A question for all you smart people

[ron103067]

A friend of mine gave me a 12 volt 3 amp supply will this run a cb radio like a grant xl or and older cobra 29

 

[MisterFatty]

short answer it will most likely have no issues on the 29, or the Grant on AM. SSB may be a bit light but see below...

Long answer it depends on quite a few variables which you did not specify. Who makes the supply, are the radios stock? is that 3 amp constant 5 surge? What voltage is the supply set at? Are the radios stock? Tuned up?

It would be preferable to go probably 5 or 6 amps constant to give a little breathing room, If I were you I'd probably just hook them up, run it, and see.

 

[W5LZ]

What size fuse does the radio require? If the power supply won't supply at least that much (and a few amps more), then no, it won't work. Might receive fine, but the transmitter may over load the supply.
- 'Doc

 

[190]

it will barely work. 5 or 6 amp as stated above.

 

[N9RZD]

A friend of mine gave me a 12 volt 3 amp supply will this run a cb radio like a grant xl or and older cobra 29

do the math , 3 amps at 12 volts =36 watts
look at the rating plate on the radio , it should say
what its power requirements are ,

even a peaked radio shouldnt pull more than 15 or twenty watts
if it is a CB ,

if its modified ten meter stuff then it may not

but it looks like its a safe bet

 

[hotrod]

it will run the 29 no problem .but not the grantxl on ssb.
for the grant id get at least a 5amp.7amp will give ya a little more
headroom there

 

[park]

As a rule of thumb a 100 watt transmitter at 13.8 volts will draw 10 amps. (but I would'nt want to run a 100 watt rig with a 10 amp PS) So 50 = 5 amps and 25 watts = 2.5 amps like N9RZD stated, you're ok.

 

[Wire Weasel]

As a rule of thumb a 100 watt transmitter at 13.8 volts will draw 10 amps. (but I would'nt want to run a 100 watt rig with a 10 amp PS) So 50 = 5 amps and 25 watts = 2.5 amps like N9RZD stated, you're ok.

Ah....I dunno Park. I'd change your 10 amps to 20. All 100 watt ham rigs come with 20 amp fuses, and along with the rest of the circuitry, a ham rig at full output can draw upward of 22 amps. Most hams, including myself, run a 100 watt rig on a 35 amp supply to give the needed + headroom.

I agree with everything else said. Go with 5-7A for a 12W SSB CB.

Good luck

 

[MisterFatty]

A 3 amp supply is not going to run the grant properly on SSB, if at all, the one weakness in the Grant 8719 chassis is the 3756 switch/regulator... Low voltage is going to cause issues.. My Grant XL draws close to 7 amps on SSB, yes its not a stock radio hence my questions come into play...

Do the math all you want but there is more to consider then meets the eye...

 

[ron103067]

Mines stock except for a little tune and peak which on am keys about 8 watts on my meter which gives out watts very freely on sideband when i key up and speak the watt meter shows about 25 watts not really going to run it all the time on the power supply cause I bought a cobra 89 gtl base lastnight. I should get it soon so I will just use the power supply to work on radios

 

[park]

Ah....I dunno Park. I'd change your 10 amps to 20. All 100 watt ham rigs come with 20 amp fuses, and along with the rest of the circuitry, a ham rig at full output can draw upward of 22 amps. Most hams, including myself, run a 100 watt rig on a 35 amp supply to give the needed + headroom.

I agree with everything else said. Go with 5-7A for a 12W SSB CB.

Good luck

My 125 watt IC-728 draws 11 amps indicated on my Astron 70 watt amp P.S. I use to run a 500 watts amp with it and it showed 55 amp draw?

 

[Robb]

Besides the RF output vs amp draw, one has to add in the inefficiency of other parts of the radio circuits that use current. I look at it as output watts divided by voltage draw PLUS 40% = peak amp draw.

So, a radio that puts out 23 watts will draw 1.6 amps for TX power, then add 40% more for circuitry inefficiency -about .6 amps- and you come up with ~2.3 amps. It's better to have a little headroom in the power supply; so a 3 amps power supply is pretty skinny but should work. If the radio you have is real talker and has SSB, then forgedaboutit. 5 or 6 amps would be the minimum then,
Just two cents...

 

[park]

Ah....I dunno Park. I'd change your 10 amps to 20. All 100 watt ham rigs come with 20 amp fuses, and along with the rest of the circuitry, a ham rig at full output can draw upward of 22 amps. Most hams, including myself, run a 100 watt rig on a 35 amp supply to give the needed + headroom.

I agree with everything else said. Go with 5-7A for a 12W SSB CB.

Good luck

You're right. I got my numbers all mixed up double all my numbers, and it was a 350 watt amp I had not a 500 watt.