eHam

eHam Forums => Station Building => Topic started by: KF7SRB on December 04, 2011, 09:15:49 PM



Title: Just getting started, need help...
Post by: KF7SRB on December 04, 2011, 09:15:49 PM
I am purchasing a 2m Kenwood tm-281A this week with 50' RG-8x coax and a roll up jpole antenna. What I need to figure out is what power supply. I have a 0-15w 2A adjustable and would like to know if you think it will work?

All help appreciated. I just got my Technician License on 11/23 and have been looking for info all over on this question.


Title: RE: Just getting started, need help...
Post by: K2OWK on December 04, 2011, 09:51:28 PM
Hello KR7SRB,

      I am sorry to inform you that the 2 Amp power supply you have is way to low to operate this transceiver. The transceiver you have requires a minimum of 14 Amps on transmitt and  1 Amp on receive. It might work for the receiver, but you would not be able to transmitt. I would get a power supply with a minimum of 20 amps to operate this transceiver. They are not very expensive.

     I am not sure weather you are buying this radio new or used, but if I were you I would go to he Kenwood site and download the manual. It will have all the information you need to power up and operate the transceiver.

    Hope this helps.

    Welcome to ham radio.

    73s

    K2OWK











    73s


Title: RE: Just getting started, need help...
Post by: ONAIR on December 04, 2011, 11:12:40 PM
  I second that.  Get at least a 14 amp power supply...  better yet a 20 amp or higher!  Eventually you will probably want to get on HF, and you will need the bigger supply to power those radios.  Welcome to amateur radio! :)


Title: RE: Just getting started, need help...
Post by: KF7SRB on December 05, 2011, 02:22:12 AM
Thanks for the advice!
A 20A it is.

Greatly appreciated.   


Title: RE: Just getting started, need help...
Post by: KB2WIG on December 05, 2011, 02:02:24 PM
Like  "OnAir", I'd advise you to get the biggest power supply that you can afford.   



Title: RE: Just getting started, need help...
Post by: KF7SRB on December 06, 2011, 09:35:06 AM
I found a 13.8v 30A unit. It looks to me as though that one should do it.
Thanks for the help everyone!



Title: RE: Just getting started, need help...
Post by: ONAIR on December 06, 2011, 12:46:41 PM
I found a 13.8v 30A unit. It looks to me as though that one should do it.
Thanks for the help everyone! 


   That should keep you powered up for a long time.  When you get your first HF radio, you will be all ready to rock!


Title: RE: Just getting started, need help...
Post by: W8JX on December 07, 2011, 05:21:25 PM
Thanks for the advice!
A 20A it is.

Greatly appreciated.   

This is over kill. I have had my only dual band kenwood mounted on a Astron SL-11a for over 12 years. You do not need a boat anchor to run a FM rig but then there are some that think a 35a door stop is a must have for a 20a HF rig. 


Title: RE: Just getting started, need help...
Post by: N0YXB on December 08, 2011, 05:43:19 AM
Not over kill in my book.  Like most of us, KF7SRB will likely buy more equipment down the road and will need a power supply that can provide more power than his current rig requires.


Title: RE: Just getting started, need help...
Post by: W5LZ on December 08, 2011, 12:10:36 PM
That "over kill" is sort of like saying you've got too much money in the bank.  May not be able to spend all of it right now, but it's nice to have in case you need to add something later that would require more 'current'cy.
 - Paul

(all puns intended!)


Title: RE: Just getting started, need help...
Post by: K1CJS on December 21, 2011, 07:03:34 AM
You never should want to run a power supply at its full capacity constantly.  If you're in a pinch, you can do it--but you're going to make that power supply fail faster if you continue to do so.  The best idea is not to draw more than 75 to 80 percent of the rated continuous capacity of a power supply--not its PEAK capacity, its CONTINUOUS capacity.

A good rule of thumb is to add the total current draw of all devices you're going to want to run off the power supply, then divide that total by .75.  Yes, I said .75.  So, if your rig manual says it draws 14 amps on transmit, you would divide 14 by .75, getting 18.666.  You should get a power supply that would supply 20 amps continuous.

In doing your power supply selection this way, you'll be running your power supplies cooler, and they won't fail from overheating or being continuously current overdrawn.  A good power supply treated in this manner may well outlive your equipment--or even you!  73!