Power Cord Questions
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I am rebuilding the power cord from my RM35M to the K3. Questions..... 1. Do you need fuses to be in both the positive and negative lead? Or, since I am a "fixed" station, can I get away with one fuse in the positive lead? Currently, I have both leads fused. 2. What length should the power cord be....considering that there will be some power consumption (voltage drop) in the line which is longer than shorter? My current length is over 6 feet. 3. Should the fuse(s) be mounted at the radio or at the power supply? Currently, mine are right at the power supply. The reason why I am rebuilding the power cord is that I am getting somewhat of a voltage drop on key down. According to the K3, the voltage is at 13.8 but goes to 11 volts at key down at 100 watts....around 21 to 22 amps. So, I suspect something might a tad glitchy in the power cord. Maybe I just need to reinstall the Anderson Power Poles. Comments? Lee - K0WA In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense divine? Common Sense is the image of the Creator expressing revealed truth in my mind. - John W. (Kansas) Never interfere with anything that isn't bothering you. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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On 3/9/2012 6:37 PM, Lee Buller wrote:
> > I am rebuilding the power cord from my RM35M to the K3. > > Questions..... > > 1. Do you need fuses to be in both the positive and negative lead? Or, since I > am a "fixed" station, can I get away with one fuse in the positive lead? > Currently, I have both leads fused. Physics and EE challenged student here -- one fuse, in the positive lead if you never -- ever -- take your K3 into a vehicle. > > 2. What length should the power cord be....considering that there will be some > power consumption (voltage drop) in the line which is longer than shorter? My > current length is over 6 feet. Short. Shorter is even better. Minimize the number of connection points going to and from the radio. > > 3. Should the fuse(s) be mounted at the radio or at the power supply? > Currently, mine are right at the power supply. Doesn't really matter ... unless things in your configuration are going to move. If things move, shorts can happen in many places. You really want the short to happen "after" the fuse, so I'd put it as close to the power supply as possible, just on general principles. > > The reason why I am rebuilding the power cord is that I am getting somewhat of a > voltage drop on key down. According to the K3, the voltage is at 13.8 but goes > to 11 volts at key down at 100 watts....around 21 to 22 amps. Well, "Over 6ft" could be a kilometer or so, but for a reasonable shack length, that's a little more than expected. There's a couple of tenths volt drop in the K3 to the voltage sensor. The problem with fuses in moderately high current applications is that the fuse connections often offer a lot of voltage drop themselves. The automotive spade lug fuses in their appropriate holders tend to be lower resistance than the in-line guys, but that sometimes involves additional connections. 73, Fred K6DGW - Northern California Contest Club - CU in the 2012 Cal QSO Party 6-7 Oct 2012 - www.cqp.org ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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I will differ with Fred - the fuse should be mounted close to the power
supply - you are protecting the wire, and not the radio.. There could be a fault in the wire (actually more likely than a fault in the radio), and a fuse at the power supply end will trip - think about a fuse at the radio end and a short in the wire near the mid-point - the wire itself may act as the fuse unless the power supply shuts down due to overcurrent protection first. 73, Don W3FPR On 3/9/2012 10:13 PM, Fred Jensen wrote: > On 3/9/2012 6:37 PM, Lee Buller wrote: > 3. Should the fuse(s) be mounted at the radio or at the power supply? > Currently, mine are right at the power supply. > Doesn't really matter ... unless things in your configuration are going > to move. If things move, shorts can happen in many places. You really > want the short to happen "after" the fuse, so I'd put it as close to the > power supply as possible, just on general principles. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by k0wa@swbell.net
Lee,
