[Hackrf-dev] Hack RF TX/RX switching

[Gavin Jacobs]

Dana,
For applications which require switching rx/tx, I use gnuradio, osmocom source/sink blocks, and the soapysdr-hackrf driver. As far as I know, this is the only combination that can switch rx/tx on the fly.

For 2m use, I have a homebrew power amp to boost the hackrf tx output, but I only want the power amp enabled when I am transmitting. I took the cover off the hackrf and soldered a 6 conductor ribbon cable to the unpopulated socket P5. You can see on the hackrf schematic that P5 has signal LED3 on pin 6 and GND on pin 1. LED3 is the same signal that drives the TX LED. It is 0V when the LED is off (rx mode) and 3.3V when the LED is on (tx mode). I then wired LED3 & to an input on my antenna controller (which is a PIC 18F2550). I put some logic in the firmware of the antenna controller such that when the hackrf is in tx, and the antenna controller is connected to the 2m yagi, and I have enabled what I call Pass-Through, then the antenna controller drives an output with a 2n3904 npn transistor to put the the power amp also in tx mode. So, I didn't use an opto as suggested by Bernie; I just directly tapped the signal that drives the tx LED.

I don't have a schematic of the connection to P5, it's just GND and LED3 wired directly to a GPIO pin on the PIC controller.

Hope that helps!

Jake

________________________________
From: Dana Shtun <ve3dss at hotmail.com>
Sent: June 21, 2018 8:01 AM
To: Gavin Jacobs
Subject: Hack RF TX/RX switching

Gavin
Can you share your circuit? I’m in the same situation here re switching…
ie. anything special re opto? Is there enough current for the LED and to drive switching?

Also what software are you using?

Thx
Dana VE3DS
Toronto
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://pairlist9.pair.net/pipermail/hackrf-dev/attachments/20180621/bb6809d3/attachment.html>