[FARC] Local source for antenna connectors?

[Brian McEntire]

Thank you for all the pointers!

I'm an inexperienced ham and the receive-only aspect of ADSB makes it a fun
project for me to cut my teeth on.

I tried making two antennas. The first, based on this Compact 6dBi
Collinear Antenna (http://martybugs.net/wireless/collinear.cgi) was a
failure despite calculating the lengths for 1090 Mhz. It got worse
reception than the tiny antenna included with the dongle. Maybe my copper
wire was too thick or it was due to not soldering the wire to the
connector, it wasn't a very tight fit.

The second, based on this Coaxial Collinear Antenna (http://www.balarad.net)
was a major success in my book, doubling the amount of packets I'm
receiving. For the second one, I made a choke (I think that's the word for
it) with three tight loops of coax just before it connects to the antenna.

Right now, I'm using RG-6 left over from a cable TV install but the runs
are very short, just a few feet. Probably some room for improvement, I may
try out Mt Airy Communications to get a short length of RG-8X and see if
that makes a better Coaxial Collinear Antenna.


On Wed, Apr 29, 2015 at 11:02 AM, Popowsky Louis via FARC <
farc at mailman.qth.net> wrote:

> Brian, At that frequency you need to be very careful about matching
> impedances, antenna lengths, measurements, etc.  Reduced emmissions due to
> RF losses are very high and greatly reduce your communication range.
> RG-59 is 75 Ohm coax and you're transceiver is probably a 50Ohm device.  I
> suggest you use RG-8X coax, and don't cheap out on it.
>
> Your wavelength is only about 9.8", so a half wave dipole is about 4.9".
> You have to be very careful in when measuring and cutting.
> UHF connectors are not made for that frequency and will greatly attenuate
> your signal.  I suggest you use either BNC or SMA.  "N" is of course the
> best, but they're too big for your application.
> One of the easiest antennas to build is a Ground Plane.  I would use a
> "female chassis mount SMA".  Google it and you'll see what I mean.
> If you go with a sleeve dipole, you will probably need to make a balun to
> isolate the RF from the coax.
> Good luck with this project.  It should be more challenging than you think.
> Regards,Lou Popowsky  KB3RNT
>
>
>
>
>
>      On Wednesday, April 29, 2015 8:33 AM, Mike Barrett <
> mm.barrett at comcast.net> wrote:
>
>
>  The nearest one I know is RF Connections. They are in Gaithersburg on
> 355. The are cable and connector central.
>
> Sent from my Verizon Wireless 4G LTE DROID
>
> Brian McEntire <brian.mcentire at gmail.com> wrote:
>
> >Hi,
> >I just got a fun dongle device that connects to a Raspberry Pi and can
> >receive ADSB signals (1090 MHz.) It comes with a stock antenna and the
> >system is working, now I want to experiment with a few home brew antennas.
> >
> >Is there a local store were I can buy a handful of various coax
> connectors?
> >The dongle has an MCX female antenna port. I ordered a UHF SO239 PL259
> >female to MCX male connector and a RF coaxial coax cable assembly BNC
> >female to MCX when I ordered the dongle, so I'm looking for the
> appropriate
> >matching/mating connectors for those to solder to my home brew antennas.
> >
> >I'm going to start with a Coaxial Collinear Antenna made from RG6 in my
> >garage and a Collinear Wire Antenna from thick copper wire left over from
> >some electrical work. May also try a wine cork dipole or a ladder line
> >based J-Pole if I can find a short section of cheap TV ladder line.
> >
> >Guessing the Radio Shack at 7th street no longer stocks these connectors
> >but would be happy to hear if they do or there's a good local parts store.
> >
> >Brian / KB3TCC
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