New Sirio Tornado 27

[camaro1]

the antenna is not dc grounded,, there is no continuity between the center pin and shield, I have explained this before on this site and been told im wrong,,lol,, I have the antenna right here in front of me,,, I think I can work a meter

the center pin of the coax connector goes direct to the coil,, loops around the radiator and attaches to the radiator,, it is not tapped anywhere to the ground side

the threaded (ground) side of the coax connector goes directly to the mouning base and the 4 ground plane radials

that's it , no connection between the 2 sides anywhere

 

[222DBFL]

It's not a true DC grounded antenna. Here is my old base coil although it's been dismantled partially. Here is what I have Marconi for the bottom section, notice how the coil attaches to the antenna itself. Not a true DC grounded antenna. Don't mind the the other pipe above the base it's not the original aluminum piece. Like I said, I had taken this antenna apart. Here is what I do have though. The coil is approx 7 turns long and is approx 68" long made of 1/2" solid aluminum. The stub for the connector is approx 4.25" from the top to the bottom of the SO-239 connector or 3" for just the stub itself and about 1.25" for the connector under it. The coil connects to the main center radiator and then terminates at the bottom to the stub for the hot side of the antenna. The ground is achieved by going to the actual radial hub. Look at the photos and it will make more sense. Take into consideration that the measurements I took are approx. on the coil. The stub is actually correct length. I used a piece of wire wrapped around the coil for the measurement I got. It may not be that long, but it appears to be. Anyway. Here are the pics I have of the bottom section. Like I said, don't mind the hose clamp or the top piece of pipe as it is not the original piece. It's just there as I was going to rebuild antenna but the connector is shot. Also from bottom of base of antenna to the radial hub is 10". Not sure of measurement above this point as part of the antenna was cut off. But you can get an idea of what it's supposed to look like. Best measurements I could get Marconi. Hope it helps some.

 

[222DBFL]

Camaro1 is absolutely correct. This IS NOT A DC grounded antenna. It's transformer grounded. It shows no continuity between center and outer pin just like stated and attaches just like stated above by Camaro1. He beat me to the post LOL!!

 

[222DBFL]

More photos showing the continuity.

 

[222DBFL]

yeti-communications-ltd, didn't you take and make one of the sirio tornado antennas into a true DC grounded antenna at one time?? Or am I thinking of someone else? If you did in fact do the mod, any way you could post a couple pics of the way you did it as I think it would be very beneficial to some!! Thanks for any and all replies.

 

[camaro1]

last time this debate came up I posted pics, highlighted them and explained how the base and coil were set up and some on here that are posting about it again told me I had to be wrong and how the antenna wouldn't work if it wasn't dc grounded somewhere in the coil,lol

 

[222DBFL]

If they would make a few upgrades to the tornado antenna it would be a lot better of an antenna I beleive. True DC ground, beef up all joints and make all connection points less susceptible to water intrusion if not sealed properly. But I suppose if they added more to this antenna the price point would jump. But heck I would pay $50 extra for a more begged up antenna and one that is true DC ground. They have a good platform. Just needs some tweaking IMO.

 

[Marconi]

Thanks for the drawings...they are just fine and look professional to me, and using Paint no less. This confirms the old saying, "...a picture is worth a thousand words."

Yeti, the small spacing works, but I would agree it is a bit close.

the antenna is NOT dc ground in any way

Thanks for the info. Don't worry about the dimensions. I wasn't planning on modeling the inside, but I need to know where the isolation is and this helps a bunch.

I'll fiddle with the idea and see if I can get this 5/8 wave model to show a good match.

 

[Marconi]

last time this debate came up I posted pics, highlighted them and explained how the base and coil were set up and some on here that are posting about it again told me I had to be wrong and how the antenna wouldn't work if it wasn't dc grounded somewhere in the coil,lol

I remember that thread and you taking a flaming of sorts. I didn't have anything to add, so I hope I didn't give you any grief. You did good.

 

[Yeti Communications Ltd]

yeti-communications-ltd, didn't you take and make one of the sirio tornado antennas into a true DC grounded antenna at one time?? Or am I thinking of someone else? If you did in fact do the mod, any way you could post a couple pics of the way you did it as I think it would be very beneficial to some!! Thanks for any and all replies.

yes i did

this is the first insulator that the close by lighting strike blew out . the hole turned to carbon and shorted the antenna out @rf (also weakened the insulator to the point it cracked it but not evident by the pics.).lucky i saved these pics to my server as the original thread 222dbl is on about the pics have disappeared from (on another nameless forum)

 

[Yeti Communications Ltd]

to convert to true dc ground....as the pics are long gone i will try to descibe it

i removed the long brass rod from the so239 and cut it to about 20mm and screwed it back on the so239..this is where the tap point wire was soldered to (for the tap on the coil) ..the other end of that same brass rod i cut to 20=30mm long and left it on the coil (the other end of coil tap wire soldered to that.)

