Base Sirio 2008 vs 2016

[Greg T]

I've decided to get a new antenna and have narrowed it down to a comparo between the Sirio 2008 vs Sirio 2016. I'm sure there are people here that know a lot more about antennae than I. So, the 2008 has 8 GP radials at 1320mm each. The 2016 has 16 GP radials at 700mm each. Question: Is one going to be better than the other when it comes to all around use? The gain is the same on both at 1.3 DBd and the total length is similar. Pics are below. I was always taught that long radials will out perform the short ones. But then I see ham guys burying 16, 32 or 64 radials in the ground.
Thoughts will be extremely appreciated.

 

[The DB]

The short version of all this is ground mounted antenna systems that have all those radials and elevated antenna systems have very different needs.

The not so short answer...

When it comes to the number of radials of a ground mounted antenna vs elevated antenna for hams, that is something that is mostly referring to 1/4 wavelength antennas. Most home made ground mounted antennas are 1/4 wavelength, and for some frequencies these can get to be very big. Some of these get to be so big that what many people would think is a tower to add antennas on is actually the antenna itself... Many of these antennas simply cannot be mounted at any height do to their size and weight. In addition to size, sometimes their are other reasons to mount an antenna directly on the ground. Perhaps it is an experiment, or perhaps do to HOA rules, or perhaps other reasons.

The earth itself is the greatest enemy for antenna performance, so in the case of ground mounted antennas, more radials effectively makes the earth more favorable to the antenna, and not just for performance. The upper limit is about 120 radials, but as you add more and more you get diminishing returns. From here it basically depends on how much of a perfectionist you are. 20 is acceptable for a lot of people, especially those who take such antennas with them and set them up and take them down often, while others insist on their own amounts.

Elevated radials work somewhat differently. 1/4 wavelength elevated antennas need to have said radials, but longer antennas such as 1/2 and 5/8 wavelength antennas simply don't need them as much. In these cases it is entirely possible to set up an antenna that has no need for radials at all. That isn't to say radials don't benefit these antennas, for example, 1/4 wavelength radials are very good at attracting RF energy, and keeping it from the feed line and mast below. They also lower the natural feed point impedance of the antenna, generally making matching more efficient, and often smaller in size as well.


The DB

 

[Greg T]

The short version of all this is ground mounted antenna systems that have all those radials and elevated antenna systems have very different needs.

The not so short answer...

When it comes to the number of radials of a ground mounted antenna vs elevated antenna for hams, that is something that is mostly referring to 1/4 wavelength antennas. Most home made ground mounted antennas are 1/4 wavelength, and for some frequencies these can get to be very big. Some of these get to be so big that what many people would think is a tower to add antennas on is actually the antenna itself... Many of these antennas simply cannot be mounted at any height do to their size and weight. In addition to size, sometimes their are other reasons to mount an antenna directly on the ground. Perhaps it is an experiment, or perhaps do to HOA rules, or perhaps other reasons.

The earth itself is the greatest enemy for antenna performance, so in the case of ground mounted antennas, more radials effectively makes the earth more favorable to the antenna, and not just for performance. The upper limit is about 120 radials, but as you add more and more you get diminishing returns. From here it basically depends on how much of a perfectionist you are. 20 is acceptable for a lot of people, especially those who take such antennas with them and set them up and take them down often, while others insist on their own amounts.

Elevated radials work somewhat differently. 1/4 wavelength elevated antennas need to have said radials, but longer antennas such as 1/2 and 5/8 wavelength antennas simply don't need them as much. In these cases it is entirely possible to set up an antenna that has no need for radials at all. That isn't to say radials don't benefit these antennas, for example, 1/4 wavelength radials are very good at attracting RF energy, and keeping it from the feed line and mast below. They also lower the natural feed point impedance of the antenna, generally making matching more efficient, and often smaller in size as well.


The DB

Excellent info, and I thank you. So, to sum it up, because there are fewer and longer radials on the 2008, it would be a better choice?

 

[Shockwave]

The truth is both of these antennas are just about identical in signal performance. If it used four 1/4 wavelength radials, you might pick up .2db on the horizon. When I first tested the 2016, I really thought those short radials did almost nothing at this frequency. Until I started pulling every other one off, one by one and watched how much the impedance and resonant frequency shifted.

