• You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Sigma 4 / Vector 4000

smalltiredart

Active Member
Apr 26, 2005
190
56
38
Been playing with a Vector 4000.

Built a teflon high powered gamma for it, and direct fed it.

When mounted on the tower performance is great. Was able to dial in resonant on the analyzer, however when I install my 4 element Yagi 12 feet below the Vector, the match and resonance change, which tells me that it is interacting with the Yagi.

The antenna does have a feedline choke, and shows no signs of CMC.

Anyone ever run into this ?

I know there are a few on here who have ton's of experience with this antenna.

Any input appreciated.
 

Attachments

  • gamma 1.jpg
    gamma 1.jpg
    1.5 MB · Views: 24
  • gamma 2.jpg
    gamma 2.jpg
    478 KB · Views: 23
  • Like
Reactions: Redbeard U812

Whenever I have to work around problems like this, I measure the direction and amount the bandwidth is shifted when the second antenna is added. If resonance shifts upwards by 300 Khz. I tune the antenna 300 KHz. lower before the second antenna is added. Then the shift makes the resonance drop right into place where I want it. There will still be some interaction with the antennas but it should not be all that noticeable once they are tuned as suggested.
 
  • Like
Reactions: CB590 and L2
When mounted on the tower performance is great. Was able to dial in resonant on the analyzer, however when I install my 4 element Yagi 12 feet below the Vector, the match and resonance change, which tells me that it is interacting with the Yagi.

STD, I assume the beam is horizontal, right?

What was the match before and after the change?

Did the beam change too?


Below are 2 Eznec models of your idea. One with a two element yagi 12' feet below and the NV4K standing alone. There is a very small difference in the match, and the overlays of these two show the patterns are almost identical.

Before you try and fix the NVK4 match, maybe consider to move the beam around the mast a bit (maybe 1/4 turn,) without moving the Vector, and see if that makes a difference in your match. Might try watching the match on the beam too.
 

Attachments

  • V4K with and without a yagi 12' below.pdf
    1.2 MB · Views: 10
Last edited:
  • Like
Reactions: gamegetter
STD, I assume the beam is horizontal, right?

What was the match before and after the change?

Did the beam change too?


Below are 2 Eznec models of your idea. One with a two element yagi 12' feet below and the NV4K standing alone. There is a very small difference in the match, and the overlays of these two show the patterns are almost identical.

Before you try and fix the NVK4 match, maybe consider to move the beam around the mast a bit (maybe 1/4 turn,) without moving the Vector, and see if that makes a difference in your match. Might try watching the match on the beam too.

Yes sir Marconi the beam is horizontal.

The NVK4 behaves like it is electrically long once the beam is added to the mast pipe.

I'll study the models.

Thanks for doing them.
 
STD, I assume the beam is horizontal, right?

What was the match before and after the change?

Did the beam change too?


Below are 2 Eznec models of your idea. One with a two element yagi 12' feet below and the NV4K standing alone. There is a very small difference in the match, and the overlays of these two show the patterns are almost identical.

Before you try and fix the NVK4 match, maybe consider to move the beam around the mast a bit (maybe 1/4 turn,) without moving the Vector, and see if that makes a difference in your match. Might try watching the match on the beam too.

If this helps the NVK4 is 51 feet at the feedpoint
The 4 element yagi is 39 ft at the feed
 
If this helps the NVK4 is 51 feet at the feedpoint
The 4 element yagi is 39 ft at the feed

Shouldn't make much difference except for the gain and angle possibly due to the increase in height.

How about the 2 questions I asked?
 
Last edited:
STD, try the search feature on this forum...it can be a real timesaver.

Below is an old post I found in a WWDX search that talks about an idea using an Imax over a horizontal beam. I think it also talks a little about some points that Shockwave mentions above.

I think the Imax probably acts better being close to the Yagi, in the link below, than your NV4K will, but you might find something else doing another search...that talks about your idea.

Below is an example only.
Imax 2000
 
Whenever I have to work around problems like this, I measure the direction and amount the bandwidth is shifted when the second antenna is added. If resonance shifts upwards by 300 Khz. I tune the antenna 300 KHz. lower before the second antenna is added. Then the shift makes the resonance drop right into place where I want it. There will still be some interaction with the antennas but it should not be all that noticeable once they are tuned as suggested.
Shockwave, do you use a choke with this antenna as standard practice ? Or only add it if needed ?
 
Shockwave, do you use a choke with this antenna as standard practice ? Or only add it if needed ?
I do not use chokes in my installations. I only see Common Mode Current issues when the antenna is not properly matched to the 50 ohm line or it is being operated outside of its bandwidth.

If you use it over a wide range of frequencies or with an antenna tuner for more coverage, a choke may not be a bad idea. But if you want a choke to work, you have to isolate the mast at the same point you choke off the transmission line. Another thing to consider is the CST modeling indicates any residual CMC directly under the feedpoint is in a constructive phase for up to another 1/4 wave.
 
I do not use chokes in my installations. I only see Common Mode Current issues when the antenna is not properly matched to the 50 ohm line or it is being operated outside of its bandwidth.

Steve, I don't believe I've ever heard this idea on Common Mode Currents explained this way before. This thread is about the S4/Vector4K. Does your idea here work the same with other CB vertical antenna designs, or is this idea unique with the S4/V4K design?
 
Last edited:
  • Like
Reactions: Shadetree Mechanic

dxChat
Help Users
  • No one is chatting at the moment.
  • dxBot:
    Tucker442 has left the room.
  • @ BJ radionut:
    LIVE 10:00 AM EST :cool:
  • @ Charles Edwards:
    I'm looking for factory settings 1 through 59 for a AT 5555 n2 or AT500 M2 I only wrote down half the values feel like a idiot I need help will be appreciated