Homebrew Merlin Experiment

[hotrod]

I've been sick, and it's been too cold and/or nasty of weather to do more.
I'll get back to it.

sounds good.hope u feeling better

 

[HomerBB]

I got sick, and it got cold, so I lost time on it. But, I can tell you what my impression is so far, and that it could change with more testing.

So far:

the Merlin I made is not perfect, but close enough to have observed a trend. I can say that so far the antenna proves over and over again that it is a good design in terms of getting the job done. It consistently hears better 8 of 10 times than the 5/8 I made for the project, and slightly better than the 1/2 wave oddball antenna I threw together, and gets my signal back to who I hear. Because the noise level is lower than the 5/8, and slightly lower than the 1/2 wave, I am usually able to get a bit better noise to signal ratio which sends me to the Merlin most often. What I have not been able to check so far is whether the noise floor is due entirely to the antenna design, or the location of the antenna mast it is on. I'll have to move the antennas around to be sure.
I have not seen any of the 1 - 2 db or more signal improvement over the other antennas some have claimed for this one, but I can say it is a good antenna.

I like it.

If one wants a consistent performer, small sized, light weight and apparently well built by all reports, this somewhat pricey antenna will do the trick.

 

[Marconi]

I got sick, and it got cold, so I lost time on it. But, I can tell you what my impression is so far, and that it could change with more testing.

So far:

the Merlin I made is not perfect, but close enough to have observed a trend. I can say that so far the antenna proves over and over again that it is a good design in terms of getting the job done. It consistently hears better 8 of 10 times than the 5/8 I made for the project, and slightly better than the 1/2 wave oddball antenna I threw together, and gets my signal back to who I hear. Because the noise level is lower than the 5/8, and slightly lower than the 1/2 wave, I am usually able to get a bit better noise to signal ratio which sends me to the Merlin most often. What I have not been able to check so far is whether the noise floor is due entirely to the antenna design, or the location of the antenna mast it is on. I'll have to move the antennas around to be sure.
I have not seen any of the 1 - 2 db or more signal improvement over the other antennas some have claimed for this one, but I can say it is a good antenna.

I like it.

If one wants a consistent performer, small sized, light weight and apparently well built by all reports, this somewhat pricey antenna will do the trick.

I can and have reported what Homer sees when I'm using my Starduster compared to my Gain Master. I don't have my antennas mounted at the same tip height either, they are at the same current maximums...with the tip of the SD about 3'- 4' feet below the tip of my GM.

My SD is almost always quieter when conditions are quiet and the signals I see, compared to the GM, are about the same. However, these responses do vary, one to the other, at times just like Homer indicates. Unlike Homer, I might see 1-2 db difference at times and at different locations around me, but I have never seen 1-2 Sunits difference in signals...like many CBr's claim.

So, I see and report just about what I've always seen over the years...my CB antennas respond pretty much the same, and I don't just depend on one signal report, close by or one far off, to tell me what I report.

Here is what Eznec indicates for me comparing the Merlin to my Starduster.

View attachment Merlin vs. Starduster.pdf

I figure the gain advantage noted here with the Starduster is due to the increased slanting downward of the radials.

 

[BOOTY MONSTER]

........... What I have not been able to check so far is whether the noise floor is due entirely to the antenna design, or the location of the antenna mast it is on. I'll have to move the antennas around to be sure. .............

looking forward to that .

 

[Marconi]

Information is beginning to emerge from several sources to assist with the project, some of which others who'd like to give it a try will find useful:



I am good here except I will have to remove 1/2 turn of the coil.



The length of the Cap Hat radials is the same from both of these sources, but there is a bit here that seems to indicate two different iterations of the Merlin. From other discussions/sources I am seeing a separation between the Hat and the Coil of only 1"


I am good here, too. We know that tuning is apt to show small increments of differences in adjustment lengths from place-to-place.


My radials are two piece units and are 4 instead of three, If anything, the 4 should be better, but certainly not a disadvantage to the antenna's performance.


I am still looking forward to a measurement of the distance between the center of the mast and the radials at a distance down from the hub. I will check mine again and determine whether they are at exactly 45° degrees angle until more detailed info arrives. I think they will be tighter than that by looking at the pictures - closer to 25° -30°.

And last, but not least, there is the wife ingredient that keeps us from having all the radio time we'd like to have . . .

*added for clarity

Homer, I am mostly interested in the stock dimensions for the Merlin. There are still differences among these reports noted above.

Did you make any design or dimension changes as a result of this information?

If so, do you think it made a difference in performance?

Do you think you have a good idea now...as to what the true dimensions for the Merlin should be?

Could you post your dimensions on the images below, so I can check them on my model?

View attachment Merlin.pdf

 

[HomerBB]

Coil
Height of coil = 4.3/4" tall. 1.5 total turns.

Cap Hat
top hat is 24 in. radials from end to end, or 12 in. from the center out, 1" from top of coil

Vertical
total assembled length* = 73 5/8 from top of hat to top of radial lugs.
(*there is a 2-5/8" adjustment sleeve on the top of the hub into which the vertical slides)
Radials
over all length as they are now = 100. 3/4" (three sections, adjustable length)

Angle Of Radials
best I can tell for you is 45 degrees*

*When I look at the photos of the Merlin I see the angle of the radials is tighter, like the Starduster. To arrive at that conclusion I looked at my radials, and photos of them, at 45 degrees, and then again when I tightened the degree of angle. The similarity to the available photos of the Merlin improved as I tightened the angle between the mast and the radials..

Some of the variables reported indicate differences in the dimensions based on individual setups, ie center frequencies preferred, local variables.

I have not lengthened the Cap Hat, nor have I removed 1/2 turn of the coil yet. It is just too cold to be out on the roof. Perhaps I can catch a warmer day over the next few days.

I also have a local clamoring for the antenna . . .
I'll likely be trading him for some aluminum tubing, etc to do more things with.