What size wire are you using ? Should not be smaller than #12. The length should be as short as comfortably possible. That means as short as possible with enough extra length to dress the cable around the operation bench if/as needed, and to be able to pull the radio out of its operation position easily with out pulling the power cord out of the radio either on purpose or by accident. No need for any more length. Also, Be sure that the connections at the power supply terminals are solid. I used to work summers at a power supply house. They made very high current regulated power supplies for the military. There were instances where the customer would connect the test load to the PS with clip leads, and when the voltage at the load was out of spec, send it back. There was nothing wrong with the supply. The clip leads had too much resistance, and at the rated load, would drop too much voltage because of the bad connection at the PS terminals. Be sure your connections to the PS are clean and tight. Fuses should be mounted close to the supply, just like they are in your house. In the event of a short, you want to break the circuit before a fire starts. Present (currant?) thought says to fuse both leads. Use low loss auto blade type fuses. Other fuse holders can have a lot of resistance, and under load, drop the voltage. I have seen the cheap clip type de-solder a fuse cap ! You can get the auto blade holders with red and black leads at your local auto parts store to build your own, or buy them from Quicksilver Radio http://qsradio.com/index.htm or Powewerx all made up. http://www.powerwerx.com/fuses-circuit-protection/atc-inline-fuse-holder-ring-terminals-10-gauge.html 73, Gene K1NR On Fri, 9 Mar 2012 18:37:44 -0800 (PST) Lee Buller <[hidden email]> wrote: > > I am rebuilding the power cord from my RM35M to the K3. > > Questions..... > > 1. Do you need fuses to be in both the positive and > negative lead? Or, since I > am a "fixed" station, can I get away with one fuse in the > positive lead? > Currently, I have both leads fused. > > 2. What length should the power cord be....considering > that there will be some > power consumption (voltage drop) in the line which is > longer than shorter? My > current length is over 6 feet. > > 3. Should the fuse(s) be mounted at the radio or at the > power supply? > Currently, mine are right at the power supply. > > The reason why I am rebuilding the power cord is that I > am getting somewhat of a > voltage drop on key down. According to the K3, the > voltage is at 13.8 but goes > to 11 volts at key down at 100 watts....around 21 to 22 > amps. So, I suspect > something might a tad glitchy in the power cord. Maybe I > just need to reinstall > the Anderson Power Poles. > > Comments? > > Lee - K0WA > > > > > In our day and age it seems that Common Sense is in > short supply. If you don't > have any Common Sense - get some Common Sense and use it. > If you can't find any > Common Sense, ask for help from somebody who has some > Common Sense. Is Common > Sense divine? > > Common Sense is the image of the Creator expressing > revealed truth in my mind. > - John W. (Kansas) > > Never interfere with anything that isn't bothering you. > > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: > http://www.qsl.net/donate.html --------------------------------------------------------------------- Web mail provided by NuNet, Inc. The Premier National provider. http://www.nni.com/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by k0wa@swbell.net
Lee: Please see answers inline.
-----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Lee Buller Sent: Friday, March 09, 2012 6:38 PM To: Elecraft Reflector Subject: [Elecraft] Power Cord Questions I am rebuilding the power cord from my RM35M to the K3. Questions..... 1. Do you need fuses to be in both the positive and negative lead? Or, since I am a "fixed" station, can I get away with one fuse in the positive lead? Currently, I have both leads fused. There are arguments that support fusing the ground lead but I do not buy them. The national electrical code says never to fuse a ground. While are rigs are not covered by the NEC I still do not see a reason to fuse ground. 2. What length should the power cord be....considering that there will be some power consumption (voltage drop) in the line which is longer than shorter? My current length is over 6 feet. Shorter is obviously better but the K3 will compensate for voltage drop. I cut mine to fit with a little extra for service. 3. Should the fuse(s) be mounted at the radio or at the power supply? Currently, mine are right at the power supply. Assuming some disaster will befall your cable, fuses should be at the power supply. Having said that, I put mine where they are accessible and cool. Cool because the ambient temperature will affect the current they blow at. It is a good idea to put a clamp-on choke around the power leads. Again with a good antenna system you don't need the choke but it help the RF out of the shack when things are less than optimal. They are cheap and easy to install so why not. Fred, AE6QL. The reason why I am rebuilding the power cord is that I am getting somewhat of a voltage drop on key down. According to the K3, the voltage is at 13.8 but goes to 11 volts at key down at 100 watts....around 21 to 22 amps. So, I suspect something might a tad glitchy in the power cord. Maybe I just need to reinstall the Anderson Power Poles. Comments? Lee - K0WA In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense divine? Common Sense is the image of the Creator expressing revealed truth in my mind. - John W. (Kansas) Never interfere with anything that isn't bothering you. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by k0wa@swbell.net
My answers will be different from some you have seen.
