Sirio M-4000

[BammBamm]

I have been reading about antennas and am a little confused. If the Sirio M-400 is a 18 foot 1/4 wave ground plane couldn't one build this antenna out of say aluminum tubing themselves? Roughly figuring a 9 foot element as the radiator and 3 9 foot long ground radials at 30 degrees using a coax connector to connect all of this together. Maybe putting a "ugly balun/choke" at the feedpoint. would a home built have the same characteristics and performance? I guess what my true ? is would be why buy this if you could make it so much cheaper and/or stronger? Something tells me that Marconi and Booty are going to be all over this post

 

[HomerBB]

The answer is yes, you can build it.

 

[Marconi]

I have been reading about antennas and am a little confused. If the Sirio M-400 is a 18 foot 1/4 wave ground plane couldn't one build this antenna out of say aluminum tubing themselves? Roughly figuring a 9 foot element as the radiator and 3 9 foot long ground radials at 30 degrees using a coax connector to connect all of this together. Maybe putting a "ugly balun/choke" at the feedpoint. would a home built have the same characteristics and performance? I guess what my true ? is would be why buy this if you could make it so much cheaper and/or stronger? Something tells me that Marconi and Booty are going to be all over this post

I don't know the cost of the M400, but you might expect to pay about $60.00+ dollars for retail aluminum, and you may waste about 30% at that in unused tubing if the minimum purchase is 6' feet. With about $5.00 for ss hose clamp hardware, an unknown price for a hub machined to hold this all together, and insulate the radiator...you might be better off with a lot less work and maybe even better results if you just buy the M400. I have several different knockoff M400's and most are not the same as the original. I find these knockoffs with wider angled radials do not work nearly as well. I don't know about the Sirio either and have not read any reviews on it.

I make a Starduster type vertical using a mobile mirror L-bracket and a hub from an A99 GPK attached to a suitable mount and if I make it with two hubs I can use 3,4,5,6,or 7 ss 102" whips and it works well. This is expensive also due to the cost of the whips. Image here:





I find this antenna very effective, with a nice wide bandwidth, that works well, and is very quiet if conditions permit. I often can copy signals on this antenna that I can't copy with some of my other vertical antennas. It is very durable and light.

 

[HomerBB]

Awesome little homebrew, too!

 

[Marconi]

Awesome little homebrew, too!

Homer, the wires look a bit short, are the supports part of the radials too? I may have asked already, but how did your antenna respond with BW, signal, hearing, and noise?

 

[HomerBB]

The antenna was made for use on a friends 40 channel CB, and when I had it up it had a SWR of <1.3:1 from 1 to 40.
As for performance, it rocked. It outperformed the A99 that was up in the same spot and height immediately before it. The receive was really good, too. We did not do any testing, but did note that it did really well.

The appearance of the radials wires being too short it due to the disproportionate length of the vertical. There is a wire running upward through a fiberglass fishing pole making up the vertical. The pole is 13' long, so the wire is about 4' shorter. Use your imagination to shorten the vertical and it will be better.
Also, the yellow part of the mast is a fiberglass post hole digger handle, and is about 4' long.

 

[Marconi]

Homer, I was thinking maybe the top was aluminum tubing. I Ctrl+x in on the image a little, but can't tell if that's a choke or part of the FG handle. How did you feed it? Do you remember the dimensions in case BamBam wanted to try it? Is it holding up at your buddies?

BamBam, if you use tubing and depending on the diameter used...you may end up way too long at 108" for the length to start. I think the M400 is made up of .625"/.50" material and the hub is maybe 2" x 3" long as well.

When I used 102" whips, with the radials slanted down in the A99 GPK hub, the antenna showed:
Resistance = 50, Reactance = 0, SWR = 1.00, @ 27.230 mhz.

With the radials horizontal the antenna showed:
Resistance = 47, Reactance = +1, SWR = 1.06 @ 28.280 mhz.

