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The N9TAX Slim Jim Antenna Review

by Don Butler, N4UJW

Well here I go again reviewing another antenna when I said in a previous review, that "I don't review antennas".

As the operator and "web guy" for Hamuniverse.com and a long time ham radio operator interested in antennas, I am constantly in search of antenna designs that are inexpensive, easy to build and simple to use with good performance and especially easy for the new hams out there.

While doing some research on the web for Slim Jim antennas, I ran across some ads for the Slim Jim type of antennas buried deep on eBay and I decided to check them out.

Enter the N9TAX line of Slim Jim antennas

Joe, N9TAX presented what I thought were some really inexpensive Slim roll up antennas made from 450 ohm ladder line for 2 meters, 2/440, and other frequencies. His prices and the quality was what caught my eye.

I did a bit of math in my head and determined that in fact, I could not go out and buy all the material needed to complete a working, ready to go, antenna like he has for sale, already built, on eBay!

In his ad describing his antennas, he had swr charts that showed very good plots across the 2 meter band and 70cm and several pictures of various models he has to offer along with some excellent reports of feedback to him from his customers. The pictures he has on eBay really show the quality of his workmanship in his products, and in my opinion...very professionally built.

I then looked back at the prices for them, read each description again for the different models and this made my decision to get one of the 2 meter/440 Slim Jims and review it here on Hamuniverse.com.

Some background on the Slim Jim antenna.

Basically it is an end-fed, vertically operated, folded dipole using a 'J-type Integrated Match', hence the word J'I'M. It's construction makes it "Slim".

The upper section above the J type match is a half wave long at the operating frequency. The antenna is tuned at the matching section by the sliding up and down of the feed points which can be time consuming and requires an swr meter or antenna analyzer.

It looks like a standard J Pole with another section folded over from the top and going back down toward the matching section.

Main advantage of a Slim Jim type antenna

The main advantage of it is it's very low angle of radiation, reported to be around 10 degrees or less to the horizon which makes it "perform" much better than standard J poles because the radiation pattern is much closer to the horizon where you want it in the first place! This is the major plus for the Slim Jim type antenna!
As an added note, some time ago, I built a Slim Jim from aluminum tubing and did some "angle of radiation" testing using a satellite tracking program tracking the ISS...in every pass of the ISS, I noticed a peak in signal strength on the S meter from their 2 meter transmissions from hams onboard at 8 degrees above the horizon, on both the approach and decent passes! Now this may not be a good scientific test, but it seems to confirm the very low angle or radiation pattern of the Slim Jim! Others who have built them report hearing and communicating much further than with other types of verticals including commercial built "high gain" antennas. All due to the low angle of radiation!

New ham station setup!

For new Technician class hams wanting to get on the air as soon as possible without a major expense for antennas, the N9TAX Slim Jims's will certainly do the job. The model I reviewed and tested is a dual bander and come 99% ready to put you on the air.....all you do is hook your coax to it and hang in a suitable location! Easy as pie! Truly "plug and play"...and no tuning.

Many hams are very limited as to where they can install antennas, especially those living in restricted apartment, condo situations or with landloards who are only interested in that rent money and not ham radio.

So where can the roll up Slim Jim be used?

Due to the physical size and very little weight of the Slim Jim antenna, only about 5 feet tall and about 6 oz, they can be used in the below locations:

In an attic suspended from the rafters,

Taped or pinned to an outer wall inside, preferably near a window,

Suspended from the ceiling,

Hung from above on a small patio balcony,

Supported from a roof overhang outside near a wall,

Hung from a tree limb,

Used as a fixed (non moving) mobile antenna using a short PVC pipe mounted to the bumper or other support with the antenna hanging from a short cross arm,

And many other locations limited by the imagination of the user!

And the best of all location, hung from an insulated mast up as high as you can go.
As with any antenna, they should be mounted or hung as far as possible from conducting materials.

So you can see that if you are a new ham wanting to get on the air simply and cheaply with a non complicated antenna installation, then the Slim Jim antennas offered by N9TAX are a fine choice.

