Posted: 10/27/2010 4:24:26 PM EDT
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I have a 12 watt 10m radio. What amps will this require from a power supply?
Running 12 watts power. |
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I have a 12 watt 10m radio. What amps will this require from a power supply? Running 12 watts power. figure 50% RF amplifier efficiency, plus another 1A for the receiver and lighted dials etc. so 12W RF output @ 50% efficiency requires 24W DC input. 24W/12Vdc = 2A, so that's 2A right there as a start. now add 1A for the receiver and power windows/locks/seats etc, and you get 3A total 12Vdc input needed. now let's do a reality check: http://losdos.dyndns.org/public/ham/icom-703plus/IC-703-user-manual.pdf Use a 13.8 V DC power supply with at least 3 A capacity when operating IC-703 with AC power. Specifications Current drain : Transmit 2.0 A typ. (TX 5 W at 9.6 V DC) 3.0 A typ. (TX 10 W at 13.8 V DC) Receive squelched 300 mA typ. (at 9.6 V DC) max. audio 450 mA typ. (at 9.6 V DC) 1.2 A (at 13.8V DC) so, comparing our initial calculations with a radio of approximately the power output gives good correlation. for your 12W radio, if you have a 12Vdc power supply with 4A or 5A output capacity you will have plenty of input power. ETA: note that you did not give any details on the radio architecture; if this is an old vacuum tube-based unit the TX and RX power consumption will be somewhat (and in some cases markedly) higher than a modern transistor-based transceiver. ar-jedi |
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I have a 12 watt 10m radio. What amps will this require from a power supply? Running 12 watts power. figure 50% RF amplifier efficiency, plus another 1A for the receiver and lighted dials etc. so 12W RF output @ 50% efficiency requires 24W DC input. 24W/12Vdc = 2A, so that's 2A right there as a start. now add 1A for the receiver and power windows/locks/seats etc, and you get 3A total 12Vdc input needed. now let's do a reality check: http://losdos.dyndns.org/public/ham/icom-703plus/IC-703-user-manual.pdf Use a 13.8 V DC power supply with at least 3 A capacity when operating IC-703 with AC power. Specifications Current drain : Transmit 2.0 A typ. (TX 5 W at 9.6 V DC) 3.0 A typ. (TX 10 W at 13.8 V DC) Receive squelched 300 mA typ. (at 9.6 V DC) max. audio 450 mA typ. (at 9.6 V DC) 1.2 A (at 13.8V DC) so, comparing our initial calculations with a radio of approximately the power output gives good correlation. for your 12W radio, if you have a 12Vdc power supply with 4A or 5A output capacity you will have plenty of input power. ETA: note that you did not give any details on the radio architecture; if this is an old vacuum tube-based unit the TX and RX power consumption will be somewhat (and in some cases markedly) higher than a modern transistor-based transceiver. ar-jedi You have this correct for anything modern. The "RIght Answer" though could have just as easily been - "Look in the Owner's Manual" Fusing for one of these is typically a 10 amp, and though some of the manufacturers fuse only one side (the one connected to the battery positive) better fusing practices should be considered. Typical published specs for 12-15w "10m" trucker's rig is 3 amp draw. 73 Steve K9ZW |
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The "RIght Answer" though could have just as easily been - "Look in the Owner's Manual" i'm guessing that since the OP is asking, he a) doesn't have an owners manual for the radio, or b) it's a homebrew radio with no owners manual, or c) might actually be interested in understanding how one might make a rough calculation of the current needed by a radio based on RF output power. "look in the owners manual". sigh. ar-jedi |
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This is a total guess, but I'm going to say 7 or 8, no more than 10. This, especially if it's a SSB rig. how did you come to this conclusion? ar-jedi Way back when, when I used to work on CB radios for a living, we would pop 3A fuses on SSB rigs like the Cobra 148GTL when transmitting in SSB. These radios came from the factory with a 6A fuse installed. |
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we would pop 3A fuses on SSB rigs like the Cobra 148GTL when transmitting in SSB. These radios came from the factory with a 6A fuse installed. manufacturer-specified maximum current draw on TX is 2.2A on AM, and 2.0A on SSB. source: http://www.universal-radio.com/catalog/cb_radio/4634.html http://www.universal-radio.com/catalog/cb_radio/4634spec.html ar-jedi |
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we would pop 3A fuses on SSB rigs like the Cobra 148GTL when transmitting in SSB. These radios came from the factory with a 6A fuse installed. manufacturer-specified maximum current draw on TX is 2.2A on AM, and 2.0A on SSB. source: http://www.universal-radio.com/catalog/cb_radio/4634.html http://www.universal-radio.com/catalog/cb_radio/4634spec.html ar-jedi Not to get into a pissing match with you jedi, but I've " been there done that" with 11 meter rigs. A Cobra 148 GTL in SSB will smoke a 3A fuse in short order regardless of what the manual says. They must be giving an RMS spec, the 148's came with a 6A fuse when new as well as a heavier power cord as opposed to the Cobra line of AM rigs. |
