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How Long Should a 20M Dipole be in Meters?
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- čas přidán 24. 03. 2023
- RE-UPLOADED TO CORRECT TITLE ERROR A fellow ham, callsign S54LD, says "I have a Balum BU-50 Diamond. I have a 2.5 m2 soft wire. Ho many meters must I have on each side for 14 Mhz. from 14,000 to 14,350?" Dave here to help.
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2.5mm^2 works out to be about 0.070 inches (70 mils) or about #13 AWG wire (FWIW)
This must be a "special edition video" as the leaning lamp is back! Enjoyed it's surprise return appearance. Oh the tyranny of gravity.
20m ÷ 4 = 5m approx per element. Then just play around with the length of the wire to get the best SWR for the freq you are going to use.
Some time ago I read a comment about antenna length that I found easer to remember. All I need to remember is 1234, where 1 side of the dipole is 234/freq. in mhz.
Does it make much difference if a fan dipole is spread like a fan?
I'm thinking of antenna projects that used multi-conductor antenna rotator cable for the radiating elements.
What are your opinions on using electric fence wire, or copper clad MIG wire (available cheap at a certain discount tool store nationwide) for antenna wire? 73 AE7EC
You can also type this in a Google search: speed of light / 14 MHz / 2 in feet
dipole total length ((300/fMhz)/2) then *.95 velocit factor? no need for feet. si units C/f = wave length
Easy for us to say in Metricland but in the USA they have no exposure to the metric system whatsoever. At least in in Ireland we have measuring tapes in BOTH Metres and Feet. People in the USA don't have that luxury. Mind you I have seen measuring tapes in Metres only also in Europe!
I work in PCB design and US keeps push for imperial measurements.
Dave, What do you think of using ladder line to make a folded dipole? essentially shortening the lemgth going out, but retaing the !/2 wave length of wire?
300/freq in m
MHZ =A THEN A× VELICTICY FACTOR OF CABLE YOU USI G ANF FOR DIPOLE /2 TO GET EACH LEG ALLOW EXTra for tieing off toends
2.5mm is around 14 gauge wire roughly (13.???) and is normally used as main house wire in Europe, 15 amps roughly.
If I remember the figure would be 150/frequency for 1/2 wave as 300/frequency is the figure for full wave, or the legs would be 75/f for meters.. if I actually remember my UK test questions..lol.. easier for me to remember the 468/234 math for feet though..
and when I was in london I found that the .95 for velocity factor etc was not really necessary.. it was more a worry about height or not.. it usually got it to where the radio was fine with it for most uses.. simply folding the end and tapng it worked fine.. and yes, I prefer stranded myself..
I can only have one length of antenna . so I chose Inverted-L attach to out door automatic antenna tuner. it is compromise. wish if I can do full size mono band dipole. AG6JU
Show us digital SW radio receiver how it works in real life. Standard is Called drm30
About 10m.
Love your channel. In the Metric system when I look for wavelength I divide 300 by the frequency in megahertz to get the length in metres and divide by 4 for the length of each dipole element. if you multiply by velocity factor you get the answer you got ie 10.05 metres. I guess the 468 takes care of the velocity factor in feet. I was wondering about that. 73 ei2jmb
It baffles me how much of a meal North Americans make out of this backward and forwarding.
Photons travel a 300,000 km per second. It really is that simple. 300/freq.
@@TonyLing that number can vary through different materials
Divide by 2, not 4, no? What velocity factor do you use and where do you look it up if you don't know or are using random wire?
@John Bauman it varies by wire type and coated or uncoated...bare copper is usually around 95%..But you have to also look up your Coax VF as well...I just cut my wire longer than needed and then test and trim and test and trim until I get the best SWR..
@John Bauman if your asking about say a 40 meter dipole you would need about 40m or 66 feet of wire...20m on one side of the feed point and 20m on the other...but cut it a little long and test and cut if necessary