How Much Spectrum in One SDR??

[mstephens741]

Are there SDR which cover LW to UHF? How much spectrum is possible in one SDR? Are there limits?

(Learning newbie)

 

[KC4RAF]

In both of my SDR dongles (NOOELEC),

they show from DC to ~1.75GHz. They are not very sensitive with the encluded antennnas, but I still can receive one, sometimes two of the NOAA weather stations, which are about 75 miles as the crow flies. HTHs in your question.
So LW and UHF are possible.
(also, there's no gaps that I could find.)

 

[Token]

Are there SDR which cover LW to UHF? How much spectrum is possible in one SDR? Are there limits?

(Learning newbie)

Yes, in the hobby market there are SDRs that cover LW to UHF and above. The big brother to your Excalibur is the G39DDC Excelsior, and it covers 9 kHz to 3500 MHz. That is the widest I am aware of that is an “SDR” in the aspect that hobbyist have become used to. The AOR AR6000, with the I/Q module, would also be an SDR, and covers 40 kHz to 6000 MHz.

Outside the hobby market and in the professional realm there are many SDR type systems covering from LW to above 18 GHz. They also are very often much wider “banded” in instantaneous bandwidth (the bandwidth that can be sampled or recorded at acceptable levels, not the same as the tuned bandwidth), 4 MHz is pretty wide for the hobby market, 100 MHz or more is common at the professional level, and much wider can be found, it only cost money.

One thing all of these wideband SDR based systems have in common is that at some (or all, depending on design) frequency range they become “hybrid” systems, using an SDR as the base band detector and a superheterodyne approach to down convert higher frequencies to the baseband.

Way over simplification here:

An SDR has the ability to directly sample a frequency range. The upper frequency limitation is dependent on the speed of the ADC used and what kind of resolution you want, but they all top out someplace. ADCs can be very fast, but higher speed translates to higher cost. For simplicity lets say a specific SDR has a bandwidth of 1 MHz (1000 kHz). This means it can directly sample from 0 to 1 MHz. To receive a signal at 1800 kHz you could down convert the 1 to 2 MHz range to the 0 to 1 MHz range, and then use the SDR to sample that range, it would then see the 1800 kHz signal at 800 kHz and be able to receive it. To receive a signal at 15500 kHz you would down convert the 15 to 16 MHz range down to the 0 to 1 MHz range, and then the SDR would process the 15500 kHz signal just as if it was a 500 kHz signal.

The very broadband SDRs covering up into VHF and above do this. They may be, for example, 16 MHz wide direct sampling, and then break the entire spectrum they can receive (say up to 3500 MHz) up into 16 MHz chunks with downconverters. They then sample those downconverted 16 MHz chunks and display them for you as if they were “at” that frequency range.

T!

 

[mstephens741]

Good info as always guys. I realize now it was a bit of a dumb question. But since I am only a few days into this world, I'll grant myself a "newbie" excuse here!

I almost wonder if I should have bought the Excelsior then instead of the Excalibur, using a kind of more is better approach. Although I can't find the disclosed price of the Excelsior anywhere without making a phone call. Usually that means "pricey!"

I'll be happy enough to get something on the HF bands for now, but there is a lot of territory out there to be covered.

 

[SouthOrRadio]

The Excelsior is over twice what you paid for your Excalibur. I think you have your hands full learning the in's and out's with the Excalibur which in my opinion is an excellent quality piece of hardware/software. You made a good decision in your purchase. Get that antenna up and enjoy.

 

[mstephens741]

The Excelsior is over twice what you paid for your Excalibur. I think you have your hands full learning the in's and out's with the Excalibur which in my opinion is an excellent quality piece of hardware/software. You made a good decision in your purchase. Get that antenna up and enjoy.

"Twice the Price" - - - Ok, that would rule it out for sure. But nice to know for the future. Yes, just from playing the Excalibur with a hank o' wire I can see that it will be more than a lot of fun. The first antenna is on the way and will be here in a couple more days. It seems like it will be an easy one to install. Hope so.

 

[Token]

Actually, the Excelsior is well over twice the price of your G31DDC Excalibur. It is more like a tad over 5 times the price. It is well over 2 times the price of the G33DDC Excalibur Pro.

T!

 

[prcguy]

I got to work with one of the first SDR radios in the early 1990s and it would simultaneously receive and demodulate several signals at the same time from AM broadcast through cell phones at 800MHz.
prcguy