The R390A is one I still need to try out.
It is somewhat of a lightweight pound for pound though compared with say the
DST100 which tunes down to 50KHz and uses a VP41 RF amplifier to handle 10V RMS
signals without distortion or so they claim. Is this the ultimate valve
receiver I wonder, although for VLF maybe the CJD wins.
Alas mine is yet persuaded to work so I
cannot tell.
Allan G3PIY
From:
main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of jdow Sent: 24 December 2021 08:07 To: main@SDR-Radio.groups.io Subject: Re: [SDR-Radio] NDB -
Airspy HF+ DIscovery versus Hermes Lite 2
I suspect you are not
running them correctly.
I have listened to the best of the best analog. In fact I still have my R390A;
but, it is retired just before I redesigned it for semiconductors. (I've been
planning that for decades now. The earliest and most complete set of notes
comes from the 1970s.) The basics of the designs for noise and dynamic range
are basically the same. And the very basic detail that on large antennas
attenuators on the receiver front and are an exceptionally good thing at MW and
HF. Most SDRs have headaches from hitting their heads on their A/D's ceiling.
The more bits of resolution (and precision) from their A/D converters helps.
You may be suffering from a nearby large signal radio. For most (all) other
front ends run the gain up until one of two things happens. The first thing,
the good thing, is you reach a point where the signal to noise ratio does not
improve. You can see that on the spectrum display. The second thing, the bad
thing, is the display very suddenly shows a whole lot of signals you had not
seen before. Go to a much higher gain and work down until these spurious
signals become invisible. That's the best you'll get out of that front end.
For any AirSpy HF+ leave its internal AGC on. You lose the ability to calibrate
it. But you get the best possible dynamic range that way.
Once you get good settings it should be as usable as any other
radio for these frequencies and more usable than most because of digital only
features.
{^_^} (Poor thing. She only has 63 years experience and a couple
college degrees as a result.)