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Booty,
Great link thanks for the reading.
I do know from experience building forced current arrays, that a choke, ugly balun or whatever is not used it can be a heck of a headache to tune.
I do not see where an ugly balun can force equal amounts of current in a balanced antenna, IE dipole or yagi, true yagi not one used with a beta,hairpin,or gamma match, where as a 1:1 current balun will force equals amounts of current.
On everyone of the omni's I experiment with or repair, rebuild I put an ugly choke at the feedpoint, so far no TVI, RFI, problems and some run as much as legal limit in the middle of the suburbs with no complaints.
The ugly balun does work for "choking" the Rf off the feedline, coax, it has a use in omni type applications, as far as multi band, I have used one for an 160 meter dipole, over 20 wraps of coax, worked well and was able to tune other bands with good RS reports both local, within the continent and also DX.
I took that down and used 450 ohm ladderline to feed the 160 meter dipole and made it an all band doublet, better results but more noise on recieve as the ladderline now became part of the antenna so I got the vertical side of the antenna also, performed better on DX with the lower angle of radiation from the vert part of the ladderline.
Great thread guys, good info thanks for all the replies and different view points.
Great link thanks for the reading.
I do know from experience building forced current arrays, that a choke, ugly balun or whatever is not used it can be a heck of a headache to tune.
I do not see where an ugly balun can force equal amounts of current in a balanced antenna, IE dipole or yagi, true yagi not one used with a beta,hairpin,or gamma match, where as a 1:1 current balun will force equals amounts of current.
On everyone of the omni's I experiment with or repair, rebuild I put an ugly choke at the feedpoint, so far no TVI, RFI, problems and some run as much as legal limit in the middle of the suburbs with no complaints.
The ugly balun does work for "choking" the Rf off the feedline, coax, it has a use in omni type applications, as far as multi band, I have used one for an 160 meter dipole, over 20 wraps of coax, worked well and was able to tune other bands with good RS reports both local, within the continent and also DX.
I took that down and used 450 ohm ladderline to feed the 160 meter dipole and made it an all band doublet, better results but more noise on recieve as the ladderline now became part of the antenna so I got the vertical side of the antenna also, performed better on DX with the lower angle of radiation from the vert part of the ladderline.
Great thread guys, good info thanks for all the replies and different view points.
Picture the ugly balun as an unknown black box with two input terminals and two output terminals.
Now compare the magnitude and phase of all four terminals with unbalanced R.F. applied to the input TO THAT OF a so-called 1:1 current balun.
Result will be exactly the same at frequencies where the ugly balun has adequate choking reactance.
Now compare the magnitude and phase of all four terminals with unbalanced R.F. applied to the input TO THAT OF a so-called 1:1 current balun.
Result will be exactly the same at frequencies where the ugly balun has adequate choking reactance.
Wavrider,
remember that even though you choke off those CMC's from the coax by using a coax choke; they will still radiate down your metal mast if you dont isolate your antenna from it.
not saying you dont already know this, just that many people dont consider it.
think about it; why wouldnt they flow right down that metal mast?
LC
remember that even though you choke off those CMC's from the coax by using a coax choke; they will still radiate down your metal mast if you dont isolate your antenna from it.
not saying you dont already know this, just that many people dont consider it.
think about it; why wouldnt they flow right down that metal mast?
LC
LC, check this Website out. AA5TB - The End Fed Half Wave Antenna
AA5tb did some work on a related issue regarding how an end fed 1/2 wave with a 1/4 wave matcher really works. I think it is similar to the A99. He tested and evaluated what is necessary to provide a return path, the actual Ground Plane needed for such an antenna to work. Something to consider at least.
Actually I think he claims the end fed 1/2 wave radiator needs only a very small length counterpoise, in the area of .05 wavelength wire connected to the ground side of the matcher to make the opposite pole. He notes that this will allow for a full functioning CMC return path to make the EFHW work. For years we have heard stories about how the A99 uses the feed line as a counterpoise or GP and in part that is true---and it may be a lot shorter that we think if AA5tb is right. The question then is---what part of the feed line?
I was curious and thought after reading his articles on EFHW's, what could I do that might support his idea. He had done a lot of work and he shows how in detail right there in the article. He may even have a video on this work. Anybody with better skills than me might be able to check him out, so I thought---maybe he's on to something.
I asked myself, what if I remove the feed line and tested the antenna's feed point, and what if AA5tb was not right and the A99 in fact needed the feed line as a ground plane, would I see some issues with the match. Well, I hooked my Autek VA1 directly to the feed point and instead of a bad tune, I saw virtually the same numbers compared to using a 14'5" foot length of RG8x, a tuned jumper cut to 27.205.
