Sunday, August 05, 2012

Fake or genuine?

Buying radio gear on eBay is like gambling. It's addictive, but often you lose. You win often enough to keep you coming back in the hope of finding that absolute bargain.
Is the antenna on the right a fake?
I thought that I would buy a dual-band handheld antenna that was long enough to have a bit of gain but not too long to use in the shack. (I have several gain antennas but at over a metre in length they are not suitable for indoor use.) I have a Nagoya NA-701 which works very well for its length (22cm) so I thought I would get a NA-771 which is 40cm in length and ought to perform a couple of dBs better. I know only too well that there are a lot of fake antennas on eBay so I bought this one from 409shop, or rather from radiobanker which is one of the eBay IDs used by 409shop. The general consensus is that 409shop is a trustworthy trader and doesn't sell fake stuff.

When the antenna arrived I was concerned to see that instead of the silver-on-black label showing the make and model number the details were printed on in blue. I have had other fake antennas with printed-on labels, even ones with the same shade of blue so it was not a good omen. When I tried the antenna on one of my handies I found that it performed no better than the much shorter NA-701.

SWR of the alleged NA-771
I put it on my AA-200 antenna analyzer and found that the SWR at 145.000MHz was about 4:1. There were two dips to the HF of the 2m band, the best of which was at 195.000MHz with 2.7:1. This is not the worst I have found but it explains why the antenna did not perform optimally.


SWR of Nagoya NA-701
For comparison I looked at the SWR of the NA-701 with the silver-on-black label. This was a really good match - better than 1.5:1 at 150.000MHz though closer to 2:1 at 145.000MHz. Given that the resonance at any given time will be affected by conditions surrounding the hand-held antenna that's close enough.

So is the NA-771 from radiobanker a fake or not? The plastic sleeve the antenna came in bears a silver hologram label that says "Nagoya", and the name "Reuex Industrial Co. Ltd." That is the name of the company that manufactures Nagoya antennas and apparently they do use blue lettering.

So I conclude that this antenna is probably genuine and performs as well as it was meant to, which unfortunately happens to be not as well as I hoped. The Nagoya NA-771 is not worth its extra length.

FYI using an SWR/power meter I measured the SWR of the two antennas at 433.000MHz to be: NA-701 3.4:1, NA-771 4:1.
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