W4FT on Amateur Radio

Do you have an MFJ-434 attached to your Yaesu FT-1000MP, but your microphone doesn’t work well or the radio starts retuning downward when you engage the EDSP?  Then it’s time to check those 434 jumper settings!

For years, I’ve had an MFJ-434 voice keyer that I wanted to use with my Yaesu FT-1000MP during contests.  Sometimes, it would work fine.  Other times, the combination of the radio and the keyer would do strange things. Often, I would just disconnect the keyer and set it aside – I wasn’t in the mood to troubleshoot during a contest.  Afterwards, once I recovered, I wasn’t really in the mood to troubleshoot the problem.  I spent a lot of time searching the internet for a solution, but never found anything that worked.  In fact, I didn’t find much on the topic at all. Anyways, with Field Day approaching, combined with the relay problem that I had (see http://w4ft.com/2010/06/yaesu-ft-1000mp-transmit-relay-replacement/ )  I decided to spend some time really digging into this one.  The good news:  I found a solution – the correct jumper settings for the MFJ-434 to work with the FT-1000MP!

Strange Behavior

Sometimes, the combination of the MFJ-434 and the Yaesu FT-1000MP would start doing strange things.  The most common “strange behavior” was quite easily duplicated, once I figured out the conditions that caused it.  First of all, I had set all of the jumpers in the 434 using the default Yaesu setup as described in the manual.  This appeared to work, at least initially, but there were two problems.  First, recordings created using the external mic, the Yaesu MD-100 desk microphone, sounded terrible and very weak.  The 434′s internal mic did a much better job.   Unfortunately, this should have been a clue.  The desk mic also sounded terrible and extremely weak on the air too. 

The second problem was much more interesting, even entertaining except when I was trying to make contacts during a contest.  Under certain conditions, the radio would start changing frequency all on its own!   Specifically, if the Notch, NB-1, NB-2 and EDSP buttons were all activated while the 434 was connected and configured with the default Yaesu setup, the radio would start scanning downward when the transmitter was keyed.  It is the same behavior as using the ”Down” scan switch on the mic.  Are you starting to see the problems? For full disclosure, I don’t remember 100%  if I had to key the radio to start this behavior.  I’m also reasonably sure that it did this when I used the Heil headset and boom mic too. These would be easy enough to duplicate and verify. Either way, the EDSP was a no-no when the 434 was hooked up.

So, two serious problems – low mic output and unwanted retuning when I used all the noise supression tools.  Definitely unacceptable.

Two Solutions Are Found

By now, you’ve figured out what I instinctively knew, but didn’t want to accept for a long time.  The default Yaesu jumper setup inside the 434 doesn’t work with the FT-1000MP.  So, with Field Day approaching, I decided to spend an evening diagnosing and researching the problem.  It took a couple hours, but I solved both problems and the system works just as you’d expect.  It just takes a couple undocumented jumper settings.

1. The microphone problem:

One of the microphone pins carries +5 volts to power the microphone.  Unfortunately, the default Yaesu setup suggested in the instructions for the 434 doesn’t pass this through.  There is a setup that puts +5v on the 434′s mic connector, but it doesn’t seem to work as well.  The solution has three steps:
         1. remove the jumper between JMP-3 (Yaesu) pins 15 and 16 (8th pair), and,
         2. install a jumper across JMP-4 (Icom) pins 5 and 6 (3rd pair).
         3. remove the jumper from JMP2.  (When installed, it shorted the +5v directly to ground.)

This routes the +5v signal from the radio through to the same pin on the 434′s microphone connector.  The result is that the MD-100 or any mic that requires the +5v supply will now work approximately as expected.  It may not be perfect, but it works. I say this because mic audio quality might be slightly degraded.  You may find that recording messages with the 434′s internal mic may still be the best, but now you can effectively use your mic while attached to the Voice Keyer without a serious dop in audio levels.

2. The Scan Down problem:

  Okay, I confess, I have no idea exactly what was causing this or why.  Pin 3 carries the ”Scan Down” signal and is a straight passthrough, according to the schematic.  Logically, it should not be a problem. I do know that once I sat down and traced the connections through the schematic of the 434 and made sure that each pin had exactly the right connections or passthrough, the problem disappeared.  If I were to guess, I’d say it had to do with the ground signals, but that’s just a wild guess.  I really haven’t figured it out yet.  I just know that my final setup (below) solves both problems.

MFJ 434 Jumper Setup for a Yaesu FT-1000MP

So here is the complete setup.  Note that for jumpers JMP-3, -4 and -5, the pins are numbered fron left to right and top to bottom, starting at the back of the unit and working towards the front.

1. JMP-1: Leave this jumper set.  It enables PTT Automatic Override (See manual, pg. 6)
2. JMP-2: Remove jumper.  When set between “Y” pin and center pin (default), it shorts the radio +5v line to ground.
3. JMP-3: There are 8 pairs of pins.  Set the jumpers on all pairs(default), EXCEPT remove the jumpers on pair 2 (pins 3 & 4) and 8 (pins 15 and 16).
4. JMP-4: Set a jumper on ONLY pair 2 (pins 3 & 4).  This enables +5v for the mic connector to power an external mic.
5. JMP-5: Set a jumper on ONLY pair 3 (pins 5 & 6).  This enables the pin 5 ground from the radio to the mic.
6. JMP-6: Leave the zero volt setting in place (default). The radio is providing the voltage.  
7. HD-1: Leave default jumper between pins 7 and 8 (default).

Using these settings enables the desk mic to function correctly and eliminates the downscan problem.  It also works with my Heil ProSet Plus.  If you’re using a different microphone, or some other combination of hardware, your best bet is to examine the schematics of all the equipment involved and trace it all out. 

Finally, note that this is for the MFJ-434 and the Yaesu FT-1000MP.  It may or may not work with the MFJ-434-B or the Yaesu Mark-V, or any other subsequent models, but this discussion should give you a lot of ideas on where to look!  Good luck!  If you try this, or try it on another combination of hardware, leave a comment here so that we can share the knowledge. Let’s share what works, what doesn’t and why!

73,
W4FT