How does this relate to our issues with CMC's and the need for a balun. What we hope happens with a choke is to create high impedance point at the feed point in order to help stop CMC from flowing down the feed line and the mast. In order for this to be effective, we also need a conductor (a ground plane) to redirect these currents back into the feed point and keep all the RF flowing in the antenna and not on the feed line or mast. If we don't, I understand that CMC's will just flow right on past the choke whether the mast is insulated or not.
I did some work with my A99 this past summer. I insulated it from the mast by placing some PVC in the mounting hardware.
I got some mixed results, but my strongest Signal Reports were with the A99 insulated without a GPK. I did not raise the antenna above the mast with the insulator and that may account for a difference. Reports from Bob85 and Multimode200 note nice increases in signals when insulated with a ground plane kit. I don't think either one used a choke however.
I forget who started this thread. I hope I didn't get off track.
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So, it would be prudent for me to isolate/insulate my !MAX from the mast and run a GPK for maximum gain?
Would I still need a choke on it for best results?
Or -as you have already pointed out - that won't be necessary so long as I isolate it and put the GPK on...
I've got the GPK and haven't put it on yet.
And I've been holding off making a choke too.
What is my next move?
If you don't mind my asking...Thanks...
Would I still need a choke on it for best results?
Or -as you have already pointed out - that won't be necessary so long as I isolate it and put the GPK on...
I've got the GPK and haven't put it on yet.
And I've been holding off making a choke too.
What is my next move?
If you don't mind my asking...Thanks...
B
BOOTY MONSTER
Guest
its an old thread started by me marconi . i have absolutely no problem with a thread going off topic if its sill good information being discussed . 
i actually think that other forums loose a lot of peripheral information by not allowig it .
heres some info on what CMC's/common mode currents are if theres anyone reading this that isnt sure what they are and don't want to ask .
Common Mode Currents
i actually think that other forums loose a lot of peripheral information by not allowig it . heres some info on what CMC's/common mode currents are if theres anyone reading this that isnt sure what they are and don't want to ask .
Common Mode Currents
B
BOOTY MONSTER
Guest
this thread may be helpful to you Robb
http://www.worldwidedx.com/cb-anten...endfed-antennas-their-support-structures.html
the information i am basing my opinion on comes from the US Army technical manual on antennas and feedlines. (1953)
yes, this book is old, but have we really changed what we know about antennas since then?
they explain it much better than i can, so i will bring this book with me tomorrow and quote from it.
i should probably start a new thread to do that, so look for it in this section.
Robb,
end fed vertical antennas need more than 4 radials to properly do their thing, but that is all we get most of the time.
because of not having enough "counterpoise" some of the current that flows to the radials gets reflected back down the shield of the coax as Common Mode Currents.
using a coax choke keeps these currents from flowing down the coax.
they still need to go somewhere though, so they flow right down the metal mast.
so, to me, the best situation is where the antenna has a counterpoise (radials) at the feedpoint, is isolated from the metal support structure, and uses a coax choke at the feedpoint.
this does force you to ground things in a certain way to maintain lightning protection.
the coax must be grounded at the station end before it enters the shack.
best to use a quality lightning arrestor such as a polyphaser and more than one ground rod.
yes, a lightning strike will take out your antenna and fry your coax, but at least you wont have a fire inside your house from it.
this is how i see things and others may disagree.
Marconi,
thanks for the info on the A99. interesting test results for sure with the analyzer connected to the feedpoint. i would have bet that the SWR would have been higher somewhat.
well, at least we are always learning!
dont forget to look for the new thread about the army tech manual.
LC
yes, this book is old, but have we really changed what we know about antennas since then?
they explain it much better than i can, so i will bring this book with me tomorrow and quote from it.
i should probably start a new thread to do that, so look for it in this section.
Robb,
end fed vertical antennas need more than 4 radials to properly do their thing, but that is all we get most of the time.
because of not having enough "counterpoise" some of the current that flows to the radials gets reflected back down the shield of the coax as Common Mode Currents.
using a coax choke keeps these currents from flowing down the coax.
they still need to go somewhere though, so they flow right down the metal mast.
so, to me, the best situation is where the antenna has a counterpoise (radials) at the feedpoint, is isolated from the metal support structure, and uses a coax choke at the feedpoint.
this does force you to ground things in a certain way to maintain lightning protection.
the coax must be grounded at the station end before it enters the shack.
best to use a quality lightning arrestor such as a polyphaser and more than one ground rod.
yes, a lightning strike will take out your antenna and fry your coax, but at least you wont have a fire inside your house from it.
this is how i see things and others may disagree.
Marconi,
thanks for the info on the A99. interesting test results for sure with the analyzer connected to the feedpoint. i would have bet that the SWR would have been higher somewhat.
well, at least we are always learning!
dont forget to look for the new thread about the army tech manual.
LC