Question about the beam pattern of an M103C

[loosecannon]

hi all,

never owned a beam before, and im considering picking up a maco m103c to play with.

my question relates to the width of the beam pattern created by this antenna.

i will be running it vertically for now, with the boom about 35ft. off the ground.

i will not be using a rotor for a while.

ok, until the DX picks up, i will be doing mostly local talking, so thats what i want to set the antenna up for.

i live in the northwest corner of my city, and im not worried about hearing people behind me, or directly off the sides, but i would like the beam pattern to be wide enough to cover about a 10-20 mile width, 10-15 miles out from my location.

am i in dreamland?

what is the typical "capture area" of a maco 3 element beam?

also, has anyone done any optimizing for the maco 103c using the software available?
what configuration has given the best gain?

one more,

is the MFJ 1:1 balun the right thing to use on this antenna?
should i be making a "choke balun"?
what about 3-4 type 31 snap on ferrite beads?

thanks for any answers/advice you can give to a first time beam owner.
LC

 

[Beetle]

Need a little more information:

1. What are you using for a support for the antenna (tower, pole, tree...)?

2. Is the support metallic?

 

[Captain Kilowatt]

A typical 3 element yagi has a beamwidth of about 60 degrees in the horizontal plane. Check a map and see what 60 degrees will cover from your location. BTW that is at the -3 dB points so the signals at that limit will be only 1/2 S-unit down from directly in front.You will be fine for what you are seeking I would think.

 

[Beetle]

QRN - he's talking about mounting it vertically, so half of the -3db point will be going where it won't do any good. And, if his mast is metallic, it will likely cause quite a bit of loss with the driven element right beside it, vertically aligned.

I'd mount it horizontally and never look back.

 

[Captain Kilowatt]

QRN - he's talking about mounting it vertically, so half of the -3db point will be going where it won't do any good.

OK Pat. You lost me with that. I know he wanted to mount it vertically but the typical 3 element yagi exhibits a 60 degree beamwidth in the E-plane (horizontally towards the horizon) and about 90 degrees in the H-plane (towards the ground and sky).Agreed the mast may skew things a little but 60 degrees is still realistic.

 

[loosecannon]

thanks for the replies guys,

the antenna would be mounted on a 30 foot push up pole with a 5 foot mast on top.
all metal.

i have thought about the interaction between the element(s) and the mast, but i figured that this is a concern with any beam that is mounted vertically.

doesnt everyone use a metal support pole when using a vertically mounted beam?

is mounting a beam vertically generally a bad idea?

see, in my city, there are maybe 2-3 old timers who own beams, and they only talk when the DX is rolling.

everyone else is either in a mobile, or on a vertical base antenna.

isnt there a big loss in signal when transmitting from a horizontally mounted beam to a vertical base antenna?

the whole reason im trying the beam idea is to get some gain.

if i mount the beam horizontally arent i shooting myself in the foot so to speak?

thanks for any advice,
please let me know about the balun question above.
LC

 

[Beetle]

QRN/LC - I've seen too many problems with vertically-polarized antennas being installed with vertical support structures (or other metallic vertical members) within the very near field of the driven element. So many that I can't encourage it.

LC, you can always experiment with different configurations, but based on what I've learned from installations on Navy ships and shore facilities tells me that much of the gain you might realize due to polarization will be offset by the signal coupling to the mast/tower and thence to ground.

 

[BOOTY MONSTER]

i cant help with your questions but i just thought id let you know that sparkys has rebuilt CDE rotors with controll boxes for $130 when you get ready to get a rotor .
http://www.sparkyscbshack.com/rotators.html

 

[W5LZ]

Just a few things to think about concerning polarization of antennas, and beams and so on.

There is no 'best' polarization in general. One will work about as well as the other as far as distance goes. Just depends on who you want/have to talk to and their polarization. Vertical polarization is sort of mainly for mobile stations. That's cuz that's the type of antenna that is easiest for mounting on a vehicle, doesn't require a lot of 'extra' stuff, like huge underpasses, car doesn't fall over from the weight of a tall tower, etc. It's frequency dependent too. While vertical antennas have a lot of 'pros', they also have a few 'cons'. Verticals are typically noisier than horizontal antennas (QRM and QRN, sorry 'QRN'). That does not mean that horizontal antennas are not noisy, they are, just not quite as much as the 'Vert's at times. It also changes, just like propagation, and you just can't get around that.
Oh, and that's another one'a them thingys that changes all the time, usually at the worst possible times, and unless you just happen to have a couple of the same antennas polarized differently, pointed in the exact correct direction, at the 'right' height, just don't worry about it. It'll change. "What the @#$$ are you talking about now?"... why, propagation, of course. And since that's been talked about till it seems a lot like a 'dead horse', I won't beat on it too much. Best thing to say about it is that it changes, just wait for it (easiest thing to do huh, wait?).
And maybe the biggest 'problem' in the whole mess is that 'beauty is in the eye of the beholder'. Your 'beauty' ain't gonna be the same as your neighbor's, or your better half's, or someone who has no idea what the @#$$ that thing is anyway. Some of that can be ignored. Some can't be (if you're smart). I happen to like the looks of a horizontal beam, which on the average, is probably the ugliest. [Insert whatever comments you like here.] If it does what I want it to at least some of the time, who cares, right? And, NO, I'm not comparing them to politicians! Go wash your mouth out with carburetor cleaner.
And lastly... If you put the thing up one way, find out that it doesn't suit you, change it. Nobody says you can't change things later. Budget enough so that you can change it again, just in case, sort of. (Or mount the @#$ thing on a hinge so you can change it at will?)
Having said all that, I'll quit. I wanna go to the library and see if they got any more 'dirty' books anyway...
- 'Doc

 

[Highlander_821]

I had an M103c set up vertically, and didn't have any problems. It definitely had gain over my Shakespeare Bigstick. SWR was near perfect, side rejection was great, front to back was good.

 

[Marconi]

Loosecannon, I would suggest you listen to 821. Don't make too much about needing a balun either, unless you end up with a very bad antenna and the problem is actually related to feeding. The M-103 uses a gamma match and this device is not so prone to problems that will require a balun. The M-103 design also has been pretty well tested and if setup vertical it should show a modest gain over a good working vertical ground plane.

I am surprise that you feel you need some additional gain in the very modest range that you mention however. Within this very close range you should see some modest attentuation at points around your station, but it won't be like day light and dark. You should still be able to communicate within a full omni pattern at this short range whether you set it up horizontal or vertical. It's not like you will never see an exception in this regard, but these directional and attentuating affects of a small beam are just not as pronounced as you might think.

Good luck and keep us posted.