10 MHz Bandwidth Question

[VK3MHZ]

Last night I again came across something that has plagued me pretty much ever since I got the RSP2.
This is not a fault with the RSP, more than likely the way I am using it or my understanding of the 10 MHz (SR) band-width feature.

Excuse me if I am not using correct 'SDR' terminology here...

I listen to aviation a lot, okay almost exclusively - the lowest freq on VRX0 is 125.8, VRX1: 127.4 VRX2: 126.0.
Now I wanted to follow a plane over to approach, which is 134.32 which I thought would be within the 10 MHz SR range (*see below). Alas nothing was received and the VRX on 134.32 didn't receive a sausage.

*As 125.8 is my lowest freq I was working on the 10MHz been 125.8+10 = 135.8 - As such I thought 134.32 should be within the working range.

With 125.8 as the lowest freq, is 134.32 within the 10 MHz range?
If not, can someone explain how to calculate what the frequency range is and does it start from the frequency indicated in VRX0 - or is it 5 MHz either side of the VRX0 frequency?

Just to clarify, there here's a screenshot (minus the 134.32 VRX)

[sdrplay]

The 10 MHz range is the LO frequency - 5 MHz to the LO frequency + 5 MHz

The LO frequency is ALWAYS at the centre of the spectrum.

Best regards,

SDRplay Support

[Mikesimpson]

Hi VK3MHZ,

Do what I do, set VRX 0-00 as the LO frequency, in this case, make it 130.80 MHz and just mute that VRX. Then set up VRX 1 at 125.8 and your highest at 135.8MHz and this will cover the whole 10MHz spectrum for you.

The following picture should explain this.

[VK3MHZ]

Thanks Mike, nice idea.
Setting the LO at 127.6 should do the same trick to I guess, I will give your suggestion a go.

Be nice to have a receiver that could see 20 MHz worth of real-estate, that would cover the whole aviation band then

[Hoss23]

So there is no way to set the LO directly in order to span the desired band without setting up extra VXR's? I can't find any such function per the manual. Sure would be a great feature in future versions so a person could use the minimum SR.

[Hoss23]

I found that if I tune the VXR-0 to the LO frequency desired, such as the middle frequency of a desired 5mhz SP, then lock the LO, I can keep the desired SP spread centered among the frequencies I want to monitor without having to run 3 VRX's.

[VK3MHZ]

So there is no way to set the LO directly in order to span the desired band without setting up extra VXR's? I can't find any such function per the manual. Sure would be a great feature in future versions so a person could use the minimum SR.

When you first start SDRUno the LO is always the center frequency of whatever band you are on. What I do, as do a lot of others, is click the mouse in the Main SP a little to the right of the center LO line. Then enter the freq directly into the VRX(s). That way you are not tying up a VRX with just the LO.

Reason I asked the question was I was mistaken in the bandwidth limit, I thought (not sure why, but I did!) it was 10 MHz, or whatever you have your SR set to from your lowest VRX frequency. Thus if your LO was 120 MHz and the SR was set to 2MHz for example, that would give you 120-122 MHz. It is actually 119-121 in this case. Half the SR either side of the LO.

Not sure about it if you are using ZIF.

[KC4RAN]

Can a VRX save data as raw I/Q? My eventual goal is to set up a system that records all amateur HF allocations (1.8-30 MHz).. but only the amateur allocations (with a little overlap on the edges). I'm guessing I can't have multiple processes hitting one receiver, but each process only receiving a portion of the 10 MHz - the receiver hardware (RSP1A) would be locked to that process, correct?

I'd like to eventually do this in a headless fashion, maybe on something as small as a Raspberry Pi (4?). One primary receiver process receiving 1.795 - 10.155 MHz. VRX processes centered on each amateur allocation, with a 5 KHz overlap at the edge, recording I/Q data.

160: 1.795 - 2.005 MHz
80: 3.495 - 4.005 MHz
60: 5.325 - 5.410 MHz
40: 6.995 - 7.305 MHz
30 10.095 - 10.155 MHz

That would give me 5 bands within the 10 MHz for receiver 1. I'd like to run this from the command line as the recording process only, outputting the data to an NFS share.

Has anyone tried this? Does this require the VRX feature, or can I 'chop up' the primary receiver process like this?

[VK3MHZ]

This might be a question for the more technical, but I am going to say no (in respect to bandwidth coverage).
It is 5 MHz either side of the LO. So if the LO is dead on 7Mhz you will get 2-12 if my understanding/calculations are correct.