Sirio 3 element SWR Question

[DXcarpenter]

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...

 

[freecell]

is that the SY 27-3?

 

[fourstringburn]

I don't have any experience on this antenna but I can say you are tuning it like the instructions and CB shops say to tune a mobile CB antenna. Don't do this! You usually get a balanced higher SWR across the CB band at best by doing that.

Plus, what are using and where in the antenna system are you checking the tuning? You should check and tune the antenna with a jumper at the feed point into an analyzer for best results.

You Have an antenna with good bandwidth, it's best to tune it like that accordingly.

Tune the antenna at the frequency you operate most at and let the antennas bandwidth cover the rest of the frequencies above and below that point.

If you are using an antenna analyzer, you can sweep the SWR curve and see how much bandwidth of frequencies you have for a +/- 2.0 SWR at your lowest SWR you tuned. Operating at 1.9 SWR or less is perfectly fine.

You can use an antenna tuner in your shack which will let your radio see a much lower SWR but your antenna still remains the same. This maybe necessary if you run an amp that maybe sensitive to SWR readings over 1.5 as some manufactures claim.

We Hams often use antennas on bands that have a very high SWR. My wire antenna on 30 meters has a high SWR of 14:1 but my tuner can bring it down to a respectable 1.4:1. so I can operate on that band even though the losses are high. I can compensate a portion of those losses by using an amp so I can use the band and I often do and have made plenty of world wide DX contacts with it.

Your antenna appears to be similar to a Maco 103c and I use this for 10 and 11 meters to cover both bands. I tuned mine for the flattest SWR around 27.900 which is close enough to be in the middle of both bands and my tuner cleans up the SWR above and below that point.

 

[tecnicoloco]

3 element yagi beam by sirio

http://www.dnjradio.com//product_info.php?cPath=27_59&products_id=258

Mine is tuned at 26.500, 20Feet high and the swr is 1.2.1 bandwith is a little over 800 khz

 

[Robb]

*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 . . .

 

[midnight special]

yep what robb said,,,,,

 

[DXcarpenter]

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.. Atleast we got sunny weather today.....

 

[BJ radionut]

Never liked antennas, that did not utilize telescoping elements.
Thus require "cutting" to optimize frequency usage.
Spacing of elements vary also "slightly" to optimize.
Key though is to sit length and spacing to where you use antenna the most.
Thus, in your case by your discussion, this antenna should be set-up for best around 27.450 +/-. Then forget the rest, where it falls is where it falls.
GL
All the Best
Gary



WC7I Antenna info PLUS SWR explained

 

[Shadetree Mechanic]

I have a 27-4 that I have not put up yet. I don't plan on cutting the elements. I am going to slit the ends with a hack saw, and use stainless hose clamps. This way, I can slide the elements in instead of cutting.

 

[DXcarpenter]

Never liked antennas, that did not utilize telescoping elements.
Thus require "cutting" to optimize frequency usage.
Spacing of elements vary also "slightly" to optimize.
Key though is to sit length and spacing to where you use antenna the most.
Thus, in your case by your discussion, this antenna should be set-up for best around 27.450 +/-. Then forget the rest, where it falls is where it falls.
GL
All the Best
Gary

View attachment 48677

Thanks for the chart Gary... Very informative..
73's
Phil

 

[DXcarpenter]

I have a 27-4 that I have not put up yet. I don't plan on cutting the elements. I am going to slit the ends with a hack saw, and use stainless hose clamps. This way, I can slide the elements in instead of cutting.

Hmmm? Sounds like a good idea.. I wish I did have an antenna analyzer.... It looks like I'll be busy today...

 

[fourstringburn]

Hmmm? Sounds like a good idea.. I wish I did have an antenna analyzer.... It looks like I'll be busy today...

Yes, an analyzer will save a lot of time because it'll show where your antenna is at and which way to adjust it so you can get it where you want it. Anyone you know have one to borrow?

Robb's advice of taking it down and tuning like so is an option. This can let you use your radio and external SWR meter( assuming you have a decent one) be at the source by taking your power supply outside.

Your antenna is just a bit too long for where you want it and I would think it has enough adjustments on each element and the Gamma match to shorten it up to the frequency you want it without cutting.

