Well a quarter wave antenna would be 234, the 246 is for an actual
qarter wavve length not counting in what is called "end effect" which is
about 5%
73
Butch
WA0VJR
Node 3148
Wallace, ks.
On Sun, 18 Aug 2013, Steve wrote:
> True, but typically I was always taught that you don't take ground effects
> into consideration when computing counterpoise lengths for ground. I always
> used 246/Freq in MHz. But, you're only talking an inch difference, max.
> ----- Original Message -----
> From: "Butch Bussen" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Saturday, August 17, 2013 5:59 PM
> Subject: Re: 2-meter Antenna Challenge
>
>
>> not true for antennas. You have to count in what is called end effect.
>> formula for a half wave is 468 and a quarter wave 234 over freq in mhz.
>> Only time you use the 300 for meters or 984 for feet is if you are
>> calculating tuning stubs and such, then you would also multiply by the
>> volocity factor of the coax.
>> On Sat, 17 Aug 2013, Steve wrote:
>>
>>> ABout 20.2 inches is a quarter wave. Wevelength = 300/Freq in megahertz
>>> 300/146. Then divide that result by 1/4 to get your quarter wavelength
>>> counterpoise.
>>>
>>> Steve, K8SP
>>> ----- Original Message -----
>>> From: "Tom Behler" <[log in to unmask]>
>>> To: <[log in to unmask]>
>>> Sent: Saturday, August 17, 2013 4:00 PM
>>> Subject: Re: 2-meter Antenna Challenge
>>>
>>>
>>>> Mark:
>>>>
>>>> So, now I'm thinking of two things here.
>>>>
>>>> First, the magmount I have is sealed, so I'm not sure how I would get to
>>>> the
>>>> shield of the coax to make the connection you describe.
>>>>
>>>> Also, I'm doing some mental calculations as to the length of the
>>>> counterpoise.
>>>>
>>>> Can someone refresh me as to the formula you would use for that, keeping
>>>> in
>>>> mind that I'd like the antenna to perform best around 146
>>>> megahertz--pretty
>>>> much in the center of the band.
>>>>
>>>> Tom Behler: KB8TYJ
>>>>
>>>> ----- Original Message -----
>>>> From: "Mark WZ0K" <[log in to unmask]>
>>>> To: <[log in to unmask]>
>>>> Sent: Saturday, August 17, 2013 2:45 PM
>>>> Subject: Re: 2-meter Antenna Challenge
>>>>
>>>>
>>>>> Hi Tom,
>>>>> On The antenna situation. Some years ago, I had a 5/8 wave mag
>>>>> mount
>>>>> that I used in a window sill. It performed well enough. However, After
>>>>> hearing about using a counterpoise, I loosened the antenna from the mag
>>>>> mount and slid a thin piece of wire between the antenna and the mag
>>>>> mount.
>>>>> I
>>>>> made sure it touched the metal part of the bracket that was connected
>>>>> to
>>>>> the
>>>>> braid of the coax. The wire was cut to a quarter wave. Suddenly my
>>>>> reports
>>>>> were better in all the repeaters, and I started reaching in to machines
>>>>> that
>>>>> I could not reach before. I hope this helps.
>>>>>
>>>>> God bless,
>>>>> Mark
>>>>> God loves You!
>>>>> My personal website: Http://www.christiantraditions.info
>>>>> The Blind Computer People List:
>>>>> http://christiantraditions.info/mailman/listinfo/blindcomputerpeople_christiantraditions.info
>>>>> Follow me on Twitter: https://twitter.com/TorgersonMark?refsrc=email
>>>>> -----Original Message-----
>>>>> From: [log in to unmask]
>>>>> Sent: Saturday, August 17, 2013 11:32 AM
>>>>> To: [log in to unmask]
>>>>> Subject: Re: 2-meter Antenna Challenge
>>>>>
>>>>> Two suggestions:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> Hi, all.
>>>>>>
>>>>>> I hope I am not wearing out my welcome back to the list, but I have a
>>>>>> challenging antenna situation I'm currently facing in the new faculty
>>>>>> office
>>>>>> I will be occupying starting this Spring semester.
>>>>>>
>>>>>> I currently have an old Kenwood TMV7A in the office, with which I have
>>>>>> always had at least some luck, in terms of getting into our local
>>>>>> 2-meter
>>>>>> repeater. The repeater is about 15 miles from the University.
>>>>>>
>>>>>> However, in my new office, I am finding that the small mag-mount
>>>>>> antenna
>>>>>> I
>>>>>> have always used simply does not allow me to reach the repeater
>>>>>> consistently. Currently, I have the magmount sitting on a small metal
>>>>>> bracket on the window sill in the office. It is right next to the
>>>>>> window,
>>>>>> so I would think that should help. However, I do not have much of a
>>>>>> ground
>>>>>> plain for the magmount. I also think there is some de-sensing going
>>>>>> on
>>>>>> with
>>>>>> the steel of the office building, and with other surrounding computer
>>>>>> equipment in the office complex.
>>>>>>
>>>>>> I do have a filing cabinet on the other side of the office that I
>>>>>> could
>>>>>> use
>>>>>> as a ground plane, but the top of the filing cabinet is too high, and
>>>>>> there
>>>>>> is not enough space between it and the office ceiling to accommodate
>>>>>> the
>>>>>> magmount antenna.
>>>>>>
>>>>>> This obviously is a very challenging situation, and I also have to be
>>>>>> at
>>>>>> least somewhat concerned with appearance, in terms of not having an
>>>>>> ugly-looking antenna that might draw more attention to what I am
>>>>>> trying
>>>>>> to
>>>>>> do than I might want.
>>>>>>
>>>>>> Do any of you have any suggestions as to how to help the mag-mount
>>>>>> perform
>>>>>> better in this situation?
>>>>>>
>>>>>> Or, might I be better off considering another type of antenna, such as
>>>>>> a
>>>>>> J-pole of some sort.
>>>>>>
>>>>>> I would appreciate any thoughts.
>>>>>>
>>>>>> Tom Behler: KB8TYJ
>>>>>>
>>>>>>
>>>>>
>>>
>>>
>
>
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