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Reviews Categories | Antennas: VHF/UHF+ Omnidirectional: verticals, mobile, etc | N9TAX Dual band slim jim portable antenna by 2way electronix Help

Reviews Summary for N9TAX Dual band slim jim portable antenna by 2way electronix
N9TAX Dual band slim jim portable antenna by 2way electronix Reviews: 18 Average rating: 4.8/5 MSRP: $$25.99
Description: Roll up portable 2 meter/70cm antenna with 16' lead and your choice of connector.

Product is in production.
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KX4O Rating: 3/5 Aug 16, 2016 15:11 Send this review to a friend
VHF Perfection, UHF much less so  Time owned: 0 to 3 months
Going beyond simple SWR tests, measurements of the antenna patterns were made of the N9TAX single band 2m, dual band 2m/440 & dual band MURS/GMRS rollup SlimJim antennas plus other checks for stray currents that tell the real story of antenna performance.

At VHF all three antennas work pretty darn well yielding a freespace H-plane gain a bit over 2 dBi plus or minus the usual small J antenna gain perturbations. This agrees well with models for J style antennas (traditional, G2BCX SlimJim, whatever). I was suspicious of the ferrite choke working at VHF, but testing confirms it does mitigate current flow back down the feed line - a surprising and happy finding. The conclusion of VHF performance is the N9TAX antennas are as good as any dipole in freespace with no apparent interactions with the feedline to spoil things. This is the best an antenna of this length can be and N9TAX nails it.

Unfortunately the performance at UHF for the two dual band models was questionable. Each dual band antenna tunes quite well for the 440 and GMRS bands respectively, but even a simple hand test easily reveals the existence of RF current along the feedline. This suggests the choke just isn't up to the task of functioning at such high frequencies. This is no surprise as ferrite choking at these frequencies is difficult; These examples prove the point. The other problem found is the, likely Ed Fong inspired, inline coaxial chokes in the upper radiator appear to have negligible effect. I found UHF RF currents flowing just fine on the antenna elements above the chokes - not good. The measured E-plane antenna pattern shows the classic multi-lobe beam pattern of a 3/2 wavelength antenna. In a pinch the N9TAX dual band antennas will function at UHF, but with reduced gain towards the horizon plus the effects of the radiating feedline. It's still much better than a rubber duck antenna however.

The "VHF only" model at its 3rd harmonic:
It is very important to emphasize that while the dual band models do a good job of facilitating a superb SWR to the radio at the UHF frequencies, the antenna patterns confirm they provide no beneficial pattern modification whatsoever. In fact the UHF antenna pattern of the dual band antennas are almost exactly the same as the mono band model run at its 3rd harmonic. If you can deal with a bit higher SWR at the UHF frequency, the less expensive mono band model will perform the same.

Fantastic. The attention to detail is obvious. The heatshink placement is logical and gives a polished look.

Solid conductor limits use:
A ladder line with stranded conductors would be more appropriate for antennas intended for frequent deployment - aka backpackers. I'd pay $10 more for that.

For VHF this antenna shines and provides great value for the incredibly low price.

While N9TAX obviously knows how to mechanically build an antenna exceptionally well, his actual antenna knowledge beyond basic design and how to tune them up is in question. This is apparent with his "6db of gain" claim (note the lack of dBi or dBd) on his sales web site (retrieved August 16, 2016) and zero antenna patterns of any kind, simulated or measured. In his defense, the whole SlimJim 6 dB over something-or-other kerfuffle is a myth that just won't go away and he is just another victim of it with his parroting of the obviously nonsensical gain claim of what is essentially a simple dipole. Quelling that myth on the Internet is like playing whack-a-mole, but vendors such as N9TAX are not helping.

As for the failure of the inline UHF coaxial chokes on the radiator, N9TAX is obviously relying on Fong's design inspiration to bear fruit so cannot be blamed entirely in trusting Fong's promises. However, if you are selling antennas, you really need to confirm their performance if you are making performance claims (aka promises) in your sales literature.

The likely Fong inspired VHF/UHF roll-up antenna by the well intentioned N9TAX, works exceptionally well at VHF and has compromised performance at UHF no better than a single band version run at its 3rd harmonic. I always wondered why Fong only showed the "before" antenna patterns and not the patterns of the resulting design in his DBJ-1 and DBJ-2 articles. Curious, I did build a DBJ-2 using 300 ohm feedline per Fong's documentation and guess what... the DBJ-2 coaxial choke does indeed work as designed resulting in a pattern at the 3rd harmonic practically identical to that of a regular dipole - the Fong choke chokes. It is important to note, Fong does not utilize any G2BCX SlimJim characteristics whatsoever in his design. Being this is a significant difference between the DBJ-2 and N9TAX's dual choke SlimJim design, I would venture to say this is a design issue in the latter.

The construction quality of the N9TAX antennas is so fantastic, I hope he can work through a design change to yield a better dual band antenna meeting realistic specifications. Alternatively, he can dial down the gain claims to measured values and keep things the same since his dual chokes do improve the match at the higher frequency. Until one or the other happens, only the VHF mono band versions function as designed and also function at the 3rd harmonic albeit with less gain towards the horizon and feedline radiation issues.

One star off for not vetting or patterning your product. One star off for not meeting your inflated gain claim in your sales literature.

