Jim Wilhite w5jo at brightok.net
Sun Mar 9 09:43:57 EST 2008

The quad,  folded dipole and loop are the only types of antennas that I 
can think of where this would work.  You have a complete circuit with 

A dipole or beam doesn't have that unless you have a balun on them.  In 
that case, the current would go up the feedline to the balun and come 
right back, doing nothing for the antenna itself.

Many broadcast antennas use this scheme, but they are folded dipoles.


>>-----Original Message-----
>>From: Joe Crawford
>>I knew a guy who used a 30 amp variac to feed a 5 volt, 30 amp 
>>transformer on his quad driven element.Worked real good to melt the 
>                                       Joe W4AAB
> Joe,
> This is a great idea but the variac can be much smaller. The current 
> needed is reduced by the turns ratio of that filament transformer. If 
> the primary is 120 vac, then the turns ratio is 120/5 or  24. 
> Therefore, if we take the 30 amps and divide that by 24 we get 1.25 
> amperes. The variac only needs to be rated for a little over one 
> ampere. I might be tempted to use a light bulb in series with that 
> transformer primary where the current to the load will vary by the 
> bulb wattage rating, and the load resistance. Remember that the 
> resistance of the bulb is very non linear where the cold filament has 
> a much lower resistance than a hot filament. So I'd start with a 100 
> watt bulb and see if that works. I would not go over 150 watts with 
> the bulb rating though. Having a clamp on AC current probe would be 
> handy in a case like this.
> I picked another solution to the ice storms. Back in 1976 I moved to 
> central Texas. Getting any ice or snow here is pretty rare. ;-)
> Regards,
> Jim

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