The bandwidth on it should easily cover the CB band once you get it centered there. A flat match across the whole band isn't likely, probably about 3 channels on either side and you'll start seeing the SWR rise some. This is where a tuner can be used once the SWR gets higher as you move even further away from the lowest SWR point.

Below is a sample of a Rigexpert SWR graph. The antenna shown is being tested at 28.850 MHz at a total bandwidth of 1700 kHz or 850 kHz per side as shown. You can see by the cursor arrow at the bottom of the screen the lowest SWR is to the right so the antenna needs to be shortened if a flat match is desired. You can easily see and estimate how far your antenna will cover at a flat match and how far it can go to stay below a 2.0 SWR. I would have set the analyzer to sweep at a 2000 kHz range to cover more of the right side of center.

So this antenna tuned at this point would let you easily go up or down 800 kHz or 80 CB channels and stay just below a 2.0 SWR.

See how nice and easy an antenna analyzer can be?

 

[DXcarpenter]

Yes, an analyzer will save a lot of time because it'll show where your antenna is at and which way to adjust it so you can get it where you want it. Anyone you know have one to borrow?

Robb's advice of taking it down and tuning like so is an option. This can let you use your radio and external SWR meter( assuming you have a decent one) be at the source by taking your power supply outside.

Your antenna is just a bit too long for where you want it and I would think it has enough adjustments on each element and the Gamma match to shorten it up to the frequency you want it without cutting.

The bandwidth on it should easily cover the CB band once you get it centered there. A flat match across the whole band isn't likely, probably about 3 channels on either side and you'll start seeing the SWR rise some. This is where a tuner can be used once the SWR gets higher as you move even further away from the lowest SWR point.

Below is a sample of a Rigexpert SWR graph. The antenna shown is being tested at 28.850 MHz at a total bandwidth of 1700 kHz or 850 kHz per side as shown. You can see by the cursor arrow at the bottom of the screen the lowest SWR is to the right so the antenna needs to be shortened if a flat match is desired. You can easily see and estimate how far your antenna will cover at a flat match and how far it can go to stay below a 2.0 SWR. I would have set the analyzer to sweep at a 2000 kHz range to cover more of the right side of center.

So this antenna tuned at this point would let you easily go up or down 800 kHz or 80 CB channels and stay just below a 2.0 SWR.

See how nice and easy an antenna analyzer can be?

View attachment 48680

Awesome information.. Thank you... I am gonna set to specs using the 27.0 tuning table.... I can't take down whole antenna and use Robs advice being I have no help today.. I'm on my own... I'll keep you guys posted.... Thabks again ya'll..

 

[freecell]

element lengths for 27.000 mhz.

reflector element = 19.133 feet or 19 feet 1.59 inches
driven element = 18.222 feet or 18 feet 2.66 inches
director element = 17.310 feet or 17 feet 3.75 inches

element lengths for 27.385 mhz.

reflector element = 18.864 feet or 18 feet 10.36 inches
driven element = 17.966 feet or 17 feet 11.59 inches
director element = 17.067 feet or 17 feet .80 inches

element lengths for 27.450 mhz.

reflector element = 18.819 feet or 18 feet 9.82 inches
driven element = 17.923 feet or 17 feet 11 inches
director element = 17.026 feet or 17 feet .31 inches

element lengths for 28.375 mhz.

reflector element = 18.205 feet or 18 feet 2.46 inches
driven element = 17.339 feet or 17 feet 4 inches
director element = 16.472 feet or 16 feet 5.66 inches

for one half element length measure from boom to end,
divide all measurements listed above by 2 for center.

 

[DXcarpenter]

Hey everbody.... UPDATE on my Sirio tune.... We did set everything to 27.0 on specs... Had to cut almost 2 inches off on each element..1:1 1 405 "perfect" SWRs starts moving up around 805... I'm happy.... I am using a Yaesu G-450A rotar... Have Antron right on top.. Good SWRs on both antennas... Alpha Delta switch box... Thanks for all replies regarding this matter.. You guys are awesome!! The 11m band is hopping right now... I'm usually on 385 LSB.. Hope to hear some of yous on my RX... 73's
9144 NorCal South Bay
Aka CDX-501