Power Supply

Ya’akov

Joined Jan 27, 2019
6,856
If the radio is the Bearcat 980 you mentioned, it’s going to be hard to do more than guess at the power supply current capacity required. This is from the owner’s manual:

1668968834008.png
The general case, not even considering the particular radio, might be understood by long ago experience with CB radios of all types. The output is only 4W by law, so the current requirements are not great. In the days I cared about CB, about …mumble… years ago, the “standard” power supply was ~4A.

Considering the 4W RF PA, and the 3W audio PA, and ballparking the efficiencies involved, it would seem that this Pyramid 5A supply is a good option. I was surprised to find a Pyramid supply because that was the very brand that was considered “good stuff” back then.
 

MisterBill2

Joined Jan 23, 2018
13,754
How about an Atx PSU, that will work ok.
An internal computer type power supply is a poor choice for any other application. Quite a few articles are published, mostly by those without adequate understanding.
Noise levels that are OK for a desktop computer are far to noisy for a radio of any kind, especially a transceiver.
 

Ya’akov

Joined Jan 27, 2019
6,856
While there are certainly a multitude of applications for salvaged computer power supplies, HF radios are not one in general.

An AM receiver on the 11m band is likely to see a fair bit of unintended transmission from any switching supply. The switchers marketed to hams have a "noise offset" so you can move the switching frequency somewhere else if you are badly affected by it.

That said, it is not likely the TS will be trying to work weak signals so the squelch may be normally set high enough to block the interference. If he's got a supply around it is worth trying to be sure, but a linear supply of 5A like the one I linked above is very affordable and pretty much purpose built.
 

MisterBill2

Joined Jan 23, 2018
13,754
Hi Bill,
That statement is misleading nonsense, I and many others have used old ATX PSU's successfully on many applications.
E
The adaptations that I have seen all required adding a resistor load to the 5 volt output to keep the supply operational. So that adaption leads to wasting about 20 watts as heat. That alone makes it a poor choice as I see things. Possibly some supplies do not need such a load.
 

ericgibbs

Joined Jan 29, 2010
16,789
Bill,
Where on this conversion video is a 20Watt fixed load required.??
I suggest you research a problem/solutions and stop guessing, before posting.

On conversions that do require a 5V load, a useful load is a bench inspection lamp.

E

 

MrSalts

Joined Apr 2, 2020
2,611
ATX power supplies were poor choices when they had massive iron powder toroidal cores and SMPS running at 20 to 80kHz. Today, you can get 600 to 800w ATX power supplies that are a quarter the weight and running at 800k to 1MHz. The DC ripple will be minor and some small filter will easily handle.
 

MisterBill2

Joined Jan 23, 2018
13,754
Mostly, if somebody is looking for a power supply cheap, they do not buy a new one, but rather get a retired supply from an older computer. Thus my remarks are not aimed at state of the art supplies, but at used ones.
AND, does it really make sense to re-purpose one of those supplies with all of the other voltages that they produce?? And all of the wiring that must be dealt with??
And who believes everything they see on youtube???
 

MrSalts

Joined Apr 2, 2020
2,611
Mostly, if somebody is looking for a power supply cheap, they do not buy a new one, but rather get a retired supply from an older computer. Thus my remarks are not aimed at state of the art supplies, but at used ones.
AND, does it really make sense to re-purpose one of those supplies with all of the other voltages that they produce?? And all of the wiring that must be dealt with??
And who believes everything they see on youtube???
Ok, you have me there. 800MHZ smps have been used only since about 2014 or 2016 era so much too new for someone to use as scrap from an old desktop [/sarcasm]. That said, when was the last time you attempted to use an ATX power supply for something besides powering a PC? 2002, 1998?
 

MisterBill2

Joined Jan 23, 2018
13,754
Ok, you have me there. 800MHZ smps have been used only since about 2014 or 2016 era so much too new for someone to use as scrap from an old desktop [/sarcasm]. That said, when was the last time you attempted to use an ATX power supply for something besides powering a PC? 2002, 1998?
Actually, I examined one and concluded that it in no way met any of my requirements and so I built a power supply from assorted parts. Then later I built a few more from assorted salvage parts. I never saw an ATX supply that had the form factor for any of my applications, which included powering various transceivers and amplifiers, and some logic circuits as well.
Also adapted a few switcher supplies that were NOT made for PC applications.
 

Reloadron

Joined Jan 15, 2015
7,078
Am I the only one that read the attachment in @ericgibbs post #6? It states the radio needs 13.8VDC, not the ATX 12VDC.
No, I also read that and in a few places. :)

To really get the best out of the radio I would look for a PSU designed for the intended application. They do make power supplies that will deliver 13.6 VDC at 5.0 Amps which will be adequate. I also figure it this way. I have over a $100 USD bill in a radio I am going to buy a good name brand power supply and for stationary base use a quality antenna and lead in cable. However that is for the thread starter to decide. Buy once and cry once works for me.

Ron
 

MisterBill2

Joined Jan 23, 2018
13,754
Given that the equipment to be powered was designed for operation in a motor vehicle, and given that the radio should also function adequately in the vehicle with the engine off and the charging system inactive, and because the battery voltage at rest is rather close to 12 volts, it is true that while the supply should be 13.6 volts for rated output power, , but the performance will be quite satisfactory when the radio is powered by 12.0 volts DC.
All well designed mobile electronics are designed to operate over a wider voltage range, because most mobile power systems that include an engine driven charging system do vary quite a bit. At least in the real world they do vary.
 
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