Hello folks,
Is it a good idea to use a long active USB cable (> 5m) to connect the rtl-sdr dongle to the raspi instead of a long coax from the antenna to the rtl-sdr (directly connected to the raspi) to reduce the signal losses?
Can such long usb cable revert any noise to the rtl-sdr dongle or disturb the work of the raspi/satnogs somehow?
I am planning to mount the antenna on a 6m long mast.
73s
Ivan
I would suggest using a preamp at close to the antenna feedpoint as possible, and coax to the RTLSDR rather than run a longer USB cable.
Keep USB noise as far away from your antenna as possible.
I’m using a 5m passive usb 2.0 cable for station 1272. Seems to work great.
Note that according to the usb specifications, the maximum length for a passive usb cable is 5m. If you want longer, you’ll need an active cable. Those are pretty expensive, so it might be better to use a good rf cable and a lna.
This is what I have experienced on VHF at station #180 KJ7SU Prime. I’m going around between a few combinations and trying to determine which is best. The USB is an active cable. So far I have used the following; This […] is stuff inside my antenna-mounted enclosure:
(1) VHF Turnstile -> 0.5m RG58 -> [ RTL-SDR ] -> 15m USB -> RasPi
(2) VHF Turnstile -> 0.5m RG58 -> [ LNA -> RTL-SDR ] -> 15m USB -> RasPi
(3) VHF Turnstile -> 0.5m RG58 -> [ RTL-SDR -> RasPi ] -> 15m PoE Ethernet
(4) VHF Turnstile -> 0.5m RG58 -> [ LNA -> RTL-SDR -> RasPi ] -> 15m PoE Ethernet
(5) VHF Turnstile -> 0.5m RG58 -> [ LNA -> BP Filter -> RTL-SDR -> RasPi ] -> 15m PoE Ethernet
The two (config 1 and 3) without the LNA appear to be about the same and provide marginal/acceptable performance. Could be way better. Introducing the LNA seems to have swamped any signal with a ton of noise. I need to experiment more with turning the gain of the RTL-SDR way down before I move on further.
Then I will try the next thing:
(6) VHF Turnstile -> 0.5m RG58 -> [ LNA ] -> 15m TimesLMR400 -> BP Filter -> RTL-SDR -> RasPi
Kind regards and 73,
Glenn, KJ7SU