Re-tuning a Sirio 4 element beam for 27.555mhz

[rfoutput]

To Robb

Your decision to transmit on 27.255mhz makes you illegal.
This frequency is controlled by the FCC in the Industrial/business band. Unless you have the appropriate license, and not CB, you may loose everything if caught!
You are taking a very big chance if transmitting there. Listening is fine!
Signed
A license Amateur Radio operator who follows the rules and regulations.

 

[Marconi]

Robb, since you have received a warning of sorts, why not try setting the beam up with a better bandwidth if possible. I use to run my 4 element Wilson with a bandwidth well over 2.0 mhz <2.0:1 by using a 54" spacing for Dr/D1. It didn't like going much below 26.965, but it worked at 28.000, with about 1.6 SWR or less and centered at the top end of the CB band.

The Sirio 3 element shows 1.8 mhz BW and the 4 element shows .6 mhz. The difference is 48" of spacing between Dr/D1 on the 3 element and the 4 shows about 40" inches. If you can move the driven element back toward the reflector a bit you might see some increase in bandwidth, and if you're lucky you may not need to adjust and tune much. The wider spacing is a bit more forgiving. The narrow spacing they use is primarily used for max gain at the expense of BW and rejection. You may find that a little less here and a little more there will work both frequency ranges best in your case without a noticeable loss. But, if it don't work out, then you can always try to get it perfect on 27.555.

I never found going for max gain to be the best setup. I always settled on a well balanced setup rather than the optimized ideas. In other words, I like the old Moonraker 4 setup...with almost equal spacing across the boom. I saw good gain, with great BW, rejection, and was very directional.

Some of the optimized designs I found to be almost omni-directional when on-the-air.

 

[Henry HPSD]

@ RFoutput,
Thank you for pointing that out!
Im sure he will be just using the antenna for lisning if it isnt allowed in his country


@Marconi,
Bare in mind: SWR does not tell anything about GAIN/Front to back / efficiency.
I wouldnt recommend to just change the driven element distance towards the reflector as that is quite critical. Not only do you change the resonant frequency it doesnt have the effect on bandwidth as you think it migth have.
As i read your post (i could be wrong) you draw that conclusion by going over the 3el and 4el version. If that is the case please dont, they are two different antennas and changing element spacing will have different effect on both.

Maximum gain for a antenna design can indeed been seen as a bad design for many.
The good thing is, often with a reduce in maximum gain (just a couple tenths of a dB)
in most cases you can produce good results. And no one will notice that sligth difference in forward gain.

Im not sure how thick the elements are of the wilson but if they are different from the sirio
If i recall correct wilson is quite large and sirio isnt, though i could be wrong.
You will also get different results compared to any other that you have had in the past.

It is possible to get a 50 Ohms antenna with 8,4dBI and 23 FB. A SWR bandwidth of 2 Mhz (but again that bandwidth does not tell you if the gain and FB is high over that region).

Narrow spacing is never "primarily" for gain. WIDE spacing is.
Wide spacing resolves into the biggest boomlength. The longer that is the more gain you have. Boomlength is primarily (not alone) responsible for gain.

The 4el Sirio is for "normal" antenna terms perhaps a bit on the small side.
A 3elements yagis these days on a similair or sligthly less boom (3,6 meter instead of 4m) will do exactly the same when you look at gain/FB.

Im not sure what has happend to some of your "optimized" designs.
If you call them almost "omnidirectional". That would also implicate it has no gain.
Perhaps i can have a look at them?

Regards,

Henry
11 meter Dx antenna systemx

 

[jazzsinger]

Your decision to transmit on 27.255mhz makes you illegal.
This frequency is controlled by the FCC in the Industrial/business band. Unless you have the appropriate license, and not CB, you may loose everything if caught!
You are taking a very big chance if transmitting there. Listening is fine!
Signed
A license Amateur Radio operator who follows the rules and regulations.

Quality !!! pmsl,

i'm sure the original poster is well versed in the legality of what he is proposing, and i'm also sure he's aware that rx'ing on 27.555 is perfectly legal worldwide.

