开云体育

GMK tec KB5 . On Ali Baba and Amazon.

Just Google it or here is a link.

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https://es.aliexpress.com/item/1005007007191836.html?src=google&pdp_npi=4%40dis!MXN!7563.38!2487.63!!!!!%40!12000039054050007!ppc!!!&src=google&albch=shopping&acnt=742-864-1166&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shopping&aff_platform=google&aff_short_key=UneMJZVf&gclsrc=aw.ds&&albagn=888888&&ds_e_adid=&ds_e_matchtype=&ds_e_device=c&ds_e_network=x&ds_e_product_group_id=&ds_e_product_id=es1005007007191836&ds_e_product_merchant_id=5369286629&ds_e_product_country=MX&ds_e_product_language=es&ds_e_product_channel=online&ds_e_product_store_id=&ds_url_v=2&albcp=22055462289&albag=&isSmbAutoCall=false&needSmbHouyi=false&gad_source=1&gbraid=0AAAAA99aYpdHlLdXN0qD2CeDhlGoq7_na&gclid=CjwKCAjw--K_BhB5EiwAuwYoyuQpxrCkrA171Plh8Kg-6pebbEJzo3aihbAXKfIBqM6bjUM2rF1bDhoCw24QAvD_BwE

On Thu, Apr 10, 2025 at 02:52 PM, Bruce Akhurst wrote:

Hope you’ve got your fault protection sorted.?
Prospective short circuit will be 10kA and an auto fuse ain’t going to stop that arcing ..

It can be as simple as a fusible link.? Go down 4 wire size numbers, so for example #16AWG link in #12AWG conductor, a foot long, connected in series with the main 12AWG line with compression crimp splices NOT solder.?

The link including splices and at least an inch beyond (I cover about 2-3 inches), is covered with fire sleeve.?

I use an 18 inch long sleeve for a 12 inch link; the idea is to contain and cool the hot gases if the link fuses so leave room.? Close each end of the sleeve with a zip tie or flat lacing tape.? Extra style points for two ties 1/2 inch apart.

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More folks should be aware of the advantages of lacing tape over zip ties in applications like this, especially where someone has cut the zip tie surplus with a diagonal cutter, leaving two flesh-shredding hooks exposed.? A tool like this will properly tension and cut the tie with a blunt end, save time and avoid much bloodshed: ?

Lacing tape:

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Of course an appropriate fuse is generally needed to protect against nuisance overloads as well; they are easier to replace than a link.

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Let's be safe out there.

73, Don N2VGU

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This is the exact scenario where TN0110 shines. 100V breakdown and its lower threshold voltage precludes the need for additional drive capability. Why not try these Randy?

Tony AC9QY?

Hi Stan!

I just got finished installing the new buck board. I used 7V and 250mA to power the device this time. With USB-C cable plugged in I plugged in the barrel connector and immediately saw that the QMX showed up on my PC and the power supply indicated about 200mA were being pulled. This is still concerning since the instructions specifically state there should be zero power draw until the left rotary encoder is pushed in.

I tried unplugging and replugging a few times, also attempted a firmware flash, but the behavior of immediately powering on still persists. After attempting the firmware flash, the device still powers on immediately upon being connected to power, but I now see black squares across the screen where as before the flash I saw no characters at all. I'm still puzzled as to where things are going wrong. I assume the issue that blew out the components mentioned in my earlier post is still lingering somewhere. The reduced power supplied is probably preventing anything from blowing but I'm at a loss as to what's going wrong. Any guidance would be greatly appreciated!

Braden,

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Tisha is saying that linear regulators burn the difference between Vin and Vout as heat.

Your DROK is a switcher, not a linear regulators, that's a good solution if it doesn't create too much noise.

About half of the posts in this thread are about linear regulators.

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Tisha's advice on linear regulators is good.

1)? Linear regulators should have caps on input and output to keep them stable, or they may oscillate and cause noise.

2)? Also check the datasheet for the dropout voltage, some require that Vin be a couple volts greater than Vout.

