![xdax rumlogng voice keyer xdax rumlogng voice keyer](https://oe6fte.com/wp-content/uploads/2016/04/IMG_20160406_193029-1140x641.jpg)
The concoction shown in Figure 2 worked like a charm. Soon after the last parts arrived, I tack-soldered the individual components together. It will be getting a lot of use and the heavy-duty description appealed to me. I have a decent junk box, so I found the 50 ♟ capacitor, two-pole double-throw relay, 3.5 mm stereo jack, and a piece of perforated board in the garage.Įven though I had some 3PDT switches on hand, I elected to buy a “Foot Pedal Stomp Switch” from eBay. D1 is used as a “snubber” to short counter-electromotive voltage spikes from the relay coil to ground. The recorded message being sent to the transceiver’s mic input can also be heard through the keyer’s speaker.Ĭ1 is used to isolate the Record/Playback DC voltage from the transceiver. I start with R1 at zero and increase microphone input until the transceiver RF output is equal to the output with the microphone. R1 is a 10K ohm potentiometer used to set the audio input to the transceiver to around 40-50 mV. The recorded message is sent to the transceiver’s microphone input. Relay (K1) simultaneously keys the transceiver’s PTT circuit and “turns on” the playback module. The Repeat Cycle Timer’s normally-open output contacts are used to energize K1: a two-pole double-throw relay during the On cycles. These cycles continue to repeat as long as the timer is energized. At the end of the off-delay, the On-Delay cycle starts over again.
![xdax rumlogng voice keyer xdax rumlogng voice keyer](https://i.ytimg.com/vi/qOVnJPARINo/maxresdefault.jpg)
contacts open and remain open for the length of time set by the timer’s Off-Delay potentiometer. When the pushbutton switch turns the keyer on, the Repeat Cycle Timer is energized and its normally-open output contacts close for a length of time set by the On-Delay potentiometer.
![xdax rumlogng voice keyer xdax rumlogng voice keyer](https://funktechnik-dathe.de/media/image/product/592/lg/mfj-434b-contest-voice-keyer.jpg)
A DC-DC “buck” voltage regulator supplies power to them whenever the keyer is on. The Record/Playback Module and the Repeat Cycle Timer are both 5 VDC devices. The 3PDT switch also controls 12 VDC power to the circuit. In the Keyer On position, the switch connects the output of the Record/Playback Module to the transceiver. In the Keyer Off position, the switch connects the original PTT microphone to the transceiver’s microphone input jack. A three-conductor cord connects the two ungrounded contacts of a stereo phone plug to the center pins of a manually operated three-pole double-throw (3PDT) pushbutton switch. Although I designed it for use with a Microbitx (♛ITX) high-frequency transceiver, it can easily be adapted to any transceiver utilizing a push-to-talk (PTT) microphone. The circuit is simple and straightforward. With all the major components available from eBay, I drew up the sketch in Figure 1 to put them together.
![xdax rumlogng voice keyer xdax rumlogng voice keyer](https://i.ebayimg.com/images/g/pHoAAOSwBtJglxdC/s-l400.jpg)
The receiver would automatically listen for any replies between messages. I could use it to “turn on” the playback message, then turn it “off” for a predetermined period of time before turning it on again.Ī relay could be added to key the transmitter’s PTT circuit every time my CQ message was played. I also found a repeat-cycle timer (variable on and variable off delays) on eBay for $2.38. I found a 20 second record-playback module on eBay for $2.59. For field operation, I could live with a single CQ. Could I get by with fewer amenities and shrink the size, weight, and power requirements to something more backpack friendly? It was worth an investigation. The MFJ-434 has 11 buttons to push, three potentiometers to turn, and two LEDs to show me the keyer is doing what I told it to do. The enormous number of contacts warranted a closer look at a keyer for shorter field trips. What a difference that keyer made! In less than three months, I worked stations in 31 countries and five continents running a 10 watt transmitter and a dipole antenna! Since that stay was planned to last longer than my normal field trips, I decided to take my MFJ keyer for its first outing. Last winter, I was packing a QRP “Go Box” for a trip to Florida. I always run out of voice before I run out of battery. On the other hand, I’m absolutely positive the lack of a keyer has resulted in fewer radio contacts. An “accessory” measuring 6-1/2 x 7 x 2-1/2 inches fills up a lot of backpack. I have never taken the MFJ keyer, primarily due to its size. Most of the time, it’s important to pack only the bare essentials for these mini-DXpeditions. One of my new favorite pastimes has been operating QRP radios from remote off-the-grid locations. It has been a big asset during ham radio contests and when I’ve been calling CQs with reduced power (QRP) transceivers. I have an MFJ-434 voice keyer that has saved a lot of wear and tear on my vocal cords over the years.