As for you sticking to the rules and regulations, i'm sure i'll sleep better tonight knowing that and that every capitalist scumbag in charge of the radio spectrum and the profiteering from it will all sleep easy tonight too, knowing you've never broke,bent or ignored a law/rule in your life.

it must feel great to be in such a moralistic position. me personally i'm much happier on 27.555 banging out a couple of hundred watts and totally not giving a fuck about what some capitalist retard in some office who probably has never even used a radio thinks where i should be able to transmit.

infact if you give me the exact frequencies the fcc control on that band i'll be quite happy to dx there and f@ck up their cash creaming enterprise to the best of my ability.

 

[Marconi]

You may be right on point Henry, you have a lot more experience with beam construction and design than I do. I was being very simplistic, trying to not go into a lecture. I just found wider spacing at Dr/D1 to be easier to work and tune. I also saw bandwidth increasing. Even though I didn't know why, I did notice my antenna using a gamma did like the driven element to be a tad longer than self resonance suggested also. I could never make the point clear for my buddies however.

I also liked using the Moonraker boom which is pretty much balanced by its larger diameter center section and smaller but equal length end pieces. I think my center section was about 54" so that was my Dr/Di spacing using the muffler clamp styled Wilson hardware. While I used 54" spacing I noticed that Maco M104/M105 use 45" and 43" respectively, and I understood that Maco used an optimized design for their Old Hygain models. I tried the new ideas, but never found them as effective as the older more well balanced ideas. I can't tell gain even on my best day Henry, but I can see and measure bandwidth, and I don't believe you can prove that a narrow bandwidth beam works better (except maybe on paper) in your beams than one with a nice large bowl shaped curve. I worked mine since the 80's and have never found better performance in a beam at my location.

It was a fluke in construction when I took an old Wilson Y-Quad, use the dual polarity elements to build a 4 element beam with 3/4" to 5/8" to 1/2" tubing in the reflector and D2 at whatever length in tapper they happened to be, and Dr and D1 being 5/8" to 1/2" using whatever tapper they happened to be. Note: I had two reflectors and two driven elements in that old Y-quad and just a dream with my first ever beam antenna.

A real mis-mash in design and construction, but that thing is still in shape to be functional I think. I have other beams including a 3 & 4 element Maco's to a 5 element Long John made by HyGain, but none have ever worked as good as the one made from scraps. If I was going to design a beam antenna I surely wouldn't use the ideas I note here, but I can tell you that thing worked as well or better than any.

Maybe our own member, DxMan, can recall how my beam use to talk to the group during the CDX contest, all day long mounted just 27' feet high on my 17' foot high roof deck. I never won a contest, but I was proud to participate and considered I was successful none the less.

 

[Robb]

Quality !!! pmsl,

i'm sure the original poster is well versed in the legality of what he is proposing, and i'm also sure he's aware that rx'ing on 27.555 is ; the perfectly legal worldwide.

As for you sticking to the rules and regulations, i'm sure i'll sleep better tonight knowing that and that every capitalist scumbag in charge of the radio spectrum and the profiteering from it will all sleep easy tonight too, knowing you've never broke,bent or ignored a law/rule in your life.

it must feel great to be in such a moralistic position. me personally i'm much happier on 27.555 banging out a couple of hundred watts and totally not giving a fuck about what some capitalist retard in some office who probably has never even used a radio thinks where i should be able to transmit.

infact if you give me the exact frequencies the fcc control on that band i'll be quite happy to dx there and f@ck up their cash creaming enterprise to the best of my ability.

I couldn't agree more - G . . . eg - the gubment allows for export radios on the country and gladly accepts the import duties. While the other hand collects money/penalties for those who use them out of spec/band. I also agree that while all other countries don't have a problem with .555; the US does. <sigh>

rfoutput:
What I am hoping to accomplish by this retune - is to make it closer to the 28.3-5mhz with better resonance and a better SWR. Using an antenna tuner to make up the difference. The antenna 'stock/OEM' from Sirio is centered @ 27.205. On one side of the bandwidth curve - it is flatter than the other side. I don't do the ch 6/AM thing; but I do talk on 38LSB with that crowd. So long as CB ops stay off of the Ham bands - I don't mind it much myself. I also enjoy that portion of 10m and use it just as often as it is open. Sorry for the misunderstanding . . .

