1 wire dual polarized quad

[HomerBB]

The 75 Ohm transformer section made of coax with .66 VF I use is 6' long for channel 38.
The air choke should be between the 75 Ohm transformer and the element wire - "at the feedpoint".
I usually just buy a 6' long A/V coax already made up and use two type F to PL-259 adapters (available at Radio Shack) to put it in line .

 

[johnny9]

Fit chokes as close as you can to the feed point.Without it your whole unused coax becomes part of the radiator detuning your antenna.Sorry about the swrs thing no offence meant .

none takin even if i make the choke like in the high gain antenna it also has a beta match..i could make a good one but have no way of getting the measurments of the wire used..
BTW thanks for that link..thats some good info there.. i will print it out ,since quads will always be part of me

 

[johnny9]

The 75 Ohm transformer section made of coax with .66 VF I use is 6' long for channel 38.
The air choke should be between the 75 Ohm transformer and the element wire - "at the feedpoint".
I usually just buy a 6' long A/V coax already made up and use two type F to UHF adapters (available at Radio Shack) to put it in line .

View attachment 15086

thanks for this valuable info! this is looking like a few extra lbs lol

 

[vkrules]

6 turns on 90mm pvc pipe will do it.

 

[johnny9]

im starting to re think this maybe..i do have plenty of the dx engineering 75 ohm coax..but i dont have enouhg "hands on " to understand it all perfectly enough just yet.seems like a few lbs weight added to the fiberglass spreaders too.
i already have another wire cut exactly for ch 40 and could re string it and just build another quad for vertical and put it on top of the horz one..and have a low swr on both like before..hmmmmmm.
im sure some of you guys "hams"use antenna tuners...is it not worth using one to fix the 2.5 or so swr? or better to get best swr w/out a tuner,like i can on 2 seperate quads thats extremly light weight,adjustable in every way,and will take what fla can give when it comes to ice storms
reason of my adventure is to have a true vert beam as good as my flat side beam is..my 42 yr ole astroplane is great,,but if a vertical quad is as good as my horz quad like i think it will be then i just have one to see for myself..and to play with like a new toy ..then the astro plane will get its own tilt over pole i just built from a 6 inch 12 ft post..maybe if i would have just built another it would have been done tomorrow..

 

[HomerBB]

Naturally, you can approach this any way you want, but you are nearly done now. The only changes required is shorten your 75 ohm transformers to 72''.
Your SWR readings indicate the possibility that you are getting no impedance transformation at all from the current length.
The coax choke has been suggested to add pattern improvement for your antenna' but is optional. If it is confusing you just leave it/them off and move on. You can study on it more and circle back around to it later.

 

[johnny9]

Naturally, you can approach this any way you want, but you are nearly done now. The only changes required is shorten your 75 ohm transformers to 72''.
Your SWR readings indicate the possibility that you are getting no impedance transformation at all from the current length.
The coax choke has been suggested to add pattern improvement for your antenna' but is optional. If it is confusing you just leave it/them off and move on. You can study on it more and circle back around to it later.[/QUOTE
my 75 ohm line isnt .66 vf tho its way higher iirc.
just looked,what i have is from dx engineering and says " dxe rg-11/u 14 aug pe "

 

[vkrules]

I agree with homer I think your 75 ohm transformers should be shortened . Can you tell us the cable type printed on the jacket of the cable to confirm.Your almost there don't give up. But I think the chokes are not optional in this design, without them the radiator is a random length long wire .(Have another look at the diagram) The chokes can be made by making 6 turns in the coax on a 4 inch non metallic former close as you can to the feedpoint ( in other words your coiling up the coax)Overall this is not adding weight but it is moving the weight out on the spreaders a bit.All very simple changes.

 

[wavrider]

http://vk5ajl.com/projects/baluns.php

good reading for understanding baluns
you are well on your way to understanding how antennas work, Best part of the hobby to me is antennas

http://www.g0ksc.co.uk/creatingabalun.html

look at the pawsey stub section, this should work great for your antenna

http://www.aeroelectric.com/articles/BALUN/Huggins on Coax Velocity Factor in Baluns.pdf

little bit techy but worth reading

good luck on the dual polarity quad

 

[johnny9]

http://vk5ajl.com/projects/baluns.php

good reading for understanding baluns
you are well on your way to understanding how antennas work, Best part of the hobby to me is antennas

http://www.g0ksc.co.uk/creatingabalun.html

look at the pawsey stub section, this should work great for your antenna

http://www.aeroelectric.com/articles/BALUN/Huggins on Coax Velocity Factor in Baluns.pdf

little bit techy but worth reading

good luck on the dual polarity quad

homer,will my 75 ohm work since it is not the .66 vf you mentioned? mine is .84 vf iirc on the web site..
if you think i can shorten the new .84vf to 72 inches and be better then now im willing to try it..

on a side note ive talked on vert and horz tonight on the beam and people say im booming in,and cant hear them on the astroplane at all lol..and while doing this my diawa cn 801 meter has never went over 1.7 swr on the flat side on ch 46lsb,and radio isnt hot..but i do have dual fans and fan in the power supply..

maybe this shorter length is just my ticket since you guys are a big help im willing to learn for sure.. johnny9

 

[johnny9]

http://vk5ajl.com/projects/baluns.php

good reading for understanding baluns
you are well on your way to understanding how antennas work, Best part of the hobby to me is antennas

http://www.g0ksc.co.uk/creatingabalun.html

look at the pawsey stub section, this should work great for your antenna

http://www.aeroelectric.com/articles/BALUN/Huggins on Coax Velocity Factor in Baluns.pdf

little bit techy but worth reading

good luck on the dual polarity quad

thank you! i will be checking this out next couple days when time allows..

 

[johnny9]

this is what i have .84 vf http://www.dxengineering.com/parts/dxe-11u

 

[HomerBB]

If you are using .84 VF 75 ohm coax then the transformer should be 90.5" for 27.400 MHz, however, every other source for the vf of RG-11 states it to be .66. I am more inclined to believe it is not .84 as the DX Engineering site says, and that it is actually .66. If all else is right with your antenna build the SWR you have seems to indicate you have an ineffective transformer. A quad loop will be somewhere around 100 - 130 ohms impedance if my memory serves me well (someone can correct me), and if so, that is nearly two (2) to three (3) times the impedance you need to have. If so, then you can expect SWR readings of ≃ 2.0:1 or higher.

 

[johnny9]

i can only go by what the site says,but it very well could be .66 vf dont say on the cable i looked again...and my length is 7ft 6 inches in the 75 ohm line so thats exactly what you mentioned if i added correct,minus half a inch..thankfully that works perfect for the quad when i had just horizontal past 6months or so...
just re checked swr and 1.9 flat side ch 40, 2.5 ch 1---this 75 ohm stub is aprox 2 inches shorter due to repair in the stub..and swr is lower here maybe because getting closer to the shorter length???
3.0 vert ch 40,but better on ch1,,that seems opposite.. this 75 ohm stub is exactly 7ft 6 inch and would be perfect in length if this were only a vert quad.

i will gladly lower the tower monday to try and get this corrected how ever long it takes,just let me no what ya think the next move would be .and thanks for all the replys and help on my learning curve

 

[wavrider]

RF choke,, either ugly balun type or ferrite beads, or pawsey match would be needed so the coax doe snot become part of the antenna.

Then start working on the 75 ohm impedance matching run of 75 ohm coax.


With the CMC on the coax it will definitely have you pulling your hair out trying to adjust the impedance of your antenna.

Once you get that dual polarity quad going point it up North and lets see if we can make a contact.