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Alpha Delta DXCC multiband dipole modification?

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,194
1,674
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I'm using an Alpha Delta DX-CC multiband dipole, which has worked well for me. It is resonant on 10,20,40,80 meters. Each of the elements (except 80), is just a wire dipole cut for the frequency. I haven't actually measured the elements, but I'm assuming they're close to standard dipole lengths.



I've been using a tuner to get 12,15, 17, and 30 meters, but I'm wondering if anyone has tried making a similar antenna with elements added that are cut for those frequencies? I've been thinking of trying to mod the antenna and adding the elements for the appropriate band. However, some of those frequencies (12,15,17,20) start to get a little close to each other. If I start adding wires, do you think the closer bands' elements will affect each other? I'd kinda like to know if this is worth trying before I go through the trouble of pulling down the antenna.



Moleculo


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Mole',

Is it possible? Sure, but I don't know if ~I~ would tack the additional sections onto the Alpha-Delta. Not that it can't be done! Just, why mess with an antenna that's working for you if you don't have to?

Then there's the 'flip-side' to that, you'd have a 'do everything' antenna instead of multiple antennas, that has it's attraction too. Like listening to the, "You're gonna put MORE crap up there? The place looks like a junk yard now!", sort of stuff.

(Don't you just hate it when someone argues both side of an argument? lol).

- 'Doc



PS - Sounds like you've got the 'tinkering' bug. The only way to 'cure' it is to indulge it for a while. Just remember how things were to start with so you can change it back if you want to...






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I don't suppose theres anything to stop you adding new elements outwith the fact they will all interact with each other and you will have to retune the elements you have now as well as those you add.

you may find it a demon to tune though for all bands,but as your using an atu then i suppose tuning ain't that critical as long as its in the ballpark.if you were trying to do it without an atu then i think you'd be taking on a nightmare of mammoth proportions.
 
What Jazzsinger said. Each element you add will mean starting all over with the tuning on every existing element, and the more you add, the more changes are going to be necessary. I would leave it as is, and build a new fan dipole for the additional bands you want to cover. Much simpler.
 
Can ANYTHING be done to modify this antenna for better 80m bandwidth?
I suppose it is limited by its design...

Limited by physics. There's no such thing as a perfect antenna.

A typical half-wave, center-fed dipole, cut for ONE band, will have a 2:1 SWR bandwidth of maybe 3% of the center frequency. 3% of 4 MHz (75 meters) is 120 KHz. If the dipole is cut for 28 MHz (10 meters), that same 3% comes out to 840 KHz. That's why a dipole seems narrowbanded on 75/80 compared with one cut for 10.
 

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