FT-470 information

Since information on my old Yaesu FT-470 handheld is starting to become hard to come by, I thought I’d start a post where I put stuff I need to remember or often look up about it.

There won’t be much here to start with, but it might well grow over time.

Headset pinout:

Pin Function
3.5mm ring ground
3.5mm tip rx audio
2.5mm ring ground
2.5mm tip mic audio

This is shared in common with these radios:

FT-411, FT-470 , FT-530, FT-51R, FT-11R, FT-41R, FT-23R, FT-203R, FT-416, FT-703R, FT-109R, FT-109RH, FT-209R, FT-209RH, FT-709R, FT-709RH, FT-727R

(credit Argent Data Systems)

They sell such a cable here.

Item 322904869921 on eBay appears to be a headset with the right plug, as does this item on Amazon.

The pin centres are NOT the smaller 8mm apart from each other – more like 9.5 to 10mm.

I find the connectors to be too loose to use separate 3.5mm and 2.5mm jacks – it is not a reliable connection.

The manual is here.

Fed with 12V, the radio will manage 5.0W VHF and 5.0W UHF, according to the manual. The rig can be fed with anywhere from 5.5V to 15.0V.

The microphone is a 2-kilohm condenser.

Mirroring a post from 1991:

From thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!bloom-beacon!micro-heart-of-gold.mit.edu!wupost!zaphod.mps.ohio-state.edu!mips!cs.uoregon.edu!ogicse!emory!wa4mei!ke4zv!gary Sun Sep 29 20:54:05 EDT 1991

In article <1991Sep27.033057.22510@agate.berkeley.edu> ajk@garnet.berkeley.edu (Adam Jacobs N2LAW) writes:
>1.  Does anyone have the exact wiring specifications for the Yaesu
>side of the cable to the TNC?  Is "where do I plug it in" a stupid
>question?  Presumably the MIC and EAR jacks, but how is the MIC jack
>configured -- if it's (as the manual specifies) a 2-conductor
>micro-mini phone jack, then what do I do with the PTT signal?  Or is
>there something else I should know?  I can wire the cable all right,
>but I have no appetite for blindly trying configurations on an
>expensive piece of equipment.  Do I have to open the unit up?

The FT470 is wired like an Icom. You connect the audio from the TNC
to the tip of the mike plug through a capacitor and connect the PTT
to the tip with a resistor. The Icoms and Yaesus use a "leaky ground"
to generate PTT. The problem with this approach is there is a tradeoff
between rapid PTT and audio level and response. Typical values are
.1 ufd and 2.2 k ohms. The RC time constant limits TR turnaround.

A better scheme is to use a tiny audio transformer sideways like so,

TNC PTT----------))))))))))))------------> radio tip (audio)
TNC AF OUT-------))))))))))))----X--------> radio sleeve (gnd)
TNC GND--------------------------|

You can rip a suitable transformer out of an old transistor radio or
buy one from Radio Shack.

>2.  Suppose I want to run the HT off a 12V external power supply.
>Where do I feed the power?  Not the battery terminals, I hope.  I
>would have expected a DC power jack somewhere on the unit, but again I
>don't see anything except a mysterious looking rubber plug-which-might-
>hide-a-jack-but-I'm-afraid-to-pull-it-and-look.  The manual, again,
>says nothing about this.

The 2 meter only model does have a power jack under the rubber plug, but
the 470 doesn't. There's a place on the board for one, but Yaesu recomends
that you use a PA-6 module instead. This is a module that mounts in place
of the battery and contains regulators for running the radio and charging
a battery connected to the bottom of the PA-6. This is a really nice
accessory and well worth the price.

>3.  Anything else (useful modifications, hints, caveats) I should know
>about the FT-470 (or PK-88?)

Just the standard remarks that you should carefully set the audio level
so you wind up with a 3 khz deviation for your tones. Don't exceed that
level or many units will have trouble decoding your packets. Make sure
you have the power saver on the 470 turned off when you run packet or
you'll miss the first part of every packet. This can drive you nuts
because everything seems to be working but nothing prints.

One last note. Use a separate antenna and use shielded cables on your
TNC. Otherwise the RFI and RF feedback will ruin your packet operation.

Gary KE4ZV


TNC wiring:

TNC TX audio -> 0.1uF cap -> 2.5mm tip
TNC PTT -> 2.2k resistor -> 2.5mm tip
TNC RX audio -> 3.5mm tip
TNC gnd -> 2.5mm / 3.5mm ring

or the transformer method, which I’ve never tried.

Headset / speaker mic wiring – unverified – need to tear apart a headset I have somewhere to check.

Mic + -> 2.5mm tip (presumably the cap isn’t required as in the TNC)
Mic – -> 2.5mm gnd
PTT will be 2.5mm tip -> 2.2k resistor -> switch -> 3.5mm tip
Headphones is just 3.5mm tip and 3.5mm gnd

Again, that is unverified.

Any speaker mic must be a design where the PTT switch is double poled, where the second pole interrupts the speaker connection, else audio feedback happens on TX.

Footswitch PTT adapter for FT-450d, FT-857

Here’s a really simple footswitch PTT adapter for at least the Yaesu FT-450d and the FT-857d. Any rig compatible with the Yaesu MH-31 fist mic with modular 8 pin (RJ45) connector.

