VOX cable, RadioMail, FT60 or VX8, not working - getting the 1k tone on my TX audio

W2MRD · January 1, 2025, 9:49pm

I just bought the VOX cable and a Yaesu HT audio cable to use with my FT-60. I intended to use with RadioMail on my iPhone (iPhone SE2, IOS 18.1.1).

I also purchased the Apple Lightning to Headphone adapter cable (from Target, so I assume it was authentic).

It does not work for me. The radio PTTs when I set the phone’s headphone level at the correct point, however I also get a tone (assume the 1K PTT tone) on my transmitted audio when trying to connect to a node (when listening on another radio). I might hear the packet data as well, but not certain. Definitely getting a steady tone on the TX audio when I try to connect to a node in RadioMail. Even if the packet data is there, I assume the superimposed tone would make it undecodable.

In RadioMail, I chose Packet KISS TNC Modem, Default TNC: Packet Modem (Internal).

If I send some regular audio from the phone (not in RadioMail) and manually PTT the radio, I do hear that audio on the listening radio (and no 1k tone). If I max phone’s headphone volume all the way, it will (intermittently) key the radio itself (from VOX on the spoken audio I assume).

I also had a complete Digirig setup for a VX-8, so I borrowed that HT and audio cable and tried with the purchased VOX cable and same issue.

I checked the iPhone under Accessibility and Balance is set to middle (0.00) and Mono Audio is Off. I found an app in the Appstore that allowed me to generate a tone and balance right vs left. When tone is generated on the the right channel only, the radio keys up AND presents the tone to the transmitted audio (I hear it on another radio). When it’s set to the left only, the PTT stops (but if I hold the PTT button, I hear the tone).

It’s perhaps like the PTT keying tone audio is getting mixed and sent to the radio. If I understand how the VOX cable works, only left audio should go to the radio, and the right side is only there to PTT the radio. The VOX cable assembly seems to be sending the PTT tone side to the radio. Am I missing a step, do I have a bad VOX cable, or ??

W2MRD · January 1, 2025, 10:14pm

A little more troubleshooting…I was able to try another iPhone (an iPhone 13). While I didn’t buy RadioMail for that one, I did download the free tone generator software and I was able to replicate the problem. If I generate the tone and balance to the right, the radio keys up but also presents that tone to the transmitted audio.

(in case anyone wants to try, the iOS app is called “Tone Generator: Audio Sound Hz” and has a green icon. Disclaimer: No affiliation with it and I can’t be certain it is working properly, etc. It’s just an app I found looking for a free tone generator.)

Constrainted · January 5, 2025, 8:14am

I do not have Radiomail or your HTs, so take what I say with a grain of salt.

From VOX PTT Cable for Smartphones – digirig

audio payload from smartphone via left headphone channel, attenuated for transceiver’s mic input

low latency VOX PTT by the tone or audio payload on the right headphone channel

If PTT by tone setting is available in In digital modes app then set the tone to the right channel and audio payload to the left channel. The tone frequency works at 1KHz, but higher frequencies can improve (reduce) the PTT latency. Experiment to determine the best option.

If audio prefix, suffix setting (tone on the payload channel before and/or after actual data) is available, start with about 300mS and see what works reliably without adding too much time to the transmission.

You must determine in Radiomail whether to use VOX or Tone for PTT. It is not clear to me whether or not you are doing that. If you are using Tone for PTT, the convention is payload audio on the left channel. Likewise, once you choose VOX or Tone in the communication program, you must set the transceiver HT to be VOX on, or VOX off. Once you are pulling PTT on the HT, you must determine if you have RFI causing PTT lockup.

If you reduce the options, your troubleshooting will go quickly:

pick one radio for TX, the other for monitor maybe with the antenna off
pick VOX or tone PTT in the communication app
if tone PTT, set the payload audio to left channel
based on (2), set VOX on or off in the transceiver HT
go ahead and test

Good luck! I think you are close to success!

73 Constrainted

W2MRD · January 5, 2025, 3:27pm

RadioMail’s internal TNC was specifically designed to work with the DigiRig Lite and the VOX cable (it says so right on the app’s screen )
I do not see any settings for which channel to use for payload, I believe that was coded into RadioMail to work with the VOX cable.

I am not using radio VOX, that’s why I’m using the VOX cable.

Also, as I put in my follow-up, even with the tone generator software app, the tone appears on the transmitted audio when I send it to the right side.

Constrainted · January 5, 2025, 3:50pm

I took a look at radiomail.app and there was nothing I could find to answer my questions.

Have you identified a Winlink Packet RMS node for connection?

