QS1R: Software Defined Radio for Shortwave Radio - A Review
I recently got back into shortwave radio after staying away due to the horrible urban RFI situation. I previously used a Drake R8 original. That was a great radio, but having a software defined radio is a vastly different experience.
I bought a QS1R used for $750. New it is $900. The QS1R is a top-notch software defined radio for 0 - 62 mhz - covering longwave, AM, shortwave, and up through the 6M ham band.
My setup includes a Wellbrook 1530s+ "magnetic" loop (aka low noise) with a rotor on a ten foot pole in my backyard. It works well with this loop as it does not require tuning (unlike a traditional ferrite loop antenna used for AM) and it provides more than enough amplification.
The SDRMAX V GUI software is amazing. It has a couple quirks and it takes a while to switch from using dials for everything -- but the ability to view up to 2 Mhz spectrum and the selectivity makes it all worthwhile!
(Philadelphia, PA - AM dial at night)
SDRMAX does use 100% of one of my cores. I've got a low-end (slightly old) Intel Q6600 CPU quad-core. Having two or more cores is useful, so that you can run SDRMAX in its full glory and still do other things on your computer. I like to look up radio stations by frequency on Short-Wave Info to see what I'm hearing.
The one software improvement I most want to see is a better spectrum playback. Currently you can record and re-tune the radio. However you cannot jump ahead or back to a time in the recording. This makes reviewing a long recording very difficult.
I've enjoyed using CamStudio to record the screen and post videos to my Youtube channel of some of my catches. Camstudio can be a bit quirky to setup. If you are running a recent version of windows you may need to follow these instructions for recording audio
The selectivity is superb. I don't know the specifications but it crushes the Drake. The synchronous AM outperforms the Drake (which had locking issues). You can vary the bandwidth in each mode to the nearest 1 Hz. I enjoy matching a filter to the size of a signal - often listening with 7-8 khz filters on wide signals (like Greece on 9420 khz which is 9.6 khz wide). For some reason using a 9 khz filter adds too much high pitch hiss, even on strong signals. But 8-8.5 khz is more than adequate. The sound quality is much better than the Drake's 6 khz filter. The ability to use a wide 4 khz USB or LSB filter allows for good audio quality while rejecting a lower or higher adjacent station.
I haven't compared the sensitivity to other radios - but it seems superb. At my location, I'm limited by the urban noise level and do not need any higher sensitivity.
The noise reduction provides marginal improvements on weak signals. It is not a miracle. It also makes it easier to listen to signals that have moderate noise.
The two noise blankers are useful. NB2 is effective on power line noise. I can hear WWV on 60 khz thanks to NB2 (and a very narrow CW filter). They are quirky. At a NB setting that is too high signals bleed all over the dial and things go generally hay-wire.
I don't like the auto-notch filter as it appears to be too wide or too deep. However in practice, I never need it because you can avoid the heterodynes by using tight filters and USB/LSB. The manual notches work great and you can have up to ten.
The graphical display is very useful to find stations. For instance, it is easy to see Transatlantic MW carriers (with their 9 khz spacing). It is also useful for determining what filter size to use, and for peaking or nulling a signal. The display also makes it easy to find the exact frequency of a station. This is very useful in identifying weak radio stations, often from Latin America, that are slightly off frequency. You can do a search on the frequency and generally find what the station is.
The documentation is limited. However there is support via a moderated YahooGroups.
If you live in a city, you may see a weak image of FM stations around 30-35 Mhz (probably the 55 mhz low-pass filter is not strong enough). There are also several spurious signals that appear as multiples of the spectrum width that you are viewing - however they can be eliminated by changing that width.
The radio runs a bit warm. Not as bad as my Drake R8 though.
DRM (digital shortwave radio) - the radio does not have built-in DRM support, but you can decode DRM using the free DREAM software. You may need to compile it or find a binary online. Then you can use Virtual Audio Cable to get the audio from QS1R into Dream. I was able to do this and have it say that it was successfully decoding the signal - but I didn't figure out how to get audio.
The radio is probably roughly equal to the competing Winradio Excalibur and the Perseus -- which are all roughly similar in price.
The Future
I'm hoping that software defined radios start using USB 3 and better A/D converters - which will allow them to increase the spectrum size that can be displayed and monitored at one time. I also think the frequency range will increase. I'd love to be able to record the entire FM spectrum (20 mhz)! I hope that someone develops a software-radio phaser which will allow you to null stations (and local RFI) more effectively than the current phasers (MFJ 1025/1026, Quantum Radio Phaser, and DXE NCC-1) do. Also, I suspect the prices will drop and you will eventually be able to get this quality of radio for as little as $50 or $100. Currently there are very cheap software defined radios for as little as $20 (based on USB-tv chips), but the quality is poor.
Resources
QS1R manufacturer - SRL-LLC
Yahoo Groups
Eham.net Reviews
Ferrite Chokes - essential for eliminating RFI
A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing -- essential reading on RFI
My Wellbrook Loop Resources List
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Update
HDSDR has a MUCH better noise blanker. The RF noise blanker is especially useful.
HDSDR's SAM mode (synchronous) does not work properly and sounds worse than the AM. So you need to use USB or LSB, or listen to AM signals with SDRMax for the best audio.
Using HDSDR software
I recommend trying HDSDR software for controlling the radio. While I still prefer QS1R's SDRMAX software, HDSDR is essentially for exact frequency measurement as it allows you to set the RBW to 0.1 hz and measure carriers with 0.1 hz accuracy (by using USB, apparently LSB only does 0.2 hz).
For instance, if I wanted to measure the frequency of a station on 800 khz, I'd tune to 799.800 khz and then check to see how offset the carrier is from 200 hz. Before doing this I'd use a similar process to align the radio to a time station (and regularly update it as the radio drifts while warming up). For instance, if the audio signal from the carrier was at 202 hz - I'd know that the station was at 800.002 khz. If you measure AM/MW carriers you will typically see 3-20 of them on each channel.
HDSDR also has two noise blankers that sometimes perform better than the SDRMax ones.
HDSDR also had a better recording feature - though I haven't used it much.
Now if I were buying a radio, I'd probably get the Elad FDM-S2 as it has about the same performance at less cost. I have heard that it isn't good for exact carrier measurement, but in exchange you also get FM coverage which is pretty amazing - though it is with reduced sensitivity. The QS1R can also be modified to get FM and higher frequencies with reduced sensitivity, and I should probably try this. I need to get bandpass filters to do it.