Not only can new hams take advantage of the simplicity of the Slim Jim,
it can be used very effectively in emergency communication setups for those disasters where hams really shine!

Emcom people love them due to their simple and quick setup.

The N9TAX Review!

The model I reviewed was the 2m/440 version.

{ As of the date this review was written, I did not have a way to review the 440 band performance other than on receive so the "transmit on the air" performance nor swr readings are not included in this review for the 440 (70cm) band).  I have no doubt that it will perform well on 440. }

Since that comment, I have reviewed the antenna on the 440 (70cm band) see below!

Update! 09-27-2012 440 band performance

As I suspected in my earlier review, the N9TAX performs admirably on the 440 band!

For my testing, the bottom of the antenna was about 12 feet off the ground and suspended vertically away from a temporary PVC tubing arrangement shapped much like the letter C. Very temporary of course.

The swr was checked using low power (5 watts) FM on 4 different frequencies across the 440 band and there were no modifications or additional tuning of the antenna as it came right out of the box:

425Mhz  1.4
430Mhz  1.4
440Mhz  1.3
444Mhz  1.1

On the air performance using 45 feet of LMR-240 coax gets me into many of the Dallas, Texas 440 band repeaters which are on the average about 50-55 miles away! Most of the repeaters give me a full scale reading on the S meter on a Aninco DR-635T dual band radio. I can also get into other repeaters that are further away but not as strong as would be expected.

So my expectations on the 440 (70cm) band were confirmed in style!

Let's get down to the review.

First, I must let you know that my QTH is about 55 to 60 miles from the "local" Dallas, Texas repeaters with others spread around in all directions. The testing locations I used was at home, single story house on a concrete pad located in a mostly flat terrain area out to about 20 miles in all directions.

I had two conditions for the testing locations in mind for the review, inside a structure and outside. This should be a good test of the overall performance of the antenna under severe (inside), and much better surroundings, outside.

The inside test....
I realize that may new hams just starting out may live in apartments or other restricted locations so this indoor test was nothing more than hanging the Slim Jim antenna suspended with a nylon tie from a ceiling fan in the center of the room. The bottom of the antenna was very close to the floor, within only about 6 to 10 inches from the concrete pad.

I used an old Radio Shack HTX-212 2 meter radio for the on the air testing.
It has 2 rf power settings, 15 and 50 watts.

I used an MFJ-259B analyzer for the swr readings taken at the end of the feed line in the "shack".

After hanging the antenna and attaching a short length of old RG-58 coax to the connector supplied at the base of the antenna,  and the other end to the MFJ-259B, I proceeded to take some swr reading across the 2 meter band.
Remember, these readings are with the antenna hung from a ceiling fan inside....yes, I turned the fan off! GRIN.

144mhz = 1.5:1
145mhz = 1.3:1
145mhz = 1.1:1
146mhz = 1.1:1
147mhz = 1.2:1
148mhz = 1.3:1

On the air from inside the house results:

Keep in mind that my location is 55 to 60 miles from most of the repeaters in the Dallas, Tx area and there are no major obstructions, hills or things getting in the way of rf other than a brick wall and whatever may be inside that wall facing the Dallas direction.
I was able to hit many of the Dallas repeaters with S meter readings from S3 to "pinning" the meter on a couple.

I find this remarkable for such a restricted setup and the distances involved!
This one test should show anyone that the true nature of the low radiation angle of the Slim Jim really does improve performance when in restricted locations and situations.

The outside testing:

Like many hams, I had a length of PVC pipe laying around that was exactly 15 feet long that I knew would clear the edge of the roof with the antenna mounted "in a fashion" from it. The PVC pipe was just a "lean up" mounting secured at the bottom by a fence. I hope we don't get any wind!

The PVC support pipe was made from a couple of sections of pipe from a previous antenna adventure. I jury rigged a 12 inch "elbow" extension at the top of the pipe so I could hang the N9TAX Slim Jim from it without the PVC interacting with the antenna. In other words, you might call this a "free space" test....not scientific of course. There was no metal of any kind within a couple of feet or more near the antenna base or top. The completed support looked much like a very long thin upside down letter L.

