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
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