Quad or Horizontal Beam ?

[Robb]

Seriously considering a PDL 2 beam . . .

Would it be possible to mount a IMAX above it?
Or would it just screw it up?
What are all of the factors to consider.

I was also considering a 4 element Maco M104C horizontal; but with a 19 ft boom length it seems hard to do at my location. The quad beams have a 9 ft boom length - right?

 

[airplane1]

I wrestled with the same question at one time. I was told the mast running throu the PDL-2 for the Imax would mess up the PDL and would not be a good idea so I decided on 104C and Imax. I am working on a 104C converting it to 10M with an Imax on top. The 104C has 16ft boom not 19ft if this helps with your space problem. You could even play with the spacing and element lengths to make the 104C better.

You would have a good setup with 104C and Imax just above it from what I gathered from here on the forum so I hope it helps.

AP

 

[hookedon6]

well, theory says that it will ALTER the radiation pattern, notice i said "ALTER" and not DEGRADE.

i have put a fiberglass vert in the middle of a PDL and a PDL II .
there were no NOTICIBLE bad effects with the vert feedpoint mounted about 1 1/2 ft above the PDL boom.

thinking about it,...... perhaps the best method is to mount the IMAX on a non conductive (fiberglass) mast above the highest part of the PDL

YMMV

 

[Highlander_821]

I'd go with the M104c. Less hassle. If the boom is too big, go with the M103c. The 103 still compares favorably with the PDL-II for gain.

 

[Robb]

well, theory says that it will ALTER the radiation pattern, notice i said "ALTER" and not DEGRADE.

i have put a fiberglass vert in the middle of a PDL and a PDL II .
there were no NOTICIBLE bad effects with the vert feedpoint mounted about 1 1/2 ft above the PDL boom.

thinking about it,...... perhaps the best method is to mount the IMAX on a non conductive (fiberglass) mast above the highest part of the PDL

YMMV

I was wondering the same thing - if using a fiberglass pole to mount it. But what is the cost of such a pole? A ten foot piece? Who makes it? Would the coax running up to the IMAX negate the effort?

I wrestled with the same question at one time. I was told the mast running throu the PDL-2 for the Imax would mess up the PDL and would not be a good idea so I decided on 104C and Imax. I am working on a 104C converting it to 10M with an Imax on top. The 104C has 16ft boom not 19ft if this helps with your space problem. You could even play with the spacing and element lengths to make the 104C better.

You would have a good setup with 104C and Imax just above it from what I gathered from here on the forum so I hope it helps.

AP

I thought that would be the case, as in the IMAX altering it so badly that it would not make it practical.

Thanks for correcting the dimension length of the boom of the M104C. It has a large turning radius. The rotor I have is a CDE that I was going to use on the Gizmotchy review; I already have the other hardware to make it happen. The PDL II appeals to me for a few reasons: because it has a short boom, there is one close by that I can get for next to nothing/free, and the reputation it has.

I'd go with the M104c. Less hassle. If the boom is too big, go with the M103c. The 103 still compares favorably with the PDL-II for gain.

"DXman" on this forum runs the M105C, talks to the world on 30 watts on a regular basis, and has nearly 200 different countries logged in the last 30 years. That's pretty impressive in my book.

The price of the 3 element is better than the 4 element. But side rejection suffers at this level; yes? But I will put that under consideration as well.

 

[airplane1]

One more diciding factor for you to consider. If you put an Imax above the pdl2 you will need to get up over 7ft above the pdl2 boom, this will mean a heavy mast,bearing on top of tower because of more stress of the leverage above your tower. A flat side beam can be mounted just a few inches above your tower bushing and the Imax inches above that. Very little masting and stress on everything.

AP

 

[Robb]

One more diciding factor for you to consider. If you put an Imax above the pdl2 you will need to get up over 7ft above the pdl2 boom, this will mean a heavy mast,bearing on top of tower because of more stress of the leverage above your tower. A flat side beam can be mounted just a few inches above your tower bushing and the Imax inches above that. Very little masting and stress on everything.

AP

Interesting point.
That's a vote for the Maco.

