Page 1 of 1

FT-5DR - C4FM half deviation

Posted: Wed Jun 22, 2022 5:39 pm
by oxoocoffee

I just received my 4 Pro. After upgrading the firmware to the latest, then reading the documentation I stumbled upon this statement "If the openSPOT4's modem is in C4FM (or C4FM Half Deviation) modem mode" in Wires-X section.

I could not find any information about it in Owners Manual so next step I emailed Yaesu support about it.
Here is what I go.

I do not know what C4FM half deviation is so I‘m not sure what RF Shark is referring to, there is in FM mode WIDE and NARROW which you can find under TX/RX, then MODE. I am assuming maybe they are referring to DN which is 6.25Khz wide rather than VW which is 12.5Khz wide?

When settings OpenSpot4 Pro there is an option Modem Mode.
C4FM and C4FM Helf Deviation mode.

I am not sure which one to use with my radio.
Is there a setting on a radio I need to change? And which one to use on OpenSpot4

My radio and 4 Pro are set to 433.900 Simplex (DN mode) and I selected C4FM Modem mode.
I was able to connect to one of YSFReflectors to do a test. It connected. So far no one has answered so I am not sure how it sounds.

Another thing I noticed on my iPhone 13 was after toggling the little speaker next to the volume slider,
when I did try to do a test call my voice coming from the phone speaker was quite distorted. It sounded like it was played with 0.5 speed. Not a normal speed.


Re: FT-5DR - C4FM half deviation

Posted: Thu Jun 23, 2022 4:26 am
Please read these conversations. viewtopic.php?t=2530 viewtopic.php?p=7349&hilit=Yaesu+FT+70DE#p7349 The FT-2DR / DE has this option. The FT-70DR/DE has VW on/off function so this option has been created in the Openspot menu. You can use the full 25KHz for digital voice or half it to use 12.5 KHz. If this option is not available on your radio, please use DN mode.


Re: FT-5DR - C4FM half deviation

Posted: Thu Jun 23, 2022 7:07 am
DN and VW modes have nothing to do with half deviation, they are voice codecs.

Standard C4FM calls use 12.5kHz deviation and half deviation C4FM calls use 6.25kHz. Some transceivers support changing from standard deviation to half deviation in the transceiver's settings, usually found under the DV settings menu (for example, you can find this setting under the DISP menu's TX/RX -> MODE menu on the FT2D).

Re: FT-5DR - C4FM half deviation

Posted: Thu Jun 23, 2022 3:28 pm
by oxoocoffee

Thank you for your explanation. I just checked on my FT-5DR (F-Menu / TX/RX / MODE) and I see three options there.

So under 2. I see WIDE or NARROW. So it looks like it was renamed? Default is WIDE.
"Set the FM transmission modulation level" - from Yaesu manual Operation Manual

WIDE - Normal FM mode (Full deviation) - from Yaesu Advanced Manual
NARROW - Narrow FM mode (Half deviation)

Since the default is WIDE, we should stay with WIDE.

BTW: Does Spot 4 Pro only supports Simplex? Or can it be set to duplex?


Re: FT-5DR - C4FM half deviation

Posted: Thu Jun 23, 2022 3:40 pm
Try setting it to wide and then you should be able to use plain C4FM modem mode on the OS4. The device is simplex only.

Re: FT-5DR - C4FM half deviation

Posted: Thu Jun 23, 2022 4:11 pm
by Zviratko
It's disturbing when even Yaesu are confused by their own naming.

I own a FT-5DE and it works great with OpenSpot.
What you should do is go into TX/RX -> 1 MODE -> 2 FM DEVIATION and make sure it is set to WIDE, that means 12.5kHz. Technically you sometimes should only use 6.25kHz depending on your frequency plan - some VHF frequencies here have a max width of 10kHz so I _should_ use half deviation here, but in practice it isn't observed. Just use WIDE with OpenSpot.

Using VW/DN doesn't affect the RF bandwidth, just the bandwidth of the voice codec. With DN there's still space to send data along the voice, like callsign or position (so even if you tune into the middle of the conversation you get this info). With VW, only the first packet delivers this info, so jumping into the middle only gets you voice, but the voice has higher bitrate. Only DN "codec" is interoperable with other AMBE codec implementations, like DMR.

@HA5OGR do older Yaesu radios use DN/VW to switch between RF bandwidths as well as codecs? Sounds strange.

Specifications by Yaesu with more details can be found here ... tion%2Fpdf

And those slides are quite informative (but dated) ... 4fm-v7.pdf