If I get a SDR can it be used like a scanner? I read all these things like 80 hz spectrum are something like that, what does that mean? I watched a video and I saw the guy move his cursor over a peak and it tuned into the frequency, thats cool, but do the work up in the VHF range? Lets say my towns frequency is 169.050, could I put my cursor over the peak that is 169.050 and hear our town workers?
The short answer is yes, kind of.
SDRs do not generally have spectrum windows as narrow as 80 Hz (although you can make some that narrow). I think you mean kHz instead of Hz, very few signals are that narrow. Most SDRs have maximum bandwidth windows from 40 kHz up to several MHz.
Yes, there are some SDRs that work in the VHF range, but they tend to be very expensive and really not all that applicable because the band scopes are not really wide enough. Here is what I mean.
In a 190 kHz chunk of HF you might cover almost half of an entire SW band, say the ham 40 Meter band. In fact that would be over half of the 40 M band. In that 190 kHz range you might have 40 or more conversations happening, and a great deal more if we are talking about the CW portion of the band, potentially hundreds. That is because with SSB you can stack the conversations every 3 kHz or less and still be good to go. On CW you can stack them every 200 Hz and be good. You could call each of these a channel, but that is not quite right.
But, on VHF and in FM, 190 kHz does not give you that many potential “channels” of coverage. Typically the channel spacing is more like 25 kHz to keep a good guard band. If this is the number in your area/local system you might only have 7 potential channels you could cover with the same kind of SDR. And in most locations they try to spread comms out further to reduce interference, say 100 kHz or so. In that case you are only covering at most 2 channels visually.
So, on VHF and UHF you need more bandwidth. And, that is possible with SDRs, but it is not cheap. So systems like the AOR 2300 or AOR5001D will do what you are asking if you add the I/Q option, but at a cost of over $4000 USD after you add the options you would need. The AOR Alpha is even better yet, but at a cost of over $9900 USD.
The WinRadio WR-G33WSM will also do it, with 20 MHz of bandwidth and coverage from 30 MHz to 1000 MHz, and the cost is only about $1000 USD. But I don’t believe that radio works with the Trunking option and such, it is really meant as a measurement device, not so much a scanner.
So, what about that WinRadio G305e that was mentioned by mojoco in this thread? A good radio, to be sure, and the vendor does call that an SDR. However, it is not an SDR in the way an RFSpace SDR-IQ, SDR-14, SDR-IP, NetSDR, Microtelicom Perseus, or WinRadio WR-G31DDC or WRG-33DDC is. These SDRs range in price from $475 to about $1800 and they all only function from 60 MHz down, the exact top end being model specific (the G305e works up to 1800 MHz and cost $750). The cheapest and least capable of the SDRs I just mentioned will have an instantaneous bandwidth of 190 kHz, and one of them goes all the way up to 4 MHz of instantaneous bandwidth while two have 50 MHz of real time monitoring bandwidth (meaning you can see signals across a 50 MHz span and click on them to tune, all in real time). Plus, they are true DDC, Direct Digital Conversion, SDRs. The WinRadio G305 (indeed all of the G3XX series) are really traditional superhetrodyne receivers with a very small SDR-like DSP as the final IF and detection stage (other manufacturers do not call this technique “SDR”, but rather “DSP”, as far as I know WinRadio is the only maker calling this 15+ year old approach SDR). And this means the G3XX series have an instantaneous real time spectrum bandwidth of 30 kHz (because the IF bandwidth, something a DDC SDR does not have to deal with, can not be more than twice the IF center frequency), or about 1/6 the instantaneous bandwidth capability of the smallest and cheapest DDC SDR.
By the way, not everyone shares my opinion on the WinRadio G3XX series not being an SDR except in name. But for sure they are not DDC SDRs, that is not a matter for opinion, it is a technical fact. WinRadio is probably leveraging the term “SDR” to differentiate their product from other radios using a DSP as the final IF and detector, and they are successful at it because their radios are and have been 100% computer controlled, with no front panel, like an SDR is. I am sure that if it came to it WinRadio could defend their marketing the radios as SDRs because they use the same basic technique as a DDC SDR, but they do it in the final IF (2nd or 3rd IF, depending on the exact WinRadio model) of a traditional superhetrodyne receiver. And they display the narrow spectrum of the DSP as a amplitude over frequency graph, visually, like a DDC SDR does. It is a hybrid, like pretty much every upper half of the market radio designed in the last few years.
The WinRadio G3XX series does have a “Spectrum Scope”, like many radios not billed as SDRs (say the Icom PCR-2500 or PCR-1500, and most HF ham radios, among many). This spectrum scope can be very wide, even 100 MHz. And so you can see signals spread across whatever width the spectrum scope is, and click on those signals. But the way the system does this display is to basically scan the receiver and visually plot the responses. And this is not in real time, the scope only updates as fast as the radio can scan across your selected bandwidth, so you do not have the detection probability with one of these G3XX radios that you do with a “true” SDR. DDC SDRs see everything inside their instantaneous bandwidth affectively all the time, no scanning required.
Today’s SDRs tend to be useful for any mode except FM comms. Sure, SDRs can easily do FM modes of modulation, but the benefits of the SDR do not really translate to the types of communications that are generally done in the FM mode at VHF and UHF frequencies. SDRs today are not really ready for “scanner” type applications yet at an affordable level. The technology is relatively young on the hobby market.
Now, there are ways to do what you want. You can take an SDR and build a downconverting front end for it. This will put the DDC SDR bandwidth up into the VHF and UHF comms areas you want. Or, you can use a DDC SDR on the IF of an existing radio, assuming the IF is high enough frequency and wide enough bandwidth, that already tunes to the VHF / UHF range you want to tune. I do this with my WinRadio G31DDC on the 10.7 MHz IF of both an Icom R-7000 and an R-8500. Combining this hardware allows me to visually see a 12 MHz + wide chunk of spectrum anyplace from 10 kHz to 2000 MHz, and click-to-tune on the signals I see.
T!
