF is apaprently pretty high at 124.487 MHz, making it slightly less than trivial to use a buffer amplifier, but his process appears to give a reasonable IF output without dragging down the stage too much.
UK Diode Matrix, 5MHz + 70MHz 6308 6316 6324 6342 1 1 1 0 1 1 0 0 0 1 1 0 0 0 0 0 1 0 0 1 0 0 1 1 1 0 0 1 0 0 0 1 6301 6309 6317 6325
UK Diode Matrix, 5MHz 6308 6316 6324 6342 1 1 1 0 1 1 0 0 0 1 1 0 0 0 0 0 1 0 0 1 0 0 1 1 1 1 0 1 0 0 0 1 6301 6309 6317 6325
North America Diode Matrix 6308 6316 6324 6342 1 1 0 0 1 1 0 0 0 1 1 0 0 0 0 0 0 0 0 1 1 0 0 1 1 0 0 1 0 0 1 1 6301 6309 6317 6325
Japan Diode Matrix 6308 6316 6324 6342 1 1 0 1 1 1 0 0 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 1 0 1 0 1 0 0 1 1 6301 6309 6317 6325
A document published by Icom available here describes the diode mods for MARS/CAP as follows:
Remove D6315 and D6316
0.1-199.999999MHz
400-470MHZ
Remove D6315
1.6-25.999999 MHz
28-29.999999 MHz
50-54 MHz
144-146 MHz
430-440 MHz
Remove D6316
1.6 - 54 MHz
68 - 74.799999 MHz
118 - 174 MHz
430 - 470 MHz
Remove D6310
5.255 - 5.405 MHz ONLY
The RF connectors on the radio are trivial to remove. There is a clip on the PCB which holds the centre pin of the RF connector, so swapping a connector is as simple as unscrewing it, pulling it out, and putting in a new one. The two-hole N-Female connectors sold by M0MAT on eBay are high quality PTFE insulated jobbies and fit perfectly. It's probably worth removing the top cover when you do this just to ensure that you are sliding the pin home correctly and not mashing the little clip.
On 70cm, into a quality dummy load, my transmit SWR was ~1.6:1. After swapping the connector the transmit SWR was close enough to 1:1 that the radio didn't display anything on the meter.
M0UKD has done a great write up on this with some good photos. Not a scary mod!
Some of these radios appear to have a problem with their ALC circuit (and / or possibly the compressor) causing them to put out low-ish power on transmit. The radio I have doesn't do this, but there are two potential solutions according to the interwebs.
1. Upgrade the firmware, there are reports that Icom fixed this by changing ALC / Compressor parameters
CPU 1.11
DSP 1.03
2. Solder in a capacitor to slow down the ALC response
TRX Lab on Youtube shows a modification which dramatically increases the average and PEP on SSB. This is “too much” IMO, but a smaller capacitor value (100nF?) may well give a more controlled improvement without entirely losing the ability to change transmit power. Experimentation required by someone with a radio that has this issue!