Larger / higher gain antenna

[zogthegreat]

Hi everyone,

Does any one know if the Hack Shop will be offering a larger / higher gain antenna? If not, can anyone recommend a source?

Thanks!

zog

[krustkore]

there is how to's on building your own antenna. Actually really inexpensive and you get exactly what you want. There is a few things to consider when choosing a new antenna. a great resource for information is the rtl-sdr site

[fuzzy_bunny]

The ARRL (National Ham Association, or Amateur Radio Relay League, something like that) has a ton of information on antenna design.

Really, it comes down to what you are trying to receive. Because of physics, your antenna needs (optimally) to be designed to pick up the signal at the frequencies you are interested in. I have an old Parabolic I used for Wifi, I am interested in seeing what I can do with hooking it up to the dongle. For ADSB reception, Amazon carries both powered and unpowered unidirectional antennas.

For doing this on the cheap, ham swap meets carry a bunch of radio gear, including antennas that can be applied to this application. Learning is your best bet, as you can get an idea of what is necessary, and also take advantage of interesting atmospheric phenomena like ionospheric skips, which allow you to pick up remote signals that otherwise would be inaccessible.

I have an ARRL book from the 1930's (and more recent material) that still has good designs for a variety of tasks.

If you really start to dig into it, I recommend getting in touch with your local ham group, as there is a bunch of guys just about everywhere that are quite willing to point you in the right direction, and show you some tricks of the trade.

Some material can be learned from books, other information is learned from experience or word of mouth.

[fuzzy_bunny]

Oh yes, a more recent copy of the book I have from 1938 from the ARRL is:

http://www.amazon.com/ARRL-Antenna-Book-22nd-Softcover/dp/087259694X/

-FB

[Darren Kitchen]

This isn't one size fits all. It isn't like buying a bigger wifi antenna because we're interested in a huge swath of spectrum. Thankfully building them isn't difficult and we'll be showing that off soon.

[fuzzy_bunny]

Coolness. What is so funky is that the antenna book I was reading predated FM, lists everything in kc (kilocycles/second) and was in the era of tubes.

Since everything in the book is pre FM, that means the modulation in use is.....

You guessed it, Amplitude Modulation.

When you start thinking about how fast basic radio technology evolved and spawned FM (the most important advance in radio tech since the invention of radio itself), and from this, TV, the whole computer revolution going from glass based computers like the IBM 650 my mother worked on when she was pregnant with me (I'm only 46), to the technology that we have today, with hand held computer phones (cell phones) that make Kirk's communicator look like a model T, Tablets, Rabbits (a Z80 based C programmable platform that came before the Rainbow Pi's), Roku's, HDTV, laser printers, 3d printers, satellites, microwave, networking and the Internet, well when you start thinking of all the topics I am discussing and how far we have come in an incredibly short period of time, it is nothing short of just flipping A amazing.

I mean really, think about the technology they were using when they typeset, on a printing press, the information in my 1938 Antenna Handbook, and that was only 76 years ago, you really develop an appreciation of just how far engineers and yes, hackers, have brought us in the space of time of one lifetime, you develop an appreciation of just how incredibly smart at least one portion of the human race really is.

I eagerly look forward to your next episode, and Friday, my Realtek Dongle should be here, so I can start some serious playing/hacking/having an amazing amount of fun.

Back on the main topic, an antenna is an antenna. The Hakshop could carry antennas, but it really doesn't make any difference from antennas you get from any other source. An antenna is an antenna. Coupling other antenna designs is pretty much an issue of having the right connectors, cabling, impedance matching, etc.. For both transmitting and receiving improving the design of your antenna by twice will improve your reception by more than improving the radio by double. The antenna is where all the action is in acquiring a basic signal, what you do with it afterwards, well, you can do with SDR or traditional radio technology. The advantage of SDR is you don't have to wire a whole bunch of "stuff" to demodulate, amplify, and render the information present. It also offers a way of visualising the signal in a way that used to cost thousands of dollars, or even further back, was only possible to visualise in the human mind in the days before oscilliscopes, spectrum analyzers, etc.

The antenna is where everything starts (in reception) or radiates from (transmission), so focusing on your antenna design is going to reap massive rewards. In radio reception, you can amplify a crappy antenna all you want, but if the received waves aren't on the antenna to begin with, all you will amplify is noise or a lack of signal.

Darren seemed to hint that the next Hak5 was going to focus on antenna design (a Yagi?), and so I expect you will see a relatively simple and inexpensive design that will provide massive improvements off of the base antenna that is included with the realtek usb kit.

No antenna will provide optimum reception for all wavelengths, as the physics of receiving a waveform always has the possibility that the wave reflected from the edge of the antenna will cancel out the primary wave of interest. Imagine two sine waves 180 degrees out of phase being added together, and if you can visualise this, the result of the two waveforms is zero at all points in time, or no signal. Amplifying zero still equals zero.

It will be interesting to see what he comes up with, and what he manages to grab out of thin air.

Edited February 27, 2014 by fuzzy_bunny

[fuzzy_bunny]

I found a Yagi antenna in the hakshop, which is a directional antenna that will provide gain over what is included with the Realtek SDR kit, but will have limited bandwidth. It is listed as being useful for wifi pineapple, so I expect this is what the target frequency for the design is (2.4Ghz).

If you still have a tv aerial hooked up over your place, you have a long periodic dipole array, which, if you are fortunate, is on a rotor controlled in the house. Connecting this into the Realtek may provide interesting results. Since these antennas are useless for the digital standard now in use in the US, quite often people will just about give them away. The only warning I have regarding outside aerial setups connected to SDR's is be careful and disconnect it when you are not using it, or if you know a lightning storm is coming.

Having a lightning bolt hit your outdoor aerial and travel into your Realtek and computer would be bad, and in the worst case, would not only fry the Realtek, and the computer, and any equipment (displays) hooked up to the computer, but could cause a fire.

Fire and lightning are bad, m'kay?

Other than that, have fun.

-FB