Elad FDM-S2 Review

I have had the Elad FDM-S2 for almost three weeks and thought it was about time I gave a write-up. This SDR receiver has been discussed on the new Skywaves forum here and I have been giving a running account of my initial experiences with it. Plus I have had a lot of correspondence off the forum as well, with fellow DXers asking how I find it.

In a nutshell, I think I can say that my experiences with the FDM-S2 have been very positive on the whole and I have been hugely impressed by a number of things, but this is not a 'radio' in the traditional sense. There were a few small oddities with the software too, but I can put most of them, if not ALL of them, down to my own issues with Windows 7 and the fact that my computer is long overdue for a full re-installation. Here is a bit more detail:

First impressions: 
The S2 is a neat little unit, solidly constructed and pleasing on the eye. My main reason for buying the S2 was to use it on the FM broadcast band - 88 to 108 MHz. Selectivity is not an issue and is exactly as you would expect from an SDR. i.e. brick wall selectivity where you need it. IF bandwidth in FM mode goes from 100 Hz to 24 kHz and wideband FM takes you from 25kHz up to 192 KHz. Both ranges are continuously variable.

Personal Requirements:
Before I bought the S2 I had read reports that it was lacking in RF gain at band 2 frequencies and that it may require a pre-amp. This was exactly the case for me too. Without a pre-amp I found the sensitivity was poor and considerably lacking when compared with my XDR-F1HD, my Kenwood KT6040 and in fact all my other FM receivers and tuners. Such was the lack of sensitivity that I couldn't have done without additional amplification. An old Fringe Electronics 20dB band 2 pre-amp came to the rescue and this increased the sensitivity to match that of my XDR-F1HD (with Konrad modification), which is probably the most sensitive FM receiver I have known.

Strong Signal Handling:
Since I get strong signals from the Belmont transmitter, I was concerned that the pre-amp might cause a degree of overload to the S2 when beaming towards it, as does my XDR-F1HD which produces noise-free images of national BBC stations appearing around 70 MHz WITHOUT amplification. This did not happen at all with the S2. Belmont gives the S2 a -20dB signal WITH amplification. I suspect that if any DXers live close to 100kW"+ transmitters then overload may occur, but all reports I have read so far indicate that the S2 is virtually bomb proof. A friend gets a few spurious images when beaming at his nearby 240kW national BBC transmitter, but reports that they are few and far between. His directional antenna solves the problem when not beaming at this transmitter. Let's face it, all receivers will overload at some point, but the S2 does seem very solid in this department.

RDS Capabilities:
My other main requirement in an FM SDR receiver was to have good RDS decoding and I am pleased to report that this has been exceptionally good and beyond my expectations, though there are one or two points which I should probably raise here. All comments above relate to me using the S2's own "SW2" software, but I would like to bring in another excellent software package too and one which I would recommend - "SDR Console", produced by Simon Brown of Ham Radio Deluxe. Firstly, SW2 has delivered unparalleled RDS decoding to signals which have propagated by meteor scatter. Such signals are notoriously difficult to decode due to the nature of this kind of propagation. SW2 has usually been able to accurately decode RDS data at low level and more quickly than SDR Console did. BUT, SDR Console, which also offers enhanced RDS decoding, produced quicker and more accurate RDS with groundwave signals and was way ahead of the SW2 software in this area. I guess each software package has its own set of algorithms and, used together, I have a 'best of both worlds' scenario, so I would recommend DXers use both software packages when decoding RDS.

The SW2 software can route the RDS data to RDS Spy, thus offering another excellent RDS decoding method. You will need to use VAC (Virtual Audio Cable) to route the data from the S2, via your computer and into RDS Spy. Although the procedure to do this is not overly complicated, it has been a problem for some DXers, including myself, but there are videos available on YouTube and elsewhere which give step-by-step guides, showing you how to get this working.

Wideband Recording & Computer Requirements:
The S2 can be used to record wideband IF, just as the Perseus receiver does and offers a bandwidth of 6 MHz. This splits the FM broadcast band down into five bite-sized pieces, but be warned that you will need a fairly powerful computer and lots of hard drive space if you intend to run the S2 at this bandwidth.

It's not just processor speed which is required too. Some S2 owners have found that lesser spec'd computers can perform satisfactorily with the S2. It all depends on your computer's architecture. For instance, I have an old Toshiba Satellite laptop containing a Celeron mobile processor. This is VERY slow by today's standards and has only 4 MB RAM onboard. Yet this seems to handle the 6 MHz bandwidth reasonably well. There are a few stutters here and there but the laptop holds up very well considering, though struggles to run anything else at the same time. I believe Elad recommend an i5 processor and at least 6 MB RAM to get good performance at 6 MHz.

The use of a USB3 socket should help a lot, but USB2 should also deliver enough 'juice' to handle the S2.

