Testing out the SDRplay with SDRuno and Characterizing RF HF Filters
Over on YouTube user Mile Kokotov has uploaded a video showing him using the SDRplay on the recently released official software SDRuno. In the video he first shows reception of some HF signals, then goes on to show how he can characterize some HF filters using a noise source.
Mile also wrote in to use to expand on his video. We quote:
“SDRuno” is new specialized software for SDRplay – RSP1 receiver. Besides many others excellent features, the new one is 10 MHz spectrum span on the window screen. The 10 MHz frequency span you can use it for characterize the HF Band-pass, Low-pass, High-pass or Notch filters. All you need is one noise source (noise generator) which you can find on eBay for about 20 USD.
With addition of directional coupler (for another 20$ USD), you can using SDRplay and SDRuno for HF antenna analyzer, measuring SWR like poore-man`s HF Vector Network Analyzer!
An RF filter is an electrical circuit designed to have specific characteristics with respect to the transmission or attenuation of various frequencies that may be applied to it.
There are three general types of RF filters:
1. A high-pass filter (HPF) similarly has a cut-off frequency, above which there is little or no loss in transmission, but below which there is considerable attenuation. Its behavior is the opposite of that of the low-pass filter.
2. A low-pass filter (LPF) is one that will permit all frequencies below a specified one called the cut-off frequency to be transmitted with little or no loss, but that will attenuate all frequencies above the cut-off frequency.
3. A band-pass filter (BPF) is one that will transmit a selected band of frequencies with substantially no loss, but that will attenuate all frequencies either higher or lower than the desired band.
The Filter connected in the front end of the receiver can be very much useful and it can improve the reception of the weak signals rejecting all others unwanted signals that can produces interference, intermodulation and as a results, the weak signals can not be copied !
With bandpass filter for particular frequency band, Receiving weak signals on that band is much easier, without problems from out of band strong sugnals.