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Sirio Preformer 5000 Magnet Mount Antenna

fourstringburn said:
Think of the caphat like lengthening the whip. The longer you go the more upper bands you lose but you start gaining better effiency on the other bands.

You will lose 6 meters anyway(no big loss I think) so Ideally you probably want to keep 10 meters tuned with minimal coil left.

I use three 24 inch rods fed thru the hub holes centered out making a 6 radial cap hat 24 inches in diameter. This tunes 10 meters with only a couple of coil turns.

So a 24 inch caphat tunes 10 through 60 meters easily on this antenna with an inch or so of coil leftover on 60. If 6 meters is open, I can just put the stock whip back on. For 80 meters I use the telescoping whip.

222DBFL advice is good and something I wish I did in the beginning...

"SPEND THE MONEY ONCE AND DO IT RIGHT"

So there you are, Good luck!
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4 stringburn: I have one question.
First. I have made a shunt coil before. On my new set up I have a Breadlove 4in.
mount on the roof of my 2009 ram crew cab, and a Sirio 5000 trucker antenna. I have tryed EVERYTHING I can think of...I even added a bonding strap to the mount. Now here is the big question I can not find an answer to: Can I mount my SHUNT COIL to the top side of the mount, not the coax side but the top above the cab, and at the base of the radiating element, and ground,or what?20160831_154912.jpg
 
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One end of the coil has to go to ground, the other on the Hot side of the antenna. Where ever is convenient at these two points is fine.

Look again at the example pic below. You can see the Hot side is on top of the nylon insulator directly coupled to the antenna while the Ground side is on a bracket mounting bolt.

I don't know your antenna mount to answer your question directly but I hope this clears it up for you.



IMG_4975.JPG
 
Question, why would this be needed for an antenna with a loading coil already built onto the antenna. I never had an issue tuning any of my Sirio performer 5000 antennas with an analyzer. Granted they aren't the trucker version, but the concept is still the same. All that has been done is the loading coil has been moved up 8" or so. Or am I missing something here? The antenna should tune to R=50, X=0, VSWR 1:1 or there abouts depending on how well you install it and other factors as well. All of mine have tuned very well and all work very well. Like I said, I could be way off base here. But why the need for a shunt coil on an antenna that has a loading coil to match it to 50 ohms or near 50 ohms?
 
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In the mobile environment of the CB band with an antenna designed specifically for use only on said band, you are not generally going to benefit from a shunt coil. In such a case where a shunt coil might be needed, it is more likely you have an antenna problem. That being said, I can see them coming in handy in some limited circumstances, such as a newer vehicle with a fiberglass body. When used in a mobile environment shunt coils are generally used as a means to compensate for the impedance mismatch caused by a lack of a proper sized ground plane.

They they far more commonly used on 80 and 40 meter ham radio mobile antennas. Luckily, when used on a multiband antenna, you tune such a coil for the lowest frequency used, and it has less and less of an effect as you move up in frequency range.

When it comes to its effect on an antenna compared to a loading coil elsewhere on the antenna, the effects on R when it comes to tuning, a loading coil is in series while a shunt coil is in parallel. Series and parallel circuits are inversely related, which is a fancy way of saying they have opposite effects. If you have a base load on an antenna, and a shunt coil at the feed point of the antenna, you have an L matching network, which is the bases of all matching networks. Looking at it this way, loading coils, and shunt coils are each half of a matching network.


The DB
 
222DBFL said:
Question, why would this be needed for an antenna with a loading coil already built onto the antenna. I never had an issue tuning any of my Sirio performer 5000 antennas with an analyzer. Granted they aren't the trucker version, but the concept is still the same. All that has been done is the loading coil has been moved up 8" or so. Or am I missing something here? The antenna should tune to R=50, X=0, VSWR 1:1 or there abouts depending on how well you install it and other factors as well. All of mine have tuned very well and all work very well. Like I said, I could be way off base here. But why the need for a shunt coil on an antenna that has a loading coil to match it to 50 ohms or near 50 ohms?
Click to expand...

In an earlier posts I said this...

As I stated in the original thread on how to do make a shunt coil, It's not going to make a big difference on your antenna performance but it is for being somewhat of a perfectionist if you want to see an Ideal 50 ohm reading on your anaylzer and a lower SWR for your 1/4 wave whip and it's also a good learning experience.

Yes a coil loaded mobile whip antenna shouldn't need any other matching if it was designed properly.
 
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Yes I can understand why for a 1/4 wave whip as the impedance wouldn't be near 50 ohms. But on the Sirio performer 5000 type antennas with a loading coil I wouldn't think one would have been necessary like you stated, as long as it's designed prooerly.
And I'm which case I my own experience I have found them to be well made and very easily tuned. But that is just my experience. Every install is different. But I just didn't see the need for a shunt coil on the Sirio trucker 5000. JHMO. And thanks for the reply. Have a good one and be safe out on the road!!
 
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rabbiporkchop said:
After putting this Cap hat on here I'm kind of curious to see how much copper I'll be removing from the coil to bring it back to Resonance
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Your right on track and that antenna should work well.

I been leery about using closed loop hats because they can be a tree branch catcher. Just keep that in mind when driving down city streets.
 
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Man this is a god thread with a lot of great info. Keep up the good work gents. It helps a lot of people when things like this are posted and also recorded. Good stuff!! Hope that antenna does well Rabbiporkchop! Looks nice. Just keep it on the road and it should work well!! And please post up some pics of the final results. Always nice to see what things do in real world versus modeling them. Not that modeling doesn't help tremendously. But some people are easier taught by seeing and being hands on with things like this. Again, lots of good info here. You guys keep at it!!!
 
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222DBFL said:
Question, why would this be needed for an antenna with a loading coil already built onto the antenna. I never had an issue tuning any of my Sirio performer 5000 antennas with an analyzer. Granted they aren't the trucker version, but the concept is still the same. All that has been done is the loading coil has been moved up 8" or so. Or am I missing something here? The antenna should tune to R=50, X=0, VSWR 1:1 or there abouts depending on how well you install it and other factors as well. All of mine have tuned very well and all work very well. Like I said, I could be way off base here. But why the need for a shunt coil on an antenna that has a loading coil to match it to 50 ohms or near 50 ohms?
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Breadlove mount 4in. w/ extra bonding. I can not get a good swr or even a good X or R. I think I will take the Sirio 5000 apart and see if anything is wrong. It worked on the mag mount, why not with a hart mount?
 

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