Power supply for Uniden Grant

[Hamin' X]

All brands of power supplies are not created equal.

Rich

 

[995]

a 5 amp power supply will support 63 watts output...

Doesn't work quite like that. The transmitter is nowhere near 100% efficient.

These CB amplifier builders like to toss that around, "watts in = watts out"....it's not true.

Switch kits experiment proves this....voltage drop when transmitting. And you're right....the Grant does no where near 63 watts.

All brands of power supplies are not created equal.

Amen. Another good reason for going bigger....but how far is reasonable? (rhetorical question)

 

[dway87]

How relaible is the pyramid power supplies?

 

[KingCobra_CDX882]

I use the Iota
(exelent power supplys..spoken of elsewhere on the forum)
also use the trippLites
(very decent as well)

 

[Carl]

correct but i was stating maximum. the transistor will still pull maximum power even though its output will be far less (70% at best).

just trying to make it easy for him to understand.

 

[Moleculo]

Wow, I never thought I would see a 3 page response to "what size power supply for a grant..." In fact, I was ignoring the thread because I figured there where so many good responses taking care of the question. When I saw 4 pages, I started to worry....

Early on Carl used Ohm's law to demonstrate how to calculate how much current the radio would draw. 995 just hinted at the missing ingredient: efficiency. It's pretty safe to assume that the Grant is around 50% efficient since the final PA section would be an AB bias. I'm going off the top of my head without looking up the schmeatic for the radio, but let's just go with that assumption for now. A well tuned Grant will put out about 25 watts, max. If you're power supply puts out 13.8 volts, you take 25 watts / 13.8 volts= 1.8 amps. Then take 1.8 / .5 efficiency = 3.6 amps. It's generally not a good idea to run any type of equipment at it's full max potential all the time (insert your favorite engine analogy here), so with a little cushion, you end up with a 5 amp supply. If you see more power from the radio when you vary the size of the supply, it's because the voltage has increased. Basic Ohm's law.....

 

[Switch Kit]

I love amps , I often wish I had more. )-: (either power supply or alternator) I think I like to push it once in a while and that can be risky at times. Just knowing one has more then enough is surely a comfort in itself. Better safe then sorry later.

 

[PLUTO]

Also, don't forget that there's other circuitry in the radio as well. I would say 7 amps to be on the safe size. BUT why not geat a 20 amp, then you could power just about any radio without having to worry.

.........Whew, that's what I run my Grant XL on....and when I want to change over to my 2950, no problems.

 

[995]

Wow, I never thought I would see a 3 page response to "what size power supply for a grant..."

LOL...I'm always good for one more post!

 

[dway87]

Geez! I never thought that I could create a topic that has 3 pages.

 

[PLUTO]

How relaible is the pyramid power supplies?

........I have 2, 21-KX(20amp) and a 26-KX(25amp) they do a good job for me. There are better ones made, also more costly.