Comparing FT8 and FT4 with VARA and P3, P4 is like comparing a
golf cart to a Porche!
FT8, FT4 are great for exchanging minimal information (call sign,
signal report, Grid square) and they do that well BECAUSE they are
so SLOW and narrow bandwidth (Higher Eb/No ....just as Claude
Shannon describes in his 1948 landmark paper on channel capacity.
They satisfy a niche especially if one is trying to make the
maximum number of contacts at low power each exchanging a very
VARA, P3, P4 Transmit much larger data (text + attachments up to
say 30 K bytes) at ~1000 x (or more) than the FT8 or FT4 rate .
They require stronger signals than FT-4 of FT-8 and a wider
bandwidth. These modes again operate in exact accordance with
Shannon's thesis (now proven). They are what you want to use if
you are transmitting a sizeable message/attachment or have to send
a large amount of traffic. These modes are also automatically
adaptive (changing their Eb/No and FEC level automatically) so
they can follow a changing path over 20 dB or more and with
varying amounts of multipath.
As hams we should all try to understand the basics of what
Shannon proved. It would make better use of our limited spectrum
an different bjectives. But comparing VARA and FT8 is like
comparing an High Definition commercial TV transmission with a
deep space photo taken from NASA Voyager using a 10 watt
transmitter at 10 bits/second. Both have their uses but are not
Rick Muething, KN6KB, Winlink Development Team
On 7/6/2020 2:46 PM, Andrew OBrien
I think FT8 and FT4 have shown that wide adoption of a digital
mode is achieved when popular awards , like DXCC , are associated
with use of the mode . If , for some odd reason, ARRL developed an
award for receiving email from 100 or more DXCC entities via VARA
... VARA would have many more users . Despite VARA , Ardop,
Winmor and Pactor having some utilization in emcomm . these modes
seem destined to be niche products in the ham world .
Digital modes via SDR = Multipsk or SDR-Radio.com