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Author Topic: Linked Dipole  (Read 858 times)

CPR

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Linked Dipole
« on: June 20, 2018, 08:29:30 AM »
For quite a time I was interested in building a resonant multiband dipole or linked dipole.
I see a lot of benefits in it, especially no tuner is needed therefore no loss for qrp. Although you have to carry a bit more of equipment, the linked dipole should perform the best regarding noise and stuff - so they say.

Anyway, I got myself the dipole center with a 1:1 balun kit from sota beams.
I found a great tutorial on how to trim the wire :

http://amateurham.co/4-band-linked-dipole-how-to/

So in the following days I intend to build the linked dipole and will keep you updated.
I'm quite curious about the performance compared to the random wire end fed antenna. I intend to use this linked dipole with my 6 meter telescope pole.



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« Last Edit: June 20, 2018, 11:13:36 AM by CPR »

vwflyer

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Re: Linked Dipole
« Reply #1 on: June 20, 2018, 01:04:10 PM »
Sotabeams makes some good stuff. That looks like a nice balun. If you can set up a wispr beacon it might be a good way of doing direct comparisons of the antennas.

CPR

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Re: Linked Dipole
« Reply #2 on: June 20, 2018, 02:33:54 PM »
I still need a wolphilink for my 817, but yes, thats a good idea for a comparison!

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CPR

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Re: Linked Dipole
« Reply #3 on: June 25, 2018, 08:33:45 AM »
I was out in the field this weekend. Setting up the linked dipole I realized it picks up much more noise than my endfed random wire. The wire is at S1 max, the dipole at S4 sometimes 5. A lot of QRM. I tried to make a contact but there was this damn contest on all bands, no one responded as everyone were cq contest. Very disappointing.
Although I somehow prefer the linked dipole because its resonant without a tuner, I am quite sad because of the QRM.


vwflyer

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Re: Linked Dipole
« Reply #4 on: June 25, 2018, 05:17:03 PM »
More noise often times simply means youíre antenna is more effective.

CPR

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Re: Linked Dipole
« Reply #5 on: June 27, 2018, 03:17:21 AM »
Never thought of that haha. The noise is really irritating. But it could be it was so noisy because of the global contest ongoing? (king of spain contest)

Jon_Garfio

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Re: Linked Dipole
« Reply #6 on: June 27, 2018, 08:36:12 AM »
Low noise in Rx maybe indicatethe antenna doesn't work properly, loops antennas is another concept, but dipoles and verticals yes, loud noise (S3-S4) could be fine.

Congrats for balun and linked dipole, It is a Big deal in the mountain.

I have one for 40/20m and works really well without swr

Never thought of that haha. The noise is really irritating. But it could be it was so noisy because of the global contest ongoing? (king of spain contest)

Enviado desde mi Redmi Note 4 mediante Tapatalk
« Last Edit: June 27, 2018, 08:38:31 AM by Jon_Garfio »
Sapere aude

CPR

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Re: Linked Dipole
« Reply #7 on: June 27, 2018, 09:07:45 AM »
I see most of you use RG174 as a feedline. I am currently using RG58.
But RG58 is pretty heavy when its connected up in the air, resulting to bend my pole. I then checked and found that coax loss calculator:
http://kv5r.com/ham-radio/coax-loss-calculator/

With 10 meters of RG174 on 20m I got a 20% loss. On my 5W rig thats 1.1W.
With 10 meters of RG58 on 20m I got 11% loss. Thats 0.55W

Would you still recommend using RG174 despite such loss?

vwflyer

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Re: Linked Dipole
« Reply #8 on: June 27, 2018, 10:44:27 AM »
Everything is a trade off. If you can handle the size and weight of RG58 you have a bit of an advantage using it over RG174. But itís a personal choice. Many people go to great expense and inconvenience to squeeze every last dB out of their rig. Others say, ďwith one feedline my radiated power is 4 watts and with the other itís 3.5 watts. If they canít hear me at 3.5, chances are they wonít hear me at 4 eitherĒ.

I will say though, that if youíre going to put up with the size and weight of RG58, you might as well switch to RG8X. Itís basically the same size and weight as RG58 but with markedly less loss.

You might consider a compromise. Use a length of 58 and a length of 174. Connectors add very little loss if theyíre clean and tight. You might also want to use zip ties or Velcro ties or tape or something to attach your coax to your mast below the feed point to act as a strain relief to the higher part of the mast where itís too thin to support the weight of all the coax.

CPR

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Re: Linked Dipole
« Reply #9 on: June 27, 2018, 10:55:44 AM »
Everything is a trade off. If you can handle the size and weight of RG58 you have a bit of an advantage using it over RG174. But itís a personal choice. Many people go to great expense and inconvenience to squeeze every last dB out of their rig. Others say, ďwith one feedline my radiated power is 4 watts and with the other itís 3.5 watts. If they canít hear me at 3.5, chances are they wonít hear me at 4 eitherĒ.

I will say though, that if youíre going to put up with the size and weight of RG58, you might as well switch to RG8X. Itís basically the same size and weight as RG58 but with markedly less loss.

You might consider a compromise. Use a length of 58 and a length of 174. Connectors add very little loss if theyíre clean and tight. You might also want to use zip ties or Velcro ties or tape or something to attach your coax to your mast below the feed point to act as a strain relief to the higher part of the mast where itís too thin to support the weight of all the coax.

Looking at the calculator (results are questionable anyway), RG8X has 0.1W less loss on my configuration than RG58. I thought about zipties, but they are hard to untie. Maybe I should get some reusable ones. I could, like you suggested, use RG174 for the pole only with a female connector and then add the RG58 to the station. I think that's a good idea.
I already ordered some RG174 via Ebay recently, I may do that indeed.

gil

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Re: Linked Dipole
« Reply #10 on: June 27, 2018, 08:28:19 PM »
Now I use RG-316. It is stronger than RG-174 but not as flexible. I have no idea about the losses. With RG-174 and RG-316 I avoid lengths over 10m, and try to stay on the lower bands. For the antenna on my roof (80010P), I use 10m of RG-58 plus 10m of RG-316, LOL. Even with only 3-4W on 80m I have no problem making tons of contacts. If you really want extra-low losses, try LMR-240UF. I personally don't care much, just try to keep it short and prefer 10mHz and below... RG-174 after a while will break...

Gil.

Andywragg

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Re: Linked Dipole
« Reply #11 on: June 28, 2018, 02:56:12 AM »
It's a small world. That linked dipole article was written by one of my club mates.
Once a 'STAB in the Dark'
M6UAW

CPR

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Re: Linked Dipole
« Reply #12 on: June 28, 2018, 04:08:52 PM »
I was out today on my closest registered SOTA peak. I've done 3 qso with Spain on 15m, with Russia (kaliningrad fifa event station not Sota) on 20m and one with England 15m (was very hard to copy but confirmed). And chased one French guy while he was doing SOTA too. I am quite satisfied with that dipole. And actually 5W isn't that low.

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gil

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Re: Linked Dipole
« Reply #13 on: June 29, 2018, 07:17:14 AM »
Quote
And actually 5W isn't that low.

You are absolutely right! You wouldn't believe how hard it is for a lot of people to accept that idea...

Gil.

CPR

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Re: Linked Dipole
« Reply #14 on: June 29, 2018, 07:43:45 AM »
I ordered a wolphilink today. I will compare the antenna to others. And I want to compare if using rg174 vs rg58 makes any difference on wspr.

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