1 wire dual polarized quad

[johnny9]

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.

the dual polarity is running and working great to be honest listening to locals 50-400 miles away this am and talkied to england/uk and everyone booming in right now..talked on flat side half hr last night and while talkin on "46lsb where i hang out with bluesky members" the swr while talking never got over 1.7 or so on flat side..

well,im on the radio noiw,,blue sky 106 south of ocala fl 34432 zip..im aimed 30 degrees nort east right now and switching back and forth on the astroplane..i can hear the world as usuall lol..

ok so get me going on this choke thing? i have bunch of tv cable also im lost other than that but do understand the 6 turns on a 3-4 inch pipe also,do i need to check the ohms on the line? i have a small multi meter but not good at using it,,

 

[johnny9]

when i look up this "a/v" cable it is just a regular audio video cable it seems,,,with rca plug ends..is this correct? i think its all rg59 with red blueyellow red ends..i have a bunch of this,prob even the right length...i have to check.
is this sounding right? and a 6ft piece with 6 wraps around 4 inch pvc,tape to pvc to keep its shape,then put it hooked to the very end of my 75 ohm matching stub and other end to the driven element wire? bs106,john

 

[johnny9]

ok,i found tons of a/v coax .yellow,red,and white colored,,goes from dvd player to tv for example...the yelolow says on it rg59u dish network
the red and white are very small and thin cables..
if this is correct do i need 2 of the yellow rg59u cables,,1 on each transformer,,,or 2 of the smaller ones"red and white"colored ones??there like 1/8 inch thick aprox??

 

[wavrider]

75 ohm cable, any flavor will work, as us cheap hams do we use what we have laying around.

Homer gave you dimensions of what length to cut the 75 ohm coax to make an impedance transformer.

formula is 234/frequency X velocity factor of the 75 ohm coax.

for 27mhz i can not remember off the top of my head but something like 5 1/4 turns on a 4 inch piece of pvc for the rf choke aka ugly balun.

 

[johnny9]

thanks,i just looked it up and realized the rg59u is 75 ohm ,,whoohhoooo.i have enough for spares..thanks to being a hoarder of phone adapters and piles of cords.
i dont understand the fomula,id need a teacher for a hr or so lol..if it had a engine or fired bullets or exploded i would be much more at home
since my heavy duty matching stub" of 75 ohm .84vf is the correct length"i assume this is the "impediance transformer you speak of" ,and hooked to the end of the spreaders with connectors to the wire,cant i just solder and seal the new a/v cable wire/sheild to the other one without the adapters?? of course i use heat shrink and spray electrical tape afterwards i think im gettin it better and better..
i do like this antenna stufff btw!

ok,heres a few pics of the cable and other stuff

 

[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 PL-259 adapters (available at Radio Shack) to put it in line .

View attachment 15086

starting to understand after reading more.. so my dx engineering 75 ohm is 90 inches of line,then the connectors..so this would be correct if it is .84vf..
BUT,if the 75 ohm i have is false advertisment and is the .66vf it would need to be 6ft long from what i understand.
the air choke i will make from rg59u from audio video cable as in the pics"the yellow ended one" dont have a threaded end like the adapter show in your link..and i also have no way to no the vf of the coax..is this cable i want to use diffrent than the tv coax cable you use?
or are all tv a/v cables .66vf ??

 

[johnny9]

ok im still thinking ..i have to assume the rg11 im using is .84vf .so my tranformer sections are correct.
so when i add the 5 and half "iirc" inch wrap of a 3-1/2 inch round coil of the rg59u at each feedpoint is this going to help lower my swr at all??
i will also appreciate help with the math as the rg59u i have thats all copper has a vf of .79 so i assume this will be longer to equal rg59 with .66vf?..or do i have to get rg59 since its .66vf?? and stay with the 6ft measurment..

 

[Captain Kilowatt]

also have no way to no the vf of the coax..

Here's an idea. Look at the type of cable printed on the outer sheath and Google it. That will get you the Vf.

Also WTF is with the A/V cables for this? That yellow cable is a really crappy cheap piece of 75 ohm cable and the red and white cables are simply shielded audio wires and not coaxial cable. Don't use them for anything and get some REAL decent RG-11 or even RG-59 cable or some decent quality RG-6 even. That yellow video cable is RG-6 but of about the lowest quality there is.

 

[camaro1]

agree,, or even some new rg6 coax,, I picked up a 500 foot spool from home depot for around $35

 

[johnny9]

Here's an idea. Look at the type of cable printed on the outer sheath and Google it. That will get you the Vf.