See what happens when the ground plane on the auto tends to fall away from the feed point correctly due to the particular body lines in a mobile, and alternatively what might happen if that doesn't happen correctly. It is difficult for us to see or imagine what the GP really looks like in mobile installs. It is mostly luck, me thinks. This may give us an clue as to maybe why guys sometimes have trouble when installing their 102" whips on a mobile. When they have to add length to add back some reactance, and then end up chasing their tails with the tune...as the resistance goes south on em'. Can''t you hear the Parrot calling now: "...put a 6" spring under the whip, that'll make it work." Well, IMO it may help the SWR meter, but will it work better is the real question?

Again, see what happens when the radials are slanted down pretty low. I think the three radial A99 GPK hub I made shows about a 30* degree slant, while we hear guys always talking about 40* degrees being the only way to go.

My original SD'r has much more slant in the radials than any of the knockoff versions I have. What does that suggest? I can actually see the difference in effectiveness in operations on this issue...just by working the antennas with various angles in the GP. Forget the SWR match as long as it is close enough, below 2.0:1 at least and I'm not too sure it wouldn't be the same effectiveness at a much higher SWR reading at the radio. I would also go so far as to say the vast majority of 1/4 wave mobile installs and maybe even most of the raised 1/4 wave GP models used are not getting the effectiveness they wish from their 40* degree and wider angled radial designs. I didn't realize this about the 102" whip until I studied it in many different shapes and configurations during my summer work of 2006.

Homer, you may be the only guy I ever met that might, if interested, confirm or deny these ideas of mine regarding the 1/4 wave radiator in particular. I'm not asking you to do what I did, but just to let you know what I think I found using the 1/4 wave radiator with a really effective ground plane and not just a decoy.

I also think I proved to myself that "more radials" than 3 or 4 can be of measurable advantage as well for the 1/4 wave radiator...which really needs a good ground plane to work right. My efforts in 2009 were not successful at duplicating that work in 2006, but maybe one day, if my Lord Jesus is willing to allow me the time, strength, and energy.

If you want a bit more technical type presentation of these ideas for a 1/4 wave radiator, I did a video a while back on YouTube.
YouTube - Marconi discussing modeling results for a 102" whip a 1/4 wave radiator

 

[HomerBB]

@Marconi,
The antenna is not up now. I loaned him an A99 until I got him another antenna. We gave the A99 away to a new truck stop so they could announce their opening up for business. In the mean time he used this antenna, and was more effective with it than the A99. When I got him a 5/8ƛ together we replaced the 1/4ƛ GP with it.

The fishing pole was inserted with a 3/16" cable, and its length within the FB pole worked out to around 99". The four wires on each side were about 112" or 114" each. I can't remember now. I know I had to lengthen them when I first put them on at 108".

Naturally, the vertical will have to be cut long and trimmed back to a match.

Maybe when the weather fairs up this Spring I'll look into the SS whip thing.

This antenna may go back up for another fellow who doesn't have a base antenna in the next few days. We'll see.

 

[BOOTY MONSTER]

heres my 12 gauge speaker wire starduster/.25wgp result .

it had some lean to it . LOL

i made the four ground elements 108 inches . i started the vertical at about 112 inches and clipped it down a inch at a time till i got to 1.3 on the vswr . i didn't measure its length after tuning though . i could have got a little lower , but i was tired and didnt feel going lower would make any difference to my tx/rx or make the radio/amp any happier .
the grounds are at a 33.7 degree angle according to this site . the X standoff is just four 5 ft. pieces of 1 inch PVC with a 4-way in the middle . it was taped to the side of the mast .

Right-Angled Triangle Calculator

i did put a air coax choke at the feedpoint . but i know now it was the wrong size and wrap count .

thats pretty interesting BB that your 1/4 home-brew beat the antron . the antron had a 9 ft higher tip height and the lower TOA of a 1/2 wave .
but antennas are just full of suprises .

