Hi Daniele
If you can find them, then I can recommend
the early models of JRC receivers. I have two NRD515s and a NRD505 and
they are all excellent at MF/LF. I also have an ex marine comms RX
from JRC, the NRD72H and that’s quite good too.
Often on Ebay are the Datong VLF
upconverters to 28MHz IF. These are excellent and I run one too.
Tx wise I have used both an IC735 and an
IC706 Mk2g on 500 with good effect (CW QSO’s out to 500km and
WSJT/WSPR/data out to 1300km). Both will generate around 15W of RF
at 500khz after the diode snip mods for MARS/CAP/5MHz and 7.2MHZ. With
the IC735 you need to be looking for a later serial number model in the black
box, the earlier ones in white boxes with green writing don’t like
working down at 500 as much and only give out about 0.5W and their BPF arrays
get hot. You need to be careful as the BPF/PA board is easily “smoked”….I
speak from bitter experience.
Also with the 735s there are issues with
dry joints in and around the antenna connector on the PA board and these can be
aggravated by warm running so you might need to get your soldering iron out and
remake all the joints. There’s quite a bit on the web about
this issue…Google is your friend!!!
The 706 mk2G is much more accommodating
and mine will churn out 15W on WSPR all day at 20% duty cycle and not get too
warm. You will need a very good 7 pole chebyshev filter
immediately after the rig as the output is a little broadband to say the least
at 500, but as these rigs were not designed for down here that is hardly
surprising and a good bandpass filter is good practice anyway.
As has been stated though, for QRO then
the way to go is a transverter or direct transmitter and in the LF today book
there are excellent schematics for some serious beasts!
Hope this helps
With best regards
Jim
Dr. James Cowburn G7NKS
E [email protected]
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well as its attachments and delete the whole from any computer.
among the so-called "communications receivers"
(0.1-30MHz, all modes, well-known brands, etc.) in the "< 300
euros" price range (used, of course :-)), which models have good
characteristics at LF frequencies?
Any recommended models (in the same price
range) outside of the "comms receivers" class?
Many thanks for your feedbacks.
