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Baofeng UV-5R PTT won't turn off?


Andrew Malota
 

Howdy All -
I'm having a bit of trouble getting a cheap chinese handy to play nice with the DRAWS hat. (I understand that these types of teething pains are why they are avoided by most, but hey, I already had the radio...)

I am using a cable from Ham Made Parts.

ptt_ctrl.sh -l on results in LED on DRAWS on, the HT starting to transmit 
ptt_ctrl.sh -l off results in LED on DRAWS off, but does NOT unkey the radio - it continues to transmit

pin 1 and 4 on the ps2 connector appear to be the sleeves for the large and small TRS connectors going into the HT

with the radio connected and PTT engaged, i see 3-ish volts on pin 1. the 3-ish volts remains when I turn PTT off until I unplug or power-cycle the radio.

Has anyone else hit this? Is it as simple as a pulldown between pin 1 and ground?

Thanks!
KF5WOR


Corky Searls
 

Biggest problem with using an HT is RF feedback into the pi from the cable which causes exactly the symptoms you are seeing. This is not unique to the Baofeng radio, but seems to be worse there.

You will likely need to use a good choke on the cable close to the pi or a remote antenna (best option) to get this to really work.

Thanks and 73,
-Corky, AF4PM


On Mon, Sep 14, 2020, at 7:30 AM, Andrew Malota wrote:
Howdy All -
I'm having a bit of trouble getting a cheap chinese handy to play nice with the DRAWS hat. (I understand that these types of teething pains are why they are avoided by most, but hey, I already had the radio...)

I am using a cable from Ham Made Parts.

ptt_ctrl.sh -l on results in LED on DRAWS on, the HT starting to transmit 
ptt_ctrl.sh -l off results in LED on DRAWS off, but does NOT unkey the radio - it continues to transmit

pin 1 and 4 on the ps2 connector appear to be the sleeves for the large and small TRS connectors going into the HT

with the radio connected and PTT engaged, i see 3-ish volts on pin 1. the 3-ish volts remains when I turn PTT off until I unplug or power-cycle the radio.

Has anyone else hit this? Is it as simple as a pulldown between pin 1 and ground?

Thanks!
KF5WOR


Andrew Malota
 

Howdy AF4PM -
Thanks for the reply.

I tried with a choke, and again with a choke + antenna outside the house, but got the same behavior.

For another test, I grabbed by Kenwood TH-D74A (cable is the same,) and it works correctly even with the rubber ducky antenna right next to the pi and no choke.

I'll try to do more reading to understand how some of the other arduino-based projects are keying this radio.

Thanks
KF5WOR


Andrew Malota
 

Howdy All -
I found some time to follow up on this. I was able to get the radio working correctly.

Another project (https://www.tnc-x.com/Baofeng.htm) provided the answer.
Evidently the resistance between the two PTT pins is too low for the baofeng to see PTT "off" when DRAWS sets PTT "off".
I grabbed a cheap PS/2 extension cable, cut it up, and spliced in a 2.2k resistor on PS/2 pin #2 (this is the sleeve of the skinny TRS connector that goes into the radio.)

So far, so good! I'm able to reliably transmit (and even more importantly, reliably STOP transmitting,) and packets that I send decode just fine.

Thanks
KF5WOR