Medium Wave Performance: (Updated!)
My experiences with the S2 on medium wave are few and far between, but I have had a quick tune around. The S2 doesn't feel quite as competent as the Perseus, for instance, but still performs well enough. I have found it sensitive but have not been impressed with the audio quality. Since my experiences so far on medium wave have been limited I shouldn't really be attempting to give too much information, but I don't see any major problems, and I understand the latest SW2 software has improved the AM audio quality by some margin. It should be extremely useful being able to record 6 MHz of IF on HF too, which would allow medium wave and the lower tropical bands to be recorded simultaneously, very useful for checking Asiatic medium wave signals against those around 3 - 5 MHz for instance.

Update:
I don't like giving negative reviews unnecessarily, especially when I haven't given something a fair trial. Initially I was unimpressed with the Am and SSB audio quality on the medium wave band, and therefore the whole of the HF spectrum. BUT, I was aware that some improvements were made to this but only today decided to give the medium wave another try. I must say that the audio HAS improved substantially, but more to the point, the audio is now sweeter than that of the Perseus. I was listening to Sunrise Radio on 972 from London - this is a very, very poor (nulled) signal off the back of my flag antenna. I can only make out the occasional word on the Perseus, but the audio is rendered to almost 100% intelligibility on the FDM-S2 since the improvements were made. That's quite a difference. The audio is much cleaner on the FDM-S2 too. And I can't help but feel that I would be able to add some level of signal amplification to this in order to boost signals further.

Bits and Pieces:
The only side which I have felt slightly disappointed with so far has been the operation of the SW2 software, BUT I must STRESS that many, if not ALL of the problems encountered could have been down to my computer and not due to any shortcomings with the S2 or the SW2 software. My computer throws many challenges at me anyway, so the S2 just pushes it to extremes all the more. Any disadvantages I have experienced so far are more than outweighed by the many advantages.

Ongoing Improvements:
I have been impressed by the dedication shown by the team at Elad. I subscribe to their Yahoo Group and have made one or two comments and suggestions over the last few weeks. These have been taken on board and improvements and bug- fixes have been dealt with swiftly. I have also been really pleased and impressed with the same level of service by Simon Brown, the creator of SDR Console. Combine this with Elad's own SW2 software and you have a powerful DX setup I cannot recommend highly enough.

Conclusion:
I would definitely recommend the S2, but so bear in mind the points I have raised above. This is NOT a typical radio (as we know it, captain) and needs to be treated very differently. If you are squeamish around computers then you might want to think again. The S2 has taken me a little more getting used to than I expected, but it has 100% been worth the effort.

The XDR-F1HD is still a force to be reckoned with, especially with the genius of the Konrad i2c Modification. The S2 doesn't have that beautiful soft mute you get with the XDR-F1HD, which I find quite desirable. Plus the automatic IF filtering is done to perfection with the XDR-F1HD. The S2 doesn't have these things, and doesn't necessarily need them, but so the overall feel of the sound and the tuning of the S2 is very different.

To recap. Just remember that you may want to use a pre-amp for band 2 and if you live very close to strong signals then you could experience some overload BUT the S2 DOES handle strong signals extremely well. Overall, I would consider the S2 to be an FM DXer's dream. I have found it to be excellent for meteor scatter and there is the obvious huge potential with sporadic E. It is really nice to have the ability to leave the S2 recording while you are away from home. You need never miss an opening ever again! Just make sure you have plenty of hard drive space as 6 MHz of bandwidth creates around 2 GB of data every minute! You may also need a Time Expander. While no such thing exists at the moment it would be sp useful to have more hours in the day, as you might find yourself needing more time to analyse all the files.

Good DX! John

Here is a bit of spec:

* HF:  9kHz-52MHz MDS: -132dBm @14MHz, Clipping lev -8dBm
* FM:  74-108MHz sensitivity <2uV 12dB SINAD @98MHz, Clip lev -3dBm
* VHF: 135-160MHz MDS -137dBm @145MHz, Clipping level -19dBm

* Separate antenna inputs for HF/6m and FM/VHF/Bypass ranges
* Max. DDC Bw 6144kHz (Aliasing free viewable bandwidth up to 5 Megahertz)
  - currently available selectable bitstreams:
  192ksps-32bit, 384ksps-32bit, 768ksps-32bit, 1536ksps-32bit, 3072ksps-32bit, 6144ksps-16bit

* Special double DDC mode of 2 x 384kHz bandwidth to be placed within one of the input ranges.
* 4 virtual receivers freely tunable within DDC window
* Each virtual receiver holds settings for mode,bandwidth,volume,squelch and audio output routing.
* Patent pending Triple Tuning Bar for coarse and fine spectrum navigation
* CWU,CWL,USB,LSB,AM,SAM,FM,WFM,DSB,RTTY,DRM,RDS modes
* Interference rejection: Noise Blanker,Adaptive Noise Reduction and auto notch, special 2 manual
   notches (directly placed in DDC spectrum)
* Integrated DRM decoding, text and station schedule update.