End Fed Sleeve Antenna

[HomerBB]

I want to respond to the request for details that Marconi made to me in the modified vector 4000 thread without side racking that thread.

This is the post I'm jumping off from;

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Once again I will post something far less scholarly than you fellows who know much more than I do.

To begin with, it would be nice to actually own one of the Vector 4000 antennas in order to make comparisons.. So I must redo the homemade when I get the time to more perfectly replicate the real construction. As it is, it seemed to out perform the offset center fed sleeve dipole I had up. On the other hand, it is getting clobbered by the end fed closed sleeve vertical I put together (photo and specs on previous post). Clearly my home made mock-up of the V4k (hereafter referred to as a Q-V4k*), although at least a dozen feet higher to the feed point, and nine feet longer over all in length, has a terrible TOA. I hear things locally and in DX on the sleeve vertical that are not audible on the Q-V4k. Likewise, what I hear on both I hear more loudly with as much as 2 -3 "S" units on the sleeve over the Q-V4k. The noise floor on the sleeve antenna is lower in all circumstances making even low RX more readable. When there is no white noise in either, the end fed sleeve out performs the Q-V4k. As for TX, I get more responses to calls on the sleeve antenna than the quasi-V4k. I find myself able to make contacts with the sleeve for which I cannot adequate hold a decent conversation due to the apparent inability to RX to the extent I am TX'ing, although this could be conditions oriented. Also, a review of the SWR curve on the two antennas show the sleeve has a significantly better bandwidth. Comparisons to my 5/8^ would be, as I remember it, similar, with the 5/8^ outperforming the Q-V4k, and the sleeve antenna edging out the 5/8^ (I attribute this to losses in the coil I had on the 5/8. If I rebuild it I will outfit it with a gamma).

So, perhaps next week, the Q-V4k goes back onto the work table (saw horses) for the more exact replication of the real V4k specs. Before I do much more, I intend to go back to a 5/8^ vertical length and attempt to tune it again to see if this Q-V4k has a better TOA at that length.

Thanks to those of you who have posted the actual dimensions on this thread.

Although I am lost to the modeling software specifics most of the time, I continue to find this an interesting read.

Charles, aka Homer

* Quasi-V4k

Very interesting report Charles. I think it is great when guys build their own antennas from scratch, but when they tell me they work great, I do wonder how they are able to really tell. Sometimes even fried chicken, which I love, taste better one day compared to the next. You will get all kinds of arguments about testing side by side, but I bet you appreciate the finer nuances you're able to see using a switch box as in this case.

The question "Why" is open at this point, but maybe your Q-V4K is not working the collinear affect we expect is going on with the Vector. Bob is very likely right, thru his testing he noticed that by adjustments maybe he was steering the maximum angle of RF. So, maybe that is what the Avanti design is all about. Maybe your Q-V4K is not doing that presently even though it seems to work just fine otherwise.

Were you surprised at the difference you see by comparison? I'll bet it was not so obvious when you first put the Q-V4K on the air, right? This is exactly why I prefer to compare antennas side by side.

I saw your new creation the other day, but have been wrapped up in the Vector discussion, and presently I'm recapping the whole mess for good information. So, I just didn't have time to ask. However, with your report today, I'm really interested in the details of how that thing is constructed and fed, if you could share.

Good luck and keep us posted.

Information here:


Q-V4k:

SWR from 25.165 through 28.755.

28.755 ---------- 4.0:1
28.305 ---------- 3.5:1
27.855 ---------- 2.0:1
27.405 ---------- 1.4:1
27.205 ---------- 1.2:1
26.955 ---------- 1.0:1
26.505 ---------- 1.3:1
26.055 ---------- 1.6:1
25.605 ---------- 1.8:1
25.165 ---------- 1.8:1


End Fed Sleeve:

SWR -

28.755 ---------------- 2.0:1
28.305 ---------------- 1.8:1
27.855 ---------------- 1.7:1
27.405 ---------------- 1.4:1
27.205 ---------------- 1.2:1
26.965 ---------------- 1.1:1
26.850 ---------------- 1.0:1
26.515 ---------------- 1.2:1
26.065 ---------------- 1.6:1
25.615 ---------------- 1.9:1
25.165 ---------------- 2.0:1



Description:

The upright vertical is a 1/2 joint of EMT 203" long with 27 1/2" of #14 common solid copper wire connected to the bottom. This runs through the center top to bottom of a yard lamp post of 3" aluminum pipe. 3 1/2" of the copper wire sticks out the bottom of the 3" tube. To that is connected the core wire of a RG58 coax that is formed into a 5 wrap 4" diameter coax choke. The shield is connected to the 3" tube. All coax connections are made at the bottom end of the antenna.