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The "RIght Answer" though could have just as easily been - "Look in the Owner's Manual" i'm guessing that since the OP is asking, he a) doesn't have an owners manual for the radio, or b) it's a homebrew radio with no owners manual, or c) might actually be interested in understanding how one might make a rough calculation of the current needed by a radio based on RF output power. "look in the owners manual". sigh. ar-jedi I'm guessing that the OM hadn't thought to do a websearch for the manual for his specific rig (or homebrew design - doubtful that thought, as if he built one I expect he'd know how to run the math). Like you it causes me a slight "sigh' when I see another lazy man's post - simple questions that 7 seconds with Google would have solved? Always wonder if the question is real, or just a lonely soul looking for some forum interaction? A "real" question would have read something like: "I bought a flea-market Russian 10m rig and the manual is missing. Can't find an English manual on the web. Face plate says it is 'Kiev Prestique 111B' and is rated for 12watts output. No supply power requirements though? Any quick guidelines on how to interpolate the Amps draw, power wire sizing and fusing based on the information I do have so I can take this neat rig mobile?" Hey maybe even a picture thrown in.... Or are we often being asked to be the research for folk too lazy to do a basic web search or even tell us what they have? Real tech questions or lonely hearts club banter? Does make one think.... 73 Steve K9ZW |
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Follow up per email received - my aside comment is less about this thread than a general trend in many forums to let quality slip:
- if a question posed has quality in description it avoids a "twenty question" section to the thread - if quality pre-thread research f is done often the question's answer is mere seconds away of with direct personal web research - if a quality generalization is included in replies in addition to the thread's specific answer a teaching point is created and shared (the give a man a fish or teach him to fish thing...) - use of a quality thread title helps make the thread appealing to more readers (I for one ignore the "Did you see that," "Whew Score last Night" and other socially labeled threads) Again I wasn't meaning to rant against any one person, but more a group-think that reduces quality. Back for second cup of coffee... 73 Steve K9ZW |
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Not to get into a pissing match with you jedi, but I've " been there done that" with 11 meter rigs. A Cobra 148 GTL in SSB will smoke a 3A fuse in short order regardless of what the manual says. They must be giving an RMS spec, the 148's came with a 6A fuse when new as well as a heavier power cord as opposed to the Cobra line of AM rigs. The old 148's are nothing like the new ones. THe old ones were 5 pin mics, and seemed alot more robust. The modern ones are 4 pins, and just seem like cheap crap. IMHO. |
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The "RIght Answer" though could have just as easily been - "Look in the Owner's Manual" i'm guessing that since the OP is asking, he a) doesn't have an owners manual for the radio, or b) it's a homebrew radio with no owners manual, or c) might actually be interested in understanding how one might make a rough calculation of the current needed by a radio based on RF output power. "look in the owners manual". sigh. ar-jedi I'm guessing that the OM hadn't thought to do a websearch for the manual for his specific rig (or homebrew design - doubtful that thought, as if he built one I expect he'd know how to run the math). Like you it causes me a slight "sigh' when I see another lazy man's post - simple questions that 7 seconds with Google would have solved? Always wonder if the question is real, or just a lonely soul looking for some forum interaction? A "real" question would have read something like: "I bought a flea-market Russian 10m rig and the manual is missing. Can't find an English manual on the web. Face plate says it is 'Kiev Prestique 111B' and is rated for 12watts output. No supply power requirements though? Any quick guidelines on how to interpolate the Amps draw, power wire sizing and fusing based on the information I do have so I can take this neat rig mobile?" Hey maybe even a picture thrown in.... Or are we often being asked to be the research for folk too lazy to do a basic web search or even tell us what they have? Real tech questions or lonely hearts club banter? Does make one think.... 73 Steve K9ZW OP is one of the moderators of the ham radio forum. ar-jedi |
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A Cobra 148 GTL in SSB will smoke a 3A fuse in short order regardless of what the manual says. with what PEP at the business end of the SO239? if it's only 12W it must of been a hell of an inefficient RF finals design. alternatively, i can imagine the transition from RX to TX was characterized by an awfully high DC current spike and a resultant broadband "splat" across many megacycles... ar-jedi |
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A Cobra 148 GTL in SSB will smoke a 3A fuse in short order regardless of what the manual says. with what PEP at the business end of the SO239? if it's only 12W it must of been a hell of an inefficient RF finals design. alternatively, i can imagine the transition from RX to TX was characterized by an awfully high DC current spike and a resultant broadband "splat" across many megacycles... ar-jedi NAM may have hit the answer. I haven't worked on CB's for 15 or so years. The OP didn't specify what rig he has so I was responding as if he had an older converted CB, like the 148GTL. The newer ones may be more efficient than the 'ol "made in the Phillipines" units. Still the factory spec for current draw doesn't make sense to me. 2A for 12 watts on SSB and what, 2.4 for 4W AM? ( I can't see the spec in your post from the edit window). So by their math, 2.4A = 4 watts and 2.0A = 12 watts ?? 
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Quoted: Roadpro Titan II RPSY-485 I found the manual online after considerable digging, It says a minimum of 10 amps. That seems high to me.....well, it is what it is. Thx for the help guys. And yes I am one of the Mods here.....is that a problem?  |
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OP is one of the moderators of the ham radio forum. ar-jedi I hadn't wanted to point that out - it isn't personal, not the problem limited to this thread at all, and status shouldn't matter.. 73 Steve K9ZW or perhaps you could be helpful instead of being condescending. if you don't care for the forum don't read it. |