Dipole question.

[BammBamm]

Other than tuning what if any difference would there be between using a sirio d-27 dipole or making a dipole yourself? I am thinking about the D-27 for my cottage due to it's size but I can make a dipole out of aluminum tubing myself and trim to tune.

 

[binrat]

Other than tuning what if any difference would there be between using a sirio d-27 dipole or making a dipole yourself? I am thinking about the D-27 for my cottage due to it's size but I can make a dipole out of aluminum tubing myself and trim to tune.

Difference?? Saving, fun of making your own thats the 2 things that come to mind. You can make it out of 2 mobile antennas as well.

 

[wavrider]

Two pieces of 1/2" EMT conduit, around $6 at the home supply stores.

Piece of wood to attach the elements to and some U clamps to hold the elements on.

Wrap an RF choke at the feed point, split the coax and connect it to the elements.

Start trimming the elements to resonance, can not beat it for the price.

 

[BammBamm]

O.K. I see. I should have asked is the gamma match on the D-27 anything that will help performance or is it just a fancy dipole that's overpriced.

 

[binrat]

O.K. I see. I should have asked is the gamma match on the D-27 anything that will help performance or is it just a fancy dipole that's overpriced.

Fancy dipole, the gamma is used to bring it to 50 ohms. A quick way to get around it is to rig it in an invert V to obtain the impedance. It you have the inverted vee horizontal you may find you'll have a slight gain in it.

 

[HomerBB]

pieces of 1/2" EMT conduit, around $6 at the home supply stores.

Piece of wood to attach the elements to and some U clamps to hold the elements on.

Wrap an RF choke at the feed point, split the coax and connect it to the elements.

Start trimming the elements to resonance, can not beat it for the price.

That'll do it.

 

[Robb]

Yes, the gamma is means to match the impedance so that it is @ 50 ohm when put either vertical or horizontal. That is what the D27 can do; be either vertical or horizontal.

If you make a home made one out of two pieces of 10ft emt tubing, making it do horizontal polarization alone with a 50 ohm impedance can be done by setting both of the elements at a 45 degree angle. However, unless you make a gamma match for it, you can only use it horizontal.

If you want to run both vertical and horizontal; then buy the D27.
It's not that expensive . . .

 

[Captain Kilowatt]

Yes, the gamma is means to match the impedance so that it is @ 50 ohm when put either vertical or horizontal. That is what the D27 can do; be either vertical or horizontal.

If you make a home made one out of two pieces of 10ft emt tubing, making it do horizontal polarization alone with a 50 ohm impedance can be done by setting both of the elements at a 45 degree angle. However, unless you make a gamma match for it, you can only use it horizontal.

If you want to run both vertical and horizontal; then buy the D27.
It's not that expensive . . .

Why is that? The antenna does not know what polarity it is configured for. A dipole can be made to function in the vertical plane without a gamma match just as easily as horizontal. The gamma match simply provides an easy means of field tuning. When making a home made dipole you cut each side to approx. the right length and then trim a little off each end until the SWR is at it's lowest. I have seen literally dozens of vertical dipoles made from 1/2 inch copper pipe fed directly with coax cable and the only method of matching was trimming the overall length.Almost all the fishermen along the coast use one as a base antenna. SWR is perfect at band center. The thing is that with a gamma match the dipole can be retuned when mounted in a different location whereas a trimmed antenna is tuned for a specific location and may not present a good SWR if mounted elsewhere.

 

[Robb]

Perhaps I should have worded it better.
Getting a D27 - which comes with the hardware to make it rotatable AND has a gamma match - makes it easier to do both.
>yawn<

 

[unit_399]

Perhaps I should have worded it better.
Getting a D27 - which comes with the hardware to make it rotatable AND has a gamma match - makes it easier to do both.
>yawn<

Robb-

So... you're saying that taking the EASY way out is the best? What do you learn from that ??. Binrat is right; designing and building a piece of equipment and getting it to work properly gives a sense of satisfaction that a person who buys everything for his station can NEVER understand. Maybe you should try it sometime.

- 399

 

[Robb]

http://www.cbradiomagazine.com/Ante...7 Dipole/Sirio D-27 Dipole Antenna Review.htm

I think that BamBam already ran their first..

Already built a dipole and a 1/4 wave ground plane many years ago. They worked fine enough. But a D27 rotatable dipole is kinda cool too!

 

[HomerBB]

I like to build my antennas.
On the other hand, as the question was asked, it was answered.
And there is nothing wrong with offering perspectives on the choices asked about - build or buy.

Dipoles are basic, and simple, and fun to make. They can be mounted vertical on a boom away from the mast by necessity, or horizontally snuggled right up to the mast which is easier.

The 27 offers several advantages over an EMT dipole.

1. Lighter being aluminum.
2. Well crafted, a challenge to novice homebrewers sometimes
3. Highly portable with the option to retune at will for different locations
4. and comes with a sturdy rotatable boom offering near instant polarity changes when chasing skip/local conditions

What does homebrew offer.

1. Same performance when the mechanical challenges are overcome
2. Satisfaction and experience with homebrew.
3. Sometimes savings over a mass produced model, but often not.

I homebrew, but maybe BammBamm wants to look at the options and choose between them.

 

[BammBamm]

I was not trying to start a argument here just considered thye D-27 and thought I could build one cheaper. I know it's not that expensive but I can build a dipole cheap and here in Chicago gas is $4.49 a gallon so every penny counts right now.

 

[HomerBB]

I wasn't trying to either argue, nor start one either. I was only trying to bring the different perspectives together in a single post.

I have homebrewed dipoles with and without the gamma match. Both worked well, but for my money doing without the gamma was quicker and easier, however my installs were mostly for a single location.
When I needed a portable I just used wire which could be folded, or made the dipole with multiple tubes so that the ends were adjustable in the same way the length of a Yagi element is. Hopefully one of the options are what you are looking for.

 

[BammBamm]

Homer I wasn't singling you out, just it seems like most posts become arguments. I was just wondering if I had missed something on the D-27 and Robb although you say it isn't expensive I feel I can make a dipole for $20 or less and the D-27 is $80 + shipping. I'm seeing this as $60 saved. Maybe I'm cheap but it's bike season here and $60 is a few tanks of gas in my R1. Besides building it myself gives me something to do and gets my wife off my back for a while. I'm not here to argue just to add my wisdom or experiences and ask for advice from others or their experiences. Besides I have a wife to argue with.