The three downward radials support arms measure "1 foot" out from the mast. The three downward radials are screwed on 30 inches above the 3 support arms bracket. I am curios to see what degree this equals and what your thoughts are on this.
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How do you adjust SWR's on a Star Duster
- Thread starter hammer0630
- Start date
0630, I figure the angle of the Sirio M400 is about 20* degrees, and that is about the same as for my Starduster.
You may find the dimensions that I suggested for 27.205 at 102.6" may be a bit short. I tuned the model again, and had to extend the radials to 107.6" and the radiator to 104.6" to get the best tune I could for 27.205 mhz.
Good luck, and keep us posted on your progress.
You may find the dimensions that I suggested for 27.205 at 102.6" may be a bit short. I tuned the model again, and had to extend the radials to 107.6" and the radiator to 104.6" to get the best tune I could for 27.205 mhz.
Good luck, and keep us posted on your progress.
Well I just spent two days up on the roof reinstalling the S/D and customizing a lot of new ideas and also figured a better way to get the coax through into the house by going through a basement window frame by notching it out just enough to get the coax through and still be able to close and lock the window and this allows me to get to the radio room by going up through the floor but this has now made me short to get to the radio so I am now waiting on 10 feet of coax and also some upgrades just for looks to the 148. I ordered both cases of the radio some Diamond plate aluminum, chrome bracket to go with my custom made base radio brackets, chrome knobs and a new faceplate in black with blue flames. MARCONI when you readjusted your S/D what gave you the idea to adjust the three radials and the top radiator, was it high SWR's or what? I really really would not be looking to take this down again. Well I won't know what's going on with mine until I get my ten foot coax extention next week
I have never found a need to adjust my SD'r for 27.205 mhz. I was talking about a model of your Sirio M400 model which I suggested in the beginning looked to setup with 102.6" for both the radials and the radiator.
This may be too late to be helpful, but here goes.
What frequency are you trying to center on 0630?
I can't guarantee any you any dimensions. It is always best to tune in situ, but if that is not possible...then you need to test the match maybe 10' feet above the Earth and well into the clear first.
If the match and the bandwidth looks like the manufacture suggests...then raise it up. If it changes going up, then take two steps backward, and take it down again, and do it over. Also use your regular working feed line to tune... if you don't have an antenna VA type analyzer and know how to work it well.
For years I've done my tunes this way and it works too, but you have to take care. Sometimes you will have things happen and you should be ready to recognize them before you raise a new antenna up.
0630, there are not guarantees in the antenna business, but Sirio does a great job in their manual with information if you take the time and effort to read for understanding. This one does not look hard to me, and I'm trying to look thru the eyes of a novice now. You only have 4 physical points to measure, so don't make this thing harder than it is.
Make sure everything is properly tightened and not overly tight so as to cause distortion in the tubing or stripping. You don't want anything loose on the antenna. If you can get some Stuf for you feed point connection, then I advise you put it in the connector and then tighten the connector well with pliars...and again do not strip the threads. A little dab of Stuf will help keep water out of your coax. I don't put plastic tips on the tubing that slants down.
When you get your antenna built and before you put it up...take some time and relax and write down the measurements you planned to your and see if you got it right. Then get some help and put er' up, check the match, and talk on it if you did it right.
If you ever plan to take this antenna apart again, you should lube the joints of all tubing. If you don't have Pentrox...use a little bit of Vaseline on your finger tips, before you slide the parts together, and then when you tighten down on those grub screwes...try to remember they will be distorting the metal just a bit so you can get it apart at a later date...that is the plan anyway. If you do it right the thing will stay together, and you should be able to get it apart later on.
Important note here. Put some quality electrical tape, suitable for outside, around the coax a few time, and then around the mast well a few inches below where the coax comes out of the shorter mast connected to the antenna about 8'+ feet below the feed point. This will help support the feed line weight from the effects of wind ill-working on the coax connector.
Do not get into a hurry and be careful of heights and electrical sources. Both can kill folks.
Good luck and keep us posted.
Great advice I did most of the things you suggested on the roof before standing it up. I used dielectric grease looks like and comes in the same type of tube silicone or gasket maker comes in. Everything is aluminum and so are the brackets and the rest of the hardware is stainless and chromed brass. From the ground to the top of the mast is 50' and to top of antenna is approximately 58 1/2 feet. All 4 foot sections of the mast are all riveted together and the top mast of the S/D is cut down to accommodate the bracket for the downward radials in between where the 4 foot masts come together because the OD was to large and the Antenna specialists SC-2 scanner antenna I had to do the same thing but it is in between the 1st and 2nd 4 foot mast sections to keep as much distance as possible the 2 antennas apart from one another. Thanks again for all of your help!!!
Get us some picutres and some close ups if you can. I'll fix you an Eznec model at your height above Earth, and send to your email if you have email on the forum. I'll also send copies of my Marcon 5x and my Starduster models for comparison. You should be real close with your new M400 from Sirio.
Give us some contact reports and comparisons if you can.