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|Main page is blank when not logged in||Apr 7th 2012, 09:48||3||719||on 7/4/12|
|Discount for multiple subscriptions?||Mar 23rd 2012, 06:59||1||720||on 23/3/12|
|Rules violations on 60 meters||Mar 6th 2012, 03:03||6||1,588||on 28/3/12|
|January DIY QST||Dec 13th 2011, 03:22||1||939||on 13/12/11|
|Ethiopian jamming wiping out 40 meters||Oct 6th 2011, 04:37||2||1,470||on 6/10/11|
|How to access info in back issues of QEX and NCJ||Sep 2nd 2011, 19:37||11||2,349||on 5/9/13|
|Calculating Impedance||W6OGC||40 minutes ago|
|Zack is right. I can't think of any one formula, table, etc.
But this, my friend, is a piece of cake for EZNEC! I believe the free version would work just fine for your simple antenna. I would download it and play with it. http://www.eznec.com/demoinfo.htm
You can use a sample model of a vertical that comes with the program, change the wire length to 31', and it will create a table of the numbers that you need very, very easily across an entire band. If I were not so busy here, I would do it for you for 40, 20, and 15 meters, every 100 kHz on each band. Maybe someone else has more time, if you don't want to install EZNEC.
|Calculating Impedance||W6OGC||1 day, 3 hours ago|
You didn't give enough information. The wire has to be fed against something. In other words, there needs to be two reference points, either another wire (such as in a dipole or loop) or a ground.
If this is a vertical wire fed at the bottom against a ground, the impedance would be different that if it was more or less horizontal (and the height above ground makes a difference).
I can tell you off the top of my head that at that length and frequency, there would be not only an resistance value but a an inductive reactance value as well.
Maybe if we knew what you were trying to accomplish someone could give a better answer.
As for formulas and equations, once we get more complex than 234/f, I tend to get lazy and would use a spreadsheet or EZNEC instead. :-)
|Joel Hallas HF Ground Plane article in 12/2013 QST||WO1X||1 week, 1 day ago|
|I don't know how close to the tree trunk it was, but a few feet away shouldn't kill its performance below 10 meters. I've hung HF antennas from trees and they performed very well.
And moving a 75 meter antenna from its lower location in the clear in amongst the trees in the woods here at greater height made a stunning improvement.
Now if it was 2 meters and especially UHF, that would be a different story.
|Can't find poem||markstar208||on 13/10/13|
|Thank you for that, Zack! I found something that way last night that I haven't been able to find in the past.
Also, if you search for the word "poem" in the Title/Keywords field, quite a few results show up.
|What Characters do I need to Know?||WB5EMX||on 4/9/13|
| Here's an updated IARU Morse character set, including "@" and others. Courtesy of VK1OD.
If you get a Server Error while downloading that, go to http://www.w0btu.com/files/misc/, scroll down, and click on that file there.