Re: Whats new in VARA 4 ? #VARA #qrp


Graham
 

Trick's  of the  trade 

The low speed  ranges  of the  2.3KHz   wide  mode ,  are  designed  for a  filter
bandwidth  of ~ 1.5 KHz , higher levels requiring the  full  channel  

As  user  data and experiences  are gathered, one aspect  has become clear ,  the 
full  2.4 KHz voice  channel  is not  always  fully  available, hence to  ensure 
maximum efficiency , ie power transfer in the  lower  ranges , the  modem allows 
for constricted  channel  bandwidth,  either by  the  various  user interfaces  or 
filter bandwidth

Thus  ensuring the  bedrock  -20 dB  is achievable ,  independently  of 
equipment  irregularities ,  two  images  make the  point , using the
opera  waterfall  display , with  mouse  pointer/frequency  as measurement 
tool ,

First  ic7100  with  2.5 KHz usable  bandwidth  in data  mode 
using digital filtering . direct USB link to  pc 

The  second , FT897D offering a  much rounded response
with  app  1.5 KHz usable  bandwidth** using  usb 
soundblaster 24 bit  audio  card , fed  from  rig  data 
out 

** Why this is so,  may  be due to  filter  ageing ?

IC7100


FT897D  { 10 years  old ]

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