On Sat, Jan 3, 2009 at 11:26 AM, jimlux <jimlux@earthlink.net> wrote:
> Martin Ewing wrote:
>
>> Chas,
>>
>> A little math shows that 5.5 Amps rms into 50 ohms is 1.5 kW. My handbook
>> says the DC "fusing current" of #26 copper is 20 Amps. RF skin effects
>> increase the resistance (perhaps by 5X at 10 MHz) and heating (25X). But
>> you're not going to have 5.5 Amps continuous. For SSB, the average power
>> is
>> going to be much less than 1.5 kW, so you might squeak by, assuming the
>> SWR
>> isn't too bad. I wouldn't use insulation. All in all, #26 wire would be
>> a
>> poor choice for high power -- but hams have been known to try these
>> things.
>> Note that the current is normally greatest at the feed point and decreases
>> toward the ends of a half wave dipole. So you could taper the wire size
>> down toward the ends.
>>
>
> Good point (although I don't think the dissipation goes up as the square of
> resistance)
You're right, of course. But I was only off by one in the exponent... :-(
-mse
--
Martin Ewing, AA6E
Branford, CT
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|