73 Constrainted

W2MRD · January 5, 2025, 5:21pm

Yes, I am trying to use a local node I have used many times. I own two Digirigs for the PCs and have used them many times, including with the VX8 I also tested. Like I said though, I can hear the steady tone on a listening radio each time it keys up. It’s not AX25 packets I am hearing.
See screenshot from RadioMail.

W2MRD · January 5, 2025, 6:06pm

A little more troubleshooting: using an older style iPad that still has a 3.5mm headphone port, I tried RadioMail with the VOX cable (and no lightning adapter). Same problem, hearing the steady tone on the TX audio.

K0TX · January 6, 2025, 3:26am

Apologies for the delayed response.
Indeed the circuitry between the PTT and audio payload is fully isolated inside of the VOX cable and there is no opportunity for crosstalk:

However, the radio you used shares the same line for the PTT and incoming audio and that’s where the signals get mixed together:

The severity of this effect may be different depending on the amplitude of the tone and with enough signal it may fully saturate the PTT switch keeping it fully open. If none of the volume levels work, the better solution would be to use the tone outside of the radio’s audio bandwidth (e.g. 5-10KHz) or even outside of audible spectrum (15-20KHz). This will also improve the latching of the PTT switch.

It may be possible to improve (resolve?) this situation for Yaesu HTs and 1KHz tone by adding some filters to the future revision. I’ll keep experimenting. The frequency change is an easier solution and it should work with the current revision. I’ve already notified the developer of RadioMail. Other apps may already have this option.

W2MRD · January 6, 2025, 11:56am

Thanks for the reply. Hopefully you can add a note to the VOX cable product page cautioning of this issue with the Yaesu audio.

Thank you for contacting the author of RadioMail with your suggestion. I also just sent him an email to find out if that modification/option is something he will implement. Obviously I can be a tester for it if he does.

Unfortunately if he is not able to make that change or it doesn’t solve the issue, I’ll probably be returning the cables.

K0TX · January 6, 2025, 6:06pm

I’ve added the note specific to Yaesu and audible PTT tones additionally to the existing note about the cable being experimental.

Did you try using the payload on both channels? In this scenario the crosstalk should not be an issue.

wh6az · January 6, 2025, 6:43pm

I have a RadioMail beta build ready with the ability to change the PTT frequency. If you have a Yaesu radio and experience this problem, contact me if you’d like to test it out.

K0TX · January 6, 2025, 6:58pm

Well that was quick. Thank you for the fix. Hopefully it takes care of the issue.

W2MRD · January 8, 2025, 1:11am

An update: I want to thank Georges WH6AZ for making such a quick change to RadioMail and pushing it out in beta. I had success with the VOX cable and my FT-60!

He provided a number of test PTT trigger frequency options in the beta and I found a couple that work well and I have provided him detailed feedback. In the next few days I will test another radio and node to make sure they work in that case as well.

Constrainted · January 8, 2025, 1:33am

Congratulations on your success!

Please pass the info on to @K0TX because his device has to pass these frequencies without mixing them.

73 Constrainted

K0TX · January 8, 2025, 1:38am

Yes, please share what frequency of the tone worked the best.

With the radio sharing the same line for PTT and mic input some crosstalk is possible, but with the PTT tone set outside of the radio’s bandwidth the tone gets filtered out and doesn’t get on the air.

W2MRD · January 8, 2025, 2:55am

6 kHz and 12 kHz worked for me, with an FT-60.

W2MRD · January 12, 2025, 11:29pm

Here is a final report on my testing that I have also shared with WH6AZ.

Good success with the FT-60 at both 6 kHz and 12 kHz. I tested with more than one node and everything seems to be working well.

However, my VX-8DR does not work. Most of the time it will not connect. But I also hear the PTT tone in the transmitted audio, even at the high frequencies. That radio uses the CT-131 adapter to get from the round weather resistant jack on the top to a regular TRRS connection. I also notice some crackling from the speaker which should be muted. It’s possible that my CT-131 is bad. Although that wouldn’t explain the tone present. It’s also possible the VX-8DR does not have the same audio cutoff that the FT-60 does.

Regardless, I’m happy as my FT-60 is the radio I wanted this setup to work with as that is the radio I normally use.

I want to say a huge thanks to Georges WH6AZ, the author of Radiomail for making an alternate set of frequencies available so quickly.

Fanboy · January 14, 2025, 2:55pm

W2MRD and WH6AZ,

Thank you both for looking at this. I have the VX-6R and VX-8DR, and have attempted to use the new Digirig VOX PTT cable with both using RadioMail 1.4.2 (15). While I’ve yet to make a successful connection to a known good/reachable gateway, the pieces all talk to each other. I am looking forward to WH6AZ’s beta changes being rolled into an app store update. Mark, N7MMO.