I have an RSP2, which I brought about a year or two ago, can't recall precisely right now. Re MW on 22MHz, it was purely operator error, I had the receiver in Zero IF mode, once I click Low IF all was good.
Since you are tech support, you may be able to answer a question that has eluded me ever since I got it:
I have read posts stating there should be no difference in reception between using LIF and ZIF - this (at least in my case) is simply not true. Listening around 9 MHz to a station, in ZIF mode, reception was fine, switching to LIF the signal completely disappeared. Correct me if I am wrong, but I believe what I was hearing in ZIF mode was actually an AM broadcast image?
I just tried the above on 11 MHz just now, again in ZIF a rather strong signal, which I believe may have been ABC National here (AM BC), once I switched to LIF the signal was no longer present
Yet on all the framed bands (presets) everything is ZIF mode.
For normal tuning through bands, should I be using LIF or ZIF, or when is one to be used over the other?
OK, to be clear, there can be different mechanisms for spurious signals, depending upon what port you are using. All RSPs use a block converter to cover from 1kHz to 60 MHz. The block converter forms part of a dual conversion architecture and such an architecture will generate higher order spurious mixing products. Separately, there is also the issue of intermodulation, but that is a completely different mechanism from higher order mixing products.
The difference is explained in the following white paper that we published some time ago:
https://www.sdrplay.com/docs/SDRplay_Op ... _MW_HF.pdf
This paper also proposes some mitigation strategies depending upon which mechanism is creating the spurious response.
On the RSP2, the Hi-Z port has the best IMD performance, but is 'Wide open', i.e. it has no pre-selection filtering or optional notches. It is therefore more vulnerable to higher order spurious mixing products than ports A or B. However, higher order spurious mixing products are easy to identify and mitigate. If when you move the LO frequency, the actual frequency of the 'signal' changes, then it is a higher order spurious mixing product. Changing from LIF to ZIF or vice-versa changes the frequency plan and so changes where these spurs appear. In other words, you can move them 'out of the way' so that you can copy the real signal of interest.
With spurs that arise from IMD, you cannot play such tricks. Here, the only solution is to attenuate the input signal and/or apply additional external filtering.
Sincerely
Tech_Support