Homebrew Merlin Experiment

[BOOTY MONSTER]

because modeling at lower heights hasn't supported the claims made by some of the owners of the merlin . so , in the interest of trying to be fair and give the antenna the chance to excel in a install that was reported to happen by a user . and you may as well put a i10k at a 75 ft feed-point too ....

or not ...........

 

[HomerBB]

Well Homer, you're right to a degree. That is all I can come up with unless y'all were using Needle Bender's idea...using the florescent light bulb and mapping the results. :thumbdown:

Right now I'm covered up in models, just trying to get the A/P - Merlin models equal in their settings and trying to make the comparison as fair as I can.

I wasn't expecting all this when the Merlin idea popped up, so I was not preparied. It turns out now that I had to consider using a mast in the project, because the A/P requires a mast as part of the antenna matching.

When I added the mast to the Merlin @ 36' feet, where I made the previous models, the Merlin pattern went to heck in a hand basket and I think that has something to do with that particular height at 27.205, but I can't prove that. That said, and I hadn't even started on trying to get the two models on an even par with the settings.

But I took a break and checked out your request for the dipole vs. Merlin at 43' feet to the tips. Notice I isolated (ISO) the mast from the antenna to help duplicate your Merlin setup.

http://www.worldwidedx.com/attachme...w-merlin-experiment-homers-43-comparison..pdf

How say you?

Really interesting. I see a gain advantage for the dipole, and it is what I may be seeing so far in the real world. I'll work with it for a few more days to find out.
The Merlin is one degree closer to the horizon, but it is hardly significant when it comes to it, I'd think.

I brought over some of the figures from your model for quick reference:

To see the smaller print clearly folks will have to look at the original model pdf.

 

[Marconi]

Really interesting. I see a gain advantage for the dipole, and it is what I may be seeing so far in the real world. I'll work with it for a few more days to find out.
The Merlin is one degree closer to the horizon, but it is hardly significant when it comes to it, I'd think.

I brought over some of the figures from your model for quick reference:

To see the smaller print clearly folks will have to look at the original model pdf.

Homer have you considered why this dipole is showing more gain, albeit is a degree higher?

 

[HomerBB]

Homer have you considered why this dipole is showing more gain, albeit is a degree higher?

Yep.

Gain:
Perhaps because it is a half wave antenna it shows more gain over a 1/4 wave antenna.
Despite some claims otherwise, the Merlin is a 1/4 wave GP. Using the Cap and Coil simply underscore that reality by being the Tools of the Trade for adjusting the physical length of an antenna downward while preserving the electrical length of the nearest physically larger antenna. They are also the time honored and accepted means of raising the current maximum up toward the highest end of a vertical antenna*.

TOA:
*Because of the Cap/Inductor combo this antenna probably has a slight edge over the straight radiator of the dipole seeing the tops of both antennas are of equal distance from the ground.
Perhaps because the dipole antenna being longer is physically closer to the ground, not to mention its feedpoint is lower in height.

 

[BOOTY MONSTER]

maybe because it its a physically taller antenna that isn't shortened by both a coil and a tophat ?

 

[Marconi]

Yep.

Gain:
Perhaps because it is a half wave antenna it shows more gain over a 1/4 wave antenna.

TOA:
Perhaps because the dipole antenna being longer is physically closer to the ground, not to mention its feedpoint is lower in height.

It might be right, but I see your mast beside the dipole that is affecting the pattern more in one direction and less in the other.

Check the pattern below, where I placed the cursor on the other side of the mast, and you will see the skewing.

BTW, I noted the height at the feed points and they are within a couple of inches of each other.

Now the only question to consider is, which side of your dipole did your real world contact come from, if you know? If the station was on the mast side, then I am wrong in all of this.

I can handle it, just let me know.

View attachment Homer's dipole install..pdf

 

[Marconi]

If you installed your dipole for this comparison work, because the dipole is the preferred test in such cases, then consider this model of the dipole by itself. It's a good idea, but I think a regular center fed dipole, well into the clear, is probably what the test has in mind.

Also check the match for both and you will see a match that is just what a dipole should show and with your installation on the side of a mast, you will see those effects caused by the mast.

View attachment Homer's follow up to the 43' idea.pdf

I hope I made this clear in explaining why I think you saw your dipole besting the Merlin. IMO the model above is the one that should have been used to compare the Merlin to the Dipole, and had we done it that way...we would have seen a different outcome.

 

[HomerBB]

I looked at both of the pdf files above. I can see what you mean.
Now the mast my dipole is on is 4' to the north of my dipole (The antenna is completely isolated from both the boom arm and the mast top).
The contact I documented above is directly east of my dipole. That station may benefit little to none from either direction or reflection due to the mast.

New Data - Dipole No Mast:

 

[Marconi]

because modeling at lower heights hasn't supported the claims made by some of the owners of the merlin . so , in the interest of trying to be fair and give the antenna the chance to excel in a install that was reported to happen by a user . and you may as well put a i10k at a 75 ft feed-point too ....

or not ...........

Here is the Merlin and the I-10K at 75' feet. One I-10K is matched, and the other is not. I did two I-10K because that one does not make a good match without a matcher.

