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On Sep 29, 2020, at 9:40 AM, bruno.d...@inrs.fr wrote:Hi, for bat radiotracking on the 148-152Mhz band, I use several types of antennas including a topfkreis 150Mhz vertical antenna of home-made manufacture. The advantage of this antenna is that it does not require a ground plane which could even allow it to be placed inside your buoy to avoid all oxidation phenomena?
The ground plane antenna also performs very well and is much easier to build than the Topfkreis.
You might also want to try the co-linear antennas often used in marine VHF which can be easily constructed from pieces of coaxial cable.
Otherwise a simple dipole might be fine, but the range might be much shorter.
There are all kinds of calculator on the internet (on amateur radio sites) to manufacture these antennas and adapt them for use on 150Mhz but all 4 are intended for use in vertical polarization.If you want horizontal polarization there would be the big-wheel or the loop antenna but I never tried...In order not to lose the directivity of the system, why not use 3 HB9CV 120 ° antennas (boom with a length of about 25cm @ 150Mhz).The inclinaison of the buoy will limit the sensitivity of the antenna downwind but this is also true for the lobes of other antennas...An LNA will bring gain but it is essential to associate it with a very high-Q bandpass filter to avoid all intermodulation phenomena. Perhaps in the open sea we could do without it but be careful anyway because the sensorgnome card necessarily generates interference and the antenna (s) will be very close to the electronic board...and there are also the maritime frequencies (around 156MHz ).
Bruno from France
-----mo...@googlegroups.com a écrit : -----A : "Jim Moore" <j...@marshlands.org>, "Motus Wildlife Tracking System" <motu...@googlegroups.com>
De : "Rubega, Margaret"
Envoyé par : motu...@googlegroups.com
Date : 28/09/2020 19:09
Objet : Re: [motus-wts] Re: antennas on buoys?Unsubscribe
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Hi Folks,I've been following this thread with interest; my group is just getting started on an effort to track small aquatic shorebirds (phalaropes), both at on-shore lake sites and offshore, for the two species that winter at sea. I'm wondering about Jim's answer -- what are the implications of using omnidirectional antennas on buoys for detection distances?Margaret Rubega(she/her/hers)Professor
CT State Ornithologist
Curator, Ornithology Collections
Dept Ecology and Evolutionary Biology
University of Connecticut
margare...@uconn.edu@profrubega
860-486-4502
From: motu...@googlegroups.com <motu...@googlegroups.com> on behalf of Jim Moore <j...@marshlands.org>
Sent: Monday, September 28, 2020 12:13 PM
To: Motus Wildlife Tracking System <motu...@googlegroups.com>
Subject: [motus-wts] Re: antennas on buoys?
*Message sent from a system outside of UConn.*
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<Station WG02.jpg><Station HB01.jpg>
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