The Scythe SDR Project came into being when we (IRC) were talking about the effectiveness of shielding our DVB-T dongles to remove the noise and stray signals within SDR# or HDSDR.
The project implements improvements to increase the frequency range and the sensitivity of a DVB-T dongle when used as an SDR. This thread will document the progress and construction of the project.
Its Frequency range is 30Mhz to 1700Mhz.
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First, the dongle, this is one of the many generic DVB-T dongles that can be found on ebay for not alot of money (i paid about £12 for mine).
This model came with the R820T tuner, and is based on the rtl2832u chipset made by Realtek.
This dongle has been modified a fair bit, the usb connector was removed and a cable soldered directly the board, and the MCX connector was removed and replaced with an SMA connector.
Why an SMA connector?? well, there typically much tougher than MCX connectors, and typically give you a more solid connection aswell.
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This is the Nooelec Upconvertor v1.2.
This allows the SDR Dongle to go down into the AM Bands, and over all, adds DC - 30Mhz range to our dongle, giving it an effective coverage range of DC to 1700Mhz.
This Upconvertor also has a Noise Generator aswell, but we wont be using it, so it has been left unconfigured.
The Upconvertor is available from
Nooelec
Just like the DVB-T dongle, the Upconvertor has also been modified, the USB B connector was replaced with a standard pin header because the USB B connector was fairly bulky.
The bypass switch was removed and changed for a new switch that can be mounted on the rear panel of the case. A pin header was fitted in place of the switch, luckly, the connectors i oldered for the Power Boards had the same pin pitch, but had to remove the even pins from the connector to allow it to fit in the same footprint.
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This is the LNA4ALL.
This Low Noise Amp was designed, built and tested by at Adam Alicajic from
LNA4ALL
Its effective range of amplification is between 28Mhz to 2500Mhz, unlike the DVB-T dongle and the Upconvertor, this board has not been modified, the only thing missing is the 5v regulator, Mr Alicajic didnt attach one to my board, as i requested, but shipped my a surface mount 5v regulator with the LNA, which was very nice of him!
[size=8pt]Image provided by lna4all.blogspot.co.uk[/size]
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Our next thought was "Can we power all this from 1 source?"
Yes, we can, but how are we going to distribute power to each device?
Well, after nattering about it for an hour or 2, Moonlit (on irc) came up with an idea to use a custom pcb to do the job, as well as help filter the usb line from noise using a small electrolytic cap.
Thats when the ScytheSDR Power board came into being.
The ScytheSDR power board, nicknamed the badger board, splits the power to each connector on the pcb, allowing use to power 3 devices at the same time from the USB Bus.
USB Data is only sent to 1 connector which is intended from the DVB-T dongle, and splits power to the other 2.
The 10uF cap is attached to the vBus and GND, this helps reduce the noise when the SDR is in use, resulting in cleaner signals.
Here is virgin board, untouched, unmolested, clean!
Badger Badger Badger Badger Badger Badger
Here is a fully populated board, with its 10uF cap installed, and ready to do its thing.
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Updates to come!
