How do you adjust SWR's on a Star Duster

[hammer0630]

I am finally getting around to do the install soon for a new base antenna coax new mast etc on a new house and I am going to use a Sirio Star Duster M-400 and by the way this new antenna is built surprisingly well everything machined spot on and not one ill fitting part Anyway I do not know how you adjust this antenna for proper swr alignment? This will be used for the normal 40 channel C.B. I'm sure many people have experience with this antenna perhaps at some time and I believe Sirio has copied the original exactly as when it was popular back in the day any advice greatly appreciated!!

 

[Lil'Yeshua]

This might help. Check it out
http://www.worldwidedx.com/cb-antennas/90349-sirio-m-4000-a.html
http://www.cbtricks.com/ant_manuals/ant_specialists/m_400/graphics/m400_starduster_om.pdf
http://www.worldwidedx.com/cb-antennas/35964-considering-m400-starduster-whats-deal-4.html

 

[Marconi]

I don't know if Sirio's 400 is considered tunable for anything but CB, but the original is not really tunable. The elements are all made fixed using sheet metal screws. Of course one could slot the elements at that correct spots and use hose clamps and maybe re tune for 2,6 or 10 meters.

All of the SD'rs I've ever owned were pretty much right on the money if assemble as instructed...and again all of the kits were of fixed design.

Give us some close up pictures if you can. I know very little about this model. The only thing I might think to be different could be the angle for the radials. My Stardusters are angled 17* degrees down out from the mast and that is a sharper angle than I ever seen with a knockoff model. Most are typically closer to 40* degrees, and I don't think they work as good.

Good luck and keep us posted.

 

[hammer0630]

Marconi: That's exactly what I was hoping to hear "they are not tunable" The Sirio sounds exactly like the original model including the angle of the downward radials. I wish I could upload a photo but the site says I need to reduce my pixel count have tried but no luck. I was wondering before your reply if the radials might have something to do with swr's as they are two piece and there is no mention of how far to insert one into another. I'm not sure in your reply if you still use a S/D or was referring to the past or still using one from the past I do believe the Imax 2000 is probably the best Omni antenna out there right now both construction and performance but if you like these SD's but will not purchase a new one the latest Sirio is made very well and not because it is about $70.00 it's just over all good using all aluminum parts machined brackets from solid blocks of aluminum and stainless steel hardware. I thought I would throw that out there because many reports say they are junk and people who once liked this antenna are staying away from it now. I think there are or where two Italian companys producing the knock offs and also China I believe that's where these comments are coming from and maybe even Sirio has changed there manufacturing process also recently it's possible someone could purchase one today and still get a junk one due to it being older stock I just don't know? I was a machinest for some years and know a little about quality and if I where to get ripped off I would be telling the world these are junk! This antenna is new to me and some what strange from the little I know about antennas and all other antennas I have owned before this one such as no swr tuning. I have not found on any site or in the instructions about swr adjustment just wanted to make sure this was correct. I have yet to drill a hole through the house for the coax and will see how this ant.works for me being in a hole I am immediately surrounded by hills and mountains "I recently just moved here" if not so good I will purchase a Imax 2000 and thank you for passing onto me your knowledge! ..Jeff

 

[Marconi]

That's exactly what I was hoping to hear "they are not tunable" The Sirio sounds exactly like the original model including the angle of the downward radials. I wish I could upload a photo but the site says I need to reduce my pixel count have tried but no luck. I was wondering if the radials might have something to do with swr's as they are two piece and there is no mention of how far to insert one into another. This antenna is new to me and some what strange from the little I know about antennas and all other antennas I have owned before this one such as no swr tuning. I have not found on any site or in the instructions about swr adjustment just wanted to make sure this was correct.

0630, how are the pieces of tubing secured? If Sirio uses screws and the elements are predrilled...then the antenna kit is designed as fixed constructions.

If the elements are slotted and use hose clamps to secure the pieces...then the antenna is likely tunable within some range.