 

[nav2010]

When I used 102" whips, with the radials slanted down in the A99 GPK hub, the antenna showed:
Resistance = 50, Reactance = 0, SWR = 1.00, @ 27.230 mhz.

With the radials horizontal the antenna showed:
Resistance = 47, Reactance = +1, SWR = 1.06 @ 28.280 mhz.

???? Why 2 different frequencies?

 

[Marconi]

When I used 102" whips, with the radials slanted down in the A99 GPK hub, the antenna showed:
Resistance = 50, Reactance = 0, SWR = 1.00, @ 27.230 mhz.

With the radials horizontal the antenna showed:
Resistance = 47, Reactance = +1, SWR = 1.06 @ 28.280 mhz.

???? Why 2 different frequencies?

Nav, sorry you will have to scroll the page, BM posted his typical life size mural on this page.

Above I have highlighted the words that are key to the point I tried to make in my spiel on why I think some guy's might have trouble and be found chasing their tails trying to make the 1/4 wave whip work on some mobile installs. We can't see the GP and don't really know how the antenna sees the GP if that makes sense.

When I did my work on the 1/4 wave, as described, you'll just have to read and try to understand my poor descriptions, sorry. In that situation I could at least see the GP, and I accepted the likely fact that the mobile was not the same situation, but I still made some conclusions on the possibilities with what I observed in testing. To that extent, I could be wrong.

The difference in frequencies is due to the different angles of the radials on the same antenna, and that is how I describe each in the post above. We have to wonder about how the antenna sees the GP, so I speculated that with such a difference in my test noted above, that the guys having problems with their 1/4 installs probably didn't understand what was going on. The SWR they might be seeing go bad when moving the 1/4 was just the affects of the resonant frequency changing due to the GP changing angles and maybe even in length.

When I read about guys having such problems, I never hear them even mention frequency, and for sure they don't indicate they ever check frequency and if they do they never go above channel 40. Some can't go above 40, and I understand that. There is way too much attention on SWR in CB land and hardly no attention devoted to resonance or frequency, so they miss the understanding, IMHO. So, if you consider this relative to two guys placing a 1/4 wave whip on two different mobiles with totally different shapes, maybe this all might start to make more sense.

 

[HomerBB]

thats pretty interesting BB that your 1/4 home-brew beat the antron . the antron had a 9 ft higher tip height and the lower TOA of a 1/2 wave .
but antennas are just full of suprises .

Yep. It seems all A99's are not created equal, too.

 

[BOOTY MONSTER]

sorry if the size of my pics are a issue , i just copy the image link from photobucket .

yep , the vehicle is half of the antenna its size and shape and where the antenna is mounted on it creates different ground elements .

 

[Marconi]

sorry if the size of my pics are a issue , i just copy the image link from photobucket .

yep , the vehicle is half of the antenna its size and shape and where the antenna is mounted on it creates different ground elements .

No problem BM, but I think Photobucket does allow you to fix the size down from 1000+ to around 400-600. The larger size output from most cameras is the problem when uploaded to Photobucket I think. Check it out on PB and see if they don't allow you to alter the upload image into their system as an option. I have to fix all of my camera snap shots produced at 1 meg or better, down to a 600 x 400 min. before the attachments feature above on WWRF will accept the images. I just hate using my horizontal elevator, that all.

 

[AudioShockwav]

How are you going to make your mobile 5% larger?

Buy a Motor home?
OK I had to do that.
Eddie, we can only add or subtract length to radiator ...and then use some type of matching network.
Mobile install`s are very unpredictabe , where it is mounted, ground losses.....many things.
Like you said in the vid, the quick answer to the problem has always been...add a spring, or prune the coax and yes it will give some comfort to the SWR meter, but it is not always the most efficient thing to do.
If you can install the correct length, then use a matching network to solve the other side of the equation is the best thing to do.
Oh, i just put in 26.5 as a quick guess in that thread, to say that adding length to the radiator lowers the frequency.
Good Info Marconi.

73
Jeff