Posted: 1/27/2016 3:14:29 PM EDT
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My wife surprised me with a cake decorated with my new call sign (got my Tech license Jan 14th) and has ordered me a Leixen VV-898s (25 watt) model radio. Primarily for use in my car but I would like the option of using it at home too. She found a used 13.8 volt power supply on Ebay and ordered it as well. It is supposed to be 2 amps continuous and 4 surge. Is that adequate for this radio? It looks like it should if I am doing the math correctly but it always pays to get some experienced advice.
Thanks guys ! |
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Hi TAC,
I used to figure FM radios being class "C" amplifiers were about 50 % efficient. 4 A x 13.6V = 54.4W for the supply is right on the edge figuring that the rig needs 50 W input power. (Twice the 25 W output. ) Run it on a lower power setting when in the house until you can upgrade the supply. And welcome to the ham radio world. 73, Rob |
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Quoted:
Hi TAC, I used to figure FM radios being class "C" amplifiers were about 50 % efficient. 4 A x 13.6V = 54.4W for the supply is right on the edge figuring that the rig needs 50 W input power. (Twice the 25 W output. ) Run it on a lower power setting when in the house until you can upgrade the supply. And welcome to the ham radio world. 73, Rob ^^^ that's good math. about 2.5x the RF output power is a good place to start, giving you some headroom. 2.5 * 25W = 62.5W / 12Vdc = at least 5.2A power supply current needed. note that i used 12Vdc, not 13.8Vdc -- which gives yet a little more margin. ar-jedi |
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Quoted:
hug your sife for being so awesome 
...but save your penny's for a 20-25amp power supply because you'll probably quickly learn that all the fun is with a 100watt HF rig (samlex 1223 is about $99) ^^^ that as well. 2.5 * 100W RF = 250W / 12Vdc = at least 20.8A ar-jedi |
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Quoted:
My wife surprised me with a cake decorated with my new call sign (got my Tech license Jan 14th) and has ordered me a Leixen VV-898s (25 watt) model radio. Primarily for use in my car but I would like the option of using it at home too. She found a used 13.8 volt power supply on Ebay and ordered it as well. It is supposed to be 2 amps continuous and 4 surge. Is that adequate for this radio? It looks like it should if I am doing the math correctly but it always pays to get some experienced advice. Thanks guys ! Damn, looked like you wifed the right woman. That's not enough power supply for the radio (rule of thumb is divide TX watts by three to get to the required amps from a 12V supply) realistically you'd want at least a 10A supply. The radios aren't 100% efficient so they need far more watts in than they put out. All is not lost, though -- you can put a small 12V SLA across the output in a pinch, and it'll provide the amps and float-charge when you're not TXing. |
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If you can solder copper pipe, you can make this 2M/440 vertical antenna. If you're in or near a town, chances are 5 Watts will put you into the local repeater(s). That way you can use the power supply you wife ordered for you.
If the majority of the action is on 2 Meters, this one should give good results. Mount the antennas as high as possible for best results. |