Watts÷volts=amps

[Cody Dixson]

So I've been hunting a power supply for my galaxy dx98vhp which by the manufacturers specs has 10-50w am 200w usb/lsb current drain 25 amps am 40amps ssb and takes 13.8v input voltage

With the given formula
watts÷volts=amps
Am I assuming correctly that I only need
At minimum a 15a power supply to run this one radio
Or that would mean the radio would put out 552w doing the inverse amps X volts = watts or do i need to get a 50 amp power supply just wonder if im using this formula right or if it applies so something different

 

[543_Dallas]

You're not taking efficiency into account. Nothing is 100% efficient. If this were an amplifier you could figure it at 40% efficiency and give yourself some breathing room but a transceiver is more complicated.

If the manufacturer says 40 amps I would consider 50 amps a minimum. Be sure to look closely at the power supply specs and look for the continuous rating.

I bought a Galaxy 95t years ago and found out my 20 amp power supply wasn't going to cut it. It worked fine on AM but SSB was a different story.

 

[Justme]

I bought a 30 amp supply for the new FT991a, that the manual stated could use 23 amp max.
Reality is the FT991A runs max 18 amp, so the power supply runs nice and cool, certainly after i replaced the 40x40x 25 mm fan by a maglev fan of 60x60x15 mm having 5 times the capacity of the tiny fan .
Yes i needed to enlarge the opening for it.

So, for 100/110 watts out the transceiver uses 13.8 volt x 18 amps or a tad under 250 watts input.
The P.A will take the brunt of that but driver section, etc needs power as well, PLL circuits, LCD screen etc.
My homebrew 2 meter amp used 35 amps at 13.8 volt to get 160 watts out on 2 meter ( MRF 247 x 2) or 480 watts in to get 160 to 180 out.
Efficiency of transistors/FET's is in the ball park of 40 to max 50%.
Still have my homebrew 80 amp supply i build 40 odd years back with a large tranformer and 250.000 micro Farad c's in it.( including soft start to charge the c's...) for that amplifier...
7 2N3771's as pass transistors...
When PSU's needed wheels to be moved...the new one weights in at 2 pounds....

 

[Slowmover]

So I've been hunting a power supply for my galaxy dx98vhp which by the manufacturers specs has 10-50w am 200w usb/lsb current drain 25 amps am 40amps ssb and takes 13.8v input voltage

With the given formula
watts÷volts=amps
Am I assuming correctly that I only need
At minimum a 15a power supply to run this one radio
Or that would mean the radio would put out 552w doing the inverse amps X volts = watts or do i need to get a 50 amp power supply just wonder if im using this formula right or if it applies so something different

— My new-guy understanding is to furnish all DC power supply (gear) rated at above maximum amp draw (with losses also accounted).

— I looked around some online and came across that the factory-supplied short power cord uses a 50A fuse.

— Maximum amp draw is said to be 45A.

Assuming these are correct I’d want a power supply that can give continuous 50A or better.

(There are also questions about constant voltage. Etc).

We might think of a base station as having shortest power-cable runs. It may not in some futures. Fit in those possibilities to ensure the power supply system isn’t ever strained.

.

 

[BJ radionut]

Galaxy DX98VHP Specifications

• Current Draw 45 Amp
• Fuse Size 50 Amp

Formula: Power = Amps x Volts...Power = 45 x 13.8 = 621 watts (apparent power)
You never want to run any power supply (IMHO) right at it's max limit duty.

So with this in mind I use this as minimum requirement.
45 amps X 13.8 volts X 1.25% (125% duty cycle) = 776 watts minimum supply required.
776 watts / 13.8 volts = 56.25 amps
So with this in mind you need a Power supply with Continuous Duty Amp rating of NO less than 55 amps.

http://www.randl.com/shop/catalog/product_info.php?cPath=9120&products_id=67343
13.8 VDC
75 Amp Surge
65 Amp Continuous

http://www.randl.com/shop/catalog/product_info.php?cPath=9020&products_id=29443
Continuous Duty 57 Amps
ICS 70 Amps
I am sure this is not what you wanted to see, but IMHO that's what I would use.
I also, IMHO dislike to "gang" multiple supplies together to gain these specs. (again just me)
My equipment is to important to me to run at minimum rating.
I presently have a 6 meter amplifier on the bench, whose OUTPUT is about 400 watts. I run this amp with either of the supplies listed above. I presently run it on the second version listed which is a Private Label commercial duty ASTRON, whose rating is listed as above (55 amp continuous/ 70 amp surge)
I run with the second as I got tired of listening to the fan run ALL the time, and having to take the supply apart every 4 or 5 months and clean the "gunk" out of it the fan sucked inside.
My 2 cents Cody
All the Best
Gary

 

[BJ radionut]

https://www.tech.txdi.org/dcwiringchart
DC Wiring Chart

The chart is calculated on no more than 2% voltage drop across the wire distance.

The distance is twice your length. If you are running a 2’ cable then your distance for the chart is 4’. This accounts for the round trip distance of the run.
I bring this up as a reference in regards to the "ganging" of 2 or more DC output power supplies.

