A Few Quick Questions About Antennas

Discuss commercial and home made antennas.
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Toasterz12
Posts: 2
Joined: Mon Sep 18, 2017 1:31 am

A Few Quick Questions About Antennas

Post by Toasterz12 » Mon Sep 18, 2017 2:00 am

I just bought my first RTL-SDR. I'm super excited to start playing with it. The bundle I bought came with 3 antennas and I bought an extra one for ADS-B. So, in total I have one 433 MHz antenna, one "UHF" antenna, one telescopic antenna, and one 1090 MHz antenna. First, I don't know the specs of the telescopic antenna; but, if it was possible to set the antenna to 1/2 or 1/4 wavelength, which is better? Second, what is a good universal antenna length? To clarify: some SDRs I've seen come with a decent all around antenna, how tall would that be? Finally, what angle should the antenna be set at (e.g. perpendicular to the horizon, parallel to the ground, or somewhere in the middle)?

EDIT: Found out that the supplied telescopic antenna is about 15-60 cm, so just over 1/2 a wavelength for my intended use, but I'd still be interested to know. Also, I though of another question! From what I've seen, a popular place to put the magnetic base is a metal pan. Would a filing cabinet work better, worse, or the same?

Sorry if these are stupid questions! I'm extremely new to the radio scene, and am trying to learn as much as I can.

Thanks!

HighSNR
Posts: 41
Joined: Mon Sep 18, 2017 8:14 am

Re: A Few Quick Questions About Antennas

Post by HighSNR » Mon Sep 18, 2017 8:34 am

A good all round antenna is the discone of you have space to mount it. These are very broadband and work on a wide bandwidth. Also log periodics and Vivaldi's are good if you need directionality. Obviously going with a broadband antenna will let strong out of band signals in that may deafen your receiver if too strong. Hence a narrow band tuned antenna is often preffered for a specific application.

The mag mount monopole will be ok on a filing cabinet. The metal base creates mirror image of the vertical element. For this the metal needs to be at least 1/4 wavelength to work best.

The angle of the element dictates the polarisation. Ideally it needs to be the same as the transmitter. Vertical is most common, but some stuff uses different polarisation. FM radio is vertical. TV stations can be Horizontal or Vertical. Cell phones can be 45degree slanted. Satalites are normally circular polarised.

Dont feel like you need to invest in all this though. What you have sounds perfect for 95% of applications.

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