Also WTF is with the A/V cables for this? That yellow cable is a really crappy cheap piece of 75 ohm cable and the red and white cables are simply shielded audio wires and not coaxial cable. Don't use them for anything and get some REAL decent RG-11 or even RG-59 cable or some decent quality RG-6 even. That yellow video cable is RG-6 but of about the lowest quality there is.

from what im learning tonight reading the rg59u foam with the yellow plug is way better than the rg59 mentioned here by others..it has a lower attenuation at 1.5 instead of 2.0 and from what im reading here is why i mention this.
http://www.qsl.net/g3yrc/coax.htm
that yellow cable i thought was crappy also till i cut into it and its real soild copper not coated like tv crap with the threaded end that has the f type connector to my knowledge..it is dish network crap tho..but im just learning this stuff reading..
like i said the rg11u foam i have is heavy 1/2 inch stuff from dx engineering with .065 or so center conductor? wtf? is something wrong with this?
i cant find any better is why i got it ..dxe says it is .84vf but this site says it is .80 http://www.qsl.net/g3yrc/coax.htm
so what i have should be the best you can buy almost id say..
this has been the matching stub for many many quads for others, and mine worked perfect on the flat side till i started playiung with this idea..i just wanna get it right ..hard to do with wrong info and numbers not matching what im told..why waste more days.

SO,if all i need is the 75ohm .84vf quality coax i have thats as big as my finger, i need to no the measurment"length" for this 6 wrap coil choke thingy again as all other measurments are wrong in this thread..

 

[vkrules]

Yes the chokes will change the VSWR
OK lets start again.
The velocity factor of your cable has nothing to due with quality. size loss or impedance .It's about the type of dielectric used .
So polyethylene dielectric is .66 ( if the V/F is .66 72 inch is the correct length) foam dielectric is between .79 and .88 and ptfe is .69. So the .84 of your RG11 U foam would be right. If its polyethylene its .66. Thats why the confusion you have to know the exact type of cable used, ( you didn't tell us it was foam to start with) Quality cable has a full tight woven braid and a copper center conductor The braid on cheap cable looks like a bald man with a comb over.
All types of rg-59 rg-11 are 75 ohm cable. The 75 ohm cable provides the impedance match. Hence the discussion about the length.Get it wrong and the antenna wont match.
Now the choke. You don't need to ad another piece of cable if you have enough length .You are just wrapping your existing cable around a 4.24 inch (90mm) former . 5 turns with the RG-11 should do it. Dont add another length of 75 ohm cable this would change the match.If you have to add cable to reach You must either extend the 75 ohm cable to 3/4 wave length x velocity factor,or add 50 ohm cable between the 75 ohm and the 50 ohm cable . Another alternative is to go buy the ferrite cores as discussed earlier.
Hope this clarifies it for you.

 

[wavrider]

VK good summation,

DO not add any more 75 ohm cable, it will mes up your impedance at the feed point of the antenna.

Just take your coax, wrap it 5 turns in a loop (4") tape it up and then check your vswr.

If the resonant freq changed at your quad then you know you were dealing with CMC.

Short easy way to check if your ugly balun is making a difference on your antenna system.

75 ohm coax is best IE RG11, since I do not have any RG11 laying around I used RG6 Quad shield and the adapters Homer mentioned earlier that he uses on his antenna builds. the adapters/connectors work great.

 

[johnny9]

VK good summation,

DO not add any more 75 ohm cable, it will mes up your impedance at the feed point of the antenna.

Just take your coax, wrap it 5 turns in a loop (4") tape it up and then check your vswr.

If the resonant freq changed at your quad then you know you were dealing with CMC.

Short easy way to check if your ugly balun is making a difference on your antenna system.

75 ohm coax is best IE RG11, since I do not have any RG11 laying around I used RG6 Quad shield and the adapters Homer mentioned earlier that he uses on his antenna builds. the adapters/connectors work great.

 

[johnny9]

thanks for clearing that up fellas..
i have had the correct length 75 ohm from the beginning and from what i understood on page 1 i would add the 6 ft OF 75 ohm choke to the feedpoint end of my existing 7ft 6 inch long 75 OHM matching stub...

so from what im getting now i will just cut off 2 rolls of tape i have on the boom ,LOL,and mast ,and make a coil with my EXISTING 75 ohm matching stub,then slide it down to the feedpoint, re hook the 50 ohm coax and barrel connector to the end and check SWR..
IF THIS IS CORRECT THERE SHOULD HAVE ONLY BEEN A FEW POSTS IN THIS THREAD LOL!

if this isnt correct i need to phone a friend and will be blowing up this computer with tannerite...one shot one kilL

GOING TO TILT THE TOWER OVER NOW,,,WILL CHECK BACK HERE IN COUPLE HRS BEFORE STANDING IT BACK UP....

 

[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 PL-259 adapters (available at Radio Shack) to put it in line .

View attachment 15086

so i ignore this ,that is still on my mind?? and why im cuntfused
this says the 75 ohm air choke goes after my 90 inches of 75 ohm matching transformer??that would make the entire 75 ohm line 13ft 6 inches with the last 6ft a choke?

you guys are saying use my existing 75 ohm matching section and wind a choke with it at the end of the spreader where goes into the feedpoint correct?