Chuck,
I have used the bias-t voltage on the hackrf to power an upconverter but it 
isn’t easy to turn it on and off. The only method I know is to use 
hackrf-transfer - but that doesn’t work when switching to/from rx & tx.

Meanwhile I have brought the tx LED signal out from P5, and it is switching the 
power amp on and off just fine.

Jake

On Jun 19, 2018, at 7:02 PM, Chuck McManis 
<chuck.mcma...@gmail.com<mailto:chuck.mcma...@gmail.com>> wrote:

FWIW the idiomatic way to achieve this as far as I can tell is to send a bias-T 
signal on the RF cable, basically its a DC offset on the cable which the PA 
picks up and switches on. This lets you have short cables between the PA and 
the antenna and its only one line to hook up (the antenna coax)

On Tue, Jun 19, 2018 at 5:04 PM Gavin Jacobs 
<apriljunk...@hotmail.com<mailto:apriljunk...@hotmail.com>> wrote:
Bernie
That’s a great idea! I looked on the hackrf schematic and the signal for the TX 
LED is brought out to a (DNP) header - all I have todo is bring that signal out 
to my PTT circuit. Thanks for the suggestion!

Jake


On Jun 15, 2018, at 5:32 AM, Bernard Kobier 
<bernardkob...@tpg.com.au<mailto:bernardkob...@tpg.com.au>> wrote:

I admit I have not tried this but what about using the TX LED to drive an 
optocoupler to switch the amp?

Bernie



On 11 Jun 2018, at 00:53, CJ Hicks 
<cjhi...@dadelus-engineering.com<mailto:cjhi...@dadelus-engineering.com>> wrote:

Why not leave your exciter on and only PTT your power amplifier (PA)?  Or use 
an RF to shunt your exciter signal into a dummy load.  Just a couple of random 
thoughts.

CJH

From: HackRF-dev [mailto:hackrf-dev-boun...@greatscottgadgets.com] On Behalf Of 
Gavin Jacobs
Sent: Saturday, June 09, 2018 5:57 PM
To: hackrf-dev@greatscottgadgets.com<mailto:hackrf-dev@greatscottgadgets.com>
Subject: [Hackrf-dev] Still hoping for PTT

Has there been any progress on implementing digital i/o from/to the hackrf One. 
I'm hoping that someday the hackrf can supply a PTT signal to an external 
amplifier.

Jake

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