Page 1 of 1
SWR meter shows 9.99
Posted: 07 Aug 2022, 23:44
by KO4TCY
Hello,
I just build the kit purchased from Amazon. I am in the process of tuning the RF section by following the official tutorial. Although when testing the radio into a dummy load the screen shows 13 Watts and 9.99 SWR. This is on CW on 20 Meters.
I have a nanoVNA like the video says and the L12 coil is reading at 27.400 MHz. I am power it from a 12 volt lead acid battery.
Any suggestions for that I can try?
Re: SWR meter shows 9.99
Posted: 08 Aug 2022, 00:22
by KO4TCY
I followed the troubleshooting done in
viewtopic.php?p=1898#p1898.
But, FWD and RVS are very high voltages. Tested on 20m into dummy load.
FWD: 3.3v transmitting. 3.6v idle
RVS: 4.3v transmitting. 4.6v idle
Re: SWR meter shows 9.99
Posted: 08 Aug 2022, 01:06
by KO4TCY
The issue was my MCU had dry solder joints that weren't making contact all the way. That also was stopping me from running off of the DC jack. The jack wasn't soldered all the way on. Some QC issues with the Amazon kit.
Re: SWR meter shows 9.99
Posted: 08 Aug 2022, 03:18
by N4XTL
Very interesting. Glad you found the issues. Someone else posted about backwards tantalums on their main board...
I'm curious about the results of your tuning. I posted about my experiences with the Amazon kits in another thread. The RF board in one radio turned out pretty good after removing turns from nearly every inductor in the filter sections. The other radio and RF board is so-so. I feel that the toroids and caps used in the Amazon kits are somewhat suspect. They are supposed to be from the same "authorized" seller but I don't know.
Re: SWR meter shows 9.99
Posted: 08 Aug 2022, 14:22
by KO4TCY
I had to remove one turn from all of the LX2 toroids to get the second harmonic close.
Removing one turn from the LX1 toroids would increase the power for those bands, correct?
Re: SWR meter shows 9.99
Posted: 08 Aug 2022, 22:32
by KO4TCY
Unfortunately the issue has returned and now my radio shows 13 watts out and 9.99 SWR. This happened just from taking the radio with me in the car to my university's radio shack.
Re: SWR meter shows 9.99
Posted: 09 Aug 2022, 00:23
by N4XTL
KO4TCY wrote: ↑08 Aug 2022, 14:22
I had to remove one turn from all of the LX2 toroids to get the second harmonic close.
Removing one turn from the LX1 toroids would increase the power for those bands, correct?
Effectively yes, though what it's really doing is moving the passband of the filter around. With your kit you almost certainly have too much inductance in LX1 so removing a turn will improve your output power across the entire band. Power will still decrease as you go up in frequency but there will be an improvement. You can further adjust the value of LX1 to favor one side of the band or the other. I think most people plan to use these radios for CW, hence the tuning often focuses on the bottom of the band, but on one of my radios I favored the voice portion of the bands at the expense of efficiency down low. In the case of the 80m band I actually made the bottom of the band unusable (power way too high, risky for the FETs) in order to improve output in the voice portion.
KO4TCY wrote: ↑08 Aug 2022, 22:32
Unfortunately the issue has returned and now my radio shows 13 watts out and 9.99 SWR. This happened just from taking the radio with me in the car to my university's radio shack.
Unfortunate. I wonder if the seller would agree to a refund, given that the boards in the kit clearly have poor soldering.
Re: SWR meter shows 9.99
Posted: 09 Aug 2022, 00:52
by KO4TCY
At this point I think my main boards are garbage. I tried to reflow the solder with a heat gun and now the radio menu is slower and the CW tone sounds fluttery.
I wish I knew if my boards were destined to be broken or if I destroyed them.
Re: SWR meter shows 9.99
Posted: 09 Aug 2022, 02:58
by KO4TCY
N4XTL wrote: ↑09 Aug 2022, 00:23
KO4TCY wrote: ↑08 Aug 2022, 14:22
I had to remove one turn from all of the LX2 toroids to get the second harmonic close.
Removing one turn from the LX1 toroids would increase the power for those bands, correct?
Effectively yes, though what it's really doing is moving the passband of the filter around. With your kit you almost certainly have too much inductance in LX1 so removing a turn will improve your output power across the entire band. Power will still decrease as you go up in frequency but there will be an improvement. You can further adjust the value of LX1 to favor one side of the band or the other. I think most people plan to use these radios for CW, hence the tuning often focuses on the bottom of the band, but on one of my radios I favored the voice portion of the bands at the expense of efficiency down low. In the case of the 80m band I actually made the bottom of the band unusable (power way too high, risky for the FETs) in order to improve output in the voice portion.
KO4TCY wrote: ↑08 Aug 2022, 22:32
Unfortunately the issue has returned and now my radio shows 13 watts out and 9.99 SWR. This happened just from taking the radio with me in the car to my university's radio shack.
Unfortunate. I wonder if the seller would agree to a refund, given that the boards in the kit clearly have poor soldering.
Would that also be the case for the SWR transformers? Would I need to remove a turn to make them 6:1? If the inductance is too high would that make the MCU think the SWR is 9.9?
Re: SWR meter shows 9.99
Posted: 09 Aug 2022, 04:13
by N4XTL
No the ratio of the transformers must stay at 7:1. It is recommended to do a mod to T2 to improve efficiency, using 21:3 turns, but the ratio is still 7:1.
I have seen 9.99 SWR on my radio before when my dummy load wasn't properly hooked up. I guess it can be taken to mean "very high SWR reading". Since you suspect bad solder joints on your boards, you might look for bad joints on the PCB interconnect headers and around the transformers. Pretty much everything here:
- tr1s.JPG (41.52 KiB) Viewed 1387 times
Perhaps also reflow the joints on your transformers in case you didn't quite get all of the enamel off of the wires.