View attachment Booty Monster's idea at 75'..pdf

 

[Marconi]

I looked at both of the pdf files above. I can see what you mean.
Now the mast my dipole is on is 4' to the north of my dipole (The antenna is completely isolated from both the boom arm and the mast top).
The contact I documented above is directly east of my dipole. That station may benefit little to none from either direction or reflection due to the mast.

New Data - Dipole No Mast:

OK, IMO your setup, with the mast, would show a gain pattern of about 270* away from the mast peaking toward the center, and would show less gain in about 90* degrees to the back. The pattern would be sorta' egg shaped. I don't think there will be much difference, but you could check if you have the contacts in the right place. You may have to be able to turn your antenna a bit to check.

I did something similar once when I co phased two of my vertical antennas at 36' apart. I could see a difference, but I could not change directions in order to check it.

BTW, my offset is only 3' feet, but it is isolated also...you see empty space between the mast and the dipole, there is no better insolator.

I hope I made this issue clear. No back to the A/P and the Merlin. This is difficult, because I didn't model the Merlin with a mast, and now everything will have to change.

 

[HomerBB]

At 75' the Merlin shows gain over the I-10k w/match. However. the I-10k is showing the best over all pattern you'd expect from a .625/.64 antenna.

The 1/4 GP has a significant set of secondary lobes at an extremely high angle where as the i-10k has its highest secondary lobes at greater advantage to the distance.

It raises again the question of just where geographically are these users talking. Nearer field contacts would benefit from the higher secondary lobes of the Merlin.

Even with the 4.59 Merlin gain at 6.0 degrees primary lobe vs the 4.2 I-10k gain at 5 degrees there is nothing in these figures to suggest even ONE S-unit of increased signals by using the Merlin.


Right now I am sitting and listening to the DX from Hawaii and New Zealand on both antennas. I detect no discernible difference 90% of the time. When a detectable difference is noted it can be either antenna at the moment. . . Conditions being what they are I have no bars on the front of the 2950 from either antenna's receive.

One thing that is appearing to be clearing up from use of the models is the Merlin does seem to put down a low primary angle at great heights (as any antenna should do), but when at one wavelength showed no better than the fundamental 1/4GP.

 

[BOOTY MONSTER]

Here is the Merlin and the I-10K at 75' feet. One I-10K is matched, and the other is not. I did two I-10K because that one does not make a good match without a matcher.

View attachment 8746

thanks

 

[HomerBB]

OK, IMO your setup, with the mast, would show a gain pattern of about 270* away from the mast peaking toward the center, and would show less gain in about 90* degrees to the back. The pattern would be sorta' egg shaped. I don't think there will be much difference, but you could check if you have the contacts in the right place. You may have to be able to turn your antenna a bit to check.

I did something similar once when I co phased two of my vertical antennas at 36' apart. I could see a difference, but I could not change directions in order to check it.

BTW, my offset is only 3' feet, but it is isolated also...you see empty space between the mast and the dipole, there is no better insolator.

I hope I made this issue clear. No back to the A/P and the Merlin. This is difficult, because I didn't model the Merlin with a mast, and now everything will have to change.

Thanks.
I went back out into the rain to double check my stand off from the mast. You are correct, it is not 4', it is 3'.

 

[Marconi]

At 75' the Merlin shows gain over the I-10k w/match. However. the I-10k is showing the best over all pattern you'd expect from a .625/.64 antenna.

The 1/4 GP has a significant set of secondary lobes at an extremely high angle where as the i-10k has its highest secondary lobes at greater advantage to the distance.

It raises again the question of just where geographically are these users talking. Nearer field contacts would benefit from the higher secondary lobes of the Merlin.

Even with the 4.59 Merlin gain at 6.0 degrees primary lobe vs the 4.2 I-10k gain at 5 degrees there is nothing in these figures to suggest even ONE S-unit of increased signals by using the Merlin.


Right now I am sitting and listening to the DX from Hawaii and New Zealand on both antennas. I detect no discernible difference 90% of the time. When a detectable difference is noted it can be either antenna at the moment. . . Conditions being what they are I have no bars on the front of the 2950 from either antenna's receive.

One thing that is appearing to be clearing up from use of the models is the Merlin does seem to put down a low primary angle at great heights (as any antenna should do), but when at one wavelength showed no better than the fundamental 1/4GP.

I tend to disagree that the I-10K pattern is better here. I look primarily at the wavefront of the workable area of the pattern. The high angle stuff does suggest waisted RF, but if the primary lobe, at a low angle, is pretty good, then I go witht the better wave front between 0* and 30* degrees.

The narrow lobe and the big dip in the null on the I-10K is a disavantage in my book, and for sure when it falls in the area around 13* degrees. A lot of antennas do good just to have a maximun gain at that angle much less lower.

View attachment Homer's issue on I-10K pattern..pdf

Check the pattern with the cursor indicating the loss in gain at 13* degrees. The Merlin is about three times better in this important angle area suitable for line of site and DX communications.

View attachment Homer's issue on the Merlin pattern.pdf

 

[HomerBB]

Yes, I see that.
I won't argue against the difference in favor of the Merlin at the 12 - 13 degree nulls. I will say that with a combined 2.5db difference we are very much short of a S-unit of measurable gain on the best of receivers. That is less than 1/2 S-unit of gain and only at that particular elevation. No big gains here either.

I can understand looking for the best figures from 0 - 30 degrees, but that one almost unmeasurable bit of less null will not account for even one half S-unit of difference.