Author Topic: Random length multiband dipoles  (Read 3323 times)

Offline iam4liberty

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Random length multiband dipoles
« on: April 30, 2017, 10:12:34 AM »
This is really great, Carl.

Another nice feature of this is that extra materials can easily be used to make a multiband HF antenna. Good insulators can be made with PVC pieces and some epoxy.  Ladder line acts as the feed line all the way back to a balanced tuner.  Antenna is simply any long pieces of wire of suitable length.  Wola, a 'random length dipole':

http://www.arrl.org/random-length-multiband-dipoles
http://www.antennex.com/hws/ws0200/insulator.htm




So while helping them get on the air at 2 meters you are developing their skills and parts kits for HF as well.

Offline Carl

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Re: Random length multiband dipoles
« Reply #1 on: April 30, 2017, 02:58:52 PM »
Often called a DOUBLET and when 51 feet on each side...a G5RV, Good antenna.

Offline Carl

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Re: Random length multiband dipoles
« Reply #2 on: April 30, 2017, 06:06:15 PM »
The DOUBLET or G5RV ,if a certain length, is a GREAT multi-band antenna though don't let the term RANDOM LENGTH fool you as it refers not to just any length ,but one that is not some multiple part of a wavelength on any of the Ham,or other bands.The best lengths I have used for 'random' are 17,25,34,51 and 84...pretty much multiples of 17 will be safe length as long as you choose a length over 1/4 wavelength of the lowest frequency that you expect to use.

  It also pays to choose your length of ladder line in the same manner and have a good tuner and 4 to 1 or higher ratio balun. Internal antenna tuners are not capable of tuning a random length antenna to ALL bands as they often only tune a 3 to 1 ratio and you need a 10 to 1 tuning ratio or better usually found in manual and some automatic antenna tuners like MFJ and better LDG tuners.

  Doublet antennas are great as long as two supports are available and you have time. The W3EDP or ZIP-ZEP single wire antenna is better suited for rapid,easy, deployment but the doublet or random length dipole is a better choice for many as it has the edge on performance.