Monday, February 26, 2007

SDR IQ vs SDR-14 First Impressions

I have finally tested the new srd-IQ for a while. It is nice, quite small, but as all knows the first batch was only the board and you have to put the casing by yourself. Thanks to OH5HOI (IJL) I managed to get the good casing to the board. Ilpo did also the small modification to the board. As you can see at the picture the unit is rather small. More pictures can be found on Ilpo´s site (look for OH5HOI). The good thing is also that you get the power via USB, so no need to have a PSU here. Sometimes (as the one which comes with sdr-14) these units can cause some noise on MF-HF bands.

Some notes after two weeks tests using both sdr-14 and sdr-IQ. I have been using a table-top pc Fujitsu-Siemens (P4, 1.8 G system, 1 Gb memory, two HDs) and also a laptop HP nx9105 (AMD 1.6G, 512M). The Spectravue softwares used were first 2.20 and later 2.21. Simultaneous listening and capture of data has been done using the F-S pc.:

* Overall reception seems to be equal what comes to sensitivity and dynamic values of the both receivers , however, it seems that the new software has RF-gain +10 dB – adjustable to minimum -20 dB (IF gain the same as earlier +0…+24 dB) and during some comparisions it could be seen (the incoming signal level was higher with sdr-iq). That made no difference to the S/N-values though. It seems that dynamic (widespaced) is even better than that of the more expensive WinR 313e – I tested that at my RF-noisy urban (home) QTH with Helsinki AM 558 kHz making spurs to my WinR 313e with an amplified loop (ALA100 3x7 meters) – no spurs was noted on sdr IQ! Usually when I used a BOG (very low antenna gain) I could have the IQ with RF +10dB and only in the evening I had to put it at +0 dB.
* Some stability problems did occur at both configuration: the recoding did not start or recording stopped after some time (1 second … 10 minutes) – this was at my systems, however some other users have not had these problems
* Some problems occurred also using the both rx´s at the same time (picture showing simultaneous capture of two 190 kHz segments). This might be a problem with the old computer as the load of the computer was rather high (up to 80…100%) or the memory problem although there was 1 Gb memory and I have heard users using the old sdr-14´s (two of them + WinR running simultaneously – as reported by TuA earlier). At the picture you see also the simultaneous capture situation – SDR 14 did everything OK but IQ stopped often and had to be started manually, so I have to check this configuration more later on – BTW I made two copies of the softaware to two HDs and capture was done also to these separated (though inside the pc) HDs
* If you want to look at a wider spectrum (like max. 30 MHz with the 14), that is not possible with the IQ: you have to stick with the 190 kHz maximum spectrum – this is not very common use if you dx on MF bands, however.
* Sometimes you might have problems with the power using older computers – this seems to be a problem with usb 1.1. – but as stated at the specifications of the rx, you should have USB 2.0 with this rx.
* You have to get used to the “harsh” audio of this (as that of most of these sdr-rxs) and should there be more adjustments to the audio, could it be even better on that respect
* no PBT nor notch are included in the software at least for the time being (with CIAO software and WinR3xx you have the notch for example)
* you can read the exact frequency at least to the last Herz, but you have to be very careful with this as you have to calibrate the machine often using a very stable and precise station or frequency reference – at least the Finnish SDR-dxers have been using British syncro channels like 1215 or DLF 1269 (NRK 1314 used to be very good earlier…)
* at last I tried the DRM reception with the IQ and there was no problem decoding the DRM-signals. You have to use USB 10 kHz wide bandwidth with demod offset of 7000 Hz when you get the IF of about 12 kHz that you can demodulate by the Dream software. For output you have to use a virtual sound card or different cards for demodulating and audio. So this seems to be rather good also for the DRM, although price is a bit more than that of DRB30, but you can also analyse and decode several DRM-frequencies later on (for example capture DRMs on 49 mb from 5990 to 6175 – when there is at least 4-5 DRM stations at the same time). I tried the AIR 7410 test to Europe, the audio was 99% ok with S/N 22…26 dB, but they used a bit overmodulated signal and a modest bit rate (mono, about 13 kbs)

Last conclusions:

Although I had some (possible computer related) problems, there has been no problems of this kind on other new IQ-owners I have been told.
However I would say this is a great machine. I do not know any this kind of receiver at this prize class: only about 400 euros you can get a spectrum analyser, rather good receiver and finally a time machine which you can program to “listen” and capture the 190 kHz segment of radio spectrum for later analysis. I have been using an old ICOM 9000 for years – yes, there is a spectrum (10…50 kHz wide cathode-ray tube!) – the prize of that machine was around 10 Kiloeuros when it was new … Of course you get PBTs, notches etc with “real receivers”, but…

I know some people think this is not for “real DX”, but there has been other breakthroughs in DXing which I have seen like a calibrator, digital frequency counter, big beverage antennas, better recording systems (reels, cassettes, MDs, pc-recorder, mp3 …). One thing with this kind of rx´s is the vision: you can see what you hear. And of course the ablility to tell the exact frequency at the same time without any special softwares. There is no way back to 1960´s or 1970´s with tube receivers and reel-to-reel recorders. Or you can do it also, if you can find those old systems - the choice is yours!

73 TK

1 comment:

Mir said...

Nice review, Tarmo. You are right about the audio, it takes some time to get used to it after the very clear audio in AOR AR7030. TUA suggested headphones that are more suitable for SDR's. I hope they will add PBT, that would help a lot. Another thing I miss is another VFO (a quick memory) for parallel programming comparisons. Otherwise after using AOR by remote control for years, I have found it easy to get accustomed to controlling the receiver via mouse.
It's nice to get upgrades after buying the receiver in form of software upgrades, that wasn't possible with traditional receivers!
I have had a couple of computer crashes while recording the 190 kHz span, I hope duplicating the memory (now 512MB) will help.
All in all, considering all the properties SDR-IQ has, I think it is very hard to imagine a better receiving entity for that price.