My guess is that Sirio makes all of their antennas pretty much fixed construction, and the two modern antennas from Sirio that I have...do this fixed thing very well. My Gain Master and my New Top One both were perfect in match following the instructions...and no tuning was necessary. The NTO came fixed and it didn't have much if any dimensions in the manual...as I recall.

I call this "plug and play" antenna kits.

 

[hammer0630]

The top section is fixed the only part that maybe considered adjustable would be the three downward radials and would those sections have anything to do with adjusting the swr's? The 3 downward radials are two piece I believe because of the size of the shipping box would be very long I'm just guessing there length to be 8 to 10 feet when assembled. Each of the 3 radials are constructed one section is bigger in diameter and hollow the 2nd section is solid and inserted into the hollow section and secured by the hollow section with a predrilled hole and using a circular solid clamp with a set screw. There is no marking or instructions of how far to insert the solid radial before tightening the set screw. All that is needed is to insert several inches and tighten set screw maybe that is all that is required? It would have been nice if they would have mentioned this part in the instructions for there is nothing else to think about.

 

[Marconi]

Well 0630, I was wrong...the Sirio 400 SD'r is tunable from 26.5 - 30 mhz, and this clearly stated at the very top of the instruction manual. I just took off the Sirio Website, so I don't know what you are reading that does not give instructions. Maybe you have some very old Sirio 400. A lot of people have made the 400 over the years, including Sirio and they all had very skimpy instructions, but that was because those antennas were not tunable...just like I said earlier.

In these instructions there is clearly a graph and instructions on how to tune the Sirio Starduster M-400 over the range noted. The overall length "L" is clearly noted by frequency for the radiator and the radials.

I get 102" for both radiator and radials at 27.205 mhz. This is also the dimensions for my homemade Marconi 5x antenna I make here. See an image of the base part below my handle above.

From what you describe you have these instructions, so I would suggest you read them again. Then try and follow what is printed, and you should be able to get this one right on the money.

If you have trouble converting millimeters to inches, then let me know and I can help you with that.

Click here: CB 27 MHz Base Antenna, STARDUSTER M-400 and then download the manual.

 

[Marconi]

0630, here are some Eznec models comparing my (Marconi 5x 102" w hub 42') to a New Vector 4000 with a base height also at 42' feet. This configuration also leave the bottom of the SD hanging down to 33.6' feet. This all means the tip of the Marconi at 50.4' feet is about 19' feet below that of the Vector at 69.4' feet to the tip. Would you call this a fair comparison? The current maximums for both antennas are not even close.

The third image is the SD'r with the tip raised up to 69.4' feet in order to make both antennas equal to the tips. I also added an overlay of these two in order to show how the 1/4 wave radiator really performs against the 28'+ foot high Vector.

So, you get your new SD'r up at least 40' feet and you should be able to run with the big boys and their big long antennas. I see the same thing in the real world too.

View attachment My Marconi 5x vs, New Vector 4000.pdf

 

[hotrod]

Well 0630, I was wrong...the Sirio 400 SD'r is tunable from 26.5 - 30 mhz, and this clearly stated at the very top of the instruction manual. I just took off the Sirio Website, so I don't know what you are reading that does not give instructions. Maybe you have some very old Sirio 400. A lot of people have made the 400 over the years, including Sirio and they all had very skimpy instructions, but that was because those antennas were not tunable...just like I said earlier.

In these instructions there is clearly a graph and instructions on how to tune the Sirio Starduster M-400 over the range noted. The overall length "L" is clearly noted by frequency for the radiator and the radials.

I get 102" for both radiator and radials at 27.205 mhz. This is also the dimensions for my homemade Marconi 5x antenna I make here. See an image of the base part below my handle above.

From what you describe you have these instructions, so I would suggest you read them again. Then try and follow what is printed, and you should be able to get this one right on the money.

If you have trouble converting millimeters to inches, then let me know and I can help you with that.

