New Sirio Tornado 27

[222DBFL]

Sorry,misread the post. Will re read through them again. If the 1ft coax jumper is showing the VSWR flat at where it'a supposed to be, but is the impedance at 50ohms? If not the you will get different readings using your 50ft coax. This is why I suggested adding a 9ft or even a 10ft coax jumper to the existing 50ft. Give this a try and see what you get as 60ft is closer to an electrical 1/2 wave tuned coax jumper for 27.400 or so.
Sorry I misread the post, but I see you edited and I got it now.
Like I said, give the longer coax jumper a try at the radio end of the coax. Post up results using a 9-10ft coax jumper if possible. Curious what you will see. I would also connect a dummy load to the end of the 1ft coax jumper and your mfj meter and set it to said freq where antenna tuned and see what you get for readings and use this as a base line for your future tuning. Make sense?? Hopefully so.

 

[222DBFL]

Don't just look at the VSWR as the impedance is off where you show a flat VSWR. You want both impedance and VSWR to be correctly tuned. Again, hope this makes sense.

 

[Galaxy 959]

Yea I need to find some longer jumpers. 3' is longest I have. I'm happy with the reading I got now with the 50" coax. Just not sure why its this good with the antenna at 35" instead of like 40.5" where it should be. Its almost right at 50ohms also. This coax was 50' when I ordered it. I have cut it some to put on the new end but not much at all. A couple inches maybe at each end. This is Ch14 where I talk most. But still the 35" top section still baffles me.

 

[Galaxy 959]

I'm gonna run with this. But I'm going to get some LMR400 with the ends installed when I get a chance. I have RG8U now.

 

[543_Dallas]

Don't just look at the VSWR as the impedance is off where you show a flat VSWR. You want both impedance and VSWR to be correctly tuned. Again, hope this makes sense.

Is the only adjustment on this antenna length? If it is I wouldn't pay too much attention to resistance. Where it falls on 50 ohms may not present the lowest SWR. Tuning for the lowest reactance would be the way to go but that analyzer may not show that. The lowest reactance likely won't be the lowest SWR...flat swr is overrated anyway.

What is he gaining by changing coax lengths? The dramatic difference between the 50 ft length and the 1 ft seems like the 50 ft run is damaged or has a bad end.

I tuned a penetrator about a foot off the ground next to a small tree this weekend. It was 1.2 on the ground with 12 feet of rg8 and 1.1 40 feet in the air with an unknown length of rg213. I didn't pay attention to anything but SWR because that's all the user would care about. Seems like the reactance was around 6.

 

[222DBFL]

The coax shouldn't change the readings so as long as the impedance of the antenna is 50ohms. At this point any length of coax should work the same as far as readings go. This is why I say watch the impedance as well the VSWR, and not just the VSWR. And I still tnink the metal roof is interacting with the antenna some. You see what cutting the branches and moving the antenna a bit did. Now take and move it totally away from the roof and it may tune differently. This is not to say that you cant get a good match, just the reflection from the roof will be more predominate with the antenna being closer to the roof IMO. As you move it up and away from the roof, it would probably fall into line with the tuning chart. As it stands I tnink you are getting some reflection back from the antenna and thus its causing some changes in the length of the antenna itself due to the added metal under it. Again, this is JMHO, and I may be way off base here. But it's just what I beleive. At any rate, like I said, keep at it and if you are happy the way it's working, leave it. Have a good one and keep us updated!!

 

[Galaxy 959]

Is the only adjustment on this antenna length? If it is I wouldn't pay too much attention to resistance. Where it falls on 50 ohms may not present the lowest SWR. Tuning for the lowest reactance would be the way to go but that analyzer may not show that. The lowest reactance likely won't be the lowest SWR...flat swr is overrated anyway.

What is he gaining by changing coax lengths? The dramatic difference between the 50 ft length and the 1 ft seems like the 50 ft run is damaged or has a bad end.

I tuned a penetrator about a foot off the ground next to a small tree this weekend. It was 1.2 on the ground with 12 feet of rg8 and 1.1 40 feet in the air with an unknown length of rg213. I didn't pay attention to anything but SWR because that's all the user would care about. Seems like the reactance was around 6.

Yes the only adjustment is the length. The top section has set screw to move it up and down. According to the chart from Sirio its showing the correct flat SWR at 35" with the 1' jumper which I know is good at freq 27.600. Its LMR240 with amphenol ends professionally done. But with my 50' coax hooked to it SWR is way off. I didn't think it would change SWR regardless of coax length.

 

[222DBFL]

He isn't really gaining anything by changing coax length other then to make the radio happy. You don't want the radio seeing a bad impedance of 70ohms do you? Like you said and so did I, VSWR is not the only thing to look at. Reactance or impedance needs to be correct as well. And yes the antenna may not tune flat this way. And yes the only way to adjust this antenna is by the tip length 543.