 

[hotrod]

maco m103 flatside with imax above it

 

[Robb]

Leaning back twards the M104C

I found this - an interesting read:
The Ultimate Guide to 11 Meter CB Antennas

 

[tecnicoloco]

Leaning back twards the M104C

I found this - an interesting read:
The Ultimate Guide to 11 Meter CB Antennas

Hello Robb:

Go for it,it works pretty darn well,I mod my 4 Elem Sirio with the dimensions from that page,at only 12 Ft about ground I can make 700+ miles contacts running 25 watts with good signal,I know is to close to ground but construction in my property did not let me raise the antenna before,now I'm working on the 60 Ft tower will see how it works at that height


Adios y hasta los tacos
Tecnicoloco

 

[Robb]

]Thinking about it a bit more . . .

The width of the Maco 3 element or 4 element is exactly the same - roughly 17 ft wide. The 3 element beam is shorter; and the 4 element is 16 ft long. That makes it nearly as long as it is wide. Because this is so; I might as well get a boom length of 16 ft with the M104C. After all - if I am going to spin it around 360 degrees - at some point it will still need to have that much clearance. The turn radius on the 103 is 10 ft; the 104 is 13 ft. Not that much difference.
That settles that . . .

After re-reading that link I posted, I was wondering - how many have experience modifying the M104C to those dimensions? The frequencies that it was tuned to in that article - is precisely what I would want to use on 10m and 11m.

Sure would like to hear more about this modification to the beam - that have done it themselves.
Thanks Tecniloco and airplane1 for the insight.

Maco M103C:

11.5 ft Boom Length
1.5 inch Boom OD
3 Elements
Longest Element is 19ft
10ft Turn Radius
4.5 sq. ft. Surface Radius
90mph Wind Survival
Tunable for 10-11 meters
11db Gain
Power Multiplication of 20x
25 db front-to-back Separation

Maco M104C:

16 ft Boom Length
2 inch Boom OD
4 Elements
Longest Element is 19ft
13 ft Turn Radius
6.33 sq. ft. Surface Radius
90mph Wind Survival
Tunable for 10-11 meters
14db Gain
Power Multiplication of 28x
29 db front-to-back Separation



Top: Computer enhanced modifications of the Maco M104C. Boom length is reduced to just over 13 ft as compared to 16 ft from OEM dimensions

Bottom right: Graph of freq vs gain of OEM Maco M104C.

Bottom left: Polar pattern of Maco M104C @27.555mhz showing poor rear rejection

From: The Ultimate Guide to 11 Meter CB Antennas

 

[DXman]

Robb,
Before you start putting the 4 together, you might want to check this out first -11 meter DX systems. Cross check the measurement that you have posted with the ones in the link.

 

[airplane1]

Go here for a free yagi program that I think you will injoy http://www.raibeam.com/wa7p1.html. I did and love playing around with length of elements, spacings, boom length and seeing what I can come up with for a certain frequency. You can get a Maco M104C and build what ever you want with this program.

Be careful though, it can be addicting and you might do like me, play too much and not get the beam built LOL.

Hope this helps you,
AP

 

[Robb]

Go here for a free yagi program that I think you will injoy I first authored this yagi modeling program in 1990. I did and love playing around with length of elements, spacings, boom length and seeing what I can come up with for a certain frequency. You can get a Maco M104C and build what ever you want with this program.

Be careful though, it can be addicting and you might do like me, play too much and not get the beam built LOL.

Hope this helps you,
AP

Thanks! I want to get it as close to correct as I can. Since DX will be increasing, I need to be equipped for the challenge. Winter is approaching, and I need to get this rolling within a month or so.

Robb,
Before you start putting the 4 together, you might want to check this out first -11 meter DX systems. Cross check the measurement that you have posted with the ones in the link.

Of course, it will work right out of the box with the OEM instructions. TO 'optimize' it is something that I need to get right; each optimization gives a different pattern. The problem with that link you posted is that the dimensions are in meters. The needs of dimensional accuracy are important of course. Did you optimize your 5 element from that link? I can do the conversion from meters to feet if you feel it is better than the link I posted. What do you think Larry?

 

[DXman]

Yes I did my beam according to the instructions there for the long boom. I just ran the figures through a conversion program and went with it. It's only for 11 meters - right! At least it is for me, so if it's not prefect I really don't care.......