Mobile two way radios are built to install and operate in automobiles, pickups, commercial trucks, off-road or recreational vehicles and, for some models, even motorcycles. The power, advanced features and versatility of the typical mobile radio allows it to be easily converted into a base station. It can be placed on a table or desk without a mount or hardware, connected to a proper antenna, powered on, and it's ready to go on the air.
Of course, there is a little matter of power. A mobile radio is specifically designed to operate on DC power from a vehicle. It has no internal power transformer or inverter of its own, so it isn't made to plug into the AC wall outlet of a home or office building. In that case, how do you power a mobile radio for use as a base station? That's easy. Get a power supply.
We carry a selection of popular mobile two way radios for business, amateur, personal and marine use at Buy Two Way Radios. We also carry a full line of reliable AC to DC power supplies from several major, name brand manufacturers. But this isn't a cut and dry, one-size-fits-all sort of thing. Mobile radios have different power requirements, and power supplies have different power ratings. Choose the correct power supply for your radio, and you may have years of clean power with no noisy interference and uninterrupted service. Choose the wrong one, and your radio may not be able to transmit or even stay on from the start.
So, how do you choose the right power supply for your radio?
First, you will need to determine how much power your radio requires. A radio that is always on, but only listening, will use a minimum of power while idling in receive mode. However, the moment the Push-To-Talk (PTT) is pressed, the power needed to transmit will spike considerably. How much? That depends on several factors, not the least of which is the transmit power level set or programmed into the radio for a particular band or frequency.
Second, you will need to consider how the power supply will be used. Will it power only one radio, or multiple transceivers at once? Will the radio sit next to or on top of the power supply, or will it be set somewhere else on the desk or bench a short distance away?
Last but certainly not least, you will need to figure out what type of power supply will work best within your budget.
Where do we begin? For starters, let's discuss how much power you will need for safe and stable operation. For this, you will need the operating specs of your radio. Since mobile radios are designed for use in a vehicle, they will typically need Direct Current (DC) between 12VDC and 13.8VDC operate. The wattage is also important, as it will fluctuate greatly depending on what state of operation the radio is in, i.e. whether it's receiving or transmitting a signal. This means the number of Amps it pulls while in each state of operation will also vary greatly.
And yes, there is a formula to calculate how much power you will need for your particular radio.
I=P/E
E= Voltage or Volts (V)
I= Current or Amps (A)
P= Power or Watts (W)
For example, let's calculate the amp draw of a 15W mobile radio on 12 volts. 15W / 12V = 1.25A. Simple, right? Well, not exactly. There are other variables to consider. For instance, there is an initial power surge or spike when the radio is first turned on, and again each time the PTT button is pressed to transmit. That surge will vary each time, and the power supply will need to be able to handle those momentary spikes in power draw.
There is variance in how many peak amps a radio will consume, and there is variance in how many actual continuous amps a power supply can handle. Plus, you have to factor in the heat produced and average load a power supply is under. Considering all these variables, there is not an exact formula for figuring this out. A better, safer amp rating to use is the maximum current consumption or amp draw listed in the manufacturer's specifications or in the owner's manual for the radio.
To the average layperson, all this sounds overly complicated. So to simplify the process, here are some general guidelines for choosing the right size power supply for your radio.
- Use the manufacturer's amp rating of the radio as the rule.
- Use the maximum, or peak load rating of the radio, not the standby or typical draw.
- If connecting multiple radios, add up the total amps of all the radios during peak load combined.
- Choose a power supply based on the continuous rating, NOT the maximum or surge rating
- Choose a power supply with a maximum continuous amps rating considerably greater than the maximum amp draw of the radio
- Consider the difference between a linear (regulated) and switching power supply
- Choose a power supply with a built-in cooling fan
- Stick with a power supply from a reliable, brand name manufacturer
- Consider the warranty, as power supplies do have a life span
- DO NOT buy a power supply based solely on price
For example, let's say you have a 50 watt radio and the maximum draw is listed at 10 amps. Buying a power supply advertised with a peak load of 10 amps might still be a bad move. First, power supplies have two amp ratings: continuous and maximum. The continuous rating is usually the number that you want to look for. Also consider the load. If a power supply is under a constant load that is close to its maximum, you'll generate more heat, and that can shorten the life of the unit. For that reason, it's a best practice to buy one with a built-in cooling fan.
Choosing a power supply isn't really that complicated, although at the outset it can seem that way. Simply put, to convert your mobile two way radio into a base station, we recommend that you buy a higher amp power supply than is absolutely needed. When it comes to power, you can't over buy. If in doubt, go bigger. At the end of the day, you'll be glad you did.
How many watts at 120 volts do I need to run your 12v 30amp power supply?
I'm thinking of buying a Yaesu FTM-3100R and a power supply. The Yaesu website does not list the current draw (continuous or spike) for any of the output power settings (5W, 30W, 65W). The P=EI formula says it would draw about 5 amps at the 65 watt setting. So I began looking for 10 amp power supplies but Yaesu only sells 23 A and 30A power supplies and both are way over $100. Can you recommend a power supply that you sell which would handle 65 watts? Thanks!
