Maco 3 element beam project...

[Oatmeal]

Hello guys, been awhile since Ive been here...have made a lot of changes since then, but as you know I sold all the big stuff off, awhile back....and a forrest fire took out the wire I used to run....so now a days my antenna is here at the shack.....have a Imax 2k, which now a days I usually just copy the mail....

But anyways, Im in the process of building a hinge plate for some mast pipe Im going to through up a 3 element beam on the flat side and go up around 27ft, not looking to get very much height due to my location....this will be setup to turn it by hand or with a pipe wrench...someday Ill get a rotor....

So, my question is, if I go with LMR 400-UF coax, and use a coax choke and mount it on the boom of the beam, would this be enough to stay out of the neighbors stuff ?...

If the brand of coax makes a differences, Ill go with the good brand coax...
Want to go with a good coax, trying to get it all right the first time..



For a radio Im going to be running a Cobra 2000 and a D-104 mic, later will go to some amp, like to have a 2 pill, and or maybe some tube amp later on..

 

[wavrider]

You should not need a choke on a yagi using a gamma match for impedance matching.

You can use one of you want to but should not be necessary as for tvi, rfi but it may help on reducing some of the static the feed line can pick up. Then again it may not.


The Cobra 2000 is a clean radio unless it has been modded and butchered up.

Clean audio and 100% modulation ( not 300%) into a transistor amplifier should work fine as long as you are not over driving the amplifier.

Sounds like you will have a great setup for DX'in.

Google CMC common mode current, W8JI has a nice write up of cause and effect on his website with ways to prevent or control TVI/RFI.

 

[Oatmeal]

10-4, yea it will be setup just for talking dx, that's my thing and enjoy doing that....don't no how well it will do with a bare foot radio, but I intend on keeping it clean, have some good neighbors and like to keep it this way....

As for coax, will go with some of the LMR 400-UF, its not cheap, but don't want to take any chances, trying to get it all right the first time around....don't no how the neighbors will react when they see my beam up here as it is, lol..So far, since the Imax 2k, has been up out back, nobody has said anything...

I hardly ever talk much local well not these guys close to me anyways....there a different breed of cb'ers than Im used to talking with these days....have never saw guys like these here before....

 

[Captain Kilowatt]

Impossible to say with certainty. LMR-400uf and a choke is not a magic combination. There are just too many variables both within and outside of your control to say you will not interfere with the neighbors "stuff". If some of that "stuff" is an audio amp or computer speakers all bets are off. It is a good starting point however.

 

[Oatmeal]

10-4, I understand what your saying CK.....but Im going to try it, I wouldn't think running bare foot would mess anything up, but Im doing this now so when I get a amp Ill already have some good coax on the beam, choke in place, just going to through this all up on the beam as I put it in the air...

Last thing I want is to have to lower it for some reason and have to put a choke on it, after I already have the coax stretch out to the shack...Im going with this coax to do to having a 120ft run to the shack...

Havent figured it all out yet how to mount the choke on the boom of the beam.....

Wonder if zip ties would last holding the choke in place ?..
Im going to use a 4" form for the choke..

 

[M0GVZ]

A lot of whether you'll interfere with them or not is entirely down to how well designed their electrical equipment is.

If they're running a cheap no-name TV with no filtering, their coax is 20 year old water filled crap and they're using pre-amps the best installed CB/ham radio system in the world will cause problems even on a few watts.

As to mounting the choke, you don't do it on the boom of the beam. Do it below the rotator. Basically you have coax coming from the radio up the mast to roughly where the bottom of the rotator is, put the choke in next then plug your rotator loop into the other end of the choke and connect that to the beam.

Personally I'd steer away from a coax choke. How well they choke depends very critically on getting the lengths and diameter spot on. As it is a reactive choke, the bandwidth of its maximum choking ability is very narrow. Slightly out and you can massively reduce the choking capability and in some cases actually make things worse. Far better to use ferrite rings to make your own. That way you can make one where you'll know that it is going to be resistive rather than reactive where you want to use it and it'll also work over a wider range.

If you're only going to go up to a few hundred watts, 8 turns of RG58 on a FT240-61 ferrite is what you need. It is literally nothing more than a case of getting a length of RG58 and wrapping it through the ferrite ring 8 times like the picture below
It'll give you over 4k Ohms choking and it'll be resistive. You can put it in a nice project box with SO239 sockets at either end to make connecting it and disconnecting it easier.

 

[W5LZ]

There are always 'two sides' to that interference stuff. Your stuff and their stuff. Either can be -the- problem, and YOU have to accommodate it to some ridiculous extent to keep any 'peace'. Yeah, well, that's the way it is.
The biggest/strongest source of any RF that you can produce is your antenna. No way around that. RFI doesn't have to, and seldom results from 'bad coax', it's a result of your antenna producing more RF than the 'interfered with device' can handle. Ain't that a hoot?? The only 'cure' for that is to get your 'producer of RF' far enough away from those 'interfered with thingys' to not interfere with them. Or, reduce the amount of RF produces (reduce poer) to whatever extent is required to stop the @#$ interference.
There are two sides to that thingy too! Most of the devices being interfered with are Part-15 thingys. Read the 'disclaimer' for those devices! They can't produce any interference and have to 'put up with' any interference they get. Now... you get to convince the one getting interfered with of that -law- and make'em accept it. Good luck with that! Honestly, good luck!
It's an almost total waste of time, several 'layers' to all that, hope you got a good lawyer, you know?
Best you can possibly do is stay 'legal', don't cause any interference, and then hope for the best. Or intimidate the hell out of'em? That's not a recommendation BTW!
Have fun...
- 'Doc

 

[hotrod]

i will say make sure the radio its limiter is intact and not disabled. andmake sure
your modulation vr insnt disabled. this imho is the cause of most tvi issues.
power mikes i dont use them anymore. but if ya really must just crack it open
1/8 of a turn, then use mic gain to fine tune.cranking up power mikes can
make minnior tvi issues worse. if ya really like your neighbors tell them ya plans
and arrange a time scheldge that allows you to use your setup without worries

 

[Captain Kilowatt]

As to mounting the choke, you don't do it on the boom of the beam. Do it below the rotator. Basically you have coax coming from the radio up the mast to roughly where the bottom of the rotator is, put the choke in next then plug your rotator loop into the other end of the choke and connect that to the beam.

The idea of mounting a coaxial choke at the feedpoint is to reduce/eliminate feedline radiation and resulting pattern skewing. If the choke is mounted at a point far from the feedpoint the portion of the feedline between the choke and the feedpoint can still radiate. Many, many HF antenna manufacturers recommend mounting a coaxial choke at the feedpoint in their installation instructions. Granted most are balanced feedpoints being fed with unbalanced feedline. I myself prefer regular baluns on balanced feedpoints and have only ever used a coaxial balun on my 6m yagi with a balanced feedpoint and a half wave coaxial balun. I do not remember ever using a coaxial choke and have always opted for something like the W2DU balun.

 

[Oatmeal]

I bought me a new Maco 3 element beam, and now have also bought a 120ft on LMR 400-UF Times Microwave coax, and have it here at the shack..
Also do have all the metal needed for a hinge plate and brackets..

Have to get the hinge plate welded up, and a few other things done...
Haven't had much free time to fool with it due to work..


Beam will be on the flat side when I get it up..
Planning on using a 4" PVC pipe for the form..

How do you mount the choke on the boom of a beam ?....
Looking for some ideas...