DUAL BEAM PRO antenna

[VK4WDM]

Anyone using one of these?  http://www.proantennas.co.uk/dualbeampro.htm

Would be any easy build. Am I right in saying that the end elements are capacity hats? Are they bonded to, or insulated from, the dipole elements?  What type of balun?

73

Wayne VK4WDM

[VK6TU]

Anyone using one of these?  http://www.proantennas.co.uk/dualbeampro.htm

Would be any easy build. Am I right in saying that the end elements are capacity hats? Are they bonded to, or insulated from, the dipole elements?  What type of balun?

73

Wayne VK4WDM

Wayne,
Do not know much about the antenna but a quick search found this site http://www.qsl.net/ei7ba/low_band_antennae.htm

Interesting reading, looks like they need ATU to work.

73 from Michael
VK6TU

[VK4ADC]

Wayne

A couple of paragraphs need close attention:

The Dual Beam Pro is a non-resonant design requiring an internal/external ATU for 20m to 10m operation. The efficiency/performance is down on 40m when compared to the higher bands and an external ATU may be required.

Coax feeder length is not critical but a recommended length is 25m, check the website for the specification of mini RG8. It is an ideal cable for use with the Dual Beam Pro. The cable will need terminating with a PL259 plugs and this service is offered on the Pro Antennas website.


The above two paras tell most of the story:
non-resonant dipole = high SWR except when approaching dimensions at half wave dipole resonance.
recommended feeder 25 metres = RG58 = lots of distributed loss to reduce effective SWR at the transmitter.

The dimensions... 
boom = 5 metres overall = 2.5 metres each side
end elements = 2.5 metres overall = 1.25 m each side of boom

effective half wave dipole dimensions = 2 x 3.75 metres = 7.5 metres
therefore resonant somewhere around 20MHz, lowered a bit due end capacity hat effect.

It should state requiring an internal/external ATU ... for all bands...


The balun ratio is probably somewhere between 4:1 and 16:1 as a best guess.

Hey, it is rotatable but would be relatively inefficient and you could probably do better with something else.

My 2c..

Doug VK4ADC

PS loss on Tx = loss on Rx

[VK4WDM]

Hi Doug

This antenna would fit nicely below my 6m-23cm LPY yagi (also a serious compromise) and still allow my aging self to raise and lower the 8m mast which I do when we are away traveling or when strong winds threaten.

I have all the bits to build the thing so I will give it a go. I will put a decent RF choke in the line though.

One of my major problems, if it is a problem (my XYL thinks it is), is that I can't stop building antennas. When I get to the nursing home all they will need to do to keep me is to give me a small piece of wire and I will sit there twiddling away until I finally blow my finals. Unfortunately small, light weight, multi-band, atu-needing antennas like this one are the norm for me nowdays  



Hi Michael

Interesting reading indeed. Thank you.

73

Wayne VK4WDM

[VK4ADC]

Wayne

That Dual Beam Pro antenna's operation is similar in concept to this V-dipole (ie multiband with varying natural SWR), just this one doesn't have the right angle end pieces. It has the option of actually tuning it to resonance on one (of some) band thus improving efficiency on that one.

JQ2UOZ liked it ... here

Have a read of some of the descriptions about dipole idea variations at KK4OBI's web site

And don't forget X-beams.

Doug