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Author Topic: Extention cord length from generator  (Read 678 times)
KU4UV
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Posts: 376




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« on: June 17, 2004, 09:02:39 AM »

Hello, my brother and I are planning on operating Field Day next weekend I had a question about the length of extention cord I need between the generator and the radio, and and what size cord I should be using.  I have seen the heavier guage cord for running things like air compressors, but is heavier guage cord better for electrical noise and spark noise suppression from the generator.  This will be first real attempt at Field Day operating, so any advise on set-up will be greatly appreciated!
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K5DVW
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« Reply #1 on: June 17, 2004, 09:10:41 AM »

It's nearly impossible to answer your question on the information you've given. One would need to know what size and type of the generator and what load you are putting at the end of the extention cord. If you're running a single 100W radio, I see no problem with 100' of cord.

Try this, take the RF output of all the radios and other electrical gear you will be using and add them, then multiply by 2. That's approximately your worst case electrical load. If it's more than 500W, I'd seriously consider using a heavy duty cord and I wouldnt expect to pass more than 1000W thru even a heavy cord. Use more than one and be sure your generator has spare capacity!

As for radio noise, you'll just have to try it and see. Different generators and setups have different noise issues. Whatever you do, it's more important to get the generator away from the antennas than from the operating position. And, very important, put all the generators DOWN WIND from the operation position, unless you like to pass out.

Have fun.
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N7NBB
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« Reply #2 on: June 17, 2004, 09:26:41 AM »

Also keep in mind the CLIMATE conditions... rain snow, lightning, etc.
In addition to preparing YOURSELVES for foul weather, make certain your equipment is foul weather compliant as well.

WEATHERPROOF all connections
Electrical, RF,  and Control.
use DRIP LOOPS on cables entering a tent, camper, etc.

GROUND the GENERATOR into the earth with at least a 4'ground rod... same goes for any tower or push-up pole you might use.

HAVE FUN ! GOOD LUCK !
Hope to catch you on the air !

CAM - N7NBB

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K5LXP
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« Reply #3 on: June 17, 2004, 09:46:28 AM »

> is heavier guage cord better for electrical noise
> and spark noise suppression from the generator

No.


Mark K5LXP
Albuquerque, NM

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WB2WIK
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« Reply #4 on: June 17, 2004, 11:23:38 AM »

Depends on the equipment, and the generator.

Obviously, you want a gauge of extension cord that is suitable for the load you plug into the end of that cord!  #16 gauge is suitable for about 8A; #14 for 11A; #12 for 15A if the cord length is 100 feet.  Going "bigger" never hurts, but might add cost that you don't need to spend.

Since most generators I've used make noise I'd rather not listen to, I try to keep generators and stations/operators as far apart as possible, and 100 feet is usually sufficient.  The generator should also exhaust away from you and preferably be sitting downwind from you; and maybe made portable enough that if the prevailing wind changes directions, you can move the generator to a new "downwind" position.

And the generator should never be sitting on or close to flammables including grass, weeds, etc.  I usually shoot for the generator sitting on sand, gravel, rocks...

WB2WIK/6

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KC8VWM
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« Reply #5 on: June 17, 2004, 11:26:59 AM »

I agree with Mark.

Generated noise is a fault of the generator itself by design - not the quality of the cord attached to it.

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KC8VWM
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« Reply #6 on: June 17, 2004, 11:28:21 AM »

I hear that solar panels are pretty quiet when generating power when attached to a battery.

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W7DJM
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« Reply #7 on: June 17, 2004, 12:46:25 PM »

I don't see how (pick a number) 50 feet or better, 100 feet of extension cable could POSSIBLY have any effect from generator noise.

First, seems to me that the length of wire is going to make the gauge a small part of anything (inductance?)

Then, seems to me that most will usually lay the cable on the ground, and that the distributed capacitance from the cable to ground will help make an effective bypass.