 

[Galaxy 959]

The coax shouldn't change the readings so as long as the impedance of the antenna is 50ohms. At this point any length of coax should work the same as far as readings go. This is why I say watch the impedance as well the VSWR, and not just the VSWR. And I still tnink the metal roof is interacting with the antenna some. You see what cutting the branches and moving the antenna a bit did. Now take and move it totally away from the roof and it may tune differently. This is not to say that you cant get a good match, just the reflection from the roof will be more predominate with the antenna being closer to the roof IMO. As you move it up and away from the roof, it would probably fall into line with the tuning chart. As it stands I tnink you are getting some reflection back from the antenna and thus its causing some changes in the length of the antenna itself due to the added metal under it. Again, this is JMHO, and I may be way off base here. But it's just what I beleive. At any rate, like I said, keep at it and if you are happy the way it's working, leave it. Have a good one and keep us updated!!

Something is up with the area or coax or something. My antron 99 was on the same pole. It was to long also. Had to adjust the rings almost all the way up to make it shorter also for a good match. It was 1.2 across the 11 meter band.

 

[222DBFL]

Makes sense. And this antenna is exhibiting the same exact issues as far as tuning and length go. Things that make you go hmmmm. Metal roof!! I'll say no more LOL. Get the antenna up another 10ft and see what happens!! The higher you go the better. Just step up your conduit. Go 2" to 1.5" to 1.25". And use a 1 15/8" 8ft fence rail top post for the top section. This will get you above 30ft and being that antenna is so light, you shouldn't have any issues with the conduit. Again, JMHO, and some food for thought. Be safe and have a good night.

 

[Galaxy 959]

I will try to get it up higher somehow when I have time and see what happens. I want it above the trees. I need a 40' pole to do that. Thanks for all you guys input its greatly appreciated.

 

[543_Dallas]

An a99 is usually flat out of the box. If you were using the same 50 ft of coax with the a99 and getting a 1.2 I would be suspicious of that coax. An a99 or imax with bad swr can be because of a bad pl259 install. I've done that myself.

He isn't really gaining anything by changing coax length other then to make the radio happy. You don't want the radio seeing a bad impedance of 70ohms do you? Like you said and so did I, VSWR is not the only thing to look at. Reactance or impedance needs to be correct as well. And yes the antenna may not tune flat this way. And yes the only way to adjust this antenna is by the tip length 543.

A 75 ohm non reactive load is a 1.5 so 70 ain't bad at all.

The antenna may have less gain if you tune it for 50 ohms. You may get a higher swr reading at 50 ohms because of the reactance. There just isn't alot of adjustment with this antenna and he's doing a lot of work for no return.

With what he's working with the best he can do is install a run of good coax and tune for equal swr on 1 and 40, or lowest swr on his channel. Keep in mind that an mfj analyzer is not lab grade equipment.

 

[Galaxy 959]

I can get 55' of LMR400 from RF Parts with the Amphenols installed for $74 plus shipping. Thinking about just getting 60' so I have my coax when I get it 40' in the air.

 

[Galaxy 959]

An a99 is usually flat out of the box. If you were using the same 50 ft of coax with the a99 and getting a 1.2 I would be suspicious of that coax. An a99 or imax with bad swr can be because of a bad pl259 install. I've done that myself.




A 75 ohm non reactive load is a 1.5 so 70 ain't bad at all.

The antenna may have less gain if you tune it for 50 ohms. You may get a higher swr reading at 50 ohms because of the reactance. There just isn't alot of adjustment with this antenna and he's doing a lot of work for no return.

With what he's working with the best he can do is install a run of good coax and tune for equal swr on 1 and 40, or lowest swr on his channel. Keep in mind that an mfj analyzer is not lab grade equipment.

Yea its same coax. I put on cheap PL259's when I first got it. When I got the new Sirio I installed Amphenol ends. But that dont mean its done right. I just have a cheap 30 watt iron.

 

[222DBFL]

If you read back 543, he has and all metal roof. This coupled with the antenna being mounted to the house and having the antenna right next to the metal roof. Not so much with the coax and length. I understand what you are saying and agree, but his issue is something different IMO.
Now if he orders new coax and we see yet another change how can we be sure that his coax is bad without first placing a dummy load at the end and transmitting through it. I have also stated this in several of my posts. It's all up to the user in the end how he/she wants to run thier station. And I would not run my radios with a 70ohm load as that is not what they were made for. Yes it will work, but is correct?? I am not trying to argue with anyone and am by no means an expert on any of this matter! I know what I know from my own testing and experience. I had one of the sirio tornado antennas up and it tuned flat and had good R and X values using an MFJ269 and a bird 100w 50ohm dummy load as my reference for baseline readings from the mfj meter itself with a dummy load connected directly to the mfj meter. With this said, every install is different and all present their own issues. All I was trying to do was help 959. If you have any suggestions or think I am incorrect for thinking the roof of his house being metal won't have an effect on the antenna as its mounted to the side of the house and isn't that high off the ground. Again, thanks for any help.