Sirio 827 with longer radials

[Marconi]

So, for all the folks that don't have the ARRL Handbook, here is a link to the study in the ARRL on Radials and Grounding, that I think maybe Connor M0GVZ was referencing in regards to this Sirio 827 radial discussion.

Report in the ARRL was published by John Stanley K4ERO and others who did their own studies. Click on link below.

https://www.kn5l.net/GroundRadialStudy/

NOTE: The Eznec model below is for an Horizontal Inverted V antenna. The title is at the very top of the box shown below. This model is presented at the bottom of this report.

It shows a Horizontal Inverted V antenna pattern at 40' feet high and is noted in black as (PRIMARY). This modeling overlay is comparing a Horizontal Inverted V to several ground mounted Vertical antenna patterns that are mounted on the ground at 14 MHz, just to be clear.

Don't be confused by the nice gain shown for the Inverted V...this is a Horizontal antenna pattern at 40' feet in the air.

Sorry if the image did not post. Check the PDF file below.

 

[Alexis Mercado]

Ok guys, here are the results.

SWR —— Short Radials— Long Radials

2.0 ———— 28,275 ————— 28,040
1.5 ———— 27,945 ————— 27,770
1.0 ———— 27,500 —— ——— 27,330
1.5 ———— 26,885 ————— 26,790
2.0 ———— 26,015 —— ——— 26,100

Bandwidth = 2,260 KHz —- —1,940KHz

As you can see, replacing the 8 short radials with 4 long radials, bandwidth got narrowed by 320Khz ,
160 KHz down and 160 KHz up on band edges.

Lowest SWR frequency went down close to channel 33.

I didn’t have to retune the antenna by adjusting antenna length.

These measurements were made with the antenna 6 feet above the roof.

What do these figures tell you ?

 

[Alexis Mercado]

Here are the results with the antenna approximately 15 feet above the roof.

SWR ——- Short Radials ——- Long Radials
2.0. ———-- 28,150 ——————-- 28,450
1.5 ——- —- 27,810 ——————- 27,880
1.0 ——-—- 27,255 ——————- 26,965
1.5 ———-- 26,540 ———- ——— 26,415
2.0 ———-- 25,820 ———- ——— 26,100

Bandwidth= 2,330 KHz ——— 2,350 KHz ( wider bandwidth of 20 KHz )

As you can see in my case, replacing the 8 short radials for 4 longer ones, It is like if you had to shorten the antenna a little bit. In my case it is beneficial because I can use a phone portion of 10 meter band as well.

Lowest SWR shifted from channel 22 to channel to channel 1.

What I don’t understand is this: How come the lowest SWR shifted to channel 1 and at the same time usable frequency went up to 28,450 ?

Also I noticed that bandwidth tend to wide a little, the higher the antenna. See previous post to compare.

RX and TX improved a little , about 1-2 db’s.

I have a Gain Master about 12 higher than the 827.

Before the change, I had to use the Gain Master for the guys of the north of the island in order to hear them better. Guys from the South could be heard better with the 827. I live between mountains, 1,660 feet above sea level.

After the change, signals from the north are the same with both antennas. Signals from the south are stronger.

What do these readings tell you ?

 

[Alexis Mercado]

Tomorrow I will take a picture of my modified Sirio 827 for you to see.

 

[Marconi]

Alexis, I would like to try and compare my earlier models with 55" vs. 105" radials on the 827, but my model was at 36' feet and I need more dimensions.

Can you be more specific how high your 827 antenna is to the feed point when you raised it up, or tell me how high is your roof?

How long did you make your 4 longer radials in this case?

What is the diameter for the longer radials?

If you know, what was your stock radiator length for your 827 with 8 short radials, measured from the top of the coil to the tip?

What was the new radiator length after you modified the 827 with longer radials?

I see you tell us you didn't bother to retune your antenna. I had to shorten the 827 with 4 x 105" radials by 12.5" inches to keep the match close to the same on both models, and I also had to change the matching coil a little.

 

[Alexis Mercado]

Marconi, here is the information you requested:

House height: 10 feet
Note: House is made of concrete. Roof is flat concrete roof.

Antenna feed point height above roof: 15 feet

4 Long radial used: 108” Super Magnum Antenna radials. First 55” are 0.325” diameter. Last 53” are 0.188” diameter.

Radiator length: 253”

• Like I said before, I didn’t adjust the radiator length after installing the longer radials. The 8 shorter radial are 55.1875 “ long. I bought the antenna used and left the antenna length unaltered from the guy I got it.

 

[Marconi]

Thank you Alexis.

Based on a comparison I made earlier...our BW results were pretty close...even though our antenna setup were a little different.

Now I'll make some adjustments, per your new details, and see how our BW results compares.

This gives me a chance to see how close an Eznec model can sometimes predict real world results.

 

[Alexis Mercado]

No problem my friend. Let us know about your results.

 

[Marconi]

Alexis, I've run into a snag in fixing my 827 models and the project will be delayed.

I mentioned earlier that my 827 model was setup a bit different from your installation and my model is set at 36' feet. I will have to delay fixing my model to get closer to your specs.

However, I did do a Bandwidth comparison below and my 2.00:1 and 1.5:1 SWR results which shows to be close to your report. My Bandwidth however is less, and that is probably due to Eznec showing the match at the feed point, and not at or near the typical TX'r end of the coax.

