you can cut one for each band though, you'll have them all over the place,
but you can do it.
----- Original Message -----
From: "Butch Bussen" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, April 08, 2011 6:31 PM
Subject: Re: antenna lengths
> The problem with using it on a vertical is the quarter wave is only good
> for specific frequencies, so that doesn't work on a multiband antenna.
> If you cut a quarter wave for 40, it wil be close to a half wave on 20
> and look like a short on 20, as a shorted half wave is a short at its
> frequency. On a single band antenna, yep, otherwise, no.
> 73
> Butch
> WA0VJR
>
> On Fri, 8 Apr
> 2011, colin McDonald wrote:
>
>> 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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