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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