Proper K2 power cord?
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I have been using a molded power cord with my recently acquired used K2. I
am sure the wire is 20 or smaller meaning there is likely a voltage drop. I need to build up a power cable with larger gauge wire. Also I need to get a connector. Does anyone know the correct Radio Shack SKU for the connector? What gauge of wire should I use. This is for QRP version of the K2. 73, Steve N6VL _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Steve:
>I have been using a molded power cord with my recently acquired used K2. I >am sure the wire is 20 or smaller meaning there is likely a voltage drop. I >need to build up a power cable with larger gauge wire. Also I need to get a >connector. Does anyone know the correct Radio Shack SKU for the connector? >What gauge of wire should I use. This is for QRP version of the K2. I'd urge you to order the plug from Elecraft. It's an Elecraft part #E620032, describes as 2.1mm male connector. R/S will have something which will work, BUT those they sell DO NOT protect the inner conductor of the connector from shorting out if left to lay out on the desktop. The Switchcraft plugs which Elecraft sells have a slightly recessed center pin, which is mostly protected from accidental shorts to ground. The R/S versions are NOT so protected. Worth getting it from Elecraft. Regarding wire... I'd suggest you use #16 or larger, #14 if you can find some with insulation that doesn't overwhelm the power plug. 73, Tom Hammond N0SS _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Steve Kallal
Steve,
Here is a chart of wire gage versus current capacity for power transmission. Gage Amps 12 9.3 14 5.9 16 3.7 18 2.3 20 1.5 The K2 10W version uses 2.0 amps for transmit and up to 0.250 amps for receive. It looks like 16 gage wire would work fine. If it were me, I would buy the connector from Elecraft. 73 Larry KB5DXY _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Steve Kallal
Steve,
I buy the 16 guage red/black 'zip' cord from The Wireman (www.thewireman.com) and construct a power cable for each K2 or K1 that I build. That size wire fits (snuggly) through the hole in the cover for the Switchcraft plug that is supplied by Elecraft. The Elecraft part number for the plug is E620032. As has been mentioned, the Radio shack plugs have a center conductor which comes all the way out to the end of the plug and poses a risk of shorting the power supply when it is in process of being plugged in or just laying on the bench - the plug supplied by Elecraft has a slightly recessed center conductor which minimizes this shorting problem. The 16 guage wire will have significantly lower voltage drop than thinner wire. 73, Don W3FPR Steve Kallal wrote: > I have been using a molded power cord with my recently acquired used K2. I > am sure the wire is 20 or smaller meaning there is likely a voltage drop. I > need to build up a power cable with larger gauge wire. Also I need to get a > connector. Does anyone know the correct Radio Shack SKU for the connector? > What gauge of wire should I use. This is for QRP version of the K2. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by KB5DXY
I'd like to add to Larry's note: the current capacities given in the table
indicate the maximum safe current for usual grade of insulation (better insulation allows higher currents and temperatures). Single wires are usually graded for their 'suspended in still air' rating and pairing up in a cable degrades this because they heat each other. In large cable bundles this can degrade the rating to less than half. What could be more important in some applications as Steve alluded to is the voltage drop. If you have long runs, a thicker cable would be better. David G3UNA ----- Original Message ----- From: "Larry" <[hidden email]> To: "Steve Kallal" <[hidden email]> Cc: <[hidden email]> Sent: Sunday, July 15, 2007 3:06 AM Subject: Re: [Elecraft] Proper K2 power cord? > Steve, > > Here is a chart of wire gage versus current capacity for power > transmission. > > Gage Amps > 12 9.3 > 14 5.9 > 16 3.7 > 18 2.3 > 20 1.5 > > The K2 10W version uses 2.0 amps for transmit and up to 0.250 amps for > receive. It looks like 16 gage wire would work fine. > > If it were me, I would buy the connector from Elecraft. > > 73 > Larry > KB5DXY > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Steve Kallal