While the difference in signal is small, the difference with RFI is not. End fed antennas simply have more CMC problems when there is not a good 1/4 wave radiator attached at the feedpoint, to bleed that current off. If you or your neighbors have nice audio systems with long speaker wires and you run a linear, the level of interference generated by CMC, becomes more important than the small change in signal.

With this CMC issue in mind, the S-827 is a step up from either of the other two. The V-58 and SP-500 are a bit better, with full length radials. Both versions of the Sirio Gain-Master, are in a league entirely of their own, as far as the ability to virtually eliminate RFI problems and use no radials. If you use the 2016 or the 2008, be sure to remove the bird perch ball at the top and retune accordingly (add a few inches). It's not a matter of if a bird will land on it, jump off and bend the top over, it's a matter of when.

 

[Greg T]

The truth is both of these antennas are just about identical in signal performance. If it used four 1/4 wavelength radials, you might pick up .2db on the horizon. When I first tested the 2016, I really thought those short radials did almost nothing at this frequency. Until I started pulling every other one off, one by one and watched how much the impedance and resonant frequency shifted.

While the difference in signal is small, the difference with RFI is not. End fed antennas simply have more CMC problems when there is not a good 1/4 wave radiator attached at the feedpoint, to bleed that current off. If you or your neighbors have nice audio systems with long speaker wires and you run a linear, the level of interference generated by CMC, becomes more important than the small change in signal.

With this CMC issue in mind, the S-827 is a step up from either of the other two. The V-58 and SP-500 are a bit better, with full length radials. Both versions of the Sirio Gain-Master, are in a league entirely of their own, as far as the ability to virtually eliminate RFI problems and use no radials. If you use the 2016 or the 2008, be sure to remove the bird perch ball at the top and retune accordingly (add a few inches). It's not a matter of if a bird will land on it, jump off and bend the top over, it's a matter of when.

Thank you, sir. The reason I am not going to get the 827 or the SPT-500 (my first choice) is because the GP radials are too long and will be nearly impossible to install due to power lines. Once the antenna is raised up over them, it would not be an issue, but I have no way to get the antenna up there with those full length radials, so I am compromising for the purpose of installation. At this time, I am using a Sigma Venom 5/8 silver rod. The one with the useless "S" shaped radials that are about 12" or so. I was hoping one of these Sirios would be a decent upgrade to what I have, since they actually have a ground plane..
Oh, and I do have an ugly balun at the feed point, and a low pass filter in the shack. Probably not necessary with today's electronics, but I had one, so, why not? Also, I can't use my DX-500 on AM because my radio is too hot, so I only use power on SSB.
Current Sigma below:

 

[Shockwave]

Thank you, sir. The reason I am not going to get the 827 or the SPT-500 (my first choice) is because the GP radials are too long and will be nearly impossible to install due to power lines. Once the antenna is raised up over them, it would not be an issue, but I have no way to get the antenna up there with those full length radials, so I am compromising for the purpose of installation. At this time, I am using a Sigma Venom 5/8 silver rod. The one with the useless "S" shaped radials that are about 12" or so. I was hoping one of these Sirios would be a decent upgrade to what I have, since they actually have a ground plane..

That info does change things. If you've installed an antenna in a spot where 8 foot radials could contact power lines during the install, that is a serious issue by itself. If any part of the those radials could touch power lines going up, any part of the existing antenna can touch them if it falls over in a storm. Simply put, if those are primary wires, the antenna must be professionally removed at once.

If they are secondary wires, you may choose to run the risk of leaving it there but I would NEVER consider going back to swap it out with anything else. Break the number one grounding rule and ground the outside of the coax back to the house AC ground with heavy wire. Not for lightning protection but in case that metal antenna ever falls on the secondary wires. You will see no signal improvement with the choices you mention and only risk electrocution for no gain. If I were ever forced into the position of installing an antenna in a location like this, it would have to be inside a fiberglass radome, to even have a chance of consideration. Number one rule with antennas, is be safe.

 

[Greg T]

That info does change things. If you've installed an antenna in a spot where 8 foot radials could contact power lines during the install, that is a serious issue by itself. If any part of the those radials could touch power lines going up, any part of the existing antenna can touch them if it falls over in a storm. Simply put, if those are primary wires, the antenna must be professionally removed at once.

