Most SSB HF transceivers are equipped with separate microphone and headphone jacks but field operations are often more convenient when there is only one device like a headset, or a handset.
Headphones with either boom or integral microphone work well when involved in steady radio operation where there is little non-radio interruption. Transmit control by Voice Operated Transmit (VOX) or by foot switch work fine. Some equipment allow cordless BlueTooth connection thus freeing the operator to use both hands and even to wander about the area unencumbered.
Alternatively, handsets allow the operator to operate in a more casual instance: To pick up the handset to answer or initiate a call, to participate in a round-table contact yet interact with people nearby. While operating pedestrian mobile the handset does little to interfere with nearby sounds like over-the-ear headphones do, yet places the speaker element close to the ear for clarity. They also allow a degree of privacy and the option of not interfering with nearby conversations or other radio traffic.
Amateur radios commonly operate "half duplex" meaning that we transmit and receive on a single frequency channel, just not at the same time. So, unless we use sound level detection to trigger our transmitter, we need to have a Push-To-Talk (PTT) control in addition to the speaker and microphone elements. Fortunately, all three functions can share a common return and that return can similarly provide shielding on the connecting cable.
In addition to the familiar 3.5mm (1/8") 3-conductor stereo cords 4-conductor patch cords have become increasingly available. These can be utilized to transport speaker, microphone, and PTT services between transceiver and handset all in one cable. Pre-made patch cords in several lengths, panel jacks, and plugs are quite inexpensive. Using a patch cord as a handset cord eliminates the bulky coiled cord and makes replacement a simple plug-and-play operation. Change a 3 foot cord to a 6 foot cord almost instantly.
To achieve that transformation we just install jacks on both the transceiver and handset.
Replacing the cord with a 4-conductor panel mount jack is usually quite straightforward. Usually you can open the handset case and slip the cord with its strain relief out of the slot. Cutting the wiring long enough to attach to the jack simplifies the conversion. The front mounting jack usually fits the vacant slot with little room to spare so if you cannot use the mounting nut then a bit of improvisation may be needed. I use hot-melt glue: Just a small dab or thread on the inside of the mounting slot.
Keep in mind that someday you will need to replace or modify that jack. Always try to keep service simple. Hot-melt glue is easy to work with. If the handset slot permits, use a short piece of 2:1 (because it is thinner) heat shrink on the jack body to bulk it up for a tighter fit.
The H250/u replica appears to be a Chinese generic with an electret microphone element and a 32 ohm impedance receiver. Both seem to be of good quality. The PTT switch removes with two long screws which gives access to the cord retention clip. The model that I purchased cost less than $15 USD and was designed to work with the Baofeng and Quansheng handheld transceivers with their "K" style connectors.
My choice of jack pin allocations was mostly arbitrary:
I removed the cord clip, slid the strain relief up the cord a few inches and snipped the wires long enough to permit attaching them to the jack. I then increased the diameter of the jack with 2:1 heat shrink then used the more robust 3:1 with integral flooding adhesive to mount it tightly to the handset case cord nub on the outside. The severed coiled cord and plug was then attached to a 4-conductor plug in case I wanted to use it as it was originally intended.
I also had on hand a couple of old Icom speaker/microphones that were intended to be used by law enforcement and first responders. These clip nicely to shoulder straps or utility vests. They both had plugs that fit my old Icom hand held VHF rigs and sounded rather nice! I removed the single screw that held one of them together and performed the same operation as I did with the H250/u handset except this time I used the hot-melt glue method to hold the jack in place.
I also had a couple of Western Electric type G5 handsets from the 1950's and '60's. These were PTT style for intercoms and such, using the familiar carbon microphone elements and the excellent receivers. I removed the coiled cord and mounted the jack like I did with the other handsets. Please note however; Although the carbon microphone has a VERY high output when used in place of an electret capsule, it sounds like a carbon microphone. Go figure!
Epiphyte 2: Mounted on the front panel. Paralleled existing headphone, mic, and PTT jacks.
Epiphyte 3: Same as Epiphyte 2.
KD1JV SlopBucket II (for 80m and 40m units): Front panel next to key jack.
QRPLabs QMX+: Right rear panel (above antenna jack).
JP301 JACK FUNCTION
QRPLabs QMX: I made a special adapter using two stereo plugs, one panel jack, mounted on 3/4" strapping. The steel strapping is easily worked with small drills and files. Two slots are cut to accept the three-conductor plugs and a suitable hole drilled for the new jack. Wire up the connections then insert the assembly into the radio audio and paddle jacks. To protect the wiring and to reinforce the positioning of the two plugs I used hot melt glue. Somewhat inelegant but practical and easy.
Icom IC7300: I made an adapter using 8-pin microphone connector and 4-conductor panel jack.
Yes, the center pin gives access to the proper audio level. Very short connecting wiring from the plug to the jack. Heat shrink tubing provides the necessary rigidity. I admit that I don't use the handset with the IC7300. It was just a lark and I had all of the materials on hand.
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