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Some linear regulators have a dropout of less than half a volt.

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Don ND6T descripted an effectively zero dropout circuit he had seen in SPRAT:

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Jerry, KE7ER

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On Fri, Apr 11, 2025 at 04:02 PM, Braden Glett wrote:

IF you getting noise form 78xx parts its your fault.

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The input need minimally 1uf cap with short leads and the

output not less than .1uf.? ?The 78xx part are linear regulators

and if there is noise its because the bypassing is poor and

its oscillating.

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I've seen that in many cases, used wrong it does bad things.

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--

Allison
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Post online only,?
direct email will go to a bit bucket.

Randy,

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I am not surprised by your results.? If you look at the datasheet from Onsemi, the device needs 6 volts gate to source to turn on fully:

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You could feed the 78ACT08 6 volts to see if that helps.? You could also try a buffer MOSFET (maybe a BS170) to increase the drive voltage.? Both possible solutions require a lot of board surgery.? Feeding 6 volts to the ACT08 is pushing that device to its limit and is over the limit for the TI part.? The Onsemi part can go to 6.5 volts.

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Better to stay with the BS170s.

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I received the inductors late yesterday and just finished replacing L501.? I'm now getting ~30mA for the bias current.

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It's still reporting 0W output in the Diagnostics when I hit Transmit into the dummy load.? SWR is back to being all over the place, too.

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Guess I'll have to break out the oscilloscope again...

Realized I'm not exactly helpful if I don't share what I'm using now... I grabbed a refurbished Dell XPS off of for about $200 that was a decently new i5 with 16GB of ram with an SSD. Plus I can take it mobile. Off-lease desktops/laptops is a treasure trove for this sort of use case.

I had one of these Beelink's briefly and returned it; the power adapter it shipped with wasn't powerful enough to power it stably, (it'd crash repeatably if you tried to output 4k, for instance. I put a good DC adapter on it and it ran perfectly, but I didn't want to dedicate my high end DC adapter to this, and it would have cost another $30 for an actually good power supply, so sent it back.

73 - KD7SKY

No joy here, but I promised to post my results.

After "upgrading", the performance was noticeably worse in my case. Especially and not unexpectedly on the higher bands. See below.

So I personally will continue using an inline regulator to protect from overvoltage but am switching from 7812s to the Low Dropout (.5v vs. 2v) LM2940C-12.

MMDV...

And thanks to Hans for providing such high quality circuit boards that we experimenters can solder, unsolder, solder, unsolder, and solder again and have no noticeable impact to the circuit traces.?

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Radio	Band										Avg.	?
?	160	80	40	30	20	17	15	12	10	6	?	?
QMX+	5	5.2	4.6	4.3	3.7	2.5	4.5	3.3	3.5	0.9	3.8	Original BS170s
QMX+	4.5	5.9	4.4	4	2.3	1.7	2.5	1.5	1.5	0.5	2.9	With FDT86256 PA Mod
QMX+	5.4	6	4.7	5	2.8	2.2	4.7	3.6	2.6	0.8	3.8	Back to BS170s (new set)

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Randy, N4OPI

Tisha,

I wanted to make sure I'm understanding what you are saying.

As stated earlier, I am using a Drok to regulate from a 12v LiFePo Bienno 3 Ah (actually 13v as I measure it), down to 11.9v. I hear you saying I might be losing more in heat from the Drok than the rig is putting out in power when transmitting (a lot more, in fact!). Yet, I don't feel any detectable heat coming from the Drok.

Is there something I've misunderstood?

TY 73

Braden Glett KD8ZM?

Thank you.?

You might find this group /g/Winmor, useful for assistance in setting up and using Winlink.

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This isn't specifically for QMX but if you repost your question there, someone may be able to help you.

JTDX

JS8 Call

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73, Dan - W2DLC

HDSDR with OmniRig.

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73 N6HAN

Thanks for the clarification,? Hans - I forgot to look at the package size.? So it would require a mini-pcboard adapter - may still be worth trying since we can't get small orders of the 4334 anymore.?