These rules need to be followed also.
When "phasing" two power supplies together, rules to follow are these.
The DC rated wiring from BOTH supplies should be sized at Greater than the continuous rating of the supply.
Next, the wires coming from BOTH supplies to the "combiner point" should be Exactly equal in length, and size. (to the terminal block etc.)
This maintains the DC resistance of the wiring keeping it equal to that point.
Why? This is due to maintaining the "balance" between the current sources of supplies.
If one supply has 5 ft. length of wire and the other is 10 ft. length to the 'combiner point" you create a mismatch of the DC resistance between the two supplies.
The supply with the shorter leads will have less resistance, thus this supply will tend to "work" harder than the other.
Then at the "combiner point" it should be noted that the wiring should be sized to the TOTAL of BOTH supplies. (and sizing adjusted up depending on the length to the load)(see chart I posted)
These are a couple of items that are many times overlooked when "phasing" two or more supplies together to accomplish the desired result.
All the Best
Gary

 

[Cody Dixson]

I've asked the question about power supplies in a different thread. Where it was mentioned to check out Mega watt power supplies. The biggest supply they have is the s-700-12

The specs megawattpowersupplies.com says it has a variable voltage from 10-14vdc
50 amps continuous
At 690 wats
Which to make the formula correct mathematically
Would mean 99% efficiency.


And even at 40% efficiency its 280w which is 80w more than what I need?
For someone whoes taken buissness calculus radios are a different animal lol especially when. It comes to numbers
From what I've understood here in this thread this power supply wouldn't do the trick?

 

[Justme]

In your post you said the radio needs 40 amp at 13.8 volt, rule of thumb is you need a power supply that can do 25% over that continuous so 50 amp continuous.
That way the power supply will run the radio in the peaks in SSB easy and without trouble and lasts a lot longer, and your radio will be happy and operate withing specifications.
So if the megawatt specifies 50 amp continuous it will do the job.
My FT991A runs on 14.4 volt, the P.A ( loss in cables etc) runs on 14.2 volt according build in meter and draws then less amps or 14 amps for 100 watts out.
The PSU ( Nissei NS2230D ) will do 28 continous and 30 max.
So running at 50% of max full load.
And better fan for cooling keeping it cold as a brick in the fridge.
Same reason i changed the factory bog standard fan in the FT991A for a quality MagLev fan that has 10% more cubic feet per minute throughput.
More silent, more cooling.
Radio hardly gets luke warm running 100 watts full FT-8.

My rule is to always overdo things and keep electronics cool, radio makers or power supply makers pick bog standard el cheapo fans i replace them with more expensive higher CF/M fans with better bearings or better Maglev fans, your equipment will last much longer certainly if you have older radio's like my FT847 with collins filters with unobtanium P.A.transistors...

 

[Cody Dixson]

@BJ radionut @Justme @Slowmover @543_Dallas

Would yall recommend the powermax 100amp power supply?

I was on my president madison talking to a guy 15 miles out and he recommend this specially. Just thought I'd get some opinions.

Here's a link to one of many websites that show stats
https://www.batterystuff.com/power-...harger-converter-power-supply-pm3-100-lk.html

 

[Road Squawker]

I've asked the question about power supplies in a different thread. Where it was mentioned to check out Mega watt power supplies. The biggest supply they have is the s-700-12...

... and you can put 2, 3, 4 in parallel to increase the rated outputs.

 

[Cody Dixson]

@Road Squawker so id need 2 in parallel
for the galaxy dx98vhp?

 

[543_Dallas]

@BJ radionut @Justme @Slowmover @543_Dallas

Would yall recommend the powermax 100amp power supply?

I was on my president madison talking to a guy 15 miles out and he recommend this specially. Just thought I'd get some opinions.

Here's a link to one of many websites that show stats
https://www.batterystuff.com/power-...harger-converter-power-supply-pm3-100-lk.html

Many people have good luck with them. The one I bought 6 or 8 years ago was noisy. My receiver had an s5 noise level with it turned on. I use it as a battery charger now.

 

[Cody Dixson]

Would a ferrite choke on the power leads help with that? @543_Dallas

Mower junky on YouTube recycled a computer power supply with chokes on the power leads and he had a pretty flat noise level

 

[543_Dallas]

Would a ferrite choke on the power leads help with that? @543_Dallas

Mower junky on YouTube recycled a computer power supply with chokes on the power leads and he had a pretty flat noise level

I tried some chokes and ferrite but it didn't help. I'm sure there's a way to filter it but I threw in the towel.

 

[Slowmover]

@BJ radionut @Justme @Slowmover @543_Dallas

Would yall recommend the powermax 100amp power supply?

I was on my president madison talking to a guy 15 miles out and he recommend this specially. Just thought I'd get some opinions.

Here's a link to one of many websites that show stats
https://www.batterystuff.com/power-...harger-converter-power-supply-pm3-100-lk.html

I have an inverter in the Peterbilt, and a generic 45A PROGRESSIVE DYNAMICS converter in the Silver Streak.

This is an item I’ll be willing to spend on.

ASTRON brand has my attention.
50A continuous is a minimum for me,
and 70A more likely as the likely end choice.

An Alinco or Nissei 30A unit in the meantime.
Items I’ll share with my son.

My trailer has to be upgraded to 50A service, so a “master plan” will incorporate all that’s relevant to this form of stationary/mobile service (sometimes on utilities and sometimes not).

An RV is a different creature. 120V + 12V.
Mains electric OR solar OR genset.
Battery bank. (A whole buncha etceteras).

This thread subject is but one component of several that I’ll need.
Not entirely relevant to a home on mains.

That said, see other threads on POWERMAX.

.