FRS/GMRS Radio Comms: Interface with Electronic Hearing Protection, Setup, and Ensuring Reliability
The purpose of this article is to serve as a basic guide to individuals who wish to use their handheld FRS/GMRS or similar radios in conjunction with their electronic hearing protection headsets for use as tactical or range communications equipment. What I'll be covering is the basic setup (required cables, PTT's, etc) and ways to ensure reliability/durability of your comms system.
Section One - Setup: Setup of handheld FRS/GMRS radios for interface with electronic earpro is quite simple and can be done fairly inexpensively.
Most electronic earpro headsets produced now have a 3.5mm audio IN port on one of the earcups. Most handheld radios use a two-pin audio interface system, a 2.5mm port for audio IN and a more common 3.5mm port for audio OUT.
To simply pipe in audio from your radio to your headset what you need is a 3.5mm male-to-male cable, such as the the one pictured below. You can pick whatever length and style suits your needs best but I recommend:
Cable length of 3 feet for a belt mounted radio setup. This length will be perfect for most users.
Both connectors are L shaped. This will keep the connections low-profile and reduce snagging/pulling of the connections which reduces wear and will minimize the chance of a connection pullout.
Non-braided cable. Something I've learned is braided cables transfer rubbing/bumping sounds more easily than non-braided cables and these sounds WILL be heard in your headset. Unless you need extreme abrasion resistance I would recommend against using a braided cable.
The above setup will play all incoming audio in your headset, keeping your radio silent. However, if you want to be able to speak without needing to grab your radio then what you need is a third component - a PTT or Push-To-Talk microphone such as the one pictured below.
These handheld PTT's are usually a speaker/mic combo. They have a small microphone inside for your speech and a speaker to play incoming audio. The reason they include a speaker is so the audio source is moved from your radio to a position closer to your head, provided you've mounted the PTT on your chest or similar area. This theoretically makes hearing the audio easier, but many of these cheap PTT speakers are quite weak even with the radio volume turned to max. For our purposes however we will be disregarding the speaker altogether, as we want to interface our radios with our headsets therefore playing the incoming audio in the headset, making the PTT speaker irrelevant.
That said these PTT's typically have a 3.5mm audio OUT port on the bottom. To create a link from your radio to your headset all you need to do is take your 3.5mm male-to-male cable and connect it to the audio OUT port on the PTT and the audio IN port on your headset. The PTT is connected to the radio and will occupy both audio ports.
Now you have comms piped directly into your headset and a remote push-to-talk system that allows you to leave your radio holstered, making communicating much easier and more hassle free.
Peltor ComTac users, a note - You can do this with your headsets as well even though they lack a 3.5mm IN port. Peltor uses their proprietary two-pin hookups on these headsets. What this means is you need an adapter cable which Peltor themselves produce in a couple lengths and coiled or non-coiled versions. Generic aftermarket versions are also available. These cables cost about $20 to $30. Pictured below is one of these cables.
Total cost of setup: The largest variable here is likely to be the headset you use. Electronic hearing protection varies widely in cost from about $30 a set to over $300 a set. The radio can also vary quite a bit in price.
Cost with basic electronic earpro, low cost radio:
~$50 electronic earpro headset (such as the Impact Sport)
~$35 radio$5 to $15 3.5mm male-to-male cable
Total approximately $115 to $130
Section Two - Ensuring Reliability: Now we will focus on protecting your electronics from water and other environmental damage. Water that isn't deionized carries contaminants that can interact with the metals on PCB's (Printed Circuit Boards) and the connections soldered on them. Water can also damage integrated circuits depending on their construction. Salt water in particular is damaging to electronics.
Aside from poor quality control or bad design the primary cause of failure in electronics is either mechanical (physical destruction/damage) or environmental (static, water, etc). Protecting all three components of your comms system from environmental factors is key to ensuring it is reliable and functions when needed.
First, let's examine the radio. This particular radio is a Midland GXT1000. This radio carries a "JIS4" rating. JIS is the "Japanese Industrial Standard". A rating of 4 means splashing water from any direction shall have no harmful effect. To see exactly what this means we're going to open the radio and look inside.
First of all the battery compartment is fitted with a gasket (the gray band) that seals against the battery door. This should prevent rainfall or splashing water from getting inside the battery compartment.
