A mixed bag, something good, something bad !

[IW2NYX]

Hi to all,

i'm a fresh new SDRplay's owner, two days ago i got this toy with a lighting fast shipping service (thanks for that) and i put it "under load" to check its performance.

I have to say in advance that i'm quite experienced SDRs user, i started to play with them lot of years ago (with very first SoftRock Kits), i spent a lot of time with self made & commercial items, i know quite well which problems play around these devices.

Well, i have to say that SDRplay surprised me in either the good and in the bad way, i still have to decide which is the balance.

The main good side is that i found an unexpected decent VLF / shortwave performer and an expected (from web review) L Band sensitive radio, the main bad side is that the frequency segment between 250Mhz - 420Mhz is practically unusable due to a HUGE amount of images from FM broadcast, GSM network, TV channels and so on.

Images are also elsewhere, but in far less amount.

I spent a lot of hours tricking ALL the various settings (with various RX programs and last API) without a decent result, the whole low UHF SAT band is effected by strong images and under this aspect all my "el cheapo" RTL dongles are sadly far superior devices.

Even if for the rest the SDRplay (vs dongles) wins hands down, the image problem prevents me to use this SDR for the intended purpose (UHF SATs reception) and shortwave wise a'm already served by a Perseus and Elad FDM S2 receivers.

To be noted that i put a high performance FM trap filter inline the receiver, a device with an attenuation not less than 40dB and up to 60dB among 88-108 Mhz band, but its not enough and in addition also GSM and TV signals rage wildly as images in the 250Mhz - 420Mhz range.

Of course if you disable the LNA and set the gain reduction to the maximum the problem disappear ... together the wanted signals !

Build and put in service a bunch of bandpass and notch filters is not a viable solution to the problem, for time, cost and switching needs.

What a pity, i fear that i (we) do not have a workaround for this, of course i will be glad to be wrong...

Talking instead about positive things, ie L-Band Inmarsat RX purpose, i did a quick an dirty test with an unusual (and unsuitable) antenna placed on the roof shingles, a fully retracted COMET SMA-99 on magnetic base, and without any external LNA i successfully got three AERO channels with enough SNR to be decoded.

With the same antenna, but fully extended (still unsuitable), i conducted some shortwave receiving tests and the sensitivity of this toy is far superior than expectected, with far less images than expected, even if i know that with high gain antennas things will be quite different, but in those cases playing with gain chain should be enough to maintain images and wanted signals in the right balance (at least what i saw playing with my wellbrook 1530+).

I left the receiver some hours with WSPR RX program on 80m band and even if it did not great things, considering the small antenna (around 110 cm) the result seems promising.

So SDRplay seems a good (for the money) ShortWave and VLF performer and a bad (in absolute and for the money) low UHF SAT band receiver.

If there is no solution for images in 250Mhz - 420Mhz segment, in my honest opinion we have a frequency range that should be advised as "sub spec" or "not covered" in the tech spec.

Do not get me wrong, for the money is a fair product, but if you need an SDR to operate among those frequencies, any 15 USD RTL820T/T2 dongle is far better.

Some images to show in pics what i above explained with words :

Images around 400Mhz


Images around 400Mhz without FM trap


Images around 255Mhz


Images around 255Mhz without FM trap


40m band with 1 meter vertical stilo


WSPR RX activity on 80m band with 1 meter vertical stilo


Inmarsat L BAND AERO channels


(unsuitable) L BAND antenna

[F1BJB]

I agree that sometimes images can be a problem.
To try to improve that would it be easy to use a different reference frequency instead of I believe 24MHz ?
Say 28.8Mhz ,25 or 24.576 as in various other design.
Of course it will shift the problem to other parts of the coverage but in some cases it could be useful.
On second thought the values I proposed are not clever as they would probably result in overclocking some
parts of the desing and thus impact reliability.
Best wishes for the new year to all.

[DaveB]

As SDRPlay will point out it is due to using a block converter to cover that frequency range. Go back six months and the SDRPlay couldn't cover that frequency range but some clever work with the API utilised the HF block converter (0-60 MHz) to down convert the missing segment. They also included the option of a choice of Lo frequencies that hopefully would allow you to move un-wanted images away from

For the price it is very good - but my main interest is FM broadcast DXing and the odd dabble in HF reception. You could send it back and spend another £50/$75 on an Airspy - but no HF for that price. The Airspy uses the same RF chip and SDR architecture as an RTL-dongle (R820T2) but 12bit ADCs. Or you could fit a really good BPF or HPF - mini-circuits do them for around £40/$60. Or you could use the RTL-dongle for that particular frequency range - at no additional cost - and use a dedicated antenna for that frequency range.

BTW the only SDR I have is the SDRPlay.

David