the the coil was lowered down over the insulator (so it covered the insulator) and the bottom of the coil was connected to ground via a small L bracket i made up ...

i MUST point out here i later replaced the coil with one the same dia but with 1.5 more turns on it as i found i didnt have quite enough inductance with the stock coil to do so in dc ground config other wise the antenna stayed the same length etc just a re-jig of the coil and how it was feed

the idea is based on this antenna which is a main stay with cbers down in my part of the world ..called a "station master' (often referred to as station disaster) or known as a "skip whip" which came in 1/2 wave or 5/8 format (latter with radials)

pic attached of the 1/2w skip whip (v26 mobileone version) for reference of what i did as far as dc ground method

sorry no pics of the mods i did to actual sirio antenna unless some one downloaded them from that other site before they disappeared

 

[Marconi]

Here is my model of the Tornado 27 made by Sirio.

It worked out OK with my guesstaments' for the dimensions and with some help from some friends. The pattern is skewed a bit, side to side, and this may be due to the way the matching is set to one side about 2" inches. It matches very well with the physical matching coil I added to the model's wire descriptions. The overlay I added, the 27 looks to compete pretty well with my Vector model, but it takes 2nd place in gain with a 1* degree increase at the maximum angle.

At 36' feet the model shows some CMC on the mast and that too might be due to the asymmetrical feed point design. I don't like the SWR bandwidth curve either. It shows a very narrow bandwidth too...at about 1.00-1.20 mhz for <2.00:1 SWR. For the guys that have a T27 does this narrow bandwidth sound about right?

Thanks to the guys that help me get the dimensions together. I'm still not sure about the length and diameter for the radials however. I used 105" x 1/3" radials and that might be wrong.

 

[Yeti Communications Ltd]

At 36' feet the model shows some CMC on the mast and that too might be due to the asymmetrical feed point design. I don't like the SWR bandwidth curve either. It shows a very narrow bandwidth too...at about 1.00-1.20 mhz for <2.00:1 SWR. For the guys that have a T27 does this narrow bandwidth sound about right?

Thanks to the guys that help me get the dimensions together. I'm still not sure about the length and diameter for the radials however. I used 105" x 1/3" radials and that might be wrong.

agreed about the common mode ...to be expected with a open feed (non dc ground) gp which is all it really is coil or not

i had 2mhz bandwidth @ 30ft to base <2.0:1 which is on par with similar antennas i have used
radials are not 105"..they are shorter than that they are 81 " long (measured from base tube to tip inserted into carrier hub)

 

[222DBFL]

The tornado is a good antenna for what it is. Sirio could easily re design the antenna to be DC grounded. The mod that Yeti Comm. Ltd. performed did not look to be that hard. If I had the chance I would have done this mod myself. Was planning on it until I broke the antenna. And I beleive this solved some CMC issues as well as helping with match and VSWR of antenna from the literature I read at another place. Correct me if I am wrong here Yeti Comm. Ltd.
What can be done for now though in the case of Galaxy 959 is to maybe to add a 1:1 balun choke isolator. Balun designs makes some pretty nice looking ones. Get a quality one Galaxy 959. And yes there are many many other 1:1 baluns that can be used as far as companies. I just listed the one I think has some quality ones. JMO you can say. This may help with his issue of tuning. But the antenna needs to be shortened for sure the way it is. With a VSWR of 1.4:1 on channel 40 and 1.2:1 on channel 1 I think antenna is still too long regardless of what other issues may be present.
959, work on getting the antenna back down at some point and marking the current location of the top whip with a sharpie. Then shorten the whip some and mark it again with a different color sharpie if possible. Then take note of all measurements. Keep at it man, I think you can still obtain better readings by doing so as it does appear that your top whip is too tall regardless of antenna height or relation to the roof. JMHO. And like I said, a 1:1 balun and also performing the mod described above by Yeti Comm. Ltd. to make the antenna a true DC grounded antenna, is a good idea if you are planning on keeping this antenna for a long time. Again JMHO.
Also make sure you weather proof the coax connector as well as the both the coil connection points and the top of the stub for the SO239 to the coil. Water can get into these areas and cause some issues. These are all things I was in the process of addressing but like I said, my antenna was destroyed after falling 20ft to the ground!! Again, DONT work by yourself!! JMHO!! At any rate, for what it's worth, the Tornado is a good antenna but definitely could use some necessary remodeling to make it a better antenna. Cost wise it's a good antenna, but as to why sirio didn't make it a true DC grounded antenna I do not know the reason. At ant rate, Galaxy 959, I hope you get your issues worked out, and be safe while doing so. Good day!!

 

[543_Dallas]

the center pin of the coax connector goes direct to the coil,, loops around the radiator and attaches to the radiator,, it is not tapped anywhere to the ground side

At a glance I thought this was the same setup that Mr Coily uses but didn't notice the coil was not tapped. After looking at the close up pic I don't see how anyone could disagree with you.