[Lowfer] Low frequency receivers and upconverters

[Douglas D. Williams]

On Fri, Dec 7, 2012 at 4:30 PM, Michael Sapp <wa3tts at verizon.net> wrote:

> Doug, Dex, John & All: Thanks for the comments on the HD-1420 and ARGO
> caputres.
>
> I have the AMRAD converter information but have not looked at the W1VD
> converter design. Basically I have a couple of +17dBm DBMs here and a 10MHz
> LPRO which should work well with a single or push-pull 2N5109 preamp and
> suitable RF and LO filters---all in good time.



>
> 73  Mike wa3tts
>
>
>


Hey Mike. I typed all this out, then decided not to send it, then decided
"what the hell"?



Regarding low frequency upconverters, I have yet to find an analog (meaning
a non software defined) receiver with VLF & LF performance that I am
completely satisfied with out-of-the-box, meaning without use of an
upconverter. To be fair, I have never owned a high grade military or
commercial communications receiver, which typically cost several thousands
of dollars new.
Some of the receivers I have owned, and used on LF, however, include a
Yaesu FT-747, Kenwood TS-850, AOR 7030+, and Icom R-75 (I'm probably
forgetting a couple more). Not a single one of these receivers were
completely satisfactory as VLF/LF receivers (10-500 kHz).
The Kenwood TS-850 boasted a very good receiver, and with a simple mod
could receive down very low in frequency (I forget how low), and, while it
had a digital display, and perhaps even 1 Hz tuning steps (I forget), the
display could only read out the nearest 10 Hz.
The AOR 7030+ was an exceptionally good LF receiver (down to 20 kHz or so),
saddled with the most unintuitive user interface I have ever had the
displeasure of using. Sadly, it too could only display to the nearest 10
Hz, though the tuning steps could go down to 2.7 Hz. Strange? Yes.
The Icom R-75 has several features that are helpful for VLF/LF receiving.
The first it a 1 Hz frequency display. Secondly, it has decent sensitivity
down to 30 kHz, which, IIRC, is as low as it will allow you to tune.
Thirdly, it has "good" frequency stability with the OCXO option. "Good"
being good enough for QRSS. Unfortunately, it has a lot of spurs below 500
kHz, as was pointed out in a recent review by John Reed, KA5QEP, in our
LWCA newsletter, the Lowdown.
A quality upconverter, on the other hand, can turn an exceptional HF
receiver (but poor VLF/LF receiver) into an exceptional VLF/LF receiver.
IMO, there are many very good quality analog or semi-analog HF receivers on
the market today, and I am including amateur radio transceivers in this
category. The Elecraft K3, and several offerings from Icom, Kenwood, Yaesu,
and Ten-Tec come to mind. Any of these contest quality transceivers, paired
with a high performance upconverter, should be extremely good performers on
VLF/LF.
With all that said, I believe the future will belong to SDRs (software
defined receivers). My experience so far, on VLF/LF with the Winradio
Excalibur Pro, is amazing. It can "hear" anything that my AMRAD upconverter
+ R-75 can. Frequency display is to the nearest 1 Hz. Drift is negligible.
VLF/LF sensitivity is more than adequate.

Your mileage may vary.

Doug KB4OER