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Author Topic: Need Recommendation For 1676 MHZ ANtenna  (Read 652 times)
KA1OWC
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Posts: 117




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« on: December 03, 2017, 01:39:04 PM »

I wish to put up a dedicated antenna for reception of NWS weather balloons which broadcast at 1676 MHZ...I would appreciate any suggestions anyone may have! Thanks...
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Steve, KA1OWC
Retired Lieutenant Colonel, US Army
Army Nurse Corps
WB6BYU
Member

Posts: 17195




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« Reply #1 on: December 03, 2017, 06:04:00 PM »

How strong are the signals you are trying to listen to?

Are you thinking of tracking specific balloons (in which case you can aim
a beam at it and get much more range) or just listening on an omni
antenna in case there happen to be any balloons in the area?  In the
latter case you would be using a lower gain antenna, so range would
be more limited.
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KJ4HVL
Member

Posts: 76




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« Reply #2 on: December 04, 2017, 05:28:35 AM »

If you aren't pointing the antennas with a rotor, I would consider a "turnstyle" or "eggbeater" type antenna. Many people use them with some success for LEO satellite work (which is pretty close to balloon work)
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KA1OWC
Member

Posts: 117




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« Reply #3 on: December 04, 2017, 09:02:46 AM »

Would a small mag mount antenna, cut to the frequency (1.6 inches)  and placed on something like a metal pizza pan have a chance?
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Steve, KA1OWC
Retired Lieutenant Colonel, US Army
Army Nurse Corps
WB6BYU
Member

Posts: 17195




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« Reply #4 on: December 04, 2017, 12:32:47 PM »

You might have problems finding a mag mount that will work well at such a high frequency,
regardless of the antenna that you put on it.

Probably would be easier to build you own, such as mounting a chassis-mount coax socket
through a ~4" square piece of copper clad circuit board and soldering a quarter wave wire
to the center pin for the antenna.  Or cutting back about 2" of shield on the end of a piece
of RG-8 coax, soldering some wires to the shield for radials, then trimming the center
conductor to 1/4 wavelength.

Whether that is adequate will really depend on how far away from the balloons are.

Something like a quadrafiliar helix might be a good choice in many cases - they are often
used for satellite work.  For longer distances where you are tracking the balloon, an
axial mode helix can give good gain with practical constructional tolerances.  An old satellite
TV dish can make a good high gain antenna, as long as you can point it at the balloon.

You might do some research to see what types of antennas are recommended for GPS, which
isn't too far away in frequency.
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KJ4HVL
Member

Posts: 76




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« Reply #5 on: December 04, 2017, 12:43:47 PM »

You might have problems finding a mag mount that will work well at such a high frequency,
regardless of the antenna that you put on it.

Probably would be easier to build you own, such as mounting a chassis-mount coax socket
through a ~4" square piece of copper clad circuit board and soldering a quarter wave wire
to the center pin for the antenna.  Or cutting back about 2" of shield on the end of a piece
of RG-8 coax, soldering some wires to the shield for radials, then trimming the center
conductor to 1/4 wavelength.

Whether that is adequate will really depend on how far away from the balloons are.

Something like a quadrafiliar helix might be a good choice in many cases - they are often
used for satellite work.  For longer distances where you are tracking the balloon, an
axial mode helix can give good gain with practical constructional tolerances.  An old satellite
TV dish can make a good high gain antenna, as long as you can point it at the balloon.

You might do some research to see what types of antennas are recommended for GPS, which
isn't too far away in frequency.

GPS almost ALWAYS uses a copperclad board milled as a patch antenna. Patches are unique beasts both in terms of design and construction. They are doable, just difficult. I've worked on a few S-band patch antenna projects.
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WB6BYU
Member

Posts: 17195




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« Reply #6 on: December 04, 2017, 10:32:03 PM »

Here is a GPS antenna design you could modify.
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KA1OWC
Member

Posts: 117




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« Reply #7 on: December 05, 2017, 09:47:19 AM »

How about this antenna for the 1676 MHz balloons?
https://www.ebay.com/itm/Lysignal-800-2400MHz-13DB-9-units-Yagi-Antenna-29inch-F-male-Type/182740548525?epid=23004570700&hash=item2a8c2f7bad:g:oXIAAOSwWf9ZpzhW
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Steve, KA1OWC
Retired Lieutenant Colonel, US Army
Army Nurse Corps
WB6BYU
Member

Posts: 17195




Ignore
« Reply #8 on: December 05, 2017, 10:55:36 AM »

Quote from: KA1OWC

How about this antenna for the 1676 MHz balloons?...




A directional antenna such as that could work well when you know where the balloon is
and can point the antenna at it.  If the balloon moves too much you would need to keep the
antenna pointed at, but it would provide a stronger signal under those conditions than a
unidirectional antenna.  That's an important consideration in choosing an antenna:  for general
listening or actively tracking a balloon, and makes a big difference in your choice of antenna.

HOWEVER,  this specific antenna might not entirely meet the specifications as described
in the ad.  First, it says it covers 800 - 2400 MHz, a 3 : 1 range.  By comparison, the 70cm
band has a width of about 7% (420 - 450 MHz in the US) and most yagis don't maintain good
performance over that whole range.  A few do, but without some specific design techniques
covering a 10% range is quite difficult.  800 - 2400 MHz is a 100% spread:  that seems rather
unlikely.

Look at the directors:  they are all very close to the same size.  That tends to be a characteristic
of a narrow band yagi rather than a wide-band design.  Judging from the width of the reflector
compared to the director, it may give some gain for cell phones down in the 800 MHz range, but
appears to be optimized for higher bands. 

A technically-competent vendor selling to technically-competent customers would provide more
information, like a plot of gain and SWR / return loss vs. frequency.  If we carefully scaled the
element dimensions from the photo we could model it and see how it works.

You could certainly try it if the "high grain" and "fastness to fix" are important in your application,
and if it were optimized for a lower frequency than you need you could trim the ends of the elements
for good performance on your desired frequency.  But I would recommend some "due diligence" on
the design before deciding it is the best choice for you.



You might look for some antenna designs for the 33cm ham band (1296 MHz) and scale the dimensions.
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