Ham Radio – QRP 2023-04-25 01:28:00
Richard Carpenter, AA4OO, is a regular contributor to AmateurRadio.com and writes from North Carolina, USA. Contact him at [email protected].
TX Relay, Power and TX REQ IN
R&L Electronics sent me a SCU-28 10-pin DIN cable by accident and were nice enough to let me keep it. Consider shopping from those guys. They offer great communication and good prices.
This cable is typically used to wire connections for an external amplifier. I don't have an external amplifier but I wanted to make use of the +12v power and transmit relay for the protection relay I built for my SDR-Play a few years ago.
I had also read that the TX REQ IN pin could be used to switch the radio into a lower power tune mode for use with external tuners. The absence of a TUNE button for external tuners is one of my pet-peeves about the FT-DX10 so I was excited to have one.
Wiring the Break Out Box and TX-REQ-IN
So I used my last spare plastic project box, some female phono jacks and found a push-button that I'd cut off of some other project in my junk box and went to work.
I used some shrink wrap for the momentary switch for the TX-REQ-IN pin.
I wired up 3 phono jacks... One for the TX relay, another for the +12v out, and one for the ALC control in case I ever do get an amp. I safed the other wires for future use inside the project box.
I connected the box and verified that I was getting power for the relay and that the Relay Switch operated
Unfortunately, the TX-REQ-IN does NOT do what it does with other Yaesu transceivers. Pressing the button grounds the TX-REQ-IN - the radio does transmit a carrier in any mode (here I tested with LSB) but rather than transmitted a reduced power carrier as it's supposed to, it just transmits at whatever wattage the mode is currently set to. In this case I had the power set to 50w into a dummy load and it transmitted the full 50w rather than a reduced power 10w or 20w carrier for tuning. See the power out on the radio's display
In my opinion Yaesu screwed the pooch on this one. I don't see any reason why they wouldn't operate like they do with their bigger brethren radios when the TX-REQ-IN is grounded. Some subsequent forum searching turned up posts from others that confirmed that the FT-DX10 does not properly respond to that signal.
My Elecraft KX3 and Ten-Tec Eagle both have a "TUNE" button that sends a low power tuning signal regardless of what the current power setting is at and there's no reason that the FT-DX10 shouldn't do the same. Having to dive into a menu to change the power setting for tuning an external matching unit is just silly in this day and age.
I have confirmed that my box is working the relay properly to my SDR-Play. I reference the relay I built to protect the front-end of the SDR-Play in this post https://www.hamradioqrp.com/2017/02/spruce-up-basic-transceiver-with-sdr.html
That's all for now.
So lower your power and raise your expectations
Rich AA4OO https://www.hamradioqrp.com/