If they are secondary wires, you may choose to run the risk of leaving it there but I would NEVER consider going back to swap it out with anything else. Break the number one grounding rule and ground the outside of the coax back to the house AC ground with heavy wire. Not for lightning protection but in case that metal antenna ever falls on the secondary wires. You will see no signal improvement with the choices you mention and only risk electrocution for no gain. If I were ever forced into the position of installing an antenna in a location like this, it would have to be inside a fiberglass radome, to even have a chance of consideration. Number one rule with antennas, is be safe.

The antenna is actually approximately 12 feet away from my house and the power lines are coming in to my house from the pole and are about 9 feet, roughly speaking, from my mast. It's not the electrical connection that worries me as I have a large rubber hose covering the lines as they enter my home. The issue with the installation would be the physical interference as I am climbing the ladder with the antenna. The antenna is mounted on an old school television Tower of 12 ft mounted on top of my storage shed. There's a very slim chance of an electrocution incident, but the wires would be physically in the way when I lifted the antenna on to the mast.

 

[Shockwave]

The antenna is actually approximately 12 feet away from my house and the power lines are coming in to my house from the pole and are about 9 feet, roughly speaking, from my mast. It's not the electrical connection that worries me as I have a large rubber hose covering the lines as they enter my home. The issue with the installation would be the physical interference as I am climbing the ladder with the antenna. The antenna is mounted on an old school television Tower of 12 ft mounted on top of my storage shed. There's a very slim chance of an electrocution incident, but the wires would be physically in the way when I lifted the antenna on to the mast.

I understand but would still leave the antenna alone. There simply is not enough signal increase to chase after, even without the power line risk to deal with. If it ever fails and needs to be changed, I'd use a fiberglass antenna. The Sirio Gain Master is safer and will give performance better than four 1/4 wavelength radials, using none.

 

[Greg T]

Appreciate the info. Thank you, sir!!

 

[M0GVZ]

If anything needs to be done it's to improve your existing installation a little would to be to improve that balun. How have you constructed it? An air wound RF choke made from coiling the coax is a tuned circuit, the frequency it works on dependent on the number of turns and diameter of it and the coax used.

On an air wound balun they're very narrow banded and going from 5 turns of RG58 or RG213 with an internal diameter of 4.25" which you need for 11m to just 7 turns moves it's resonant frequency from 26-28MHz down to 19-20MHz, an 8MHz shift from just two extra turns. It goes from having > 8k Ohms of choking on 11m to a few hundred Ohms, virtually worthless.

What's even worse about air wound is that it's all reactive and get it wrong and it can actually make things worse. I prefer the wrapping coax around the ferrite core way of doing it. Much more broadbanded in it's peak choking, typically covering 15-20MHz of bandwidth, so much more tolerance for getting the turn count out a coil or two, and it's almost all resistive.

A chart for roll your own courtesy of G3TXQ (SK)

 

[Slowmover]

Turkey vultures. Do they bring luck or just vulture-shit?

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[Greg T]

If anything needs to be done it's to improve your existing installation a little would to be to improve that balun. How have you constructed it? An air wound RF choke made from coiling the coax is a tuned circuit, the frequency it works on dependent on the number of turns and diameter of it and the coax used.

On an air wound balun they're very narrow banded and going from 5 turns of RG58 or RG213 with an internal diameter of 4.25" which you need for 11m to just 7 turns moves it's resonant frequency from 26-28MHz down to 19-20MHz, an 8MHz shift from just two extra turns. It goes from having > 8k Ohms of choking on 11m to a few hundred Ohms, virtually worthless.

What's even worse about air wound is that it's all reactive and get it wrong and it can actually make things worse. I prefer the wrapping coax around the ferrite core way of doing it. Much more broadbanded in it's peak choking, typically covering 15-20MHz of bandwidth, so much more tolerance for getting the turn count out a coil or two, and it's almost all resistive.

A chart for roll your own courtesy of G3TXQ (SK)

I've used 5 turns of LMR-240 on a 4.25" O.D. core, affixed to the mast with a stand-off so that it is about 4" away from the mast. It completely eliminated my problem with RF in the shack, and smoothed out the bandwidth as well, making it not so peaky.

 

[Handy Andy]

View attachment 43812

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CAUTION:
Do not stare at or Stand Beneath the underside of Turkey Vulture with remaining eye...
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[Greg T]

The 2008 came in today. Hopefully have some temps above 50 pretty soon. Couldnt get a 2016 in the states.

 

[TruckerKevin]

How did this work out for you? I have been eyeballing that same antenna for my own personal and selfish needs