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

[Edward R Cole]

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

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?  TU es 73
>
>Gedas, W8BYA
>
>Gallery at <http://w8bya.com>http://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, 
><mailto:kl7aj at acsalaska.net>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>http://alaskit.co
>>
>>
>>
>>On Mon, 12 Mar 2018 17:44:40 +0000 (UTC), Andy 
>>- KU4XR via 600MRG 
>><mailto:600mrg at mailman.qth.net><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>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
>>
>>______________________________________________________________
>>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
>>
>
>______________________________________________________________
>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

73, Ed - KL7UW
   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/20180312/32561aee/attachment.html>