Ambiguous SWR Bar Graph and Values in TX screen
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Author:  Ron J. [ Fri Jan 05, 2018 1:05 am ]
Post subject:  Ambiguous SWR Bar Graph and Values in TX screen

I just finished SN 1781 with the ATU! :D Everything appears to be working great with one exception. The SWR and PEP graphs on the TX screen essentially mirror each other in magnitude with the SWR lagging a bar or two behind. Furthermore, the SWR shows up as unrealistically high values 60, 80, and up to 130. My antenna analyzer and other radios clearly show the antenna load as 50 ohms with an SWR of 1.2. This is confirmed by the HR50 when I put the ATU in the "wattmeter" mode...it also shows an SWR of 1.2. Engaging the ATU on the HR50, although not necessary considering the already low SWR, the HR50 quickly returns a "tuned OK" result. Still, the SWR bar graph and value displayed on the TX screen are unrealistically and ambiguously high. Any suggestions to resolve this would be greatly appreciated.

Thank you,

Author:  jimveatch [ Fri Jan 05, 2018 5:41 pm ]
Post subject:  Re: Ambiguous SWR Bar Graph and Values in TX screen

Hi Ron,

Nine times out of ten when there's a problem with the power readings, there's something wrong with T3. If you email me some photo's of T3 I'll be happy to see if I can spot the trouble.

Take lots of shots from different angles.

jim (at) hobbyPCB (dot) com


Author:  Ron J. [ Sat Jan 06, 2018 11:33 am ]
Post subject:  Re: Ambiguous SWR Bar Graph and Values in TX screen

As an update, I've emailed Jim some photos of T3. Here are a few screen shots that depict the behavior I've observed in the transmit screen. I also completely removed the ATU and the behavior on the TX screen remained unchanged, still showing ambiguous values.

File comment: With ATU in "watt meter" mode, SWR is 1.25, and power levels are ambiguous.
KK6I - HR50 Display Photos (3).jpg
KK6I - HR50 Display Photos (3).jpg [ 58.79 KiB | Viewed 3146 times ]
File comment: TX screen showing an SWR of 80. Analyzer and other radios have the SWR at 1.25.
KK6I - HR50 Display Photos (2).jpg
KK6I - HR50 Display Photos (2).jpg [ 59.68 KiB | Viewed 3146 times ]
File comment: Opening 20m screen
KK6I - HR50 Display Photos (1).jpg
KK6I - HR50 Display Photos (1).jpg [ 59.35 KiB | Viewed 3146 times ]

Author:  Ron J. [ Wed Jan 10, 2018 5:51 pm ]
Post subject:  Re: Ambiguous SWR Bar Graph and Values in TX screen

Thanks Jim for your very prompt response!

Jim quickly realized that I had not installed the relay jumper (RLY) at W1; for some reason I skipped this step thinking it was focused on the QSK option. I soldered a jumper on top of the board and both the amplifier and ATU work like a charm! :D Issue resolved!

Author:  g0dbi@posteo.net [ Sun Nov 04, 2018 11:54 am ]
Post subject:  Re: Ambiguous SWR Bar Graph and Values in TX screen

I have just finished sn1921 with the QSK board but no ATU, and I have a very similar problem, although maybe not identical. Driving the HR-50 with 3 watts of CW and then into a dummy load, the display shows the power and SWR bar graphs at the same or very similar levels, the SWR just slightly lower. SWR is shown at anything up to 100, depending on the band (I tried 30m and 40m), and PEP is shown as 31. However, when I put an external power meter between the HR-50 and the dummy load, there is no signal being emitted at all.

I have the jumper installed in the QSK position on the main PCB. I was very careful with T3 and I thought I had got it right, but I've enclosed some photos - the red that you can see on the white Kynar wire is marker pen from where I marked the 4 connections for stripping, and I used a 30 AWG wire stripper. As far as I can tell from doing continuity testing with my DMM, the connections are all good.

Any ideas where I should start looking? Now that I look at my photos, I can see that on the 30 AWG Kynar connections on the inner side of the PCB I just soldered them underneath and the solder hasn't flowed through to the top side. I'll try soldering them on the top of the board as well, but would that be enough to cause a problem? I'll report my results when I've done that (won't be tonight).

Many thanks

Kevin, G0DBI

IMG_0330crop.JPG [ 235.54 KiB | Viewed 2179 times ]
IMG_0326crop.JPG [ 157.96 KiB | Viewed 2179 times ]

Author:  jimveatch [ Sun Nov 04, 2018 8:49 pm ]
Post subject:  Re: Ambiguous SWR Bar Graph and Values in TX screen

Hi Kevin,

It's almost certainly something wrong with T3. Very seldom does something go wrong with the SMT detector diodes and scaling resistors which are on the bottom of the board under T3. If the voltage and temperature are reading that pretty much rules out the A/D converter.

I can't see you pictures for some reason, maybe that the files are too large. Please email them to jim (at) hobbypcb (dot) com and I'll see what I can see.


Author:  g0dbi@posteo.net [ Sat Nov 10, 2018 1:11 pm ]
Post subject:  Re: Ambiguous SWR Bar Graph and Values in TX screen


Jim couldn't see any problems on my photo of T3 from the top side, so he suggested that I take a look at the nearby SMD components on the under side of the PCB. I couldn't see anything wrong with them, but my soldering of T3 was untidy - I de-soldered all 4 connections and did them again. When I re-assembled the HR-50 and tested it, this time the display showed at least 50 watts out into a dummy load on all bands, the SWR was 1:1 and an external power meter showed that it really is 50 watts out. That's with 3 watts input.

The connections on T3 are very close together and I think that probably using a little more than the minimum amount of solder was the cause of the problem, along with a tiny piece of the 30 AWG wire left sticking out at an angle, because I'd pulled the wires through and bent them at 45 degrees to hold T3 in place and maybe it caused a short. I couldn't see this until I'd de-soldered and I can't be sure it was the problem, but if it wasn't that then it was certainly one of the other connections on T3

Anyway, it's fixed now, and I'm very happy with the amp. Many thanks to Jim for his advice - he was 100% correct that the issue was related to T3.

Kevin, G0DBI

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