AmateurRadio.com

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.

I ordered a Nagoya NA-771 antenna on eBay. I was impressed with the shorter NA-701 and wanted something with a bit more gain that was not poke-you-in-the-eye long. The NA-771 had mostly good reviews on eHam.

I ordered from an eBay seller that shipped from the UK. The price was £4.99. When it arrived, I found the packaging and the antenna itself claimed to be a Diamond RH-771 not a Nagoya NA-771.

But this is clearly another fake Diamond. The lettering is white whereas the real Diamond product is lettered in blue. The lettering also contains nonsense. It claims “144/430 MHz & VDE BAND HECEMNG COVERAGE JAPAN.” Eh??? Perhaps it was supposed to say wide band general coverage? And the antenna is only 36cm long whereas the real RH-771 (and the NA-771) are supposed to be 39-40cm long.

None of this would matter if the antenna was any use, but in fact its resonant frequency is just below 120MHz. At 145MHz the SWR is more than 4 to 1 and it radiates a poorer signal than the shorter Nagoya NA-701 antenna.

Anyone want an air band antenna? Yours for a fiver. And can anyone recommend a seller that has the genuine Nagoya NA-771?

The object on the left of the picture is a 9600mAh external back-up battery for MP3 players, mobile phones and other 5V devices. I bought it on eBay (where else?) for $55.99 including shipping with the intention of using it to power my HTC Touch Pro smartphone so that it could run all day using GPS and internet connected apps like the APRS client APRSISCE. Previously I hadn’t been able to make much use of such applications when out and about on foot because if I was away from a power supply for more than a couple of hours the end result was a dead battery and a phone that could not be used to make phone calls.

The product arrived after a couple of weeks wait rather poorly packed in a jiffy bag containing the battery back-up unit, a 5V USB charger with the usual two-prong fold-out mains plug, and a USB cable with coiled lead and interchangeable power connectors. There was no box, nor any instructions so I had to figure things out for myself. Clearly the DC IN port was meant for the charger, the USB socket marked DC OUT was the output and the slide switch next to it turned the output on and off. The four LEDs showed the battery state for a few seconds after the POWER button to the left of it was pressed, and the charging state whilst charging.

There was no cable for charging, so I presumed I had to use the USB lead supplied for output and one of the interchangeable connectors. One of them did fit, though not very well, poorly enough in fact that it pulled out of the socket if there was the slightest tension on the coiled cable.

I started charging the power pack. Two lights lit up on the charger and the charge status showed two of the four LEDs lit. Next time I looked at it all the LEDs were off. Surely the batteries could not have charged so quickly? Eventually I measured the output from the charger and found it was about 0.25V. Clearly the charger had failed.

I sent an email to the eBay seller who was anxious enough about the possibility of receiving negative feedback to immediately promise to send a replacement. Meanwhile I found that the charger which came with my HTC phone had a USB output so I charged the battery pack with that. With hindsight that was rather foolhardy and I ought to have attempted to measure the current drawn first, but I got away with it. Though rated at 1.0 Amp output the HTC charger got fairly warm, but eventually the charge level reached full and the charger got cold again so I assume that it finished charging and the pack was fully charged.

The charger that came with the battery pack is labelled as an “MP3 Power Supply” and the output is rated at: DC 200mA +/- 30mA. Even the 1500mAh battery in the little Baofeng radio takes more than 400mA on charge. I managed to find a cable that would enable me to charge the battery pack from my workbench variable metered power supply and even when the battery pack is only half discharged it is drawing a current of almost 800mA. So I think the charger supplied simply blew up! I’m just hoping the eBay seller will provide a more adequate charger as a replacement. Sure, I can use my existing HTC phone charger. It may even be more convenient than having separate chargers for the two devices. But it would be nice to receive what one paid for.

By the way, if you ever wondered what is inside those Chinese wall-wart power supplies, how come they are so light, here are some pictures of the innards of the one that failed.

The answer, it seems, is not much. Call me old fashioned, but I’m just a bit apprehensive about having just a handful of components between my equipment and the 230V mains!