Three stars - only because of the perfect VHF performance, stellar craftsmanship, superb value for VHF and at least some functionality at UHF.
F1AAA Rating: 3/5 Apr 1, 2016 21:44 Send this review to a friend
VHF Perfection, UHF mediocre  Time owned: 3 to 6 months
The antenna is hanging on 10 feet off the ground.
Below are 2 antenna analysis made from an AA-600:

The VHF results are very impressive and near perfection:

On UHF however, the results are far less impressive:

SM0TGU Rating: 5/5 Jan 9, 2016 02:09 Send this review to a friend
Excellent Antenna for LEO sats  Time owned: more than 12 months
Using this antenna as an omnidirectional RX antenna for LEO satellites on VHF and UHF. It is excellent and can replace a small Yagi for elevations satellite pass under 25 degrees.

Most recommended!
KG5HFO Rating: 5/5 Jun 13, 2015 03:25 Send this review to a friend
Still Awesome!  Time owned: 0 to 3 months
Update to my review below:

I now have it hooked up to my TM-281A. Only 20' elevation in my attic. The combination of moving the antenna up another 10' into my attic and putting 65w to it has really made it shine! I can hit a 65-mile repeater at will. Simplex of 20 miles is no sweat and tx/rx audio reports are good (haven't been able to try any further). I can occasionally hit a repeater 136.6 miles from me! Of course, atmospheric conditons have to be just right and the signals are very weak, but exchanging calls/names with guys hitting a repeater almost 140 miles from you with only $130 worth of equipment is awesome! I recommend this antenna without hesitation.
W0NQ Rating: 5/5 Feb 28, 2015 11:17 Send this review to a friend
Rock Star Simple  Time owned: 3 to 6 months
Awesome dual band antenna for portable use. I use it on the third floor of our house thumb tacked to the wall and it is not quite, but almost as good as my regular base vhf/uhf antenna. I might encase it in pvc and use it for my base antenna, it does that good of a job. Please, if you are a rubber ducky commando, get one of these for your ht and make the repeater with a clean signal. Everyone will appreciate it.
AG6UK Rating: 5/5 Dec 8, 2014 11:25 Send this review to a friend
Excellent Antenna for my HT  Time owned: more than 12 months
I purchased this antenna for use with my HT during camping trips and SOTA activations. It provides a huge performance advantage over the rubber duck. I ordered it with an N connector and use 15ft of LMR-400 Ultraflex mated to 4 feet of RG-58 which has an N connector on one end and the SMA connector for the HT on the other. The slim jim and cable roll up nicely to fit in my backpack. I usually try to string the antenna up in a tree or hang it from a 16ft Jackite pole which yields excellent results. I angle the pole slightly so that the slim jim hangs free a few inches from the pole. The slim jim does have several soldered joints so some care is needed when transporting. I broke mine by stuffing it too many times into my backpack instead of rolling it up carefully. When I went to purchase another one, I mentioned what had happened and Joe offered to fix the broken one at no charge. I now have the repaired one as a backup. Great service and a great product.
KD8UEI Rating: 5/5 Oct 22, 2014 11:24 Send this review to a friend
Excellent antenna  Time owned: 0 to 3 months
This is an excellent antenna. It is far, far, far better than any whip you can buy. I have it hanging in my living room in front of a window, and I am able to hit repeaters 30 miles away with my HT. I have tested it in the attic, and it's even better. I am considering getting a second one for the attic or outdoors. The icing on the cake is that it's portable - just roll it up and go. If you have an HT and are tired of the performance of whip antennas, the N9TAX is the logical next step.
W0VLL Rating: 5/5 Oct 19, 2014 16:14 Send this review to a friend
Works great - even in the basement  Time owned: 0 to 3 months
People say you can build this antenna yourself and save a few bucks - well by the time you buy all the connectors and parts and heatshrink, etc, I doubt you would save much at all. And I wouldn't do as good of a job as N9TAX did.

I currently have it hanging from the ceiling in my basement below grade with a push pin and with it I can work the repeater on the other side of the city. Even 440 works for once. I couldn't do this with the radio's supplied antenna. Imagine how well it will work outside.

I bought it to keep in my car for emergency comms, but I like it so much, I'll probably get a second one for home use.

N9TAX sells on ebay and also direct through his website. It seems he has a wider selection of connectors available on his website and the prices are slightly cheaper. I bought one with 16 feet of coax and a female SMA to screw right into my cheap Chinese radio but I'll probably get a BNC next time and an adapter.

Summary - well made, totally worth it, works great on both bands.
AE5J Rating: 5/5 Jun 18, 2014 11:52 Send this review to a friend
Update  Time owned: 0 to 3 months
Thought I might add this. I decided I would like to have a frame to mount my N9TAX Slim Jim and there were some plans on the web site for a bow. I looked them over and decided to build an elongated U to mount mine on an old camera tripod. Got some 1/2 inch PVC, a 90 deg elbow, a Tee, and a couple of wire ties. Assembled it in 15 minutes and the antenna now free stands whoever I set the tripod. Next I will add the adapters to allow use of a big painters pole to support it when traveling.
KD8TZC Rating: 5/5 Apr 25, 2013 07:30 Send this review to a friend
Couldn't have built one any better or for less  Time owned: 0 to 3 months
This is top notch quality and the service that Joe provides is outstanding. I had an issue with my install (due to user error on my part when attaching the connectors to the coax) and Joe walked me through some great troubleshooting steps.

The antenna that he provides is top quality, and it shows. He has a nice little Velcro strap on it so you can roll it up to store it if need be, and I don't think I could have built one of these for less than what he charges.

The order shipped immediately and I received it in no time.

If you are looking for a quality 2m/440MHz base antenna, this is a great product. I would purchase another one if I had a need.
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