As mentioned in the article, the formula is only one factor in determining how much power you need. You also need to factor in the maximum or surge rating of the radio. In other words, even though the formula calculates 10 amps, you will need higher wattage to compensate for the surge whenever the PTT is initially pressed. For this reason, a 23 watt or 30 watt power supply is recommended. It is better to have more than you need than the bare minimum.
It is important to choose a power supply that is appropriate for your specific radio and operating conditions. If you are unsure about which power supply to choose, consult with a qualified radio technician or the manufacturer for guidance.
One area of base station operations not talked about in industry with switching power supplies is grounding.
SMP PSU do NOT like being dc negative ground connected to frame earth ground,big NO NO NO
Most commercial and newer cb radios (not older radios with floating chassis) now use common DC ground on metal chassis and rf antenna connector.
If that antenna connector is connected to EARTH ground your going to run into noise issues from your SMP PSU by ground looping EARTH back to DC ground potential through the mast (if metal,antenna bracket)if earthed.
I have tested this in controlled tests and test equipment to monitor RFI,DC Noise etc and can see on test equipped the minute dc negative ground is hooked back to frame earth ground of psu ,you will see nasty dc noise on rails ,increased RFI interference!
Others i have shown this undocumented problem with SMP PSU and base station installations have replicated problem.
SMP PSU are balanced DC outputs,minute you create a ground loop back to the smp earth thats when problems can start.
cures found
isolate the antenna bracket from the Earthed (for electrical safety reasons)mast pole.
antenna then floats on its internal dc ground via coax\radio\brackets\ground radials.
we found best if antenna is also a DC shorted type for best protection of static.
WE used fabricated PVC pipes ,cut with a slot to form a split sleeve that slides over the antenna mast (EARTH to ground)
DC ground of radio chassis including the mounting bracket if mounted inside a metal case or metal plate is also isolated.
SMP PSU is Earthed as normal.
This then prevents earth loops and upsetting balance of dc outputs of the smp psu .
Radio ,coax,antenna bracket are at DC ground
Mast-Earthed if metal via copper stake
PSU-Earthed
Then you will not that we have found get "issues"with SMP PSU
Tried on VHF low
VHF HI
UHF type verticals and no more smp noise issues unless its of a poor quality\design\AC Unfiltered when used with two way radios.
Hope this information is off some help help to users of SMP PSU for radio uses.
Regards
Rob
RPComms UK
thank you for the information
The CB radio is great for outdoor use, for quick updating on what is going on currently. If you want to operate your small radio station, you can make use of the ham radio.
Hello,i have an amplifier reated 12v 25A×2 fuse and current consumption is 31A( at continuous power ) ,and i have a power suppy rated 12v 40a output is it safe to use on my amplifier .thanks for your reply
Please send me prices for CB radio. Power supply s.
Hi Manuel, the prices of our CB Radios and power supplies are posted on our web site at www.buytwowayradios.com.
thank you for the information
Legal CB AM transmit is 4 watts, but isn't legal CB SSB transmit 12 watts? What would be the best power supply to get to handle an SSB CB radio transmitting at the legal 12 watts?
As stated in the article, it depends on the amp draw of your radio. Choose a power supply with a maximum continuous amps rating considerably greater than the maximum amp draw of the radio.
I think the question being asked without all the technical answers given is simply this. If using a standard simple vehicle AM/SSB 40 channel radio as a home base station, will a 13.8v 20amp power supply blow my circuit board and fry the radio? 20amp being the key factor here. Or does it matter? According to the article you can. Correct?
As stated in the article, as long as the power supply has more than the minimum amperage required to handle the power needs of the radio, you should be fine. The radio draws the amps from the power supply, so the power supply needs enough amperage to support the number of amps the radio needs. Based on your description, it sounds like you have a CB radio, which is limited to a maximum of 4 watts. As long as you aren't pumping out more than the legal limit through your antenna, your amperage requirements should be rather low. A 20 amp power supply should be more than enough needed to power a CB radio as a base station, with power to spare.
Hi. Does it matter what the amp output is? For instance, if a radio requires 6a at 13.6, is it OK to have a power supply that outputs more? I am assuming that it will only draw what you need? Is that correct? Thanks.
It does matter what the amp draw of the radio is, because you don't want to get a power supply that isn't capable of supporting it. As stated in the article, "we recommend that you buy a higher amp power supply than is absolutely needed." This means if the maximum draw of the radio is 6a, you need a power supply that can handle more than 6 amps.
Ok newbie question, i purchased a Wouxun DWC30win power supply to use with a Wouxun kg-1000g GMRS unit. The power supply has a switch for 13.8 volt dc or adjustable range. Do i just leave it on 13.8 volt? If i were to connect radio to vehicle isn’t that 12 volt? Where do i set the power supply? TIA!
It is standard procedure to leave the switch on 13.8v to power a mobile radio from a switching power supply.
I just want to ask, I'm starting to set up mobile.base radio, Using Icom.H16, heavy duty power supply 13.8V , 40 ampheres, and plan to connect my 100W amplifier/booster, CP22J aerial.antenna, is it okey? My amplifier is in UHF classification..can I use it for VHF Frequency?