Click here: CB 27 MHz Base Antenna, STARDUSTER M-400 and then download the manual.

this is correct. you can adjust it for swr. using the radials. for standard 40 cb id start at 102 inches

 

[hammer0630]

You are right about the instructions they are in metric measurements I also do not understand what the graphic charts where describing to me. with this info you guys have provided I will go over the instructions again and again and convert these measurements to inches and feet. When you say 102" is where I want to be or at least a good starting point are you referring to the three adjustable downward radials we where discussing? Please have patience with my ignorance I am really learning this stuff for the first time and really want to do this right. And again I am tuning this S/D for the regular 40 channels cb. I have always had antennas mobile and base that simply had tuning rings or set screws you just lowered or raised to get better swr's with vey simple instructions. Again 102" is what I am going with for you guys have way more knowledge than I do and am going with anything you guys suggest I just want to make sure that this measurement is the three downward radials. Thanks so much and I will wait for your conformations.

 

[hammer0630]

I just am not understanding the graphic chart enough to be able to make proper adjustments. I have measured the top section which is not adjustable but does not leave out clipping to proper height and it measures in at aprox. 110 inches and the three downward radials where I have them secured at also reads 110 inches I would have never guessed that the top section and the three bottom section would have ever measured exactly the same so now I can not guess with out your help which section should be 102 inches. I am now thinking that I am not adjusting the antenna for proper swr's but tuning it for the frequencies I will be using it for "CB" Please help Thank you!!

 

[hammer0630]

..

 

[Marconi]

I just am not understanding the graphic chart enough to be able to make proper adjustments. I have measured the top section which is not adjustable but does not leave out clipping to proper height and it measures in at aprox. 110 inches and the three downward radials where I have them secured at also reads 110 inches I would have never guessed that the top section and the three bottom section would have ever measured exactly the same so now I can not guess with out your help which section should be 102 inches. I am now thinking that I am not adjusting the antenna for proper swr's but tuning it for the frequencies I will be using it for "CB" Please help Thank you!!

0630, check out the drawing in the Tuning Instructions on page 2. You will see Sirio shows us both the radiator and the radials are set to the value of "L" just like note in the graph chart.

Find the frequency you want to use at the bottom of the chart.

Then follow the line up from the frequency until you reach the bold dark black line. Stop at this point where the small line and the bold dark black line intersect...and write down the number on the left of the graph. Multiply this number x .03937. This converts mm into inches which inches, and in this case use we get 2607 x .03937 = 102.6"...which is the value of "L" for both the radiator and the radials. "L" stands for length. Using 102" should get you tuned up right in the middle of the CB band at 27.205 mhz.

Sometimes we all can get a little brain dead now and then, and that is likely what has happened to you in this case.

I circled all the important areas of the image of the antenna and the chart, so maybe you can see the parts that allow you to adjust the tubing into various lengths for different frequencies. Sirio assumes this stuff should be well understood.

No matter if your own "mama" told you to measure and cut...forget about cutting anything on this antenna. :w00t:

0630, the parts that secure these tube elements together at different lengths use little hubs with set screws (grub screws) The screws are contend into the hub using a little Allen tool that is probably supplied in the kit. Grease those little parts up good or they will start to rust in a month.

I use a product called "Stuf" that goes right inside of the SO239 connectors. Then screw it down tight with a nudge using pliers, and you should be good to go at 27.205. Make sure all parts are properly tight.

 

[hammer0630]

Oh my God thank you so much!! I googled earlier after going over the graph 2580 mm to inches and got approx.102" so I knew I was now on the right track but for some reason I did not think the top section was adjustable?? I read and reread your post "DO NOT CUT"and the area's you circled and took apart the top section and sure as Hell it is adjustable this where I really got off track about everything thinking this is solid I don't know why I thought this? With out your help this would have been way out of tune! Thank you for going above and beyond to help out a complete stranger!!

 

[Marconi]

0630, it is always great to know that when a plan comes together and we learn or understand something that had previously evaded us.

I would sure like to know what the angle of the radials is on your Sirio M400. How long are the 3 plastic support arms on the radials?