[Hackrf-dev] How to tell if antenna is faulty

[Jonathan Guthrie]

I wasn't aware that an SMA is not a unique mechanical specification.  
Most people seem to be under the impression that it's a quarter-inch 
thread and a pin diameter of just under 1 mm.

On 2/5/2019 10:49 AM, cliff palmer wrote:
> I tried to order a multimeter test lead that fits SMA connectors so I 
> can have an easier time testing antennas.
> It turns out that "SMA Connector" can mean a lot of different sizes 
> and types.
> Does anyone have the male and female core diameter for the SMA 
> connectors used by the HackRF One?
> Thanks!
>
> On Thu, Jan 31, 2019 at 6:22 PM Michael Ossmann <mike at ossmann.com 
> <mailto:mike at ossmann.com>> wrote:
>
>     Cliff,
>
>     That sounds like a faulty ANT500.  Please contact your reseller for a
>     replacement.  Send a private email to me and
>     info at greatscottgadgets.com <mailto:info at greatscottgadgets.com>
>     if you run into any problems with that.
>
>     The two most common faults of ANT500 and ANT700 are a short
>     between the
>     center pin and shield ground or a break in continuity between the
>     center
>     pin and the antenna element.  Both of these conditions can be tested
>     with a continuity tester.
>
>     The DC resistance between the center pin and the antenna element is
>     unspecified, but I think it should be stable and low enough to cause a
>     continuity tester to beep.
>
>     Michael
>
>
>     On Thu, Jan 31, 2019 at 09:45:58AM -0500, cliff palmer wrote:
>     >
>     > Jake, the reading between the tip of the antenna and the center
>     pin varied
>     > wildly - so much that I borrowed another multi-meter to confirm
>     them.  The
>     > readings went from zero to 160+ and back.  I did secure the
>     antenna and the
>     > multi-meter leads to make sure my hands weren't the cause of the
>     variation.
>     > It looks like the antenna is faulty.
>     > Thanks for the hint on CQRX.
>     >
>     > I am using the Hackrf with the Ant500 as a starting place to
>     learn enough
>     > about SDR to tap RF data feeds from NOAA Buoys.  These buoys
>     measure water
>     > temp, wind speed and direction, wave direction, height and
>     frequency.  The
>     > buoy data will be fed into an FPGA/RISC board to calculate and
>     display
>     > marine navigation conditions, much like your local weather forecast
>     > includes a wind speed and direction display.
>     > There's no way that the Ant500 will be the right antenna for
>     this.  I got
>     > it because I needed a starting place and a number of YouTube
>     tutorials on
>     > SDR used it with the Hackrf.  Once I know more about what I am
>     doing I'll
>     > be pestering you all again for advice on antennas.
>     >
>     > Thanks again
>     > Cliff
>     >
>     > On Wed, Jan 30, 2019 at 11:24 PM Gavin Jacobs
>     <apriljunkbox at hotmail.com <mailto:apriljunkbox at hotmail.com>>
>     > wrote:
>     >
>     > > Cliff,
>     > > I have a hackrf and an Ant500. With the antenna fully
>     extended, you should
>     > > measure a very low resistance between the tip of the antenna
>     and the center
>     > > pin of the connector. Mine was about 2 ohms. If you have 75
>     ohms, then
>     > > there is a problem. Try again between the center pin and the
>     elbow (where
>     > > the extensions start) - it should be very low < 1 ohm.
>     > >
>     > > You should be able to use GQRX to receive an FM radio station,
>     with almost
>     > > any antenna. Most common rookie mistake is forgetting to turn
>     up the IF
>     > > gain.
>     > >
>     > > Tell us more about your setup and we can help you get started.
>     > >
>     > > Jake
>     > >
>     > > ------------------------------
>     > > *From:* HackRF-dev <hackrf-dev-bounces at greatscottgadgets.com
>     <mailto:hackrf-dev-bounces at greatscottgadgets.com>> on behalf
>     > > of cliff palmer <palmercliff at gmail.com
>     <mailto:palmercliff at gmail.com>>
>     > > *Sent:* January 30, 2019 3:15 PM
>     > > *To:* hackrf-dev at greatscottgadgets.com
>     <mailto:hackrf-dev at greatscottgadgets.com>
>     > > *Subject:* [Hackrf-dev] How to tell if antenna is faulty
>     > >
>     > > I have a Hackrf One with an Ant500 Antenna and I am having no
>     luck with
>     > > multiple tutorials found on YouTube, including the ones at
>     Great Scott
>     > > Gadgets.  I measured the resistance on the (disconnected but fully
>     > > extended) Ant500 Antenna using a multimeter (one lead on the
>     metal part of
>     > > the antenna and the other on the male lead in the connector.  The
>     > > multi-meter measured up to 75 Ohm resistance.
>     > > I'm really new to SDR and so I don't know if resistance should
>     concern me,
>     > > but it seems like an antenna should not have resistance.
>     > > I would appreciate some advice about how to determine if this
>     is really a
>     > > problem (and the antenna is faulty) or if I am making a
>     typical new-to-SDR
>     > > mistake.
>     > > Thanks
>     > > _______________________________________________
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>     > > HackRF-dev at greatscottgadgets.com
>     <mailto:HackRF-dev at greatscottgadgets.com>
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>     > >
>
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>
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