Category Archives: SDR Radio
Ham Radio Science occasionally get emails from our readers on suggestions for a good reasonably priced HF SDR radio that won’t break the bank. So, we spent a little time investigating what was available in the under $300 price range. Frankly, there is not much to be found with the exception of a few kits. The kits are great learning tools, but some of our readers may not prefer trying to build a kit that includes tiny sma parts. Also the kits and some of the less expensive SDR radios are still sound card based and we were really looking for a direct sampling receiver. The $249 Afedri SDR-Net HF SDR met our requirements and more. The Afedri Net-SDR allows for connection to your pc via an USB interface and what truly puts the Afedri SDR-Net in a class of its own is the ability to connect via TCP (Lan connection). After looking into the very positive comments on the internet regarding the Afedri SDR-Net, we thought it would be well worth investigating this amazing little budget HF SDR receiver. The Afedri SDR-Net is made by Alexander Trushkin 4Z5LV and is available in a case for $249 or as a board for $199 from Alexs’ website. We highly recommend the version with case, since the case is very well constructed. We contacted Alex and he sent us out a sample Afedri SDR-Net Vers. 2.3a to take a look at. We have been using the Afedri daily for HF monitoring for about a month and have been very impressed with what you get for the price.
Mac users may have felt a little left out of the RTL2832U SDR revolution since there has not been a really easy way to get the RTl2832U to run with one of the SDR software programs like HDSDR. If you are a pretty hardcore Mac user, you know that OSX is basically a custom version of Linux. So, if you really wanted to dig in to the Linux side of OSX you can get a RTL2832U running under OSX. The simplest way to get a RTL2832U stick running on a Mac is to just install Windows under Bootcamp and away you go. However, thanks to Alain de Carolis, there is now a fast easy way to get the RTL2832U going on your Mac. You don’t even have to install anything on your Mac. You can even run the software from a USB stick. Alan has created a custom version of the BorIP server and HDSR that is wrapped in some “linux magic” that will allow both the RTL2832U and HDSDR to run on your Mac. You simply download the DMG file from Alains’ website and unpack the DMG file.
One of the bonuses you get with the RTL2832U / R820T DVB-T stick is some HF reception. The RTL2832U / R820T will cover HF between 24-30 MHz. Using SDR Sharp you can easily listen to the CB, 10 Meter, and 12 Meter bands. The working frequency range for the RTL2832U / R820T is roughly around 24MHz to 1850MHz when used as a SDR receiver. I did a quick test of the RTL2832U / 820T by connecting a random wire antenna to the screw on the stock antenna base. While by no means was this the best antenna for the HF reception, I still managed to pickup a few 10 Meter SSB broadcasts and some 12 Meter CW broadcasts.
I finally got my RTL2832U / R820T DVB-T stick from China for about $9.50 shipped. While I was working up a comparison between the well known RTL2832U / E4000 and the “new kid on the block” the RTL2832U / R820T, I did a little testing of ADS-B reception with the RTL2832U / R820T. While not expecting much, I was very surprised to see that the RTL2832U / R820T handily outperformed the RTL2832U / E4000 by a wide margin.
Using the stock antenna, the RTL2832U / R820T pulled in easily double the ADS-B messages than the RTL2832U / E4000 with it’s stock antenna. The frequency range of the RTL2832U is roughly from 24MHz to 1860MHz. It also appears that it is a bit more sensitive than the RTL2832U / E4000. This was especially true on 1090MHz, by a lot. The RTL2832U also has no DC offset spike in the middle of the spectrum. The down side is that the RTL2832U / R820T seems more susceptible to RFI. I did not get to try an external ADS-B antenna on this unit because the DVB-T stick has an MCX antenna jack on it and I did not have an adapter handy. I suspect with an external antenna the RTL2832U / R820T could be very impressive.