After hooking up about 20 feet or so of several lengths of RG58 using a couple of those high loss barrel connectors, that I had laying around "collecting dust", and getting very dirty, I attached the end to the MFJ-259B...
So you can see, I used a lot of "care" in putting the antenna to the test using the higher loss RG58 and the barrel connectors at 2 meters...just like a "newbie" might do...I was attempting to "limit" the performance of it.... ......sometimes you have to simulate the real world some of us live in. 

Here are the "outside (outdoor)" readings with the antenna base at the 10 foot level. (Top was at 15 feet). You can see that the low swr for the antenna is "centered" around the middle of the 2 meter band. I intentionally checked out of band swr just to satisfy my curiosity.

143mhz = 1.4:1
144mhz = 1.3:1
145mhz = 1.2:1
146mhz = 1.1:1       Blue readings are band edges!
147mhz = 1.1:1
148mhz = 1.1:1
148.500mhz = 1.2:1
149.000mhz = 1.3:1

On the air using the antenna outside!

As expected, having the antenna up higher and outside the house made the antenna really shine.

Weak repeaters giving me an S 1 inside, were now at S 7!
Those that were S 9 were now pegging the meter.
Those that were S 5 were now at S 9.
Many of the "inside" contacts to repeaters were using 50 watts.
Now most of them only require 15 watts with the antenna outside.

A special note:
From memory, when I had built a 2 meter Slim Jim from aluminum tubing after many hours of work, my overall results were not as good as this antenna built by N9TAX, and it was higher by about 5 feet or so. I believe one of the main reasons that the N9TAX performed better than my homebrew version was the fact that I did not us a 1:1 choke at the bottom of it.
The N9TAX Slim Jim comes with a ferrite choke built in to the coax stub that is supplied. Having the choke helps to keep the pattern of the antenna down low near the horizon and also helps prevent rf on the shield of the feedline which would make it part of the radiating section of the antenna. This you don't want....my error in haste to get my antenna built and on the air!

Ok, enough of that......so what was the outcome of my review???

Here is how I rated the antenna: 20 criteria, each a maximum of 5 points.
Total perfect score would be 100.

1. The most important criteria of my review will be the on the air performance! (5)
 If I could give it a 10, I would! Excellent performance and more than I expected! If you don't read any more of this review, bottom line, get one!

Other considerations:
2. Clear and easy to understand instructions?
(4.75) There are no instructions that come with the antenna. You don't need any..this is truly a "plug and play" design unlike most antennas out there. If by chance you do have a question, Joe is certainly ready to answer any of your questions and he responds FAST!

3. Ease of assembly, any missing parts, (5)
There is no assembly, just find a place to hang it, attach your coax, your done!

4. Any special tools or test equipment required for assembly or tuning? (5)
You may want to check the swr with the antenna in it's operating location using low power the first time just to play it safe before you use full power. Anything can become damaged in shipment that is not visible. Mine arrived in perfect condition!

5. Can the antenna be put on the air with acceptable performance straight out of the box with no tuning for lowest swr? (5) After the first initial swr readings, it is really a "plug and play" antenna. Knowing what I now know, yes, you could use it "right out of the box".

6. Any special or unreasonable restrictions on location, mounting or height above ground? (5)
Just follow a good simple rule you should already know, as with other antennas. Do not locate it near conductive materials.

7. How does it perform at extremely reduced heights or severe locations? (5)
When I tested it inside the house and just off the floor, it performed well with very low swr. Keep in mind the distance to the repeaters.

8. Does it require more than one person to assemble and mount? (5)
If you have difficulty lifting a 6 oz antenna, then you may need help!

9. Was it easy and fast to setup to get it on the air? (5)

10. Was the SWR low over a good usable range as determined by the MFJ-259B as a test meter? What were the swr results? See above for swr readings for the dual band performance.(5)

11. Mechanical stability and material quality? (5)

12. Does it appear to be weather proof? (4.5)
I did notice at the top and bottom of the antenna where the ladder line was soldered that the conductors were bare. l personally would have sealed them but you have to wait until the seal is dry which prevents you from getting on the air quickly. In the long run, this should not be a problem but if you live near a salty environment, I would recommend sealing. The rest of the antenna was well sealed using heavy heat shrink.
I would also advise that the connector area between the coax feed and the S0-239 be taped well to prevent water intrusion into the connector. All of this is only my opinion, yours may differ.

