HFU HF Underground
Technical Topics => The RF Workbench => Topic started by: ION Radio on December 24, 2017, 1303 UTC
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I'm looking to replace a cheap Chinese PSU I've been using to power my Lulu TX. It was good enough I guess to get things started but I recently got a scope and it looks like I get a lot of ripple/noise from my Chinese PSU. Carrier looks terrible on scope and it may be that I don't have my scope settings correct. I'm still learning how to use the scope but I strongly suspect it's the PSU. My audio sounds good on recordings that listeners send with reports, so I don't think the PSU is affecting the audio too badly anyway, but I think I should use a better PSU. I can save the image on the scope, I still have to figure out how to do that, if anyone wants to have a look at what my carrier looks like on the scope with the cheap PSU I can send that to you.
I looked around online for a new PSU but I would like to hear about what other people are using before I spent more money. The Lulu I got from Stretchyman will run from 12-24 volts. I usually stay at 18v (12 watt carrier) so a power supply that is adjustable between 12-24 volts is what I'm looking for. PSUs I see online for Ham radio only go up to 16v. I really don't want to use battery power.
Thanks for any help!
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Variable PSU is going to be expensive.
Best deal looks to be Chinese SMPSU of 24V @ 5A at around £10, however I've no idea of how good (or bad they are) but have just purhased one to check out and will let you know (if I've not, PM me in a couple of weeks).
Another source of a decent PSU is the LAPTOP bricks as they're 19V @ 6A (120W).
The PSU's I use are all lab PSU's so cant comment on whats available, there's a lot of crap out there!
Str.
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Unfortunately it is not hamfest season (not in this part of the US anyway), but I have often seen nice linear power supplies at them. Many of the 24 volt supplies can be adjusted down via a trimmer pot, not sure if you can get to 18 volts or not, it would depend on the model. There are some well made switching supplies with relatively low noise outputs, Vicor comes to mind. Expensive new, but again pretty cheap at hamfests.
As Stretchyman said, many laptop supplies are around 19 volts, and again, they vary in quality. A genuine name brand supply (say via eBay) is most likely to be low noise, OTOH the Pride of China supplies are almost guaranteed to spew RFI. I ran into that problem when I got a replacement supply for one of the kids' laptops. S9+20 noise over all of 43 and 48 meters. Yuck.
A linear supply is going to be larger and less efficient, but guaranteed to be low noise.
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I've been using the LRS series supplies from mean well. They seem to work well enough, a 24V supply should turn down to 20V or so. Be sure to get one at least 2x your carrier power, 3X is better.
RFI can sometimes cause problems with switchers. Brute force filtration may be needed in some applications.
+-RH
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Thanks for the input!
-IR
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OK, confirmation of cheaply available and compatible PSU for my GaN Tx's.
https://www.ebay.co.uk/itm/DC-3V-5V-12V-24V-36V-48V-Universal-Regulated-Switching-Power-Supply-LED-CCTV-PSU-/151886747221
The PSU has;
JCPOWER JC-120-24 written on label.
24V 5A.
With the PSU at 26V and the Gan LuLu giving a 40 W carrier, no voltage dips were seen at 100% mod.
Caution is advised however as most of the LuLu's I've sold are 10W and ABS MAX voltage is 14V, NOT 24V.
Open the lid, look to see (thru' the hole in the PCB) if the FET has an insulating washer it's ONLY 10W.
OK!
Str.
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I'm not a big fan of Switching power supplies for rf applications for a few dollars more...
https://www.ebay.com/itm/POWER-SUPPLY-15V-5-5A-LAMBDA-LDS-X-15-47-63Hz-EXCEPTIONAL-REGULATION-NOS/322445608094?epid=734586403&hash=item4b1341849e:g:Ov4AAOSwB-1Yv57S (https://www.ebay.com/itm/POWER-SUPPLY-15V-5-5A-LAMBDA-LDS-X-15-47-63Hz-EXCEPTIONAL-REGULATION-NOS/322445608094?epid=734586403&hash=item4b1341849e:g:Ov4AAOSwB-1Yv57S)
or you can just build your own..
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I have good luck with Mean Well (they meant well...) supplies. You can get them off the shelf anywhere. If you want something built a little better, TDK Lambda makes good stuff too with a little better ripple performance.
I don't know why anyone would take a chance on a no-name chinesium wonder.
+-RH
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You said it Redhat. I've heard so many horror stories about Chinese electronics and parts, it's tough to pull the trigger on them.
I'm a hamfest man when it comes to power supplies. You can stock up on ferrite cores/chokes to tame possible problems while you're there and come out with plenty of money left over. When it craps out, and it will, someone will buy it to either try their hand at fixing it, or for parts and a pre-drilled box. It's hamfest recycling at work.
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Yes, you can get good deals on nice linear supplies at hamfests. Lambda and Power One are names to look for. Every so often a decent adjustable benchtop supply will turn up as well.
It's possible to make quality switching supplies, at a former job we used Vicor, their stuff was good, and we never had issues even though we used them in industrial process control applications where we were taking sensitive measurements. I've seen Vicor supplies turn up now and then at hamfests.
When I bought my GPS reference (used, a pull from a cell phone tower installation), it came with a Pride of China supply. That thing generated all sorts of RFI, including junk right on top of the 518 kHz NAVTEX frequency. I found a Power One linear supply with the appropriate outputs (5 and 12 volts), and it's been great since, no RFI at all.
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BTW, if you're not a hamfest vet avoid anything with a cut cord, unless you're looking for parts and a box. The cut cord means it's shot. Sniff for ozone if the cord hasn't been cut, that's a telltale sign, as are black scorch marks from arcing when you open the the box and any obviously blown parts.
90% of people at hamfests are straight shooters, it's the other 10% you've got to watch.
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But then again your dealing with hams, most of which these days don't know how to fix anything (appliance operators).
+-RH
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If you want a used one, I agree with the eBay/ hamfest idea, but also advise you to acquire a linear power supply rather than switchmode.
if you want to buy a new one, I wholeheartedly recommend Astron power supplies, I have one rated for 20 amps at 12 volts, and it will gladly provide its maximum power with almost no ripple day in and day out
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If you want a used one, I agree with the eBay/ hamfest idea, but also advise you to acquire a linear power supply rather than switchmode.
if you want to buy a new one, I wholeheartedly recommend Astron power supplies, I have one rated for 20 amps at 12 volts, and it will gladly provide its maximum power with almost no ripple day in and day out
A linear PSU is what I think I will eventually get, Astron has great reviews.
Thanks ALL!
-IR
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Astron makes great power supplies. I have one I bought back in the 90s, and it still works. The only thing I had to recently was replace the lighted power switch.
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Its funny you should mention that, the only thing wrong with mine is that the indicator light in the switch has failed.
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Its funny you should mention that, the only thing wrong with mine is that the indicator light in the switch has failed.
You can find replacements on eBay/etc, but they tend to be expensive. Mouser sells a replacement that fits perfectly, and is just $1.42: https://www.mouser.com/ProductDetail/691-LRA211RSB-125N