1.  I would not use any fuses.  The RM35M has a current limiter circuit and a line fuse to protect it.  The K3 has a circuit breaker to protect it. If you are installing a transceiver in a car, you need a fuse in the positive to protect against a wire short and you need a fuse in the negative to protect you from a loose battery ground that routes your starter current through your transceiver ground. 2.  The power cord should be at least #10 and as short as reasonable.  6 feet is fine!  Much more than 10 feet and you might consider 2 #12 or #8. 3.  I would not use a fuse unless I was using a home made supply with no limiter or a battery for power.  If Elecraft thought you needed a fuse they would have given you one.  Willis 'Cookie' Cooke K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart ________________________________ From: Lee Buller <[hidden email]> To: Elecraft Reflector <[hidden email]> Sent: Friday, March 9, 2012 8:37 PM Subject: [Elecraft] Power Cord Questions I am rebuilding the power cord from my RM35M to the K3. Questions..... 1. Do you need fuses to be in both the positive and negative lead? Or, since I am a "fixed" station, can I get away with one fuse in the positive lead? Currently, I have both leads fused. 2. What length should the power cord be....considering that there will be some power consumption (voltage drop) in the line which is longer than shorter? My current length is over 6 feet. 3. Should the fuse(s) be mounted at the radio or at the power supply? Currently, mine are right at the power supply. The reason why I am rebuilding the power cord is that I am getting somewhat of a voltage drop on key down. According to the K3, the voltage is at 13.8 but goes to 11 volts at key down at 100 watts....around 21 to 22 amps. So, I suspect something might a tad glitchy in the power cord. Maybe I just need to reinstall the Anderson Power Poles. Comments? Lee - K0WA In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense divine? Common Sense is the image of the Creator expressing revealed truth in my mind. - John W. (Kansas) Never interfere with anything that isn't bothering you. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Elecraft did provide a fuse and a circuit breaker. There is a
resettable fuse in the power line for the QPR K3 (also the K2), and a circuit breaker with the KPA3. That means the K3 protects itself. That also means that the K3 cannot provide safety protection for the power wiring nor the supply itself, so fuses at the power supply are prudent things to add - even if the power supply has overvoltage and overcurrent protection. 73, Don W3FPR On 3/9/2012 11:18 PM, WILLIS COOKE wrote: > My answers will be different from some you have seen. > 1. I would not use any fuses. The RM35M has a current limiter circuit and a line fuse to protect it. The K3 has a circuit breaker to protect it. If you are installing a transceiver in a car, you need a fuse in the positive to protect against a wire short and you need a fuse in the negative to protect you from a loose battery ground that routes your starter current through your transceiver ground. > > 2. The power cord should be at least #10 and as short as reasonable. 6 feet is fine! Much more than 10 feet and you might consider 2 #12 or #8. > > 3. I would not use a fuse unless I was using a home made supply with no limiter or a battery for power. If Elecraft thought you needed a fuse they would have given you one. > > Willis 'Cookie' Cooke > K5EWJ& Trustee N5BPS, USS Cavalla, USS Stewart > > > ________________________________ > From: Lee Buller<[hidden email]> > To: Elecraft Reflector<[hidden email]> > Sent: Friday, March 9, 2012 8:37 PM > Subject: [Elecraft] Power Cord Questions > > > I am rebuilding the power cord from my RM35M to the K3. > > Questions..... > > 1. Do you need fuses to be in both the positive and negative lead? Or, since I > am a "fixed" station, can I get away with one fuse in the positive lead? > Currently, I have both leads fused. > > 2. What length should the power cord be....considering that there will be some > power consumption (voltage drop) in the line which is longer than shorter? My > current length is over 6 feet. > > 3. Should the fuse(s) be mounted at the radio or at the power supply? > Currently, mine are right at the power supply. > > The reason why I am rebuilding the power cord is that I am getting somewhat of a > voltage drop on key down. According to the K3, the voltage is at 13.8 but goes > to 11 volts at key down at 100 watts....around 21 to 22 amps. So, I suspect > something might a tad glitchy in the power cord. Maybe I just need to reinstall > the Anderson Power Poles. > > Comments? > > Lee - K0WA > > > > > In our day and age it seems that Common Sense is in short supply. If you don't > have any Common Sense - get some Common Sense and use it. If you can't find any > Common Sense, ask for help from somebody who has some Common Sense. Is Common > Sense divine? > > Common Sense is the image of the Creator expressing revealed truth in my mind. > - John W. (Kansas) > > Never interfere with anything that isn't bothering you. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Don Wilhelm-4
