Aliexpress’s bargains – S01E01

Ludo | 1 juillet 2017
In this episode of Aliexpress’s bargains, I’ll write a few words about what’s sold as a Nagoya UT-108UV.
I don’t delude myself, what I bought is certainly just a bad copy of a terrible clone, but whatever…
The first thing I did after opening the bubble wrap package was to unbend the nicely curved antenna, then plug it to the VNA and see how horrible it could be, and I can’t say I’ve been deceived by what I saw…

VNA screenshots are available here:

I quickly checked the mag mount and noticed two things:

  • One wire from the shield braid was popping out of the coaxial cable through hole ;
  • There was no electrical connection between the coaxial shielding and the magnet.

So I contacted the seller and told him about the very bad results showed by the VNA. He assured he would do his best to solve this issue. I’ll come back later about that as I get more news from him.

Back to the antenna, I swapped its magnetic mount with another one and got much better results: UT-1008UV_VHF_AfterAdjustment.pdf & UT-1008UV_UHF_AfterAdjustment.pdf.

Since I had a proof that the original magnetic mount is faulty, I decided to disassemble and try to repair it. Once again I haven’t been deceived by the whole assembly:

  • all elements are held together with hot glue ;
  • the stacking seemed odd (see the picture below) ;
  • there was actually no electrical connection to the coaxial shielding!

Here is the original stacking:

All parts appear to be damaged. That’s because I took this picture after my first attempt to repair the mag mount. Everything was bright and shiny the first time I disassembled it.

Here is how I « improved » the antenna’s performances:

  • I’ve placed the flat metal ring just before the magnet and tinned its inner edge ;
  • gathered all wires from the braid and tinned them.

Below the result in a few pictures:

The braid passes through the white plastic disks holes and is soldered to the flat metal ring. The solder surplus was removed with a Dremel tool, in order to keep the surface as flat as possible. Then I added hot glue too to fill the space between the stacked elements and the inner border of the magnetic mount. After that I’ve placed the magnet on top of the flat metal ring, checked for electrical continuity between the antenna connector’s ground and the magnet, and filled again the remaining gap with hot glue. The bottom surface was then cleaned with what we call here in rance « Essence F », I don’t know how it’s called in english… I’ve seen someone translating it into « zippo fuel », so try this and please comment if it works or if you know how it’s called in english.

Here’s the final assembly result:

This mag mount antenna’s screw is longer than the one from the other mag mount I used to troubleshoot the issue, so I had to cut the antenna off a little bit more to get the same center frequency. The SWR and Return Loss are not as sexy as the one I got with the test mag mount but I’ll live with that and I hope to do better with the free replacement antenna I’ll get from the seller (otherwise I’ll have to post an incendiary feedback…). I bet the coax cable is as mediocre as the magnetic mount assembly!

VNA analyzes below:
UT-108UV_VHF_AfterMagMountRepair.pdf & UT-108UV_UHF_AfterMagMountRepair.pdf

Here’s how that story ended:
The seller refused to admit how crappy this antenna was. Trying to explain the situation to Aliexpress’ mediator also turned out to be a huge waste of time…

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