Modified RTL-SDR with Temperature Controlled Oscillator (TCXO)
Nobu Saito, a Japanese RTL-SDR hardware developer has come out with a modified RTL-SDR which has a +-2PPM 28.8MHz Temperature Controller Oscillator (TCXO) instead of the standard 28.8 MHz stock oscillator. (Note this link is machine translated to English from Japanese).
Normally 28.8 MHz TCXO’s are difficult to find, but Nobu was able to find a source in Japan, and he is now selling on his Amazon Store (with international shipping) modified dongles.
The oscillator on the RTL-SDR is prone to thermal drift, which means that as the dongle heats up from use, the frequency you are tuned to may change over time. A TCXO compensates for differences in temperature, and thus keeps the frequency stable as the temperature changes. This is extremely useful for applications such as receiving GPS, Beacons, APT, HFDL, and for radio astronomy.
Nobu sells the modified dongle with TCXO on this page. We expect to receive a sample of his product soon and will write a review when we receive it.
Edit: Now available at the 1090 MHz webstore.
Old man — broke — new to ham radio — looking to create an inexpensive scanner
Merry Christmas
Tom KC9UGC
Maybe I am missing something simple, but is there any reason not to use a different clock speed? A TCXO close to 28.8 which is more common and in stock? ex: 27.465 +/- 5ppm from digikey (only 1.335Mhz lower)
Provided both chips are clocked to the same source, wouldn’t the only change be that the receive frequency would shift by the delta of new clock speed and a slightly lower sample rate / receive bandwidth?
I believe the limitations on clock frequency are due to the dependency of the USB components in the RTL2832, not the tuner/AD/etc.
Yes this is correct. Folks found that changing it too much resulted in USB failure.
I also found that to some extent you can simply put a blue reverse connected SMD LED of a specific type on the high end of the crystal and this will also compensate a little for drift.