Below is a diagram and photo of the sleeve antenna. The Q-V4k is below, too:

 

[HomerBB]

I agree that the Q-V4k is apparently not working the collinear effect of the Vector. although I have no real test equipment I do have the audible and contact results, with the S meter readings, and the BW curve all on/from the same radio and SWR meter. Primitive, I know, but what I have. Working great would be for me getting the results I seek - usability, and perceived improvement.

Suspecting the q-V4k is screwy design wise, I will work on it to see if i can get it to perform at least as well as the sleeve. I hope that someone with experience and software might want to model the sleeve for better explanation of why/how it works.

 

[loosecannon]

homer, is the relationship between the 3" tube and the 1/2" conduit important?

correct me if im wrong but this is the type of antenna that can be made from just a length of coax right?

im interested in building something like you have there.
LC

 

[HomerBB]

I had read about what is called an "open sleeve end fed vertical" and put this together with the pipe I already had on hand. It may be that the distance is critical, but I just used what I had experimentally. Because mine is not open, but a closed pipe, I call it a closed sleeve end fed antenna.I was pleasantly surprised by the results.

As for the coax antenna question, there is a similar antenna that is made with coax. It is a center fed coax sleeve antenna made exclusively of a length of coax. The length is critical to its operation and tuning as with all single band antennas. What is done is to take a length of coax at least slightly longer than 18', peel off the coax outer covering without damaging the shield for 9'. Then you ease the shield by backward pressure on it until it expands enough to pass it backward over the solid coax. this form the sleeve of your antenna. The result is this reduces or eliminates CMC acting as a choke. To tune the antenna you must trim the ends of the center conductor and the shield sleeve in even increments until you get the SWR you want.
The feed of this antenna is at the point where you separated the center conductor from the shield sleeve - the center of the dipole.

 

[Shockwave]

Homer,

Your sleeve antenna is nearly identical to the Sirio CX series of antenna. The only difference I see is that Sirio shunt feeds the radiator much like the Vector. As I recall this type of antenna is sensitive to the diameter of the sleeve to inner conductor ratio. Simple coax may not have enough spacing to work as the sleeve in this end fed design. That's why we see larger diameter tubing used as the outer sleeve. The truth is both the sleeve antenna and the Vector have the same gain according to Sirio.

 

[W5LZ]

One correction about that center fed 'sleeve' coax antenna. That, "The result is this reduces or eliminates CMC acting as a choke.", is far from actual fact. that antenna will be affected just like any other 1/2 wave antenna by CMC. Plus the 'end effect', high voltages at the end of that braid 'sleeve' will be quite a problem. Most of the antennas you see like this use a coaxial choke a short distance from the bottom end of that braid sleeve. You would see the same result if you ran the feed line parallel to one side of a dipole, except even more so.
That 'close end sleeve' antenna is very similar to a 'J'-pole, an end fed 1/2 wave fed with a 'sort' of impedance matching device (that sleeve). At least, it appears that way to me.
- 'Doc

 

[HomerBB]

Homer,

Your sleeve antenna is nearly identical to the Sirio CX series of antenna. The only difference I see is that Sirio shunt feeds the radiator much like the Vector. As I recall this type of antenna is sensitive to the diameter of the sleeve to inner conductor ratio. Simple coax may not have enough spacing to work as the sleeve in this end fed design. That's why we see larger diameter tubing used as the outer sleeve. The truth is both the sleeve antenna and the Vector have the same gain according to Sirio.

Thanks for that info, SW.
I just know that the audible performance of this antenna is phenomenal compared to many of them I put up. I've done mostly homemade, so there is something to be said about possible defectiveness in my home builds. That said, I might add that I've done full wave loops, the A99, dipoles inverted V, horizontal, and vertical. 2 element Yagis, 3 element Yagis, 1/4 wave GP, slanted wire. This antenna is the best with maybe the exception of my last 3 element Yagi. Even my 2 element quad will need improvement in its spacing over the last design to best the seeming performance of this antenna in its class. The 3 element Yagi was an improvement over the 2 element quad. If it were possible to get a back door rejection from this vertical omni with forward directional gain I'd be in hawg heavin', being in Razorback Country not withstanding.

 

[HomerBB]

One correction about that center fed 'sleeve' coax antenna. That, "The result is this reduces or eliminates CMC acting as a choke.", is far from actual fact. that antenna will be affected just like any other 1/2 wave antenna by CMC. Plus the 'end effect', high voltages at the end of that braid 'sleeve' will be quite a problem. Most of the antennas you see like this use a coaxial choke a short distance from the bottom end of that braid sleeve. You would see the same result if you ran the feed line parallel to one side of a dipole, except even more so.
That 'close end sleeve' antenna is very similar to a 'J'-pole, an end fed 1/2 wave fed with a 'sort' of impedance matching device (that sleeve). At least, it appears that way to me.
- 'Doc

Thanks Doc,
My apologies for that mistake. I recall you advising me before of this because of the high end voltages on a center fed sleeve. (I need to take some ginkgo for my memory). As a matter of fact, I put a coax choke exactly where you just described on the center fed sleeve dipole I had before I converted it to this one.

