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Author Topic: Linear power supply for KiwiSDR & others, fan cooling  (Read 1938 times)

Offline ChrisSmolinski

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Linear power supply for KiwiSDR & others, fan cooling
« on: June 03, 2020, 1228 UTC »
I use an old Lamba linear 5V power supply for my KiwiSDR and netSDR (eBay special for $30 w/shipping). It runs warm, still well within specs but I decided to add a cooling fan. Of course I didn't happen to have at 5V fans laying around, so I went with a 12V fan and an old linear wall wart to power it (the fan only draws about 120 mA). The fan exhausts upwards and pulls air through the power supply. Conveniently the hole spacing for the fan matched that of the ventilation holes in the PSU chassis, so it sits nicely in place with some standoffs.

Without the cooling fan, the power supply chassis runs at about 95F powering just the KiwiSDR, and 101F when the netSDR is also powered up.

With the cooling fan running, that drops to 81F powering just the KiwiSDR and 85F with the netSDR also running. Ambient temperature of the shack at the time was 75F.

Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 400 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline ChrisSmolinski

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Re: Linear power supply for KiwiSDR & others, fan cooling
« Reply #1 on: June 03, 2020, 1707 UTC »
Version 2.0, I mounted the fan on a piece of plastic (from a kids lunchbox that was going into the recycling bin) to direct more airflow through the power supply chassis



The cutout is not terribly neat but works. I drilled a large hole and then use my 35 year old Radio Shack nibbling tool to make the cutout.

Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 400 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline CoolAM Radio

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Re: Linear power supply for KiwiSDR & others, fan cooling
« Reply #2 on: June 03, 2020, 1839 UTC »
Cool piece of "homebrewing" Chris!  lol !


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Offline syfr

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Re: Linear power supply for KiwiSDR & others, fan cooling
« Reply #3 on: June 05, 2020, 1559 UTC »
I'm using an open frame linear, dual output supply off of Ebay. Took a while to get one that works  (shipping damage)and I replaced a couple electrolytics while I had it on the bench.  These things were built to last.   I made a bottom section for it, so I could add individually fused feeders for the 12V and 5V lines along with some coaxial power jacks, since it was not as nicely packaged as your Lambda.  I added a screen on the top to keep from electrocuting myself, my wife or the cat and also bonded everything to the Al ground plate in hopes of keeping noise down. There's a second Kiwi in there now, and BCB and FM notch filters before the splitter and homebrew distribution amp. An aluminum top plate sandwiched to a 1x10 pine (the same sandwich as the rest of this is made from) forms the top of this (not shown)





I think these commercial linear supplies run warm as they're designed  with a significant resistive load in order to keep the regulation pretty tight between load and no load events.   Lambda makes good stuff, and you got a bargain!

« Last Edit: June 07, 2020, 1207 UTC by syfr »
Kiwsdr x 2. TenTec Paragon/NRD535

Offline ChrisSmolinski

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Re: Linear power supply for KiwiSDR & others, fan cooling
« Reply #4 on: June 06, 2020, 1542 UTC »
Yes, the Lambda supplies are solid. Power One also makes good supplies.
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 400 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline Charlie_Dont_Surf

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Re: Linear power supply for KiwiSDR & others, fan cooling
« Reply #5 on: June 07, 2020, 0655 UTC »
Lambda made (makes?) some very reliable power supplies.

I have a Kepco 12 V, 10 A supply that I must have purchased (used) in the the 1980's. At that age, it's a linear supply with a heavy transformer that vibrates waaay too much. Even if it's sitting on the floor, the 60 Hz vibration in the room in very noticeable, to the point where I can't leave it powered on for hours because it is just too fatiguing for me.

Aside from the noise, that supply is top notch. Kepco makes rugged stuff that holds up.
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