Hi guys We at club station going to build 80m full size vertical. We have assembled it on the ground and it is 22m (72,2ft) length. What we afraid is that lowering and raising again procedure will be
Vytenis, Sounds like a great antenna! The formula for changing it is a simple one ... first measure the actual length as is. Then put it up and measure the point where the reactance, X, equals 0. Tha
Thanks Gary K9RX and Charlie N1RR, 2nd question is clear now. Charlie also gave formula for length 246/f(mhz) = element (feet) which I assume includes length to diameter ratio or this ratio is not so
Not length to diameter, It is independent of diameter. It is a simple method to determine a difference of length as a ratio based on frequency. _______________________________________________ _______
Maybe I don't understand, but I would think that if you had a tower with an aluminum tube "stinger" on top, this might not work because of the change in percentage of the various diameters. Chuck W5P
Author: Mike DeChristopher <mfdechristopher@gmail.com>
Date: Wed, 13 Sep 2017 14:34:19 -0400
If you're reasonably math inclined, try K7TJO's calculator (http://wxtofly.net/wavecalc.htm). Instead of entering AWG, use OD in inches of your mast. Although the intended purpose is for scaling elem
I just thought that it might explain why different formulas are used. Charlie gave me formula which is widely available: 246/f(mhz) = element (feet), but I also found https://www.dxengineering.com/ t
the classic 246/f is the free space half wavelength. You'll see other numbers too (e.g. 234..) (see "Where Does 468 Come From?" at https://www.eham.net/articles/23802 for an interesting article by N
234/f is the formula used for calculating the length of a 1/4 wavelength wire or vertical element 246/f is the formula used for calculating the spacing between elements in an array 246/f x Vf is the
On 9/13/17 11:46 AM, V. Sciucka wrote: I just thought that it might explain why different formulas are used. Charlie gave me formula which is widely available: 246/f(mhz) = element (feet), but I also
Chuck, The reason why this will work is because you are FIRST determining what the formula is for that particular antenna in situ. So if it were say 22M tall and it resonated at 3.467 Mhz then the "f
these are only starting points! Local conditions - the antenna itself, the surroundings, the ground, etc etc will all conspire to move that value up or down slightly. KNOWING what your particular ant
Antenna resonance (and SWR bandwidth) are affected by conductor diameter. I don't understand why we continue to rely on formulas assuming wire as the conductor when it is trivially easy to model a ve
But you are only adjusting the smaller diameter tube and not the larger diameter. Afterward, the antenna will have a larger percentage of the large diameter than before. Therefore, it is a different
I agree. But, what was wanted is a formula where only one adjustment was needed. I think that will only work when the entire element is one diameter such as a wire. The ratio will get close, but will
Don't think so. IIRC the OP said the tubing diameter went from 4" down to 1". If you modeled in NEC with stepped-diameter correction to get an equivalent uniform length and then took a percentage be
One should be able to get within say 3% .... 5% tops to start with right?! Measuring the actual frequency of the actual antenna and changing it this much will work ... if done properly in one go. Ive
IIRC the OP said the tubing diameter went from 4" down to 1". If you modeled in NEC with stepped-diameter correction to get an equivalent uniform length and then took a percentage before changing bac
Thank you guys for all this discussion. This is my first 80m fullsize, so, some questions might have been childish. I learned a lot. What is easily achievable and what is not, what precision should I
Author: Dan Maguire via TowerTalk <towertalk@contesting.com>
Date: Sat, 16 Sep 2017 09:04:12 +0000 (UTC)
I'm late to this party but thought I'd throw my hat into the ring of responses. I happen to have a model of the DXE VA1 80m full size vertical. It has a total of 16 taper sections ranging from 2.125