In a message dated 7/14/07 10:08:03 PM Eastern Daylight Time,
[hidden email] writes: > Here is a chart of wire gage versus current capacity for power > transmission. > > Gage Amps > 12 9.3 > 14 5.9 > 16 3.7 > 18 2.3 > 20 1.5 > Where does this chart come from? In the USA, general 120 volt house wiring uses the following standard: #10 30 A circuit breaker #12 20 A circuit breaker #14 15 A circuit breaker That's for copper wire in a conduit or multiwire cable like NM or UF. The National Electrical Code (NEC) is very conservative, because a minor mistake can mean lives and property lost. IMHO, for applications like a power cord for the K2, you can't simply specify a wire size except to specify a minimum size for the current drawn. You also need to figure out the resulting voltage drops for the cable length used. 73 de Jim, N2EY ************************************** Get a sneak peak of the all-new AOL at http://discover.aol.com/memed/aolcom30tour _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Steve Kallal
The numbers look kind of low don't they? These are for DC continuous duty
cycle. Many manufacturers of mobile and 100W tranceivers ship a 12 GA power cablke for DC operation. I consider this too small and prefer a minimum 10GA. I run 6 or 8 GA in my mobiles ( also using silver plated with many more strands than the hardware store variety ). We just installed #8 on a 240 line in the house for AC that mfg specified as a 40 amp circuit - way more than the AC uses. I don't spec my DC operating Cables on basis of maximum current carrying capability, but rather for best DC resistance characteristics. Remember Ohms law when applying current to a DC supply, If you are running a 100 watt transceiver with a nominal 20 amps at voice peak on transmit and you have as little as 0.1 Ohm resistance in the power supply circuit, your supply voltage at 13.8 VDC will drop 2 VOLTS! That's at current (VOICE/CW) peaks when you need them the most. Also, judging wire gauge by insulation (85C for instance) will not be a valid measurement unless you actually plan to run currents that will generate heat in that cable. That would be a sure indication of IR losses that are way beyond anything you want to have i.e. for that 2 volt loss you'd be seeing 40 watts going into heating. Also remember that the connection points (terminals) are most likely the highest resistance points. Being concentrated heating points the terminals are usually where fires get started when they are dissipating too much heat. 40 watts is about what the average soldering iron provides (doing soldering jobs in ham rigs), so you could conceivably desolder a poorly done terminal if it has as little as 0.1 Ohm resistance. de AL, WA6VNN ************************************** Get a sneak peak of the all-new AOL at http://discover.aol.com/memed/aolcom30tour _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Steve Kallal
In a message dated 7/15/07 2:13:21 PM Eastern Daylight Time, [hidden email]
writes: > The numbers look kind of low don't they? These are for DC continuous duty > > cycle. The same is true for house wiring. > run 6 or 8 GA in my mobiles ( also using silver plated with many more > strands > than the hardware store variety ). The real issue is voltage drop, particularly in a 12 volt system where you may not have a lot of spare volts to play with. I don't think #6 or #8, or their paralleled equivalents, are overkill in such applications. We just installed #8 on a 240 line in the > > house for AC that mfg specified as a 40 amp circuit - way more than the AC > uses. > #8 is the standard house-wiring size for 40 amps - #10 is only good for 30 amps. And while the AC may not draw 40 A continuous, the initial starting surge may get up there. Don't want nuisance trips! > I don't spec my DC operating Cables on basis of maximum current carrying > capability, but rather for best DC resistance characteristics. That's the way, regardless of short or long runs. 73 de Jim, N2EY ************************************** Get a sneak peak of the all-new AOL at http://discover.aol.com/memed/aolcom30tour _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by N2EY
I got this information from http://www.powerstream.com/Wire_Size.htm.
