power output/alc

[Tim Davis]

Having a issue with my hermes lite 2, I think its dealing with b106. Sometimes my power output is around 5 watts and works great with the xiegu xpa125b amp other times I get low power output around 0.4 watts and alc warnings on my amp. I did install the heat shim at first and noticed low power so I removed it and checked the bottom of the board and everything was fine where it connects. I pressed lightly on B106 on the top side next to T3 and that seemed to correct the problem. The nut was small enough it was not making contact with anything and i held it in place with my finger to tighten it. I did try to use a small soldering iron to reattach that point yesterday evening but the next day I'm having the same issue. Also when I'm having the issue the freq read out on my tuner is not matching the output from thetis HL2 edition 2.10.0. This is a new kit received it 10/25/23. 

[Steve Haynal]

Hi Tim,

Just to rule out any shorting when installed in the case, can you try the same experiment with the HL2 removed from the case? (You can run at 5W but only for ~20 seconds without heat dissipation. The HL2 will shutdown if it gets too hot.)

It sounds like you narrowed the problem down to b106. Can you post a high resolution photo (most phone photos are fine) of this area?

B106 may need to be resoldered (even though you did so once) or replaced. Are you or someone you know comfortable with doing that? If not and you are in the US, I can arrange for you to ship the unit to me.

73,

Steve

kf7o

[Tim Davis]

Is the unit supposed to have a line like that coming off of B106? same as before low power and alc issue fault on my amp. 

[Jan PA3JRK]

Hello Tim,

Mine doesn''t.

Jan
PA3JRK

Op zondag 5 november 2023 om 23:39:51 UTC+1 schreef timda...@gmail.com:

[Steve Haynal]

Hi Tim,

That looks like a silkscreen blemish on your board. It shouldn't cause a functional issue.

73,

Steve

kf7o

[Tim Davis]

I know it has been a few days. I did resolder T3 and B106 and have had everything working until a around 7pm today. I'm going to get it sent out in the morning Steve. Can't see what would be causing the issue since I do not have the shim installed.  73 Tim/Kc8tyk

[Tim Davis]

I'm going to install the heat shim before shipping. I am going to purchase another one as soon as I understand what is going on. I'll send my information in a private message. 

thank you again. Tim/Kc8tyk

[Google Contributor]

So the PA stage is rated 5 Watts.

What happens if you set the power level to maximum (7 Watts)?

Would additional cooling make this safe, or does it cause distortion (and would the power supply voltage matter)?

[Tim Davis]

 I know when mine was hitting 7 watts i was having a issue. Was having ALC issues when trying to drive the amp even with the slider turned all the way down.  I had been talking with N8SDR who was helping me.

[Steve Haynal]

Hi Tim,

What were the results of the experiment with the unit outside of the enclosure which I requested?

When your unit stops transmitting, what temperature is reported to software? (This is to check if you are triggering the TX inhibit due to over temperature.)

Please check and measure R117 on your HL2. (There have been past cases where if this pullup is not installed or defective, strong RF will trip the TX inhibit input.)

73,

Steve

kf7o

[Steve Haynal]

Regarding the maximum power output, first the difference between 5W and 7W is about 1.5dB. One s-unit is 5 to 6 dB. So you are really not making much difference by "overpowering" to 7W. 

The N2ADR filter board is designed and rated for 5W. The larger voltage swings for 7W are more meaningful, especially for mismatched loads, and you risk exceeding the maximum rating of a component on the N2ADR board.

You will see more distortion from the PA at 7W.

I do have one unit which I run "hot" like this for FT8 and haven't seen issues.

73,

Steve

kf7o

[Phil]

Steve,

I will turn down the output to 5 watts. I am not having any issues and want to keep that way. 

73,

Phil KB3UUL

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[Meir Green]

Thanks Steve. What specific components are liable to be damaged, and what improvements could be made to the components or to the HL2 firmware to make the radio+filters more rugged or even "bulletproof"?

Should high SWR power foldback and/or overheat detection be able to prevent damage from transmitter mismatch?

On Mon, Nov 27, 2023, 4:58 AM Steve Haynal <st...@softerhardware.com> wrote:

Hi Meir,

...

I'd say the N2ADR board is speced for full HL2 power. Everything is a bell curve and probabilities with no black and white, so you just slightly increase your chances of damaging the N2ADR board when running at slightly higher power. Even at 5W output, there may be a so badly mismatched loads and a component on the edge that the N2ADR can be damaged.

73,

Steve

kf7o

On Sat, Nov 25, 2023 at 11:09 AM l... wrote:

Interesting. Why is the N2ADR board not specced to handle the full output of the HL2? Would it be hard to do so?

On Sat, Nov 25, 2023, 7:37 AM Steve Haynal <softerh...@gmail.com> wrote:

Regarding the maximum power output, first the difference between 5W and 7W is about 1.5dB. One s-unit is 5 to 6 dB. So you are really not making much difference by "overpowering" to 7W. 

The N2ADR filter board is designed and rated for 5W. The larger voltage swings for 7W are more meaningful, especially for mismatched loads, and you risk exceeding the maximum rating of a component on the N2ADR board.

You will see more distortion from the PA at 7W.

I do have one unit which I run "hot" like this for FT8 and haven't seen issues.

73,

Steve

kf7o

On Friday, November 24, 2023 at 10:20:34 AM UTC-8 l...@gmail.com wrote:

So the PA stage is rated 5 Watts.

What happens if you set the power level to maximum (7 Watts)?

Would additional cooling make this safe, or does it cause distortion (and would the power supply voltage matter)?

[Steve Haynal]

Hi Meir,

During high mismatch you can see larger than expected voltages which can damage capacitors and inductors in the filter board as well as the PA. The N2ADR filter board and HL2 PA are good designs for an inexpensive radio. I personally don't think it is worth the effort or expense to try and "bulletproof" this portion of the design.

73,

Steve

kf7o

[Meir Green]

So at 5 watts, the board will NOT be damaged?

Can we clarify what situation is damaging in order to avoid it? E.g. SWR of ?:1 at full power for n seconds?

I infer that we know this because in testing at full power, under certain conditions, some filter boards were damaged?

Can we generalize that full power is ok below a certain level of SWR?

Whereas 5 watts is ok below a certain level of SWR?

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[Steve Haynal]

Hi Meir,

I can't clarify the answer for you because as I said earlier there is no black and white scenario, it is a matter of probabilities. I have never seen a N2ADR filter board fail, even at 7-8W. This is a small kit project and we don't test extensively. Look back in this list for comments from N2ADR, the designer of the filter board. He expressed some concerns about pushing the power higher as he designed it for 5W. The filter board and PA have a small probability of being damaged at any power level under certain mismatched conditions. You increase this probability slightly when you push the power higher.

73,

Steve

kf7o

[Tim Davis]

Hello Steve I replied on Nov 5 that it was having the same issue. I should have been more specific that i removed it from the case. I apologize for the confusion.

73 Tim 

kc8tyk