On 23 Jan, 19:40, art wrote:
On 23 Jan, 16:31, Jim Lux wrote:





Tim Shoppa wrote:
On Jan 22, 3:51 pm, art wrote:

I have a home brew dipole antenna made from #22 copper What is ther
maximum power
that it can handle. Support is not a problem. I want to test it for
max power using a 8877 which will blow if the wire
opens, and they are costly. Ofcourse I would like a bit of safety in
hand. Does minimum wire size vary much dependent on band useage? I
have no idea what manufactures use for commercial style antennas!

Wow!

An 8877 could develop 1.5 to 2kW output power (if done in a part of a
world where it's legal for a ham to use that much power.)

2kW into a 50 ohm load is a current of 6 or 7 amps, assuming it's a
perfect match/no standing waves.

The fusing current of 22AWG copper wire is about 40 Amps. So if
everything is working and matched, it won't melt.

That's the DC fusing current....

As an earlier poster mentioned, skin effect means that the current is
being carried in a thin layer on the surface, so the heating might be
more. *Of course, the hot layer is also closer to the air.

The higher you go in frequency, the more you'll have to derate the
above, but for low HF it'll be not too bad.

But geeze.... you've got a multi-kilowatt amp and can't afford
anything better than 22AWG wire???

Traditional rule-of-thumb for ham wire antennas would say that if
you're pumping more than a kilowatt in, you want at least 12 gauge or
14 gauge wire. There's also the N.E.C. specs, which say that copper
antenna wires have to be thicker than 14 gauge up to 150' spans, and
thicker than 10 gauge over 150' spans.

The NEC rules are for mechanical strength, not current carrying capacity..

One might also wonder about corona discharge at the ends of the dipole....

Tim N3QE- Hide quoted text -

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Actually it is a full wave length helix winding for 160M. The teflon
coated wire was what I had on hand.I will only be using 100 watts or
so but you never know when the urge comes up. I have a motor driven
reflector on it so I will be checking out the directivity at different
close spacings.When I finally settle on a design the wire will be
thicker magnet wire.
Thanks for all the info. As for heat it is mighty cold here so short
transmissions should work out o.k.
Regards
Art- Hide quoted text -

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It has been very cold these last few days working on antennas. Just
finished putting up anew
160M antenna but have not checked it yet as I am so tired.It is like a
TV antenna at 70 feet.
Have a reflector on it made of aluminum mesh plus a motor to place the
reflector within six inches of the driven element to about 30 inches
from the driven element.Now have to wire up the rotor and the
reflector motor and then chart the LC for all bands.HopefullyI will be
close first time for the top band.Next antenna to brew will be around
1 cuft for 160M probably out of #20 wire this time but I do need a
rest from antennas!
Regards
Art Unwin KB9MZ.....XG(uk)