 

[Robb]

As a side note - I have often wondered why beams aren't isolated from the masting. I mean; doesn't the masting affect the pattern? Doesn't anybody isolate the beam? I'm sure it would change the tuning of the gamma match. Any benefits from isolating it? No one seems to do it this way - what is the reasoning?

I see guys isolating their vertical antennas from the masts and running a choke balun and the antennas work better.
What's the dealio here?

http://www.youtube.com/watch?v=claJeMNTSGI

 

[Marconi]

As a side note - I have often wondered why beams aren't isolated from the masting. I mean; doesn't the masting affect the pattern? Doesn't anybody isolate the beam? I'm sure it would change the tuning of the gamma match. Any benefits from isolating it? No one seems to do it this way - what is the reasoning?

I see guys isolating their vertical antennas from the masts and running a choke balun and the antennas work better.
What's the dealio here?

Robb I think the obvious reasons are that most antenna manufactures have problems when their designs may abuses their insulators, which are expensive to buy, costly to make and make fit, and are historically prone to failure when they don't use premium stuff or else embed the insulator inside a good support structure.

Thus most prefer to use "plumbers delight" construction in beams for sure and even among many verticals. I think most would forgo the dubious benefits of isolating the whole antenna considering the cost if nothing else, excepting maybe in particular with balanced antennas and now we find with the Sirio Gain Master there is a way around even that.

As a side note, BM recommended a company a while back that claims to sells Delrin. I bought two 26" x 1.125" pieces. I used one to insulate my A99 and had about 6" exposed on a 10' foot mast. After it had been up for about a month last summer, I took it down and noticed that it was bent. Only the heat of summer and the mild winds could have done that. You don't always get what you pay for, and I hate to say what I paid for that material.

I don't think I got Delrin.

If I've talked about insulating here on the Forum, I was probably speculating on the issue at advice of others. However, when I tried it...I installed it to the side instead of raising the antenna above the mast. So, that could have been the reason I got minimal results and did not see anything remarkable. In addition, I am beginning to understand that my location does some strange things at times, and it may be a good point to stop all my testing. It would surely be a lot easier to just start casting comments.

 

[GnG8d]

As a side note, BM recommended a company a while back that claims to sells Delrin. I bought two 26" x 1.125" pieces. I used one to insulate my A99 and had about 6" exposed on a 10' foot mast. After it had been up for about a month last summer, I took it down and noticed that it was bent. Only the heat of summer and the mild winds could have done that. You don't always get what you pay for, and I hate to say what I paid for that material.

I don't think I got Delrin.

LINK
Back when I owned a machine shop, I would use these guys if I had a nedd for a small quantity and didn't want a bunch left over in inventory. Actually they have a ton of stuff and I use them still for projects around here.

 

[wavrider]

Robb,

Some manufactures do isolate the driven element from the rest of the yagi.

Mosley, Cushcraft, to name a couple. Direct feed and may or may not use hairpin or beta matching.

The reflector and directors are all plumbers dream, ease of construction, design, or whatever reason.

You may want to research a moxon antenna. It gives you an idea of totally isolated elements and performance. I have never built one, but some friends have. They swear by them on 6 and 10 meters for light weight, small area with full performance.

 

[Marconi]

Waverider is right Robb, but I though you were suggesting insulating the whole antenna from the mast, not insulating the driven element. Sorry for my miscue.

 

[Robb]

Waverider is right Robb, but I though you were suggesting insulating the whole antenna from the mast, not insulating the driven element. Sorry for my miscue.

You are right - I was talking about isolating the whole beam from the mast.
Doesn't ANYONE isolate the beam from the masting/tower?
Can't I use a piece of PVC - along with a choke balun - to isolate it???

 

[Marconi]

LINK
Back when I owned a machine shop, I would use these guys if I had a nedd for a small quantity and didn't want a bunch left over in inventory. Actually they have a ton of stuff and I use them still for projects around here.

Thanks for the link 359, I might give them a try.