Next we have the radio internals, seen after opening the radio body. The body is fitted with a gasket (the orange band) so the internals should be at least moderately protected from rainfall or splashing water. However, the electronics are not protected directly. There is no conformal coating on the electronics, leaving them exposed to environmental hazards should something breach the radio body. If the radio were to be submerged water would come through the speaker vent or other unsealed areas and come into direct contact with the electronics. I will cover "conformal coating", how to apply it, and what it does later. While you're inside the radio you should also look for bad solder joints.
Should your radio not have a gasket a cheap, quick fix would be to apply some electrical tape to the area where the body pieces meet. You could also apply a gasket making material and form your own gasket, though you should check for chemical compatibility to make sure it won't damage the radio body. These are of course band-aid solutions and I would recommend picking up a radio with a decent water resistance rating to ensure its reliability in wet conditions.
Now let's examine the PTT internals. These are fairly simple, with a basic PCB, a couple small capacitors or similar components, and a few solder joints where wiring meets the PCB. This PTT does have a gasket (the black band) and so the internals should be protected from rain or splashing water. As with the radio you should examine the PCB for bad solder joints.
Here on the other side (the front) we have the microphone and speaker. The microphone is the small cylinder in the upper left corner. Seen in the lower left corner is the activation button for the PTT.
Should you decide you have no use for the speaker, never will, and want to ensure the PTT is silent (won't accidentally play audio out loud) you can simply remove the speaker entirely by cutting the two wires seen below.
Conformal Coating, Explanation and Application: Conformal coating is a broad term encompassing a variety of electronics coatings. Conformal coatings are typically applied extremely thin and serve the purpose of acting as a barrier between the electronics to which the coating is applied and damaging environmental factors such as moisture. To keep this simple I won't be diving into the various coatings here and will focus on just one, the one I use, that being MG Chemicals Silicone Modified Conformal Coating.
This coating applies easily, dries quickly, and is one of the cheapest conformal coatings available. It is about $15 for a 55ml bottle. It comes with a brush applicator cap. Upon application the coating will be tack-free within 5 to 7 minutes and dry enough for reassembly of the device in about 30 to 40 minutes. This coating can be soldered through if you need to make repairs.
NOTE: I am NOT an electronics expert. If you apply this coating you do so at your own risk. There may be components that are not suitable for coating. I don't know what components those might be. In addition applying this coating or making other modifications likely voids the manufacturer warranty.
To apply you simply paint the coating onto whatever electronic components you are trying to protect. You do not need to coat the entire circuit board but it's a good idea to coat the entire board surface front/back and all components, solder joints, etc on the board if possible. You certainly want to cover all solder joints and small board components entirely with the coating. With this particular coating the electronics should be ready for reassembly in about 30 to 40 minutes after application.
To aid in application you can use a UV flashlight. Conformal coatings typically have a UV tracer in them which allows the coating to fluoresce under UV light for inspection purposes, allowing you to check for missed spots.
This coating can be applied not just to the PTT circuit board but to the boards in your radio and your electronic hearing protection. I would strongly recommend coating the PCB's in your headset (if they aren't already) as they are constantly exposed to salt and moisture through your sweat. I would also examine the headset connections to make sure a wire won't come loose. The Peltor Tactical 100 headset for example has a ribbon wire that can come loose and cause function issues.
However, I would again caution that some components may not be suitable for coating. This should not be an issue in the earpro headset (conformal coatings are used in the MSA Sordin Supreme Pro-X and Peltor ComTac III headsets on all components) but radios are complicated electronics with many different components. The radio is what I would be most careful with.
Closing: A simple inspection of your electronics and proper application of a conformal coating can mean the difference between gear that will survive harsh conditions and gear that will randomly fail at the worst moment. Of course there are issues with material durability and construction, especially with these cheap PTT units, but that's a complicated issue. My recommendation is to only buy known name brand PTT units as they will likely be higher quality than cheaper off-brand units. You should also take care to select a good quality 3.5mm cord and get in the habit of inspecting all cables for wear as you use your gear.
There are of course some things not covered here, such as radios without a simple two pin connection system but that is beyond the scope of this article. My hope is to have provided you with enough information to make an informed decision about your comms equipment, know what modifications to make to enhance its environmental resistance, and know what to look for to find units with an appropriate level of durability.