QDX with 50 watt amp

N0GRP - Rob Sullivan

I built a 30 meter QRP labs amp to use with my QDX. I have it hooked to a power supply at 15 volts and everything seems to be working fine. To get it to work I had to go into the firmware and enable the PTT to work on the 30 meter band. But the fact that I could enable it for a specific band got me to wondering if I could leave it hooked up and transmit through it on other bands as long as it wasn't being activated by the PTT. 

Joshua KJ7LVZ

Yes, you can.

Ronald Taylor

No you can't. Sorry. The diode switches will not provide ample bypassing of the signal around the amp for transmitting around it when the amp is not keyed.... This is not the typical amp with relay bypassing. You can do it with external relays if you are so inclined. 


On Sun, Mar 19, 2023 at 4:19 PM Joshua KJ7LVZ <joshuajayg@...> wrote:
Yes, you can.

Bojan Naglic

I agree. Don't do it. It is very possible to jeopardize the PA' RX/TX switching.
Although theoretically, you could use the RX path of the 50W PA bypassing (D3 and D5) but just until you disturb the whole RX/TX switching. Which can easily be done when the applied input RF voltage would cause the diodes to switch, even temporarily. I would say it could work (to some extent) using up to 0.5W RF input power at +12V PA supply. But the QDX has 10 times more power.
So, the answer is no.

73 Bojan S53DZ