13. Can it be used as a permanent station antenna? Yes, with the proper support. (5)

14. Assembly time required? (5) This is where this antenna really saves loads of your time...

15. Cost versus time saved dealing with MURPHY'S LAW and acquiring materials to simply build one? (5)
This is really a huge advantage that this antenna has. It comes complete with everything you need except coax. I noticed that some of the other models do come with coax.

16. Is the advertising on their web page misleading in any way in my opinion? (5)
absolutely not....the antennas are described well with drawings explaining the overall design with swr plots and enlargeable pictures.

17. Was it shipped in an adequate container to prevent shipping damage? (5)

18. If I decide to take it down and use it at another location like camping or field day, will I have problems with the disassembly and reassembly? (5)
Joe even provides a handy Velcro strip for securing the antenna when you roll it up! Simple and a great idea.

19. If for some reason the antenna breaks at some future time, can I easily repair it myself without having to re-order high priced parts for it? (5)

20. How did it perform as a "scanner radio" antenna on VHF/UHF? (5)
This was not a fair test but as an after thought was included anyway. This antenna is not designed for other frequencies other than the 2m/440 ham bands. So it's performance may be limited outside the designed band/s. However, it did perform well as a very good backup antenna for the "Scanner buff" in me. I was very pleased with it's performance as a "scanner" antenna also. Do not attempt to transmit outside the design frequencies.

Additional comments: Bottom line and some thoughts.......

Disadvantages of the Slim Jim roll up antenna?

Although not a criteria for the review above, the main disadvantage of the rollup style of Slim Jim antennas is the fact that they are not self supporting.

They must be supported in the vertical plane relative to the earth or as near as possible. However, I see no reason why the antenna could not be used on 2 meter SSB in the horizontal position using adequate support! There are many ways to support it so use your imagination.

The antenna must NOT and can not be used coiled up while transmitting. This should be common sense. High swr will result and your radio will certainly rebel by shutting down and if your high swr protection circuits don't work for some reason...there goes a high transmitter repair bill.

It is not advisable to hang it by a length of wire. Use non-conductive string, rope, cord, fishing line, etc. The antenna comes with a handy hole at the top provided for hanging. Keep the antenna away from metal conductors, large metal surfaces like air conditioner ducting, steel masts, etc. If you experience high swr readings, move it further away from the metal conductor.

The thing that really impressed me about the N9TAX Slim Jim is the fact that during all of the fun I had with it on the air testing, I forget it was so inexpensive for the results that it gave me on the air! Now you may be thinking that my review sounds biased..... Why would'nt I be.....it works so well! It's "slim" design also makes it a wonderful "stealth" antenna if needed.

The N9TAX dual band Slim Jim has proven itself to me and I believe you will be biased when you describe how well it works for you on the air and when it gets you there with such ease and little money!

My overall score?
99.25%! Not bad at all!

Where can you see more info? Click here! or the ad banner at the top of the page!

Feedback! 09-28-2012 from a happy user!

I often refer people to your N9TAX Slim Jim review and the N9TAX site.  I had bought his Slim Jims for myself and an elderly friend who now lives in a retirement community in a small 2 room bungalo, no outside antennas.  He hangs it on his wall and hits all 10 of the Pensacola, FL area repeaters full quiet.  His and my experiences with this Slim Jim are in full agreement with yours.

And I tell people, you can't make that antenna for what you can buy it from him.  The only way is if you already had the materials and connectors. 
The N9TAX Slim antenna is a great addition to my portable kit.  I've also used it for special events, ty-wrapped to the fiberglass mast sections - using just 4 pieces, stabbed on top of the tripod.  Same stuff as my Field Day Antenna.  Used just 5 watts, as low as that radio (Yaesu FT-1802) would go and had full quieting into the repeater.
Paul - AE5JU