Unusual PTT behavior

1

Hello and thank you for your help. I scanned the forum and did not find a post that matches my question. I appreciate all who help with this.

I purchased my Digirig Mobile and cables a couple years back and have not used it until this weekend (i have been spoiled with my IC705). My unit is old enough that it does not have a green “audio” port, it is black.

My issue exists the moment I plug the cable, whether it’s the Icom cable or the Kenwood/Baofeng cable, into the HT. If the cable is connected to the Digirig, with or without being attached to the computer, and I insert the appropriate cable into the HT (ID-52 or UV-5r) the radio immediately starts a transmit. The radio will stay on transmit until I remove the Digirig from the end of the radio-specific cable.

This behavior happens every time i connect the cable, inside the house or outside (I doubt that matters) and it happens with or without an antenna attached to the radio.

I admit, its my fault I waited so long to try my unit. Is it possible there is something wrong with Digirig? Is there something else I can try to do?

2

Turn the radio off before plugging.

Matt
AL0R

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3

There is a possibility that your Digirig is predating 4 pin connectors used in current cables.
Can you please check the revision of the Digirig printed on the back side of the PCB? Digirigs up to Rev 1.5 used 3 pin sockets and switched to currently used 4 pin connectors starting from revision 1.6.

1 Like
4

It is, everytime.

Thank you for your time. Have a great day.

5

Thank you very much for your reply. The revision number says 1.8. I have attached a picture.

I hope you have a super day!

20250210_193334
20250210_1933341920×1440 96.3 KB

6

Yes, that is recent enough revision with 4 pin connectors.

Maybe there is an internal short in the connector, maybe as you plug the connector the radio momentarily keys up and then locks up in RFI induced PTT.

You can check for the first scenario by measuring resistance between the PTT and ground lines before and after plugging in the jack.

image
image747×487 85.2 KB

For the second scenario you can use a dummy load, lowest power setting or tuning the radio to the channel on which it is configured not to transmit (FM broadcast or weather channel for example).

2 Likes
7

Denis, I really appreciate your help and time with this. If I become a nuisance, just let me know and I will buy a new unit. :slight_smile:

Here are my measurements and notes.

  1. Digirig not plugged into anything: ~6.1m Ohms
  2. Only plugged into the Baofeng cable: ~45k Ohms3. Plugged into the Baofeng cable, the cable plugged into the UV-5r, the NON-POWERED UV-5r attached to a 20 watt dummy load: ~48k Ohms
  3. Plugged into the Baofeng cable, the cable plugged into the UV-5r, the POWERED UV-5r attached to a 20 watt dummy load: 0.0k Ohms and the UV-5r is locked on PTT (transmitting).

I do not know what I should be looking for, but I I can verify I followed your instructions as you wrote ttem.

I hope you have a kick-ass day!

Crittenden

8

The high resistances can be coming from contact with skin or from internal components but 40+K readings are essentially open contact in this context.

The resistance/continuity measurements are likely inaccurate while the devices under test are powered up. But what you can do is measure voltage on PTT line which will drop to close to zero when the PTT key is open.

Can you try this experiment while tuned into the channel that doesn’t allow radio to put RF power out?

9

I sure can. Just for clarification, you are asking me to test the resistance/continuity between the 2 solder points, highlighted in your picture? I am to ensure the cable is connected to the radio, no part of my body is touching any part of the PCB and the radio is tuned to a WX station?

Thank you for all your help!

10

Yes, so you can put your radio in broadcast FM mode and measure the voltage between GND and PTT pins on unconnected Digirig’s end of the cable with other end plugged into the radio. That should be non-zero value, something like 3V. Then plug the cable into Digirig - the radio will not put any RF on the air because of the channel selected, but you can measure the voltage on PTT line again to see if Digirig is still trying to key it up (e.g. voltage close to 0V).

What I’m trying here is to determine if it’s the presence of RF power that causes PTT or it happens independently.

11

Thank you, once again, for your assistance. If I am not understanding your instructions correctly, please let me know.

At no time, during this test, was a usb-c cable attached between the Digirig and a computer.

The Digirig was secured, in a vice, as seen in image named, 1.
I set my multimeter to the settings in image named, 2.

Without any cable, of any kind, attached to the Digirig, when I measured the resistance between the GND and the PTT solder points, without touching anything other than the tip of the probes to those solder points, the multimeter read 0k Ohms.

I then plugged the TRRS end of the cable into the Digirig. The Kenwood-style connector was not attached to the radio. I measured the resistance between the GND and the PTT solder points, without touching anything other than the tip of the probes to those solder points, the multimeter read 0k Ohms.

I then plugged the Kenwood-style connector end of the cable into the radio. The TRRS end of the cable was plugged into the Digirig. I measured the resistance between the GND and the PTT solder points, without touching anything other than the tip of the probes to those solder points, the multimeter read ~68k Ohms. The radio was not powered on.

I then unplugged the Kenwood-style connector end of the cable, turned the radio on and tuned the radio to a NOAA WX Station, at 162.472, and ensured reception. I turned the radio off and plugged the Kenwood-style connector end of the cable back into the radio. The TRRS end of the cable was still plugged into the Digirig.
I turned the radio on and the radio immediately indicated PTT, as seen in the image named, PTT.

Your email mentioned this phrase, “measure the voltage between GND and PTT pins”. I set my multimeter to the settings indicated in the image named, Voltage. I measured the voltage between the GND and the PTT solder points, without touching anything other than the tip of the probes to those solder points, the multimeter read ~3v.

I am more of a musician than an electrician :slight_smile: If I am performing these tests incorrectly, feel free to yell at and correct me. :slight_smile:

This behavior happens with the UV-5r and its cable as well as my ID-52 and its ICom cable.

The photos are in the attached zip file. The first reply I sent was bounced due to size.
Archive.zip
I hope you have a great weekend! Thank you for your help!

Crittenden

12

Hmm, the radio should not have tried to transmit on the WX station frequency.
There are also nuances with polarity of the probes when measuring resistance in non-passive circuits.

Unless you have academic interest in this exercise, it may be easier to mail your Digirig kit back and I’ll retest it here. Please PM your order info and I’ll arrange an RMA.

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13

Sure, I’ll send it in. What’s the preferred way to PM my details?

14

You can submit contact form on the website with order info or send a personal message here in forum.

15

Well, I dug up my original order. I placed the order, through Gigaparts, on 2/19/2022. I ordered their Baofeng kit for $99. It included some sort of case.

Let’s just forget about testing it. It’s my fault I waited this long to use the item. I guess I never really needed it in the first place. If I get around to needing one, I’ll just buy a new one.

I hope you have a great day and take care of yourself. Thank you for all your help. :slight_smile:

KJ7NUX

16

Warranty or not, I don’t mind looking at your Digirig. Offer stands.