Sirio 3 element SWR Question

[fourstringburn]

Nice, glad you got it!

Those looked like some sort of twist lock on those elements where you just slide them out to length. That would have been more convenient especially since you got few chances to cut elements and get it right.

Nice set up you have with that rotor. I run a 3 element Maco using the same rotor with a hy-gain YRC-1 rotor controller that lets me use any two of my rig control software programs to easily point and click where I want the beam heading.

Pointed west right now but nothing heard. I'll give you a shout if I do.

Good DX to you!

73

 

[BJ radionut]

So for anybody else benefit:
What were the final lengths on the elements??

 

[freecell]

well sirio was kind enough to give us the length of the reflector @ 5740 mm. from the manufacturer (if not altered) that puts the reflector @ a length of 18.832 feet.

since we know that the typical increase in length for the reflector over the driven element is 5% we can work backwards from the reflector to determine the length of the driven element.

driven element = 18.832 X 0.95 = 17.890 feet.

now given the driven element length and knowing that the typical decrease in director length referenced to the driven element is also 5%.

director element = 17.890 X 0.95 = 16.995 feet.

the operating frequency of the driven element is approximately 27.500 mhz
.

 

[DXcarpenter]

Nice, glad you got it!

Those looked like some sort of twist lock on those elements where you just slide them out to length. That would have been more convenient especially since you got few chances to cut elements and get it right.

Nice set up you have with that rotor. I run a 3 element Maco using the same rotor with a hy-gain YRC-1 rotor controller that lets me use any two of my rig control software programs to easily point and click where I want the beam heading.

Pointed west right now but nothing heard. I'll give you a shout if I do.

Good DX to you!

73

Thank you for the compliments... Yeah the elements should have some sort of telescopic tuning in them.... I think they just run them proud knowing there long and need to be cut for higher bands.. Man, I was a little nervous checking match after cutting and reassembling.. lol I got lucky.. Conditions fell out around 12:30 PST Made some good contacts prior. WI, AL, ILL, MI..
Hope to catch up with you on the band...
73's

 

[Robb]

Hey guys... Having a cup of coffee and reading replies.... Thank you for the info... One thing I didn't check was the length of the 8mm end pieces.... Reflector, driven, director.. As you can see in tuning table chart.... Just a little nervous cutting elements... I did set gamma for 27.5 specs but not the end elements.. Its up on mast now.... Looks like I'll be taking it down today to get her dialed in... I'm usually on 27.385.. And sometimes go above ch 40.... the mm to inches is a pain, but it is what it is.. At least we got sunny weather today.....

That antenna does NOT need to be trimmed - right out of the box. Not for CB anyway; 10m - yes. Be careful! You can't put it back on, lol.

I would just make SURE that the assembled dimensions are correct to the instructions. Helps if you have/use a tape mesure that also shows the mm/cm scale. I went out and bought a tape measure to be sure.

 

[DXcarpenter]

So for anybody else benefit:
What were the final lengths on the elements??

Didn't see your post till right now...Well this is what I came up with..
Gamma tuning" L1 37 1/2" L2 20 3/8"
A (Reflector) 31 3/4"
B (Driven) 21 1/16'
C Director) 18 11/16'
73's

 

[DXcarpenter]

That antenna does NOT need to be trimmed - right out of the box. Not for CB anyway; 10m - yes. Be careful! You can't put it back on, lol.

I would just make SURE that the assembled dimensions are correct to the instructions. Helps if you have/use a tape mesure that also shows the mm/cm scale. I went out and bought a tape measure to be sure.

Yes sir... I used a mm to inches calculator and a decimal to fraction conversion tool.... Thats what I thought too is it would be ready to rock on citizen band besides tha gamma tuning.... All good.... We seem to get lucky today.....
Thabks for the advice..
73's

 

[Staybolt]

*Take the antenna down (sorry!)
*Place the reflector side on the ground and then point the beam straight up in the air supported by a 2x4 or something similar.
*Keep it away from any other metal for at least 25-30 ft.
*Tune the gamma match with an antenna analyzer right at the feed point with a VERY short (1 ft/less) jumper.
*Tune for lowest SWR @ ch 20 (27.205Mhz).

Should be good to go. Had the same problem you had with the 4 element version and was told by an old salt that is the best way to tune a Yagi beam. The old salt was right, as usual . . .

EXACTLY how i tuned my Maco 5 element.

 

[Dusty1USA]

Hey guys... I just purchased a 3 element Sirio Antenna.... Everything went together good.. before erecting it; I set swr Gama tune to specs on instructions... MM to inches calculator was used.... The lowest I could get it was 1.4:1.. on channel 40.. channel 1 was 1.2:1 match..
After mounting it up on 30ft mast... I was 2.0:1 on channel 40.. and and 1 5:1 on chanel 1.... I did go below channel 1 and its flat match on 26.815..
I did tinker with it before erecting it but couldn't seem to get it down above channel 40 where I'm I'm usually QSO ing...... Any body here on forum have some expertise in these antennas?, Any help would be great.... Thank you...