Some older alternators (they are NOT generators in the strict sense) may suffer from exciter brush noise, and some newer ones may suffer from exciter rectifier switching noise, but seems to me the "radiated"  noise is going to be right from the ignition.

You might want to strip some "big" (RG-8 size) coax braid and expand it to slip over the plug wire, then bond the end to the engine case.

Once upon a time you could buy plug shield covers.

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K4JSR
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« Reply #8 on: June 17, 2004, 02:10:57 PM »

Charles said, "I hear that solar panels are pretty quiet when generating power when attached to a battery."

And Smart Alec Me says, "Especially at night!" ;-D

73,  Cal  K4JSR
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AA4PB
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« Reply #9 on: June 17, 2004, 02:15:48 PM »

If the generator outlet has a 20A breaker then you need to use a minimum of 12 guage extension cord. If its a 30A breaker then you need a 10 guage extension cord. The size of the wire will not impact RFI noise. It is a matter of 1) using a wire large enought that it will be protected by the breaker and 2) using a wire large enough for the length of the run that you will not have too much voltage sag on the far end under your maximum load.

You might also want to consider using an extension that has a ground-fault breaker built into it.

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KC8VWM
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« Reply #10 on: June 17, 2004, 05:16:30 PM »

lol Cal
 Wink
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KE4DRN
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« Reply #11 on: June 17, 2004, 11:03:23 PM »

hi michael,

One thing to factor in is that you will loose approx. three percent of your line voltage if you use 100 feet of cable.

As an example, 700 watts and a run up to 90 feet #14 is fine.

If you need to go longer then upgrade to #12.

As others have posted, you need to figure your total wattage to select the correct cable.

73 james
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AA4PB
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« Reply #12 on: June 18, 2004, 02:09:55 PM »

The idea of using wire that can handle the full limit of the breaker is a safety issue. It makes it impossible to overload the wire. Same is in your breaker panel at home. If you have a 30A breaker but use wire rated for only 15A then it is quit possible for someone to draw 30A thru the wire. If the cord is rated to handle at least the breaker limit then the breaker will trip before you overload the wire. The wire is then protected. Of course if you can *guarentee* that no one will plug any additional items into the end of your extension cord then you can get by with one rated only for the load you plan on connecting to it.

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K1CJS
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« Reply #13 on: June 18, 2004, 01:53:12 PM »

You don't need to use a certain size (AGW) cord according to the breaker on the generator.  Most generators have two outlets to plug into anyway.  You have to select the proper size extention cord for the total of the load you have connected to the cord.  First, 18 gauge cord should never be used for an extension cord.

If you are going to place the generator 100 feet from your operating position, you should use at least a 14 gauge three wire cord, and remember not to overload the cord, 10 amps should be the top limit for that length.  If you have more of a load, use a second extension cord or a larger (heavier)cord.

The best, safest way (and unfortunately the more expensive) is a hundred foot three wire ten gauge cord feeding a power distribution strip.  That would safely carry the output of a 5000 watt generator with the least voltage loss and best capacity to your operating positions.

Good luck, have fun, and BE SAFE.    
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KU4UV
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« Reply #14 on: June 18, 2004, 02:34:11 PM »

Thanks for all of the great information guys.  I should have bben more specific with what my set-up plans for Field day were.  My twin brother and I are the only people that will be operating.  We will be running 100 Watts from the generator, and maybe a lamp and a fan too, so we plan on trying to rent a generator with at least 1000 Watt capacity.  We probably won't be putting a big load on the generator with just three or four low wattage items plugged into it.  I have a four foot ground rod, so I will be able to ground the gereator for safety.  I probably won't be grounding the radio itself though.  Since we will be usind dipoles for the antennas, I don't see that a good RF ground will be much of a factor.  Thanks again for the great information, and I hope to catch you guys next weekend on the air.  We will operating as KU4UV 1 Bravo Kentucky.
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