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Transmit problem - no signal on antenna

PostPosted: Thu Sep 12, 2013 4:11 pm
by Nazim
Hi Everyone,

Receiver works brilliant, but I have a problem with a transmit. When PTT is on and test signal is inserted to the peaberry radio interface plugwh:1,0 using the gnu-radio, power consumption increases, transistors get hot and I'm able to read 1.9V sine on the gates of Q7 and Q8. Voltage at Q9 collector is 12.7, Q7 and Q8 drains are 13.5V. However nothing comes out of antenna jack. I've tried to measure a voltage on a 56 ohm dummy load and real antenna, but voltage is 0.

Already lifted and re-wound T5, but voltage at dummy load is still 0V.

Re: Transmit problem - no signal on antenna

PostPosted: Fri Sep 13, 2013 3:06 am
by AE9RB
It sounds like you did a good job of narrowing it down. I'd guess T5 too. Maybe your test setup is bad. Where are you hooking up the ground of your scope probe?

Re: Transmit problem - no signal on antenna

PostPosted: Fri Sep 13, 2013 3:47 am
by Nazim
Hi David,

I was hooking up the ground to the TP-GND loop, also tried the outer surface of BNC plug. It seems that setup is correct, because a 0.25W 56 owhm resistor is not warming up when used as a dummy load.
Probably, I've managed to toast the output mosfets somehow. Will get a new bs170 on Monday to check it out.
Thank you and all of the participants for sharing their experience and software configs, that really helps.

With Best Regards,
Nazim

Re: Transmit problem - no signal on antenna

PostPosted: Fri Sep 13, 2013 1:37 pm
by Nazim
I wonder if Q1 is damaged and transmiters signal leaks into the receiver circuit or ground. Unfurtunately, don't have a circuit at hands, will check on Monday.

Re: Transmit problem - no signal on antenna

PostPosted: Mon Sep 16, 2013 3:41 pm
by Nazim
Q1 seems ok. Soldered a 0.25W 50ohm resistor directly to the antenna terminals. It heats up in a 10 seconds when the transmitter is driven witha 0.5V I/Q signal. So, my test setup was wrong. I'm now looking for a hf wattmeter to measure the output power.

Re: Transmit problem - no signal on antenna

PostPosted: Fri Aug 21, 2015 7:54 am
by Romance1999
It seems that setup is correct, because a 0.25W 56 owhm resistor is not warming up when used as a dummy load.
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