It’s a pity that this problem has occurred because I would have liked to have been able to recommend this battery pack to other users of APRSISCE on Windows Mobile. My initial test on the workbench suggest that this battery pack is more than capable of powering the phone with GPS and mobile data connection active during a day’s outing. The battery pack itself seems well made and I would guess that it is probably supplied by its Chinese manufacturer in a nice box with instructions and an adequately rated charger. The trouble in this case would seem to be caused by a cheapskate eBay seller.

The object on the left of the picture is a 9600mAh external back-up battery for MP3 players, mobile phones and other 5V devices. I bought it on eBay (where else?) for $55.99 including shipping with the intention of using it to power my HTC Touch Pro smartphone so that it could run all day using GPS and internet connected apps like the APRS client APRSISCE. Previously I hadn’t been able to make much use of such applications when out and about on foot because if I was away from a power supply for more than a couple of hours the end result was a dead battery and a phone that could not be used to make phone calls.

The product arrived after a couple of weeks wait rather poorly packed in a jiffy bag containing the battery back-up unit, a 5V USB charger with the usual two-prong fold-out mains plug, and a USB cable with coiled lead and interchangeable power connectors. There was no box, nor any instructions so I had to figure things out for myself. Clearly the DC IN port was meant for the charger, the USB socket marked DC OUT was the output and the slide switch next to it turned the output on and off. The four LEDs showed the battery state for a few seconds after the POWER button to the left of it was pressed, and the charging state whilst charging.

There was no cable for charging, so I presumed I had to use the USB lead supplied for output and one of the interchangeable connectors. One of them did fit, though not very well, poorly enough in fact that it pulled out of the socket if there was the slightest tension on the coiled cable.

I started charging the power pack. Two lights lit up on the charger and the charge status showed two of the four LEDs lit. Next time I looked at it all the LEDs were off. Surely the batteries could not have charged so quickly? Eventually I measured the output from the charger and found it was about 0.25V. Clearly the charger had failed.

I sent an email to the eBay seller who was anxious enough about the possibility of receiving negative feedback to immediately promise to send a replacement. Meanwhile I found that the charger which came with my HTC phone had a USB output so I charged the battery pack with that. With hindsight that was rather foolhardy and I ought to have attempted to measure the current drawn first, but I got away with it. Though rated at 1.0 Amp output the HTC charger got fairly warm, but eventually the charge level reached full and the charger got cold again so I assume that it finished charging and the pack was fully charged.

The charger that came with the battery pack is labelled as an “MP3 Power Supply” and the output is rated at: DC 200mA +/- 30mA. Even the 1500mAh battery in the little Baofeng radio takes more than 400mA on charge. I managed to find a cable that would enable me to charge the battery pack from my workbench variable metered power supply and even when the battery pack is only half discharged it is drawing a current of almost 800mA. So I think the charger supplied simply blew up! I’m just hoping the eBay seller will provide a more adequate charger as a replacement. Sure, I can use my existing HTC phone charger. It may even be more convenient than having separate chargers for the two devices. But it would be nice to receive what one paid for.

By the way, if you ever wondered what is inside those Chinese wall-wart power supplies, how come they are so light, here are some pictures of the innards of the one that failed.

The answer, it seems, is not much. Call me old fashioned, but I’m just a bit apprehensive about having just a handful of components between my equipment and the 230V mains!

It’s a pity that this problem has occurred because I would have liked to have been able to recommend this battery pack to other users of APRSISCE on Windows Mobile. My initial test on the workbench suggest that this battery pack is more than capable of powering the phone with GPS and mobile data connection active during a day’s outing. The battery pack itself seems well made and I would guess that it is probably supplied by its Chinese manufacturer in a nice box with instructions and an adequately rated charger. The trouble in this case would seem to be caused by a cheapskate eBay seller.

An antenna analyzer is a very useful piece of equipment and I have never regretted buying my AA-200, though I probably wouldn’t get one now with the current model priced at £410.00. Even the basic MFJ-259B which is not exactly renowned for its quality construction will set you back £260.00. So I was interested to discover that the Chinese have entered the market with the Feature Tech AW07A which can be bought on eBay for a much more reasonable £160.00.

The unit can measure RF impedance and SWR from 1.8 to 490MHz (making it more directly comparable to the MFJ-269B model) as well as measuring capacitance and inductance. It may be used as a non-precision signal source and frequency counter, and with the addition of an inductor may be used as a dip meter. It looks like a nice addition to any amateur’s toolkit.