HL2: No RF Output

[Santiago Martel]

Hi everyone,

My name is Santiago .

Last week I purchased two Hermes Lite 2 kits. I received one of them on Thursday and assembled it together with a local operator who has been using the Hermes Lite for about two years.

We tested the unit using his known working configuration. Reception works perfectly, but on transmit the unit produces no RF output at all in any mode.

When switching to TX, the unit does draw current(0.2A) and the temperature rises as expected, but there is still no RF output.

We carefully reviewed the configuration and tried different settings, but were unable to get any output. At this point, it does not seem to be a software/configuration issue.

I have a second unit arriving this week(Today), and I plan to do some cross-testing (swapping boards) to help isolate the problem.

What would you recommend checking in this situation?

Thanks in advance,
Santiago LU2DUR

[Santiago Martel]

Hi everyone,

Apologies, I forgot to attach the configuration I’m currently using in my previous message. I’m including it here.

Thanks,

Santiago LU2DUR

[Santiago Martel]

Hi everyone,

I wanted to share a clear and complete summary of the tests performed so far.

Today I received the second Hermes Lite 2 kit, which allowed me to compare both units and perform cross-testing.

When inspecting the unit with issues (the one received last week), we noticed some solder joints around the relay and the PA transistor that look unusual to us. We would appreciate your opinion on whether they appear correct.

As part of the tests, we swapped the N2ADR board with the one from the new unit received today. However, the issue remains exactly the same, so we ruled out that board as the source of the problem.

Continuing with the tests, at one point the unit began to produce RF in TUNE mode, but in an erratic way: RF appears and disappears intermittently, as if the PA engages and disengages during some transmissions and not others.

When switching to MOX mode, the behavior was similar: intermittent transmission, with moments where there is output power and others where there is no RF output at all, without any changes in band, frequency, or configuration.

Additionally, in TUNE mode an abnormal noise can be heard coming from the TX relay. In MOX this noise does not always appear, but the transmission remains erratic.

We also ruled out a configuration issue, since the second unit received today was assembled, connected, and started transmitting correctly immediately using the same configuration.

I am attaching photos of the solder joints mentioned above, as well as a video where the relay behavior can be heard during transmission in TUNE mode.

Based on the observed behavior, we estimate that this could be an issue in the TX path, possibly related to the output relays or the main control board.

I will share updates tomorrow after testing the unit on a different computer.

RELAY NOISE
https://youtube.com/shorts/DQ01IT9XjIg?si=94S9zihj3KsUUwCC

Thanks,
Santiago (LU2DUR)

[Aaron]

What type of antenna are you feeding into?  This almost sounds like RFI making its way back into the shack or a severely mismatched or shorted antenna, at least from my own experience.  What is SWR at radio feed point?  I briefly heard this on 40M and also had some weird issues going on in the house, including knocking my NVME drive out temporarily until a full reboot on my firewall due to RFI.  I immediately ceased operation, installed a 1:1 choke at the transceiver , and re-ran tuning from my XPA125b, which solved the issues.

[Santiago Martel]

Hi Aaron, thanks for your input.

All tests were performed both with a dummy load and with proper antennas matched to each band, so SWR is not an issue in this case.

What’s interesting is that I disconnected this unit and connected another Hermes Lite that I received today (I purchased two units a couple of days apart), and the second unit does not show any of these issues under the same conditions.

Because of that, I’m leaning away from RFI or antenna mismatch and more toward a problem specific to this particular unit.

The behavior also appears under constant carrier (TUNE), which further suggests it's not related to RF feedback from the antenna system.

Tomorrow I will also test it with a different computer and report back with any updates.

[Steve Haynal]

Hi Santiago,

It is good you have a working HL2 so that we can eliminate software settings. There is a lot of information on this group (search the gui interface at groups.google.com/g/hermes-lite) for no RF output. Also, please see this wiki https://github.com/softerhardware/Hermes-Lite2/wiki/No-Transmit

Please try the following and report back:

1. Do you still experience the problem when the board is removed from the enclosure and the heat shim is removed? You can transmit safely into a dummy load for a short period of time (<10 seconds) this way. Sometimes components are knocked off or the heat shim is not installed in the correct orientation. https://github.com/softerhardware/Hermes-Lite2/wiki/Final-Assembly#heat-shim
2. With the board still removed from the enclosure, can you apply finger pressure to the relay and various components in the PA area which cause the problem to go away during transmit? This can help identify poor solder connections.
3. Again with the board removed from the enclosure, what is Vpa during transmit? If you have an oscilloscope, is it a clean (little noise) voltage during transmit?  https://github.com/softerhardware/Hermes-Lite2/wiki/Hardware
4. If you lower the RF power output in software, do you still experience the same problem?
5. Please post pictures of the quarter of the board where the PA and TX relay are located. Not with microscope and not from a distance, but a fairly closeup phone picture. We can check for missing/damaged components as well as poor solder joints.

73,

Steve

kf7o

[Santiago Martel]

Hi Steve,

Thanks again for your help.

I tested the unit outside the enclosure as suggested. The behavior is the same: the radio goes into TX, the relay engages, but there is no RF output.

I also applied light pressure on the relay and PA area during transmit. When I move one of the relays, the drive power increases slightly, but it never reaches full level and the PA does not properly excite.

Regarding VPA measurements, these are the values I obtained:

• V2: 1.18 V
• Vsupply: 13.95 V
• Vpa (Tune): 7.92 V
• Vbias: 9.99 V
• V5: 2.48 V
• V3: 3.26 V
• Vop: 10.1 V

I do not have an oscilloscope, so I was not able to check VPA noise.

Additionally, I have observed several solder joints on the board (particularly around the PA and relay area) that do not appear to be in good condition.

Please let me know how you would like me to proceed.

Best regards,
Santiago

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[Steve Haynal]

Hi Santiago,

Thanks for the pictures and measurements. I have a few more questions.

1. You posted a movie several days ago demonstrating a buzz or relay chatter. When that occurs can you feel exactly which relay or component is buzzing? The 3 larger inductors near the power supply could also be the source of the buzz.
2. With the n2adr board removed, what happens if you transmit briefly (<5 seconds) with no load connected? Does the buzz go away? Is there more current draw or measurable RF power output by listening on another radio? This is safe to do briefly even when the HL2 is removed from the enclosure.
3. Please provide a picture of your board from the angle shown in the attached picture. I'd like to see B106 and L34. They are not clearly visible in the pictures you sent.

I do not think there is a soldering issue in the microscope pictures you sent.

[Santiago Martel]

Hi Steve,

The relay that was “chattering” seemed to be the one between TX/RX. That behavior stopped after a while.

Now, when pressing TUNE or MOX, I can still hear the relay switching, but there is no RF transmission at all — neither on measurement instruments nor when monitoring with another radio.

When switching to TX, Thetis shows a normal temperature increase, and the reported current rises from 0.0 A to about 0.2 A.

I’m attaching the requested pictures. Please let me know how to proceed, as I’d really like to get the unit working.

Thanks.

Santiago

[J P Watters]

Steve,

Let me know if I should send relays out?

..jpw

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[Steve Haynal]

Hi Santiago,

I think your TX/RX relay K2 is bad. This is a common mode of failure. We can ship you a replacement relay, or you can return and exchange the HL2 board. I will contact you privately.

73,

Steve

kf7o