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Reviews For: N9TAX Dual band slim jim portable antenna by 2way electronix

Category: Antennas: VHF/UHF+ Omnidirectional: verticals, mobile, etc

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Review Summary For : N9TAX Dual band slim jim portable antenna by 2way electronix
Reviews: 22MSRP: $25.99
Description:
Roll up portable 2 meter/70cm antenna with 16' lead and your choice of connector.

n9tax@2wayelectronix.com

Product is in production
More Info: http://www.n9tax.com/Slim%20Jim%20Info.html
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
15224.8
KB1MCT Rating: 2023-01-01
Great Antenna Time Owned: more than 12 months.
I keep one in each bag. They're small, quick to deploy, and beat the pants off a stock whip. I've made 2 meter contacts that have never failed to impress me with the distances covered. Try one out, you won't be disappointed.
N8FVJ Rating: 2021-08-13
Works well Time Owned: more than 12 months.
I simply placed the antenna in a window well. All repeaters in my area to 30 miles away works well. I could place it outside, but get full quieting now.
W8BS Rating: 2020-05-28
Works Great - Have 2 of these Time Owned: more than 12 months.
I have the 2m/440 unit in my attic for local repeaters on my IC-706. No issues at all. work great. Bought a special one cut for NOAA Weather Radio and now my weather radio can hear 4 of the stations here in WV.
MURPHY625 Rating: 2018-09-24
Wow! Works Great! Time Owned: 0 to 3 months.

I bought one of these from N9TAX and it works great.

SWR measurements on 2 meters was below 1.2 and usually the needle didn't even move on most frequencies.

We use sling shots and fishing reals to get the antenna up 50 feet into a tree and it works perfectly for that.
Just a note of caution: 50 feet of coax cable can get heavy so you have to make sure the antenna is not supporting the coax.
KX4O Rating: 2016-08-16
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.

VHF:
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.

UHF:
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.

Construction:
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.

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

Conclusions:
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 www.2wayelectronix.com (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: 2016-04-01
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: http://imgur.com/AFihOlu

On UHF however, the results are far less impressive: http://imgur.com/zBQicyb

SM0TGU Rating: 2016-01-09
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: 2015-06-13
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: 2015-02-28
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: 2014-12-08
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.