[600MRG] TNX for Replies, Ending Thread - RF Ammeter Placement and Antenna Feedpoint Location

Mon Mar 12 17:42:18 EDT 2018

Hi Ed, so good to hear from you again ! I chose my words very carefully. 
Eric used the term Measured and that is what I wanted to learn more 
about. I use and enjoy modeling and know of several calculated 
approaches to arrived at the value. But again, that word "measured" got 
my attn. and was wondering if he would be willing to share any practical 
approaches at arriving at a value of R(rad)...73

Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 3/12/2018 4:47 PM, Edward R Cole wrote:
> Gedas,
>
> When I was setting up my 600m station, WD2XSH/45, in 2012, I asked 
> this and generally the opinion was it was very difficult to measure. 
> Most suggested calculating it from an antenna modeling program (EZNEC5 
> recommended).  That also gave me the reactive component of impedance, X.
>
> I did measure actual Z and moved coil taps till X was minimized using 
> a modified MFJ-269B analyzer.  That gave R of 18 ohms.  EZNEC5 gave 
> radiation resistance of 0.8 ohms and about -680 reactance for the 
> antenna without loading coil.
>
> My Inverted-L 43x130 foot.  I use four 50 to 70 foot radials, three 
> are 2-foot wide chicken wire lain on surface of the lawn.  Fourth is 
> my 120-foot 1-5/8 inch hardline with shield ties to ground rods.
>
> Do you have an idea what your local soil permativity is?  EZNEC has a 
> variable you can enter that value in the model.  If you don't know 
> then run the model for different values to see its effect.
>
> My guess is the short monopole will work better than a very low dipole 
> (1/2 wavelength is 960 foot so if dipole is 75 feet high its 4% of a 
> wavelength high).  Short monopole will be capacitive requiring a 
> loading coil to make resonant.  Horizontal wires at top will form 
> capacitance hat.
>
> 73, Ed - KL7UW
> http://www.kl7uw.com/630m.htm
>
> <http://www.kl7uw.com/630m.htm>At 10:32 AM 3/12/2018, Gedas wrote:
>> Content-Type: multipart/alternative;
>>  boundary="------------7EB5E2DF10DC7620D51AEBDE"
>> Content-Language: en-US
>>
>> I am enjoying this thread and learning a lot. Can you describe how 
>> you would measure the radiation resistance for two 630m antennas; the 
>> first being a short (400') loaded, center fed dipole, and the 2nd 
>> antenna being a conventional, short base loaded monopole with 
>> capacity hats fed against a small radial field?Â  TU es 73
>>
>> Gedas, W8BYA
>>
>> Gallery athttp://w8bya.com
>> Light travels faster than sound....
>> This is why some people appear bright until you hear them
>> speak.
>> On 3/12/2018 2:19 PM, kl7aj at acsalaska.net 
>> <mailto:kl7aj at acsalaska.net> wrote:
>>>
>>> The RF ammeter should be placed where the radiation resistance is
>>> measured.
>>>
>>> ---
>>> Eric P. Nichols, KL7AJ
>>> AlasKit Educational and Scientific Resources
>>> 3763 Lyle Avenue
>>> North Pole, AK 99705
>>> (907) 488-0483
>>> (907) 371-7120
>>> http://alaskit.co
>>>
>>>
>>>
>>> On Mon, 12 Mar 2018 17:44:40 +0000 (UTC), Andy - KU4XR via 600MRG
>>> <600mrg at mailman.qth.net> <mailto:600mrg at mailman.qth.net>
>>>   wrote:
>>>
>>>>>
>>>>> Hiall:
>>>>>
>>>>> Thank you for the replies on, and off list .. I have the answers I asked
>>>>> for .. I do not want the topic to become
>>>>> boring, or aggitating .. I have learned some things about My Particular
>>>>> antenna setup that I did not know before
>>>>> asking .. I will leave off with this bit of Clarifying Information
>>>>> ..  My Series Loading Coil - needed Inductance -
>>>>> changes with the ambient conditions, and can move up and down: ie; 30 to
>>>>> 50 microHenries, which is expected.
>>>>> Getting on the air was a spur of the moment decision, and then is when my
>>>>> needing to know the antenna
>>>>> characteristics became clearly apparent .. Still working on it , but
>>>>> farther along than I was .. 73 to all:
>>>>>
>>>>> Andy - KU4XR
>>>>> ______________________________________________________________
>>>>> 600MRG mailing list
>>>>> Home:
>>>>> http://mailman.qth.net/mailman/listinfo/600mrg
>>>>> Help:
>>>>> http://mailman.qth.net/mmfaq.htm
>>>>> Post:
>>>>> mailto:600MRG at mailman.qth.net
>>>>>
>>>>> This list hosted by:http://www.qsl.net
>>>>> Please help support this email list:
>>>>> http://www.qsl.net/donate.html
>>>
>>> ______________________________________________________________
>>> 600MRG mailing list
>>> Home:
>>> http://mailman.qth.net/mailman/listinfo/600mrg
>>> Help:
>>> http://mailman.qth.net/mmfaq.htm
>>> Post:
>>> mailto:600MRG at mailman.qth.net
>>>
>>> This list hosted by:http://www.qsl.net
>>> Please help support this email list:
>>> http://www.qsl.net/donate.html
>>>
>>
>> ______________________________________________________________
>> 600MRG mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/600mrg 
>> <http://mailman.qth.net/mailman/listinfo/600mrg>
>> Help: http://mailman.qth.net/mmfaq.htm <http://mailman.qth.net/mmfaq.htm>
>> Post: mailto:600MRG at mailman.qth.net <mailto:600MRG at mailman.qth.net>
>>
>> This list hosted by: http://www.qsl.net <http://www.qsl.net/>
>> Please help support this email list: http://www.qsl.net/donate.html 
>> <http://www.qsl.net/donate.html>
>
> 73, Ed - KL7UW
> http://www.kl7uw.com
> <http://www.kl7uw.com/>Dubus-NA Business mail:
>   dubususa at gmail.com
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/600mrg/attachments/20180312/f35efa7a/attachment.html>