I see, ok.
Do you think this type of thing can help on bass stations using a vertical
style antenna? or does it mainly only help mobile installations that
receive QRN caused by wind, dirt and that get build ups of static
electricity from the antenna moving through the air?
also, using a quarter wave DC stub might help to eliminate RFI caused by
certain frequencies I would presume? Say if you were causing your neighbors
home stereo to practically explode on 7 megs, would a properly tuned stub
for 7MHZ help to eliminate this issue along with a balun, chokes and low
pass filter of course.
I'm just wondering what other practical applications a quarter wave dc stub
could be used for other than the application for 27 meg mobile installations
that you mentioned.
does having the stub connected on a T reduce the amount of rf getting out to
the antenna? or does the open/closed aspect of having both the dc stub and
the regular antenna on the load prevent this?
also, does this only work when you are using a quarter wave antenna?
presumably, you could cut the stub to match what ever type of radiator you
are using?
73
Colin, V A6BKX
----- Original Message -----
From: "Butch Bussen" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, April 07, 2011 6:28 PM
Subject: Re: antenna lengths
> 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
>>
>>
>
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