73 Larry KB5DXY > > > >> Here is a chart of wire gage versus current capacity for power >> transmission. >> >> Gage Amps >> 12 9.3 >> 14 5.9 >> 16 3.7 >> 18 2.3 >> 20 1.5 > > > Where does this chart come from? > > In the USA, general 120 volt house wiring uses the following standard: > > #10 30 A circuit breaker > #12 20 A circuit breaker > #14 15 A circuit breaker > > That's for copper wire in a conduit or multiwire cable like NM or UF. > The National Electrical Code (NEC) is very conservative, because a > minor mistake can mean lives and property lost. > > IMHO, for applications like a power cord for the K2, you can't simply > specify a wire size except to specify a minimum size for the current > drawn. You also need to figure out the resulting voltage drops for the > cable length used. > > 73 de Jim, N2EY > > > > > > > ************************************** > Get a sneak peak of the all-new AOL at > http://discover.aol.com/memed/aolcom30tour _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Proper K2 power cord?
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In reply to this post by Steve Kallal
> Being concentrated heating points the terminals are usually where fires get
> started when they are dissipating too much heat. 40 watts is about what the > average soldering iron provides (doing soldering jobs in ham rigs), so you > could conceivably desolder a poorly done terminal if it has as little as 0.1 Oh > m > resistance. > This is, in fact, a known problem on some HP laptops; the power connectors desolder themselves at the PC board. I've fixed several. 73 de chris K6DBG _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Proper K2 power cord?
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In reply to this post by Steve Kallal
> Here is a chart of wire gage versus current capacity for power
> transmission. > > Gage Amps > 12 9.3 > 14 5.9 > 16 3.7 > 18 2.3 > 20 1.5 > > The K2 10W version uses 2.0 amps for transmit and up to 0.250 amps for > receive. It looks like 16 gage wire would work fine. This is a pretty interesting table, especially in light of the sizing of PowerPole connectors. The "30A" contact doesn't comfortably fit anything larger than 12g wire. I don't have a "15A" contact handy, but my memory is that it handles 18g OK, but I'm not sure if it will handle 16g. That's just ... broken :-) > If it were me, I would buy the connector from Elecraft. Yeah, I guess I'm going to have to get a few. I admit that my bench is littered with little cords that have "15A" PowerPoles on one end and generic power connectors on the other end, all made out of 20g or 22g zip cord. I'm having a really hard time imagining pushing 16g zip cord into the body of a 2.1mm plug! I think I've done this with 18g once, and it wasn't pretty - perhaps the cable sold by the Wireman has thinner insulation? 73 de chris K6DBG _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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On Jul 16, 2007, at 12:21 PM, Chris Kantarjiev wrote: >> Here is a chart of wire gage versus current capacity for power >> transmission. >> >> Gage Amps >> 12 9.3 >> 14 5.9 >> 16 3.7 >> 18 2.3 >> 20 1.5 >> >> The K2 10W version uses 2.0 amps for transmit and up to 0.250 amps >> for >> receive. It looks like 16 gage wire would work fine. > > This is a pretty interesting table, especially in light of the > sizing of PowerPole connectors. The "30A" contact doesn't comfortably > fit anything larger than 12g wire. I don't have a "15A" contact > handy, but my memory is that it handles 18g OK, but I'm not sure > if it will handle 16g. > > That's just ... broken :-) > >> If it were me, I would buy the connector from Elecraft. > > Yeah, I guess I'm going to have to get a few. I admit that my > bench is littered with little cords that have "15A" PowerPoles on > one end and generic power connectors on the other end, all made > out of 20g or 22g zip cord. > > I'm having a really hard time imagining pushing 16g zip cord into > the body of a 2.1mm plug! I think I've done this with 18g once, > and it wasn't pretty - perhaps the cable sold by the Wireman > has thinner insulation? > If you are just making a short jumper from PowerPole to 2.1 mm, you can fudge a bit on the wire size, since the resistance is dependent on wire length. I wouldn't hesitate to use 18 or even 20 over a very short length with my K2. Bob, N7XY _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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