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Lower Output 20M
https://www.hobbypcb.com/phpBB3/viewtopic.php?f=8&t=7164
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Author:  rbuckspan [ Wed Feb 15, 2017 8:56 pm ]
Post subject:  Lower Output 20M

SN 1202 FW 3.0D Supply 14.5V
I built and have used this HR50 for awhile, but not used much. The initial alignment and adjustment a couple of years ago (with 50mA bias each final) was straight forward and it has worked fine. While operating last week, I noticed that the output on 20M was much lower than the other bands (except 6M) and did not remember it to be so before - but it may have been like this for some time. With 3.5W drive (KX3) into a dummy load, I get 54-69W output on all bands 10-160M, except 20M which is 43W (and 44W on 6M).
Is there something I need to do?
Thanks!

Author:  kz1x [ Wed Feb 15, 2017 10:56 pm ]
Post subject:  Re: Lower Output 20M

Mine is the same way. I increased the bias a good bit but it didn't help much.
Even with 5 or 6 watts drive you can barely make full output. It's good enough for me though.

Steve KZ1X

Author:  simon.kwan [ Thu Feb 16, 2017 12:17 am ]
Post subject:  Re: Lower Output 20M

I also faced this problem before but is solved. If you are using the latest firmware, the 20M output is lowered due to protection measure of something inside HR50 (I forgot what it is exactly). You can increase the bias to 150mA per MOSFET then the output is improved significantly. Please search "150" in this forum and you can see the detail.

73
Simon Kwan
VR2ZLB

Author:  rbuckspan [ Thu Feb 16, 2017 6:19 am ]
Post subject:  Re: Lower Output 20M

Thanks guys. I may try boosting the bias this weekend......
73

Author:  rbuckspan [ Sat Feb 18, 2017 11:07 pm ]
Post subject:  Re: Lower Output 20M

Well, I increased the bias to 150mA each, but it did not make any difference :(
Guess I'll leave well enough alone............
73

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