Buy a 0.5m Ethernet extension lead, like this:

(they are all over eBay).

Buy a tattooist foot pedal – about £7, again eBay.

Buy a quarter inch in line jack socket.

Cut the outer insulation of the Ethernet extension lead half way along.

Cut a piece of two core wire the same length as from your cut to the Ethernet plug. Solder to quarter inch socket.

Strip back a bit of insulation from the brown and white lead. Connect to the shield of the quarter inch socket via its wire.

At this point you can cut the green lead in the Ethernet cable to disable the fist mic PTT, or you can leave the green lead in place to allow both the foot switch and the fist mic PTT to control the radio.

If you cut the green lead, connect the rig side of the green wire to the other side of the quarter inch socket. If you left the green lead intact, strip back a bit of insulation and make the same connection.

Long way of saying, the green wire in a standard Ethernet cable is the PTT pin, and the brown and white wire is the ground pin. Ground the PTT pin to key up.

State of charge vs voltage – SLA / AGM batteries

Here is a table of the rough state of charge of a 12V sealed lead acid / AGM battery at different open circuit / no load voltages.

State of charge 12V battery Volts per cell
100% 12.7 2.12
90% 12.5 2.08
80% 12.42 2.07
70% 12.32 2.05
60% 12.20 2.03
50% 12.06 2.01
40% 11.90 1.98
30% 11.75 1.96
20% 11.58 1.93
10% 11.31 1.89
0% 10.5 1.75

Categorised under “things I Google repeatedly”.

12V radio PSU from Xbox 360 PSU

Really quick hack. I was about to chuck out a broken Xbox 360 (already brought back from the dead 3/4 times) when I noticed its power supply was fairly beefy – rated 14.2A at 12V.

Turns out these are really easy to hack and work great as radio power supplies, so long as you don’t need more than 14A.

Chop off the plug, connect the red and blue wire together, then solder the three yellow wires to the positive side of your chosen power connector [1], and the three black wires to the negative side of your connector.

My big radio draws 15.6A transmitting 100W into a dummy load, which is above the rating on the label of the PSU, but it didn’t seem to mind! No heat detected even after quite a bit of testing – voltage dropped only to 11.93V. Safest to keep within the rating of course.

No detectable QRM showing up on the SDR, so they seem to be pretty quiet. While not small, these power supplies are certainly smaller and lighter than the vast majority of 12V power supplies you see out there for ham radio / bench use.

Not bad for £0 and about 10 minutes work. These power supplies are readily available on eBay for £10 to £15. Easy mod!


[1] I use 30A Anderson Powerpoles for all my 12V connectors – including replacing all the non-standard connectors on all of my rigs. Sotabeams sells them for the best price I’ve been able to find in the UK.

2m FM SSTV with literally just a Raspberry Pi

Stumbled upon this write-up- SSTV from the Raspberry Pi camera, with direct RF synthesis, i.e. no outboard radio required, complete with motion detection and callsign overlay. Neat!

Low pass filter mandatory.

Nothing stopping this being adapted for HF SSB, in fact it would probably work better.


Wouxun KG-UV950P / KG-UV950PL DIY hands free pinout

I have a lovely Wouxun KG-UV950PL 6/4/2/70 mobile radio, but a hands free kit doesn’t seem to be available. So I set about working out the connections required to build one. Here they are:

KG-UV950P - KG-UV950PL mic handsfree pinout

Using a standard RJ45 Ethernet cable:

  • Orange+white / pin 1: RX audio – NC for this application
  • Orange / pin 2: +5V on receive (unverified) – NC for this application
  • Green+white / pin 3: PTT – wire to one side of switch
  • Blue / pin 4: unknown, probably buttons – NC for this application
  • Blue+white / pin 5: unknown, probably buttons – NC for this application
  • Green / pin 6: +8V constant – wire to 2.2k resistor, then to positive side of mic
  • Brown+white / pin 7: ground – wire to ground side of mic and to other side of PTT switch
  • Brown / pin 8: – TX audio – wire to negative side of 100μF capacitor, then positive side of the cap to positive side of mic

Looking forward to building a version for the car and seeing how it is for road noise etc.

According to this, increase resistor size to increase mic output level (sounds counter-intuitive, but hey).

Update: that 2.2k resistor should be a 47k. That seems to produce clean audio and keeps the current through the mic element down. I’ve ordered a MAX9812 module to see whether a pre-amp brings the punchiness of the audio up a bit, since it’s a bit quiet as-is.

Considering a radio

Considering the TH-9800 (4m version) from Sinotel. Looks perfect for Raynet stuff.

Diplexer plans: Make yourself a diplexer courtesy VK3ZAV

Questions posed to the vendor:

  1. Recommend a diplexer to split the 2m+70cm side from the 4m side
  2. Recommend a diplexer to split 2m and 70cm – assuming the rig can’t handle this itself
  3. Can the cross-band repeat function be locked down to only transmit on receipt of a specific CTCSS tone?
  4. Can the TX power be set independently on the two sides of the radio?

New radio for me, if they come back with the right answers…