Air Choke or 1:1 Balun Recomended or Not Star Duster 400?

[Onelasttime]

Ok so I moved about 11 months ago and I want to put up a temp ground plane until I can afford a a tower. I have a Star Duster 400 clone I am sure. Not who made it. I purchased it on clearance ridiculously cheap from Copper over the last Winter. I have seen these before from various OEM on peoples property at a distance but have ZERO experience with them! Even though everyone has digital tv now I still want to be a good neighbor and not cause issues. I was wondering if these are known to have common mode issues and prone to producing interference. The radio is a single final radio with an MRF455 that is properly aligned and their is no other amplifier. No super swing, no NPC mod's, no ESSB. The antenna looks a bit simple and I am just a a bit worried because I live in town with a fire department on one side a court house on the other and a school on another and surrounded by neighbors. Their are quite a few ground planes on other homes in the area but they look to be ancient and not having heard any action last winter I suspect none of them are in use.

My thoughts are that a 1:1 balun would be over kill and of little use. I am leaning towards and ugly air choke though at the feed point into the antenna. I am not worried about matching since this is such an old design I am sure it has to be close to 50 ohm load or it would have stayed on the market so long and would not have the radials angled like they are if not for matching. Usually if things mess up the basics like having the proper match they tend to not stick around. This is just until I can afford to put a 50 foot tower.

So I just want to be a good neighbor and I would rather not have to take it down to do this latter if it is a known offender! It is easier to do it before you put it up. I hate to waste good coax though and add such an ugly thing to an other wise visually clean look for nothing. No way to make an air choke sexy or invisible.....LOL

 

[Tallman]

There is no need for the Balun. What you are worried about is Causing electrical interference with your neighbors.
The short and sweet of it: Keep your modulation to less than 95%, run a low pass filter, keep your output power at a reasonable level and station grounds will help too.
Just because you did not hear anything doesn't mean that there is nothing in that area.
It is still possible to cause problems with Primary Signal Overload. Too much power can still overload the circuits and get really annoying. When I lived in Victoria TX there was a CBer that had a beam antenna as long as a trailer home. He was running an enormous amount of power and he was forever screwing up my mix tapes for work trips.
He was 8 blocks away from me.
But just to be sure toss an air core common mode in there for good measure.

 

[vkrules]

Dont know about that antenna . I fit chokes to all my antennas.

It's easier to put one on and not need it than to put the antenna up and find you need one.

If your coax is radiating (cmc) it will cause more interference to you and your close neighbors , no matter how clean the rest of station is..

 

[The DB]

With the Starduster design the radial system is a natural built in choke that is as or more effective than an air choke. In most cases another choke won't help, but it won't hurt either.

Any antenna that has a full length radial system has this benefit. That is the radials primary function. I would see if you have a problem with the antenna as is before you add an air choke to the antenna.


The DB

 

[Onelasttime]

That is what I was thinking VKRules easier to put it on it at the beginning then to take it down and do it a second time. Then I will plan on making an air choke. I will have to order some more coax.

@ Tallman I do not clip limiters so I never have splatter box's. I hate noise toys, broadcasting, splatter boxes, class c amplifiers, key down competition, excessive use of power, over driving an amplifier, vulgar language, and hostility on the radio! I actually use my variable power knob on my radio to use the least amount of power I can to talk to people. Other than into a dummy-load for testing my rf power knob has never been past 12 O'clock .

You do not want to get want to get me started on amplifier's...LOL If I want 100 watts output I will by or build an amp that can do 200-300 watts rms and run it at 100 watts. If I want 600 watts again I will buy or build an amp that can do 1200-1800 watts rms. I never abuse gear or run gear to it's limit or close to it. If it is a transistor amplifier you can bet your rear it is AB thermally tracking and being feed by a transistor not sand bar resistors.

A better antenna is always preferred over more power. More power is only good if it is clean and you are in an area you can use it. Even the cleanest power can cause chaos in cheaply built unprotected consumer gear. RFI is no joke.

 

[Tallman]

@ Tallman I do not clip limiters so I never have splatter box's. I hate noise toys, broadcasting, splatter boxes, class c amplifiers, key down competition, excessive use of power, over driving an amplifier, vulgar language, and hostility on the radio!

Even the cleanest power can cause chaos in cheaply built unprotected consumer gear. RFI is no joke.

Okay I gotcha! You asked for advice for a broad topic and since I don't know you I responded with the most common errors some people make. I have my Amateur license and it is legal for me to run amplifiers and I don't run one at all. I don't need one because of my antenna.

 

[wavrider]

Okay I gotcha! . I have my Amateur license and it is legal for me to run amplifiers and I don't run one at all. I don't need one because of my antenna.

OH??? come on down to 3.865 in the early mornings, like to hear that antenna with 100 watts on 75 meters

 

[wavrider]

Starduster requires an 9' pipe for install this is the counterpoise per say as well as the three ground radials.

The 9' pipe assists/helps with any CMC, coax routed inside the pipe, and YES install an ugly choke or line isolator at the bottom of that 9',

I have put the starduster on test tower without an rf choke and swept it with the analyzer, then put an ugly choke at the bottom of the 9' mast pipe and swept it again, resonant freq chaged 200kc and the vswr bandwidth curve looked normal with the choke.

I have one installed now on top of the tower and it works great, nice quiet receive, and no problems working local or DX.

Not as bad antenna for a direct fed 1/4 wl

 

[Tallman]

OH??? come on down to 3.865 in the early mornings, like to hear that antenna with 100 watts on 75 meters

What time? I'm on eastern time.

 

[222DBFL]

That or add some good ferrite chokes at the feed point. They help as well. And they don't look so bad, or stick out like an air choke. Saw where you spoke about that to the poster. Good luck and get it right. Messing about is great fun and can teach you a lot as well as long as you are abiding by the correct info. JMHO.

 

[M0GVZ]

I never use air chokes because unless you possess the proper test equipment you can't be sure where they end up doing the most choking and the choking is reactive so get it wrong and you can make things worse. With a ferrite wound choke they're quite broad banded so its not as critical that the number of turns are exactly right and the choking is mostly resistive.

Even though this antenna has a fairly reasonable groundplane system its still not infallible and a choke will at least act as belt and braces ensuring your coax isn't radiating.

 

[222DBFL]

Also might try using ferrite chokes. Just a thought. Just make sure to get the proper mix and size for your coax. Have fun experimenting. It's addicting and also helps you learn some things that will help a bunch if you use the analyzer the right way. Have a good one.

 

[wavrider]

What time? I'm on eastern time.

Few of the forum members are on there around 4:30 am or so, just throw a call sign out someone will come back if they hear ya.

And yes a good antenna and 100 watts will talk across the country on 75 meters, I have talked to fire runner in Cali from my QTH here in FL with fire runner using just his rig. The band was definitely in great shape and noise floor low.

It is summer time now so lower bands are noisy as all heck, they were not much better during last winter either.