[ARC5] 24vdc power

[scottjohnson1 at cox.net]

Thanks.  It has been discussed before, but if you operate the old boat
anchors the way they were designed to operate, they will generally perform
better than any of the half-cocked conversions from the fifties.
Allowing that low voltage, high current supplies were hard to construct/come
by in those days.
Case in point is the BC-375, which had a horrible reputation for chirp and
frequency stability.
I have one with a S/N matched set of tuning drawers (properly neutralized),
which I operate as designed from a floated 24 V battery supply.  I get good
reports on AM, The one comment is restricted audio BW, which was
intentional.

-----Original Message-----
From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> On Behalf
Of Tom Lee
Sent: Sunday, September 4, 2022 1:13 PM
To: arc5 at mailman.qth.net
Subject: Re: [ARC5] 24vdc power

Yes, it's too bad that we don't have a section for FAQs (or do we?). 
Your solution probably ranks the highest in SAF (spousal acceptance factor).
It's also the optimum way to handle both the startup surge and the
steady-state requirements.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 9/4/2022 13:06, scottjohnson1 at cox.net wrote:
> I wish I saved my old posts on this subject since it comes up every so 
> often!  I find the best way to operate rotating machinery that once 
> operated in a mobile environment is to replicate that environment.  
> SO- Get a power supply that can handle the full load current and float 
> an SLA battery across it.  Size of the battery and power supply is 
> proportional to load, but in your case, a 10-20 A switcher. Set to27.5 
> V (for normal indoor ambient temperature) Less for hotter, more for 
> cooler, but in the range of 27-28V.  For your 10A load, 12V 7AH SLA 
> batteries would do nicely. (Two in series).  Increase AH capacity 
> proportionately for higher current loads.  Amazon and eBay have plenty 
> of inexpensive switcher that will work, just don't buy the REALLY 
> cheap ones, unless you like the acrid smell of burning components.
>
> -----Original Message-----
> From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> On 
> Behalf Of Charles via ARC5
> Sent: Sunday, September 4, 2022 10:23 AM
> To: arc5 at mailman.qth.net
> Subject: Re: [ARC5] 24vdc power
>
>> Hey guys,
>> What's everybody using to provide 24vdc for your military radios? Two
> 12vdc supplies in series?  Home brew?  Do they make a 24vdc switching 
> supply that will handle 10 amps or so?
>> Thanks for your input,
>>
>> Richard kn7sfz
> Anything with a dynamotor needs about five times the motor nameplate 
> current for the starting surge...
>
> I got a 2 KVA three-phase 115V 400 Hz rotary converter at a flea 
> market but nothing I had was big enough to start it (rated at 27.5VDC 
> at 115 amps!)
>
> So I bought a 20 VAC, 5 KVA toroid transformer on ebay, a BFBR (big 
> bridge rectifier), heat sink, a 220,000 uF cap, meters and shunts, and 
> brewed up a 24-28V 120 amp brute force supply with 240 VAC input. THAT 
> starts the converter all right. It doesn't even blink at smaller 
> dynamotors :)
>
> -Charles, WB3JOK/0
>
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