It gives the antenna a dc ground, so the static is sent right to ground.
  At 27 mhz, the stub appears open, an open quarter wave appears shorted, 
and a shorted quarterwave appears open.
73
Butch
WA0VJR

On Thu, 7 Apr 2011, colin McDonald 
wrote:

> and I bet   the antenna was matched better to the radio with that stub
> connected?
> I get that it helped to reduce static build up or something, but how does a
> quarter wave stub do that?
> 73
> Colin, V A6BKX
>
> ----- Original Message -----
> From: "Butch Bussen" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, April 07, 2011 5:22 PM
> Subject: Re: antenna lengths
>
>
>> The 468 comes in to play as dipoles have what is called an end effect of
>> around 5 percent.
>> I'm not sure where the formula for the loop comes from but if you're
>> figuring say a quarter or half wave stub, you use 300 meters which is a
>> full wave length and the speed of light.  To convert this, take meters
>> times 3.28 so 984 over frequency gives youa full wave length.  for a
>> quarter wave stub, for example, divide this by 4 and then that number
>> times the volocity factor of your coax.
>>
>> Way back when I was selling a lot of cb rigs, and people were running
>> quarter wave whips, 102 inches long.  These ghings would pick up enough
>> static here in a dirt storm, you could lay the pl259 on the dash and
>> sparks would jump from the center pin to ground.  Needless to say, this
>> was hard on fet transister front ends, so her was my fix.  I would divide
>> 984 by 27 mhz, which comes out 36.444 and 36.44 divided by 4 for a quarter
>> wave in feet is 9.111.  The coax I used which was rg58 had a volocity
>> factor of around .7 as I recall, so 9.111 times .7 is 6.377 feet.  I'd
>> make this stub, short one end and put it on a t connector on the radio
>> with the antenna to the other leg.  It was a dc short, but as a quarter
>> wave looks open at its frequency, the radio didn't know it was there.
>> Worked like a champ!!
>>
>> 73
>> Butch
>> WA0VJR
>
>