Looking for recommendations for mobile, wide band, rx only antennas.

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jgilkey
Posts: 4
Joined: Wed Nov 13, 2019 11:18 pm

Looking for recommendations for mobile, wide band, rx only antennas.

Post by jgilkey » Sun Nov 17, 2019 2:55 am

Hello everyone, I'm building a system based on a KerberosSDR. It will be vehicle mounted, and I need to find an antenna suitable to my needs. Since there are 4 inputs, I can probably split the antennas up. The majority of the frequencies are in the 450-490MHz range, but I would occasionally like to receive 770-775MHz. This will be RX only. Any suggestions would be appreciated. I'm thinking of smaller, phantom size antennas. Also, the radios will all be simplex (no repeaters) and local to where the antenna is (within 1/4 mile).

Thank you in advance.

snn47
Posts: 213
Joined: Tue Dec 27, 2016 11:00 pm

Re: Looking for recommendations for mobile, wide band, rx only antennas.

Post by snn47 » Sun Nov 17, 2019 9:19 am

Short answer: Since you don't transmit, any wire of ~10 cm should receive well enough for you at the 1/4 mile you quoted.

To have a truly wideband monopole antenna would require either the use of e.g. a Blade antenna e.g. CI-285 Imagehttps://www.edmo.com/products/antennas- ... tor-ci-285 specified for the frequency range you want to use, or that you built yourself such an antenna.

Long answer:
Depends on how you want to use the antenna

- stationary or while driving
- is one antenna with a preamplifier/splitter enough
or how many antennas you need/want on the car for which purpose
- simultanious operation on more than a few MHz removed frequencies or not
- How do want to fix the antenna stationary you have many options, mobile it depends on the max. speed if a magnetic mount works or if you have to drill into the frame.
- where on the vehicle you want to mount it, with drilling a whole
- is the car metal/conductive below the antenna.

A 1/4 wave long conductor, e.g. mounted in the center of a conducting roof, 180° inverted of course since it is shown for bottom mount on aircraft Image viewtopic.php?f=6&t=1516#p3768
or a fixture like shown in this picture adjusted to your frequencies Image https://www.funktechnik-bielefeld.de/al ... bilantenne
fixed vertically in a window should be sufficient for reception andalso while driving. With 4 windows you would have 4 antenna placement options + 1 in the center of the roof.

The difference between a on a conductiong surface fixed antenna (first antenna mounted on a larger conducting surface) is that it is a 1/4 wave monopole), while the second or any magnetic mount lack the connection to the ground of the conductingsurface and the coax at the antenna end.

The impedance and radiation pattern will be not the same as a 1/4 wave monopole, having irregular lobes and notches and gaing varying with frequency, but still as said above adequate for your use in 1/4 Mile distance.
Last edited by snn47 on Sun Nov 17, 2019 9:47 am, edited 3 times in total.

HighSNR
Posts: 49
Joined: Mon Sep 18, 2017 8:14 am

Re: Looking for recommendations for mobile, wide band, rx only antennas.

Post by HighSNR » Sun Nov 17, 2019 9:35 am

Is this an antenna array? For DF for instance.

Or do you just need multiple channels that don't need to be coherent? Kerberos would seem like overkill.

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