I just got mine in the mail yesterday. Put it together today. I used an online 3 element yagi calculator for the dimensions of each element at a center freq. of 27.235, Ch. 24 then I adjusted the elements to match the dimensions the calculator gave me.
I did not cut any of the elements. I locked the smallest tube in place with the screws where the pre-drilled holes aligned with the next section.
Then I slid that next section into the larger section that attaches to the boom until I got the desired length, drilled new holes and locked it in place. Did that with all the elements. Installed the gamma match as per the instructions that came with the antenna.
I have it sitting on 4 sawhorses in the yard about 4' off the ground. Will put it up on a 16' pole tomorrow for the final tuning before it goes up on a 43' tilt over mast I made that currently holds a Moxon beam that the new 3 element will replace.
Just for S&G I connected a coax to see what kind of ballpark I was in on the swr.
I got a reading of 1.2:1 on ch. 1, 1.1:1 on ch. 20 and 40.
Haven't even tried to tune the gamma match yet.
Will put it up on the 16' pole tomorrow and mess with the gamma match a little to see if it will get any lower but if the swr stays where it is now when I put it up on the pole it will be good enough to go with if moving the adjustment on the gamma doesn't improve it.
Sometimes you just get lucky.

 

[Crawdad]

I just got mine in the mail yesterday. Put it together today. I used an online 3 element yagi calculator for the dimensions of each element at a center freq. of 27.235, Ch. 24 then I adjusted the elements to match the dimensions the calculator gave me.
I did not cut any of the elements. I locked the smallest tube in place with the screws where the pre-drilled holes aligned with the next section.
Then I slid that next section into the larger section that attaches to the boom until I got the desired length, drilled new holes and locked it in place. Did that with all the elements. Installed the gamma match as per the instructions that came with the antenna.
I have it sitting on 4 sawhorses in the yard about 4' off the ground. Will put it up on a 16' pole tomorrow for the final tuning before it goes up on a 43' tilt over mast I made that currently holds a Moxon beam that the new 3 element will replace.
Just for S&G I connected a coax to see what kind of ballpark I was in on the swr.
I got a reading of 1.2:1 on ch. 1, 1.1:1 on ch. 20 and 40.
Haven't even tried to tune the gamma match yet.
Will put it up on the 16' pole tomorrow and mess with the gamma match a little to see if it will get any lower but if the swr stays where it is now when I put it up on the pole it will be good enough to go with if moving the adjustment on the gamma doesn't improve it.
Sometimes you just get lucky.

Tuning with an analyzer or VNA, or just a meter?

 

[Dusty1USA]

Tuning with an analyzer or VNA, or just a meter?

I just have a meter. I have not attempted any tuning yet, the readings I got were from the initial construction and sitting 4' off the ground on sawhorses.
Will be putting it up on a 16' pole this morning and will see what that does to the swr readings.
Will post an update at that time.

 

[Crawdad]

I just have a meter. I have not attempted any tuning yet, the readings I got were from the initial construction and sitting 4' off the ground on sawhorses.
Will be putting it up on a 16' pole this morning and will see what that does to the swr readings.
Will post an update at that time.

Hope you don't mind a bit of unsolicited advice. In tuning my yagi with an analyzer I learned the very lowest SWR did not also equal the best numbers on reactance. So I aimed for something in the middle and ended up 1.2:1 with very low reactance levels along with a high Return Loss number (higher the better). On-the-air results have been good.
Chasing the fabled 1:1 is not always the best approach as SWR doesn't tell the whole story. Enjoy your Yagi.

7 3

 

[Dusty1USA]

Update.
Ok, I got er up on a 16' pole. Came in and checked the swr readings.
Now I have 1.02:1 on ch. 20 and 40 and a 1.18:1 on ch. 1.
I haven't tried to tune the gamma match at all and I don't think I will.
Leave well enough alone right?
Like I said, sometimes we just get lucky.
This is the 3 element yagi beam calculator that I used to get the dimensions for the 3 elements at a center freq. of 27.235.

https://www.wa2ooo.com/yagicalculator.html

 

[Dusty1USA]

Hope you don't mind a bit of unsolicited advice. In tuning my yagi with an analyzer I learned the very lowest SWR did not also equal the best numbers on reactance. So I aimed for something in the middle and ended up 1.2:1 with very low reactance levels along with a high Return Loss number (higher the better). On-the-air results have been good.
Chasing the fabled 1:1 is not always the best approach as SWR doesn't tell the whole story. Enjoy your Yagi.

7 3

All advice is greatly appreciated. Especially since I know almost nothing about what I am doing.
Wish I had an analyzer. Barely scraped up the coins to buy the beam. This is one expensive hobby.
But when my wife complained about how much I was spending I just told her it's cheaper than a bass boat.

 

[Crawdad]

All advice is greatly appreciated. Especially since I know almost nothing about what I am doing.
Wish I had an analyzer. Barely scraped up the coins to buy the beam. This is one expensive hobby.
But when my wife complained about how much I was spending I just told her it's cheaper than a bass boat.

But you're learning with everything you do, right? I'm very fortunate to have the analyzer, found a gently used one at a good price. They say owning a boat is like throwing money into a hole in the water, playing radio seems like a hole in the air to chuck bucks into.

7 3