On 3/9/2012 7:29 PM, Don Wilhelm wrote:
> I will differ with Fred - the fuse should be mounted close to the power > supply. I thought that's what I said ... if I didn't, I was wrong ... as close to the power supply as possible. Many present era power supplies have over-current protection built in, and in those cases, I wouldn't use an external fuse at all, just more places for voltage drops. If you're on a battery [even if float charged], you really must fuse as close to the battery as possible, high capacity batteries can deliver an incredible amount of energy very very quickly. If you're in a vehicle, both + and - leads should be fused. The + lead for the obvious, the - lead in case the negative battery connection becomes faulty. In that case, the starting current would find its way back to the battery through the radio neg lead. 73, Fred K6DGW - Northern California Contest Club - CU in the 2012 Cal QSO Party 6-7 Oct 2012 - www.cqp.org ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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The standard, for vehicles, is to connect to the provided binding post, then run absolutely no more than 18 inches unfused. This allows the fuse to be placed for access. It also allows for shorted wires. --... ...-- Dale - WC7S in Wy ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by k0wa@swbell.net
I purchased the power cord with fuses from Powerwerx, item RGH-10 - http://www.powerwerx.com/fuses-circuit-protection/atc-inline-fuse-holder-ring-terminals-10-gauge.html - It is hooked up to my Astron RM-35M and I use the Elecraft provided power supply cord from the fuses to the radio.
It seems like an elegant solution. It provides me with peace of mind even if having the fuses might be overkill. At the moment I am using the 40 amp fuses that came with the adapter. I may change them out for a smaller value later but I'm not sure if I should or not. 73 Keith N8CEP K3 #6219 |
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It's too bad the overall length isn't 4 or 5 feet...with the additional
length on the APP side of the fuses. That would be more elegant. The way it is now, you have one voltage drop going through the fuse, another going through the APP to APP and then the APP at the radio. Then multiply by two for the return circuit. The only way I would use the Powerwerx power cord is if I could locate my power supply right next to the K3. Not possible for me. I'm not a big APP fan either but since the "ham radio world" brain trust has made them the de-facto standard I put up with them. On 3/17/2012 1:25 PM, N8CEP wrote: > I purchased the power cord with fuses from Powerwerx, item RGH-10 - > http://www.powerwerx.com/fuses-circuit-protection/atc-inline-fuse-holder-ring-terminals-10-gauge.html > - It is hooked up to my Astron RM-35M and I use the Elecraft provided > power supply cord from the fuses to the radio. > > It seems like an elegant solution. It provides me with peace of mind even if > having the fuses might be overkill. > At the moment I am using the 40 amp fuses that came with the adapter. I may > change them out for a smaller value later but I'm not sure if I should or > not. > > 73 > Keith N8CEP > K3 #6219 > > -- > View this message in context: http://elecraft.365791.n2.nabble.com/Power-Cord-Questions-tp7360239p7382121.html > Sent from the Elecraft mailing list archive at Nabble.com. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > -- 73, Gary K9GS Greater Milwaukee DX Association: http://www.gmdxa.org Society of Midwest Contesters: http://www.w9smc.com CW Ops #1032 http://www.cwops.org ************************************************ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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I was not sure about the power drop question when I purchased it. My astron is about 4 feet from the radio on the floor. I am not sure how long the standard Elecraft power supply cord is but the Powerwerx adapter adds an additional 1.5 feet. My K3 now shows a voltage of 13.6 volts, a drop of .2 volts? This assumes the K3 is accurate of course. I think this is well within the voltage required by the K3 is it not?
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Well I just ordered replacement fuses for the Powerwerx adapter. Looking at the power requirements of the K3, I thought the 40 amp fuses supplied were a bit too heavy. I had some 25 amp fuses here at home but I thought they might be a little light for the K3. I decided to purchase 30 amp fuses to use in the Powerwerx holders.
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