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Message-ID: <E383450813A24A3898499C2E220D8FE8@JimPC>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <7F70CDE2-FFAF-4E06-8840-133B53D04F9B@numeo.fr>
In-Reply-To: <7F70CDE2-FFAF-4E06-8840-133B53D04F9B@numeo.fr>
Date: Mon, 23 May 2011 11:07:51 +0100
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Subject: LF: Re: New RX
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Dear John, LF Group,

I have an SDR-IQ which meets most of your requirements:

>Covers LF to 30 MHz with a good communications spec,
Yes - the frequency response is flat from audio frequencies to 30MHz. The RF 
performance probably isn't "ultimate contest-grade etc etc" but is pretty 
good and compares very well with other small, portable RXs, especially at LF 
where many receivers are very poor. It is versatile; you can set up a narrow 
CW filter, or listen to AM broadcasts in "HiFi" bandwidth, generate a QRSS 
spectrogram display and so on.

>Portable and can readily be run from the car
It  has an antenna socket and a USB connection that also supplies power from 
the PC, and requires nothing much else.

>(for field strength measuement etc),
Good for that, since it directly generates a spectrum analyser type display 
with accurate, user-definable dB scale and essentially any "resolution 
bandwidth" you might want. This is very hard to beat unless you go to Rohde 
& Schwarz with a bin-liner full of money. I will certainly be using it the 
next time I do field strength measurements.

>Small and light,
It is a tiny box...

>Can interface readily to computing equipment such as a small laptop.
...Of course the PC is an integral part of the overall receiver anyway - the 
"back end" signal processing, display and audio output functions are done by 
the PC. It is supported directly by software such as Spectrum Lab and Winrad 
as well as its own native software. I have mainly used mine with a small 
netbook which is quite satisfactory... some care is needed to avoid noise 
pick-up from the lap-top, but this is a general problem for all receivers.

>Any particular thoughts or any particular products that might be 
>appropriate?
I guess other SDR receivers offer similar capability, although I have no 
experience of them. Compared to using conventional receivers, you have to 
learn a different operating process based on controlling the receiver 
through the PC keyboard and mouse, and there are computer software quirks 
and weirdnesses that crop up from time to time. I sometimes wish the SDR-IQ 
had some conventional control knobs, although the graphical interface also 
allows useful control possibilities that don't exist with normal receivers, 
and for LF use in particular, much receiver operating process is actually 
manipulating a spectrogram display anyway.

The main technical criticism I have of the SDR-IQ is that there is no easy 
way of using an external frequency standard - but the internal standard is 
no worse than the usual amateur rig/sound card combination, and is adequate 
for most things. At this QTH, it is neccessary to connect an appropriate 
filter between the antenna and SDR-IQ to attenuate the 10s of volts per 
metre from local broadcasters, but this is also true of nearly all other 
receivers, which usually don't have preselectors in the LF/MF range.

Compared to other RXs, the SDR-IQ is fairly cheap - so maybe you can 
persuade your birthday present buyers to throw in the laptop as well ;-)

Cheers, Jim Moritz
73 de M0BMU