Known-good serial port settings for FT-450d / Omnirig

On the FT-450D:

CAT RTS: Disable
CAT TOT: 100

In Omnirig:

Rig type: FT-450Dmod
Baud rate: 4800
Data bits: 8
Parity: None
Stop bits: 2
RTS: Handshake
DTR: Low
Poll int., ms: 100
Timeout, ms: 100

Not perfect, occasional lag / dropout, but pretty decent.

Omnirig is version 1.16, serial port adapter is VID 10C4, PID EA60 and reports as Silicon Labs CP210x USB to UART Bridge.

Driver provider: Silicon Laboratories Inc.
Driver date: 19/09/2016
Driver version:

FT-450D firmware version 0244 (hold down Mode while powering on)

6m Lightweight Delta Loop for Sporadic E contacts

This week I put together a simple delta loop antenna for 6m. This is a simple, cheap, lightweight horizontally polarised somewhat-directional antenna. Fantastic for the sporadic E season which is going on right now – especially in a confined space where a beam isn’t practical.

It looks like this:

I made it out of 6m of hookup wire, some 75 ohm coax, 2m of plastic pipe, and a PL259 connector. All of which I found in the garage.

It is hung on a SOTABEAMS fibreglass pole, about 6m above ground level in my case. No guys, just strapped to the washing line with velcro.

Almost immediately after plugging it in, I decoded PV8DX in Brazil on FT8. That was exciting! Even if it was a fluke. Since then I have worked Italy on SSB, and Malta, Estonia, Spain, Italy, Sardinia on FT8. Right now I’m +8dB into Sardinia, so this thing gets out okay!

A quick test on a web SDR shows a 9dB difference between broadside and end-on, so it’s reasonably directional.

A word on matching. A delta loop has a nominal impedence of 100 ohms. To match to 50 ohm coax, this design uses a simple piece of 75 ohm coax as an impedence transformer. This works by taking advantage of the mismatch between 50 and 75 ohm coax. For 6m, a 99cm length is necessary. No other matching or choking seems to be required for this antenna, so it should be fairly low-loss.

The construction details:

  1. Cut 105cm of 75 ohm coax. Strip 3cm off each end, leaving 99cm intact.
  2. Cut 2x 3.1m lengths of wire. I used RS 356-713, obsolete, but any will do.
  3. Join one length of wire to the shield of the coax, join the other length of wire to the centre conductor of the coax.
  4. Drill a hole just wide enough for the wire at each end of the plastic pipe, through both walls. My two holes were 198.5cm apart from each other.
  5. Feed each piece of wire through one of the drilled holes. Bring together, strip and twist together the two pieces of wire at the midpoint of the pipe.
  6. Put a connector on the free end of the 99cm bit of coax.
  7. Drill a hole through the plastic pipe around 8-10mm, enough to push the second-to-top section of the SOTABEAMS mast a reasonable way through it.
  8. Connect your antenna to your coax, raise the mast, tune for SWR by chopping out short lengths of wire until the SWR is low at the desired centre frequency. I found perfect resonance (50 ohm resistive, 0 ohm reactive, 1.0:1 SWR) at 50.313MHz, the 6m FT8 frequency, with 598.5cm wire.  This bit is much easier with an antenna analyser but can be done with a rig set to lowest power and an SWR meter.
  9. Finalise and seal the connection between the two pieces of wire.

Finding the perfect length of wire for resonance will depend on the accuracy and quality of the 75 ohm section, and on the velocity factor of the antenna wire, which can vary. The maths predicts that resonance at 50.313MHz should be 5.963m of wire, so 5.985m (22mm difference) is damn close.

I quite fancy making 2m and 4m versions of this. The following table shows scaled measurements for 2m and 4m, based on this successful implementation for 6m.

Band   Centre freq   Wire length   Coax length   Boom length
6m      50.313       5985mm        990mm         1985mm
4m      70.200       4290mm        710mm         1423mm
2m     144.300       2087mm        345mm          692mm

Here’s where I’ve been heard over a few hours this evening:

and these are the stations we’ve heard this evening:

If you make one of these, let me know how you get on!

Expanded callsign prefix and country list

I just compiled a non-abbreviated list of callsign prefixes and country names, including non-ITU allocated prefixes.

Data source is Wikipedia plus a whole bunch of post-processing work by me. It should therefore be up to date as of now.


Might be useful to people writing ham radio applications in future, e.g. me.

Should you use it, it would be nice but not necessary if you credited me, but please do credit Wikipedia.

CHIRP file for spot frequencies on 60m

With Exercise Blue Ham coming up again this weekend, I thought now would be a good time to put out a list of the suggested 60m spot frequencies for CHIRP, noting that the 60m band is not continuous.

You should be able to easily import this file into your compatible radio to avoid fiddling with manually programming the channels. Use of the channels rather than the VFO will guarantee you don’t operate out-of-band.

Download 60m.csv

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!!bloom-beacon!!wupost!!mips!!ogicse!emory!wa4mei!ke4zv!gary Sun Sep 29 20:54:05 EDT 1991

In article <> (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”.