Alexis 827
SWR ——- Short Radials ——- Long Radials
2.0. ———-- 28,150 ——————- 28,450
1.5 ——- —- 27,810 ——————- 27,880
1.0 ——-—- 27,255 ——————-- 26,965
1.5 ———-- 26,540 ———- ——— 26,415
2.0 ———-- 25,820 ———- ——— 26,100

BW = 2.330 MHz ------------------ 2.350 MHz

Marconi 827
SWR ——- Short Radials ——- Long Radials
2.0. ———-- 27,900 ——————- 28,100
1.5 ——- —- 27,600 ——————- 27,800
1.0 ——-—-- 27,200 ——————- 27,400
1.5 ———--- 26,750 ———- ——-- 27,000
2.0 ———--- 26,450 ———- ——-- 26,700

BW = 1.45 MHz -------------------- 1.400 MHz @ feed point

Here on the Gulf Coast of Texas we have an African Sahara Desert Dust storm coming our way and my lung health will suffer for a while. I'm already feeling bad.

 

[Alexis Mercado]

Marconi.

We had the the Sahara Storm as well mountains could barely be seen.

Thanks for posting your results. What I still don’t understand is the fact that all your frequencies went up as well as mine, while your lowest SWR went up in frequency like it is supposed to, but my lowest SWR went down to to 26.965 MHz. Uncanny for me.

 

[Marconi]

Marconi.

Thanks for posting your results. What I still don’t understand is the fact that all your frequencies went up as well as mine, while your lowest SWR went up in frequency like it is supposed to, but my lowest SWR went down to to 26.965 MHz. Uncanny for me.

Alexis, it is pure speculation and I would not expect the results to be exactly the same.

1. differences in ground (soil) conditions.

2. our antenna dimensions are a little different.

3. my antenna was set higher than yours.

4. you used coax, and my modeling results are calculated at the feed point.

I don't see enough difference using longer radials, but I would Real World test the idea anyway,

Thanks for following up on this.

BTW the Sahara dust storms never really reached my area???????

 

[Alexis Mercado]

Marconi , the Sahara dust hit was strong, like never before. Around this time ( summer) we are hit with some Sahara dust but not like this last month.

 

[Marconi]

Alexis here are 2 overlays for the Sirio 827 with 4 x 9' foot radials (Red) vs. 8 x 55'' inch radials (Blue).

The active model has an (*) beside the title below the word Primary at the upper left corner of the page.

I think the most important differences I see between my 2 models of the Sirio 827, is the increased maximum gain close to the horizon...as compared in the overlays images in the PDF file below.

See the green dot cursor for maximum gain and angle for each model.

827 with 8 x 55" radials
4.41 dbi gain at 8* degrees above the horizon

827 with 4 x 9' radials
3.66 dbi gain at 41* degrees above the horizon

IMO, this considerable difference indicates that the 4 x 9' foot radials tend to push the high angle lobe up higher, and thus putting less gain at or near the horizon where it is more desirable.

Alexis, there are several old discussions at the top of the CB Antenna section. "Sticky Threads," talking about Sirio using CST, a superior modeling program to maximize their antenna designs. In particular their New Vector 5000 is discussed.

If this story is true, and Sirio modeled their 827, and seeing similar differences as I did above using Eznec 5, then I would doubt very seriously Sirio had any questions in choosing to use the shorter radials on their premire 5/8 wave antenna.

To me, these overlays show the improved gain effects due this pattern compression effect when using 8 x 55" radials rather than 4 full 1/4 wave radials.

 

[The DB]

Here is a similar comparison at 20 feet with no mast.
[photo=medium]6394[/photo]

And here are the same antennas with masts.
[photo=medium]6393[/photo]

Based on these models, it appears to me that the different radial configurations will have different effects on common mode currents. As we can see without masts, the radial configurations have no real effect on the radiation pattern, only an effect gain with the shorter radials having slightly more (not a noticeable difference).

However, with the addition of masts, the two antennas have different radiation patterns. This suggests the different radial configurations will have different effects on said common mode currents, thus creating said different patterns.

Because of this, with various mast lengths/ground conditions/ect. it is possible that for some people the shorter radials will have better lower angle gain, and for others the longer radials will have better lower angle gain.


The DB

 

[Marconi]

DB, after I saw your results, I double checked my models and found several errors that I will have to fix. So, based on your models the short radials vs. the long radials are more similar than my models showed.

Before I tried to compare the 827 models with short and long radials...I was not expecting much if any difference either, and I was surprised to see such a difference. I should have checked my models closer.

The patterns for the models below, without the mast, look very similar...as one might expect.

I tend to agree with your results, but when you added the mast to your model with 8 short radials, as note below, you got a very different pattern as note in Blue. That particular pattern shape looks more like an antenna that is set lower to the Earth. Did that pattern surprise you?

I checked several of my other 5/8 wave antennas and I compared them with and without the mast and I saw only minor differences on comparing the patterns.

Below is an image of a SP500 model. I deleted the mast and made an overlay of the antenna with and without the mast. This shows a little difference as I might expect. The Primary, in Black, is without the mast and the model below, in Blue, is with the mast.