Slim Jim or J-pole antenna?

[bob85]

The antenna zeppelin ( j-pole now ) was invented a century ago.

The balloon gunners used to telegraph enemy data.<can not stand it>

"Radios" were motor generators without valves.^^ ab v c^^

http://en.wikipedia.org/wiki/J-pole_antenna

The slim-jim antenna has a higher resistance of irradiation, and can give better performance for it.

Also the angle of irradiation is lower in the slim-jim,

by the capacitance added by the curve of the folded radiating top hat.


nocpc.

more bullshit, you got that info from somebody that has no idea what radiation resistance is.

 

[nosepc]

more bullshit, you got that info from somebody that has no idea what radiation resistance is.

Sure you know for what reason one j-pole is not a Zeppelin ??

explain it!!

 

[Ironman1956]

What's the difference between these antennas, except design?

I built my slim jim out of 1/2 inch copper pipe. I has an 8 degree takeoff and reaches out beautifully with minimum wattage. I am on a fairly high point with my antenna. They claim about 6 dbi gain over a 5/8 wave ground plane and this would not surprise me for distances I am getting. Link attached.
http://www.hamuniverse.com/2metercopperslimjim.html

 

[The DB]

I has an 8 degree takeoff

Question 1, how was this determined?

They claim about 6 dbi gain over a 5/8 wave ground plane.

Question 2, does the antenna have 6 dBi gain, or 6 dB gain over a 5/8 wavelength antenna? You can't have both. I am also curious as to how this was determined?

I'm not trying to be mean or anything, but those are some pretty specific claims and I would love to know where they came from...


The DB

 

[Captain Kilowatt]

Question 1, how was this determined?



Question 2, does the antenna have 6 dBi gain, or 6 dB gain over a 5/8 wavelength antenna? You can't have both. I am also curious as to how this was determined?

I'm not trying to be mean or anything, but those are some pretty specific claims and I would love to know where they came from...


The DB

Good questions actually. I really do find it hard to believe that a simple 1/2 wave has 6 dB over a 5/8 wave unless it was measured at a very specific elevation angle. I am thinking somewhere in the null where the radiation from the 5/8 wave splits whereas the radiation lobe from the 1/2 wave is actually higher and not split.

 

[Ironman1956]

I built my slim jim out of 1/2 inch copper pipe. I has an 8 degree takeoff and reaches out beautifully with minimum wattage. I am on a fairly high point with my antenna. They claim about 6 dbi gain over a 5/8 wave ground plane and this would not surprise me for distances I am getting.

I got that info from the man whom has built many of them tested them and sells them on Amazon, and when you can talk over 70 miles on 10 watts I would say it definitely is one of the best, no argument here, mine has proven itself and have actually built them for friends. One of them took his factory antenna down and tried one and said there was no comparison.

 

[Ironman1956]

I got that info from the man whom has built many of them tested them and sells them on Amazon, and when you can talk over 70 miles on 10 watts I would say it definitely is one of the best, no argument here, mine has proven itself and have actually built them for friends. One of them took his factory antenna down and tried one and said there was no comparison.

You have to build one and make your own determination, I have made mine.

 

[Captain Kilowatt]

I've talked 40 miles into a repeater using the rubber ducky antenna that came on it but that does not mean it's a great antenna. If a Slim Jim beat a commercial antenna then the antenna had problems. those are my observations gathered over 35 years of radio experience. 22 of those were spent in commercial broadcasting so I really do know a few things about antenna gain etc.

 

[Ironman1956]

I've talked 40 miles into a repeater using the rubber ducky antenna that came on it but that does not mean it's a great antenna. If a Slim Jim beat a commercial antenna then the antenna had problems. those are my observations gathered over 35 years of radio experience. 22 of those were spent in commercial broadcasting so I really do know a few things about antenna gain etc.

You just want to argue, let you use a coathanger if you want, just know how mine gets out and how the experienced ham operator whom I got the design and dimensions from elaborated on it.

 

[Ironman1956]

Question 1, how was this determined?



Question 2, does the antenna have 6 dBi gain, or 6 dB gain over a 5/8 wavelength antenna? You can't have both. I am also curious as to how this was determined?

I'm not trying to be mean or anything, but those are some pretty specific claims and I would love to know where they came from...
DB not sure , check out the article link I posted k.

The DB

 

[The DB]

I got that info from the man whom has built many of them tested them and sells them on Amazon, and when you can talk over 70 miles on 10 watts I would say it definitely is one of the best, no argument here, mine has proven itself and have actually built them for friends. One of them took his factory antenna down and tried one and said there was no comparison.

So you got the data from a sales website online. Unfortunately that makes it pretty much useless, unless you also happened to mount it the same height over the same ground that they modeled the antenna at. Realistically that is simply not likely. For example, if your antenna is mounted lower then the angle of radiation over the same type of ground will be higher. If the type of ground in your area differs from the model they used that will change the angle of radiation as well. Being for marketing, the data they are giving is likely better than normal conditions to make it look better to potential buyers.

