My first post here, hey!
I wonder if there is a way to limit output power while transmitting. I have fried my BS170s this tuesday when I was transmitting FT8 with 5w (12v). Then it suddenly stopped transmitting (PWR 0) - probably my antenna SWR is too high (~2).
I checked FETs and all of them are broken.
I'm replacing my FETs today, and I wonder if there is a way to limit power to eg. 3W with software, to avoid burning anything again.
Maybe setting MAX PA Bias will do the job?
What do you think?
Limit power for TX
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Re: Limit power for TX
Pa bias max should be Set for max efficiency and Not be touched beyond that.
If you want to Limit Output Power: simply do so by reducing Input voltage.
73, Manuel DL2MAN
If you want to Limit Output Power: simply do so by reducing Input voltage.
73, Manuel DL2MAN
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Re: Limit power for TX
If you can't reduce the input power supply voltage, you can insert a 50 Ohm 5W rated 3 dB attenuator at the antenna output. The input power will be the same, but the power sent to a 50 Ohm antenna will be reduced by 50%, the difference being dissipated in the attenuator. The 3 dB attenuator will limit the worse case SWR seen by the transmitter to a max of 2:1, even with a completely open or shorted antenna on the other side of the attenuator. Thus, an inserted 3 dB attenuator makes connecting an unknown antenna (for testing, etc.) much safer for the finals.
Question: How much should the input voltage be reduced to reduce the transmitter output power by 50%?
73, Ron, N6YWU
Question: How much should the input voltage be reduced to reduce the transmitter output power by 50%?
73, Ron, N6YWU
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Re: Limit power for TX
Reduce Input Voltage down to 9 V and you will get appr. 3 Watts HF out.
But even better ist toimprove your SWR. 2.0 is to high for key-down modes like FT8 if you transmit to long.
SWR 1.5 will probably do.
But even better ist toimprove your SWR. 2.0 is to high for key-down modes like FT8 if you transmit to long.
SWR 1.5 will probably do.
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