Thanks....
We do not carry the H16 so we do not have a lot of information on it. As for the amplifier, you did not mention a specific brand or model. You may need to contact the manufacturer for support.
Switching power supplies are quiet and efficient, but keeping voltage stable while throttling out more amperes during a transmitting operation of a radio is nothing to take for granted. I have seen both a single and a pair of 30 amp switching power supplies operating in parallel permit a voltage drop that drastically lowered the radio's output power. In the same configuration, I saw a 35 AH battery offer far less voltage drop and the radio transmitted 3-6 times the output power. The load changed from 1 amp to receive to 21 amps to transmit. Switching power supplies have an increased challenge to follow a single-sideband transmission which will create a constantly changing current draw. Duplicating a automobile's battery and alternator system with a power system for home station use is a far more difficult need to accomodate. Most power supplies aren't made to operate with fluctuating current loads of SSB (Single Side Band). An AM or FM transmission is constant and doesn't fluctuating current draw as a SSB transmission. Don't be bashful and buy a small power supply. Be brave, remember that automobile alternators of 100A are very typical. A 50 Amp power supply is more aligned with meeting the need than anything smaller. Some operators use batteries and recharge them with battery maintainer/conditioners after using their radios. This is to keep noise down from the chargers.
I have a Ham radio Kenwood TM281A . It is DC 13.8V .Max is 14A. I have a Astron 13.8, then 57 Amp continuous . 70A (output) (input) 115VAC , 60Hz, 12 amp fuse ,is it ok to use continuous use .
I have a Kenwood ham radio with 65 watts. Do I use a 50 amp power supply.
That depends. As stated in the article, use the maximum, or peak load rating of the radio. What model is your Kenwood radio? What is the peak load rating?
Ok fellows I have been using mobile radios for base stations since I was 9 years old im 57 now so almost 50 years and ill tell straight I prefer it that way I had a cobra 142 GTL base station and that was a really good base radio the ears on it were very smooth the filtering was really good of course the transmit was nice of course I had a D104 lollipop power Mic on it and I had modified the modulation area of and removed the modular block love that radio but I had a cobra 2000 very pretty radio didn't care as much for it had done all of the same work on it including channels (Everyone Does it) or has it done thats just the way it is ok well a cobra 148 GTL mobile is the same radio except you have to provide your own power supply and its more affordable I believe even buying the power supply but I and lots of other people believe the 148 a better radio crazy but I assure you it is the best sounding radio I ever heard was a 25 Ltd the older ones now this is my opinion on the power supply for the normal 40 channel cobra's and such 5 amps will do you a fine job even souped up but I always tried to keep atleast a ten to twelve amp 13.8 volt or verible voltage cause some times I kept the same radio for years but I was always trying different radios and the imports required more amps and one of the reasons I think a lot of people preferred mobiles beyond price is the external power supply were better than than the ones that came in a lot of the bases one more thing I owned one of those pyramid 32 amp power supply and loved it kept it for years I used it to run a texas star Dx 350 amp and it did a great job for me it quit one time I replaced the regulator transistors never had another problem the 350 was a driver for my Denton and it worked great for years I still kept my radio on a separate ten or twelve amp triplite power supply now as far as switching power supply go it seemed evertime I got one within 3/4 of there rated amps they would grunt and on a couple of accations just let go all together sorry so long but thats been my experience and I tried to keep it brief but tell how things were all through the years accurately k guys and not tell so much the parts that fcc mite not like the main thing with them is part 15 don't interfere with others peoples stuff and if you did get it fixed rite away but I noticed the last 15 years there was not much of a problem because of better radio equipment and cable and satellite TV and lots of improvements later enjoy there's still lots of CBers out there I go by (BILLY THE KID) the badest man in the land
Hi, guys, I would like to ask for your inputs as I am looking for a switching power supply for my Icom A120. As a newbie, I have done some research to understand how it works, but still confused. The Icom A120 is a P.E.P 36 watts VHF radio with a maximum transmitting current is 5 Amps/receiving 4 Amps. I am not sure if it can be operated on a power supply rated at 25 Amps continuous, such as Samlex 1235M. Does the current drawn from the supply depend on the load? Will the radio be possibly damaged by the high current level? Thanks for your time.
The continuous amp rating on the power supply indicates the maximum continuous load it can take from the radio. A power supply with a rating of 25A doesn't mean it is sending a full 25A to your radio. It means that's the most amperage the power supply can handle from the devices connected to it. If your Icom A120 has a maximum draw of 5A and the Samlex 1235M has a continuous amp rating of 25A, it should be able to handle the radio without issue.
Hi all. I am actually looking for a power supply to operate a Texas Star DX250. I'm not exactly sure how much wattage the amp puts out but to be on the safe side, I would probably be looking at a power supply that could handle a 300 watt amp. Do you think the Pyramid PS36 KX would work or would I need a larger unit? Thank you
This is a power amplifier often used for CB radios. The use of such devices to boost the wattage of CB radios is not legal in the US, and we do not recommend our power supplies for this purpose.