Okay, just a run down.
You guys that have read some of my past posts know that I have strong opinions on radios and intercoms that I feel work well. Will a crappy unit work? Yes. Will it work well? No. As the owner, you make the final decision as to what unit will be installed in your aircraft. But as an installer I strongly recommend the units that I have found, through experience, will work the best. I strongly recommend against installing units that, again, have proven to not work well (for any reason). Since there is a lot of back and forth over audio installs, I am going to run through units that will work well on most if not all types of installations and some points concerning installation plans and workmanship.
First: Radios to avoid. Val-Com. Designed in the 70's and few changes since. No internal battery to hold the memory, which means that every time the unit is powered up, it comes up on a default freq and NOT on the freq you last used. Any Icom VHF made after the IC-A200. The -200 was a low cost replacement for the KY-97A and actually worked okay. The later models are prone to outside noise interference and squelch setting problems. Narco products. They had a place at one time. If you are happy with your Narco it means you have never had to have a major repair on it. There are reasons that they are no longer in business. And radios no longer in production have limited or no replacement parts available. For the 'miniature' radios, I only recommend Becker and Microair. Both will work well when properly installed with the correct wiring. Flight line, Xcom, etc. have all had noise issues and interference issues (Key up one radio and the other bleeds over, display flip flops, etc).
Second, intercoms: Sigtronics. 70's designs with few updates. Noisey, noisey, noisey. Did I mention noise issues? Their instructions still say it's okay to use unshielded wire and no isolation washers on the headphone jacks. Anyone that's done harnesses knows shielded wire and iso washers are ALWAYS used. It's just basic workmanship items that prevent noise issues. Flightcom. See Sigtronics.
Any audio system is vulnerable to poor installation planning and bad quality workmanship. When planning an installation, keep radios and intercoms away from anything that produces a magnetic field. Motors (like cooling fans and electric gyros) are especially bad. When the motor powers up it will make a whine on the audio lines that varies with the motor speed. Put your headset on and power up your panel. Here a whine that starts low and increases in pitch? That's a motor. Also plan out your installation to minimize any audio system wires from getting close to any coax antenna cables. Any system that transmits, such as radios (VHF or FM) and transponders will inject noise into adjacent wires. This is generally an extremely high pitch squeal. Audio wiring, when properly installed and using shielded wire can usually be bundled together. Coax cables should NEVER be bundled with each other OR with any other wires. In places like the windshield post areas where coax and audio wires are sometimes routed together, bundle the audio wiring tightly together and leave the coax loose. This is the best you can do to minimize interference when you have to route them through the same area. A tip when wires route in the same area: wires in parallel will interfere with each other, whereas wires that cross close to 90 degrees rarely do. ALWAYS use new circuit breakers with a new unit. Do you know the history of that breaker? Time installed, exposure to damp/water, exposure to salt air, etc can render a breaker inop. And you wont know until it fails to trip. And as I referenced in a post above, resistance across contacts creates a voltage drop, which reduces the voltage at the power input of the unit. Never try to reuse old wire and always clean up the avionics ground points when doing an install, for the same reason; bad connections. I can make a harness for a radio and intercom, out to four places, on my bench in four to six hours. If you develop a problem with your old harness when adapting it to the new system, how long will it take to troubleshoot it? Use the correct tool to install the correct contact to the wire. All of us have seen the pins 'crimped' to the wire with pliers or soldered when they were meant to be crimped. Those are methods used to get you home not for legit repairs or new installs. The tooling is available for sale, rental, or just plain borrowing. Get it and use it correctly. Don't ignore your grounds! Get an AC43 and see how to correctly build a ground stud. Put it on a clean spot on the airframe, without seams between it and the ground stud for the battery. It's a semi permanent install as you can remove and install grounds without removing the stud itself. Another tip is to never install airframe systems grounds with avionics systems grounds. At least keep them on separate studs. Over the course of many years, I've found that with 'trouble radios' when quality models are used, 90%+ have been wire issues and not the radios themselves. Think about it. Bench checking or repairing a radio over and over again and re installing it with the same harness and power/ground connections. What changed and what did not change? If the same repair is made each time, find find out what it is! If it is, say, the internal power supply, check your power and ground connections. Check the harness/connector for shorts between the power in and any other wires. Solder connectors are notorious for this as they are prone to individual strands of wire not being soldered but instead, touching terminals right next to them.
I'll be over here in my fox hole as I hear incoming fire already, lol.
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Dito !