Getting old(er) is so painful sometimes. ouch, I think I feel a cramp in my brain.

 

[Marconi]

Homer, I made a response late last night and something strange happened when I saved the post. When I got up this AM my post was gone and so were your images. Not sure if one has anything to do with the other, but something strange happened. It looks like most of the others who posted covered the subject nicely.

I was curious how long is the sleeve?

How far does the conduit stick out of the sleeve?

Is the conduit insulated from the sleeve top, bottom, or both?

How did you determine the lengths of the conduit, wire, and sleeve?

Good luck.

Here is a link to Bob's album with the inside working of the Sirio CX series antennas: sirio sleeve monopole :: DSC00211.jpg picture by ukmudduck - Photobucket

 

[HomerBB]

Homer, I made a response late last night and something strange happened when I saved the post. When I got up this AM my post was gone and so were your images. Not sure if one has anything to do with the other, but something strange happened. It looks like most of the others who posted covered the subject nicely.

I was curious how long is the sleeve?

The sleeve is a piece of precut pipe sold by the Home Depot for yard light post. It is a standard 80" length as it sells. I did not alter the length.

How far does the conduit stick out of the sleeve?

147"

Is the conduit insulated from the sleeve top, bottom, or both?

Both. I cut 3 circles of wood - one each for the top of the Sleeve, and the bottom of the sleeve, which do not travel, and for the bottom of the conduit, which can travel up and down with the overall length adjustment of the antenna. Were i to keep this antenna, I would cut circles from acrylic materials.

How did you determine the lengths of the conduit, wire, and sleeve?

I wanted the over all length to be in the 18' - 19' length range so as to be tunable to a half wavelength. The length of the sleeve was predetermined by the post manufacturer (no science here). The conduit had been used as the upper and lower elements of a center fed sleeved dipole. I had used an online website that offered the description of lengths for a different band and extrapolated from there. The lengths for it had been 122" for the upper element, 84" for the sleeve. Because conduit comes in 120" lengths, I used that and reduced the lower sleeve to 83". When I decided to build this I simply combined the two lengths of EMT for the conduit in the center. What resulted was the balance needed to get to the 18' - 19' length I wanted. 228" - 203" (length of conduit) = 25". I made the wire long as my usual practice is, but started with the wire folded back to 25". Though a decent SWR, it was not as good as I wanted, so I unfolded the remaining length to 27.5" with 3.5" hanging out the bottom to fasten the alligator clip to.

Good luck.

Here is a link to Bob's album with the inside working of the Sirio CX series antennas: sirio sleeve monopole :: DSC00211.jpg picture by ukmudduck - Photobucket

Thanks for the link.

I have moved the sleeve up and down as one would a gamma to see if I could move the center frequency up the band. It doesn't. I believe I may have to shorten the length of pipe sticking out the top of the sleeve then possibly readjust the sleeve location for best SWR following the suggested logic Doc proposed that the sleeve works as a type of matching system.

 

[loosecannon]

homer, i really like this antenna idea and would like to know more about the theory behind it, as well as construction details.

the next time that antenna comes down (on purpose LOL) would you mind snapping a few close up pics showing how the whole thing went together?

also, where did you find the idea for this antenna?
is there an antenna book i can look in to read up on how this thing works?
LC

 

[HomerBB]

I will have to search for the site that suggested the closed sleeve antenna, but here are a couple of sites that discussed the open sleeve model:

Open Sleeve Monopole
Open Sleeve Monopole 2

I will be taking it down soon in order to put it up higher for further testing.
I like it as well and will be glad to take some photos of it "up close and personal"

 

[Shockwave]

I will have to search for the site that suggested the closed sleeve antenna, but here are a couple of sites that discussed the open sleeve model:

Open Sleeve Monopole
Open Sleeve Monopole 2

I will be taking it down soon in order to put it up higher for further testing.
I like it as well and will be glad to take some photos of it "up close and personal"

Homer, I just noticed you're in Rogers Arkansas. There is an FM radio station in your area that operates the broadcast version of the Sigma IV antenna. It's KHEL 97.3 FM. They only run 97 watts ERP but I wonder if you can hear them at your location?

 

[HomerBB]

I'll tune there first chance and see. On the job on break right now.

 

[Mr Clean]

I talked to homer not long ago using this antenna and I think he was running a galaxy 88. Impressive signal into Indiana.