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44 foot Doublet


#1

Hello wonder if anyone has used a 44 foot doublet on an activation and how good or bad did it perform .
Was it as good as a link dipole or end fed wire. Got some spare wire and 300 ohm ribbon was wondering if I would be wasting my energy making it up.
Any thoughts would be good cheers de Ian vk5cz …


#2

I’ve used one (well, one made from flat ‘computer cable’ aka norcal doublet) and found it quite useful.
Highlights would be my first transatlantic QSO with 5w from a G/WB summit, another transatlantic QSO from a nearby hill with 2.5w (After I’d left the slab-rig cable at home :frowning: ) And first ever QSO to VK, but that was using around 80w from another local G/WB hill.
Lowlight would be… I think it was steam coming from the portable ATU, trying to match it to 40M (It was rather damp at the time!) I have used the ATU since then, so I don’t think it was smoke :wink:
I do prefer the link dipole though.

Don
M0HCU


#3

Hello Ian,
I have had good results with home made norcal doublet antenna, worked several NA chasers with QRP 5W. Easy tune on all bands from 40 to 6 m with intrnal KX3 ATU. I also have a 44’ doublet with 300 ohm twin lead and larger dia wire.Also very good results on many activations. It is worth trying, Ian.

73, Mirko


#4

This antenna sounds interesting. What is the cable type what you have used for doublet?

73, Saku


#5

I’ve used the NorCal Doublet (computer ribbon cable). It works very well and can bundle up to fit in your pocket. I use it with a 4:1 balun. Tunes up nicely on 6-40m with the KX3. Have worked all over Europe/Russia with it while portable from the northeastern US. Only reason I don’t always opt for it is the need for 3 support points. Takes a little more time to deploy versus an endfed or delta loop (also 3 support points but bottom two are typically head-high when I use that).


#6

#7

I used a 44ft doublet with my KX3 in the 2014 QRPTTF event and took first place. It’s an excellent antenna 40-10M. Feeding with 300-ohm twinlead works fine. I fed mine with twisted pair wire harvested from CAT-5e network cable, which is lightweight and cheap.

73, Barry N1EU


#8

Barry, I cheched CAT5e cable and it seems to consists of twisted pair cables with plastic mantle. If and yes the antenna works well with that cable type, it is not necessary that the cables of the landing part of antenna have not constant difference like in web page picture http://www.norcalqrp.org/norcaldoublet.htm. Have I understood it correct manner?

73, Saku


#9

The antenna is simply a 44ft doublet fed by balanced line. The configuration of the balanced line feeder is not important as long as it’s reasonably low-loss.

The use of 4-conductor ribbon cable in the original was just a cute gimmick to make a very inexpensive, lightweight antenna. I suspect twinlead or CAT5e twisted pair will perform much better (lower loss) than the original.

73, Barry


#10

Thank’s Barry, now I know what is my next project! ;-D


#11

The significance of the 44ft length is that it is the longest length that will maintain two-lobe broadside radiation pattern through 10M. The lobes get progressively narrower (higher gain) as you go up in frequency from 7MHz to 28MHz. 88-ft doublet works in a similar manner for 3.5MHz to 14MHz (but loses the 2-lobe broadside radiation pattern above 14MHz)


#12

I use a doublet made entirely out of CAT5e. The hardest part is too remove the outer insulation and the shielding foil. After this you have material for four antennas. Just measure your desired feedline length and untwist the rest. Cheap and lightweight. (Idea found here). With the right technique you do not need any winder to put it on.
I must admit I don’t care about the exact length. The ATU of the KX3 does not seem to do so either.
Works great for me.

73, Felix


#13

The CAT5e cable installed in buildings has solid conductors, which aren’t ideal for portable antennas, as they tend to fracture eventually. If you can get hold of the type of CAT5e used for patch leads, that has stranded conductors, which are much more flexible.
(Both types also come in shielded and unshielded versions)

Adrian
G4AZS


#14

I have one, they work very well in my experience - an effective multiband solution.
I use it with a 10m pole…
73 Angel


#15

I generally use a 88 ft doublet on my activations. I have found it performs very well, and is extremely packable. I don’t have a 44ft setup but I bet it would perform very well.

Here is a setup vid of my antenna (Not The Greatest!)

And a few pics of the setup


#16

thanks everyone for the great replies to my question. I posted quite late last night and I just got home from work to find all the answers to my question. So thanks again I will check out all the links as well over coffee.
I have MFJ 300 ohm twin lead like the SOTA Rangers set up and I would need to do a quick tune up test with my kx 3 as the first job. The slotted 300 ohm ribbon like Steve used with his guitar pick centre insulator is quite hard to find around here and I have some tangled old tv type 300 ohm feeder we used for tv before coax was used on tv antennas. I like the MFJ feeder because it rolls up in a respectable manner and is very light weight… Something to work on, mni tnx agn
73 de Ian vk5cz …


#17

If you’re rig/tuner can’t find a match on all bands, you might try a 4:1 balun between feedline and rig/tuner as KQ2RP mentioned.

Barry N1EU


#18

Thanks
Barry I made up the antenna last night and will test it after work Thursday and my friend and I will do a 4 summit weekend on Saturday/Sunday and give it a try. I have a couple baluns by ldg a 1t1 and a 2t1 I made. Will see what the kx3 can handle later today. checked out the links on everyone’s comments all good.
73 de Ian vk5cz …


#19

I made one my self after using VK6MB’s to activate VK6/SW-061, 7 qso’s in under half an hour with 3 VK3 and 1 VK5. Mostly on 40M. No problem tuning with the KX3.


#20

Thanks Michael for your report and success with the antenna.
I did not take the 44 footer this time out activating but will on my next one, possibly Saturday depends if the cold wx sticks around. I still have not had a chance to test it properly apart from tuning it in the passage of the house because its been raining here a lot. Yes the passage in my house is 16 m long 3 floor tiles per metre ideal for measuring out antennas in out of the elements. cheers de Ian vk5cz …