Lets look at the data and results you gave. A contact 70 miles away with an assumed 8 degree angle of radiation. Using right triangle calculations and mis-assuming the earth is flat for simplicity, that would put the main lobe of the signal at 9.84 miles high. Add in the effects of the curvature of the earth and that lobe is even closer to 10 miles up. Unless the receiving antenna is that high, for local distance contacts that angle of radiation means nothing.

Further, I can see 6 dBi gain, but 6 dB gain over a 5/8 wavelength antenna? If the antennas are mounted at the same height that simply isn't going to happen unless there is something drastically wrong with the 5/8 wavelength antenna...

Looking around the web I have seen all kinds of bogus reports about this antenna design as well as all kinds of reputable information from other forums where this was talked about. Reputable forum sites like QRZ.com and eham.net. The fact of the matter is this antenna design will function like a j-pole, no better, no worse.

Note, I am not saying that this antenna won't work for you and others. I am simply saying that this data that you believe is true about this antenna isn't as accurate as you think it is at your location, or any location that differs from the information in the model given assuming a model was ever made by the person making the claim, and the evidence you give that you think confirms the data really doesn't. That being said, have fun with it, that is why we are in the radio hobby after all.


The DB

 

[Ironman1956]

http://www.hamuniverse.com/2metercopperslimjim.html Here is the pattern I used. Choices, Choices, Choices so many choices.

 

[Ironman1956]

http://www.hamuniverse.com/2metercopperslimjim.html Here is the pattern I used. Choices, Choices, Choices so many choices.

You don't really have to say anything about it for it has been up for 6 months and outperforms any base antenna on 2 meter in the neighborhood, you can calculate till you are blue in the face, actual results are what counts .

 

[The DB]

You know, I have actually built slim jim antennas before. And you know what? They worked exactly the same as the 2 meter j-pole antennas I've built.

I have also built a 1/4 wavelength groundplane antenna out of an so239, and some small nuts bolts and washers, and some stiff solid 14 AWG wire.

There was no effective difference between any of these antennas when it comes to performance, and they performed about the same as the base antenna I was using before I made any of them.

There are days that I hit repeaters that are over 150 miles away with each of those antenna designs as well, although that was more a factor of conditions than antenna performance, just like that 70 mile contact you mentioned... I also know of people that have 900 plus mile contacts on the 2 meters ham band, although admittedly they were using horizontal yagi antennas at the time...

You are rating performance using aspects of the hobby that you don't seem to understand and claiming that it is all because of the antenna. This is a common an easy mistake to make. I suggest actually doing some research. Or you can continue to believe what you seem determined to want to believe... Your choice.

When it comes to commercially made 2-meter antennas, there are any number of which that will destroy that antenna performance wise, although in most cases people don't need such an antenna as vertical polarization on 2 meters is generally used to access local repeaters, which can be done pretty much anywhere in the us with 5 watts or less and a cheap, short, rubber duck antenna...


The DB

 

[Ironman1956]

You know, I have actually built slim jim antennas before. And you know what? They worked exactly the same as the 2 meter j-pole antennas I've built.

I have also built a 1/4 wavelength groundplane antenna out of an so239, and some small nuts bolts and washers, and some stiff solid 14 AWG wire.

There was no effective difference between any of these antennas when it comes to performance, and they performed about the same as the base antenna I was using before I made any of them.

There are days that I hit repeaters that are over 150 miles away with each of those antenna designs as well, although that was more a factor of conditions than antenna performance, just like that 70 mile contact you mentioned... I also know of people that have 900 plus mile contacts on the 2 meters ham band, although admittedly they were using horizontal yagi antennas at the time...

You are rating performance using aspects of the hobby that you don't seem to understand and claiming that it is all because of the antenna. This is a common an easy mistake to make. I suggest actually doing some research. Or you can continue to believe what you seem determined to want to believe... Your choice.

When it comes to commercially made 2-meter antennas, there are any number of which that will destroy that antenna performance wise, although in most cases people don't need such an antenna as vertical polarization on 2 meters is generally used to access local repeaters, which can be done pretty much anywhere in the us with 5 watts or less and a cheap, short, rubber duck antenna...


The DB

90% of our talk here is Simplex not repeaters, yes I do understand and I may be new to HAM but not antennas or rf. My first antenna was a copper 1/4 wave I built with heavy copper wire and an SO-239 , copper radials and used an analyzer to set the vertical height. One of the things I have ran into with HAM is that if they have a higher license than another they think they are that much smarter, bonkers on that. I will never convince you of anything and no I don't believe you ever built a slim jim out of copper pipe either or you would still be using it since it is a durable long lasting, low takeoff talking antenna for very little money, just maybe you should get more educated on why HAMS developed the slim Jim over the J pole and why they use them. It will open up an area you seem to be lacking in. We learn and we grow.