 

[Henry HPSD]

Hi Guys:

@ Marconi:
Oke, on your answer m8, only trying to point things out in a way to help!
One thing i would place a bit differently.

"marconi"Quote:but I can see and measure bandwidth, and I don't believe you can prove that a narrow bandwidth beam works better (except maybe on paper) in your beams than one with a nice large bowl shaped curve. End of Quote.

Answer:
I am not saying a narrow bandwidth antenna works better.
All i am asking for is: To get in your mind Gain / Front to Back / SWR are 3 different things.
They are not most of the time (equal) at the best point where you want them.
And yes, you can prove the difference:
If you have 2 iddentical antennas with the only difference beeing element length.
And there is a difference in bandwidth, there is also a difference in at least one of the other values.

Lets look for example at a 2elements yagi.
It is actually possible to get 6,5dBI and a FB of over 20 dB of a short boom 2 elements yagi.
It is also possible to get about 6 dBI and over 20 dB from a Moxon (reduced element length two elements yagi). (the moxon beeing one of my small favourite antennas aswell!)
The difference beeing: The Moxon keeps up that gain figure over the entire CB band.
A short "high" gain 2elments Yagi doesnt! It only applies to its "peak" frequency. Therefor i always would favour a 2elements Moxon instead of a 2el Yagi.

And just because you havent noticed any difference it doesnt mean it isnt there.
The problem i often see with people is that they claim things based on personal experience but wrong measured. You migth be intrested in a program called "polar plot" try a google search. It is quite usefull if one doesnt have the rigth setup for measurements.
Often i hear people taking measurements with a field strength measurement very near the antenna for example and base facts on it. That just aint possible as the Farfield didnt esthablished yet. The fields really close to a antenna is very difficult to understand.


@ Robb:
Quote:As a side note...etc....end of quote:

The most important thing is that the boom isnt really part of the electrical structure of the antenna. It is only there for the mechanical construction.

However, especially on higher bands! (but it still has some influence on 27Mhz):
If one calculates a beam antenna with the elements attached to the boom, the boom will cause sligth element size reduction.
Now the first couple years that doesnt cause any problems. But what happens if corrosion steps in? Yes the "optimum" of the beam will shift in frequency.
Thats why one isolates elements. It is to reduce the so called "boom-effect".
Element isolating is quite commen, especially on higher frequencies.
At those frequency the diameter of the boom is much larger in comparisment to the use on 11 meter.

For 27 Mhz a couple companies do that.

MHF 11 | made in Italy
AS-611HP
HPSD antenna's
(please note im not trying to advertise as i have a commercial intrest with the above.)
OptiBeam Antennentechnologie
(im sure they will make one for 27Mhz on demand).
DXBeam - Monobander

The fact that you sometimes only see the driven element isolated has nothing to do with boomcorrection.
It is simple cause the antenna has a "split-up" feedpoint.
Wich isnt the case for example with a Gamma-match.
So all the stuff about a gamma-match beeing the best bla bla bla...
Well, lets put it simple. If you have the same gain/FB/Bandwidth ....
A 50 Ohms antenna would be best cause there isnt any loss in a matching
system.
A gamma-match is often used cause it is easy for mechanical reason, and allows litlle construction error.

Oke, say we have isolated all the elements, wich would be best although the difference would be difficult to notice it one can notice at all! Would it be nice to DC ground the antenna ?
YES it would. (protection/noise)
Thats why the best construction would be to iisolate all exept the radiating element/loop.
makes you wonder doesnt it...

ALREADY A LONG STORY.......THE SHORT ANSWER WOULD BE:
The boom of a beam doesnt need to be isolated from the mast as the currents flow different compared to a single vertical antenna.

With a vertical you attach the antenna to the mast.
With a beam you attach the support structure of the antenna to the mast.

It is HOW the currents flow and HOW the antenna is fed in regards for verticals if one can isolate
it or not.

P.S. Marconi, if you need some good isolators, please give me the diameter ill send them towards you for cost price. They are UV resistance and dont have a "isolator correction".

Hope it helped!

Regards, Henry
11 meter Dx antenna systemx

 

[Robb]

Thanks for that info, Henry.