In a message dated 97-04-09 05:37:54 EDT, W6TG writes:
<< 1.) Ad for this radio (IC756) states it has "IF Notch". The only notch I
could find was the "auto notch". It clearly notched a hetrodyne but did
nothing for removing the signal from the agc (s meter). To me this is a
"audio" notch. ???>>
Samething was on TS870, they claim IF DSP, but the IF is the 4th IF in the
range of 20 kHz, and in the way it is implemented after the filtering and
AGC sensing circuits, for all practical purposes is like audio DSP. Signals
that get through the brute force crystal or mechanical filters will modulate
agc and cause receiver to "pump", close RF gain, even if there is more
filtering later on (too late). The only solution is to have front end that
can not be overloaded (like 807) and then sharp, if possible cascaded filters
as close to the front end as possible. Any other "magic" is just advertising
con job.
<< 2.) Icom's ads also state this radio has "adjustable DSP in both TX and
RX". Other than the mic tone adjustmants I could not find anything that to me
represented "adjustable DSP". I spent close to one hour playing with this
radio and went through every page of the manual twice. To me this looks like
a classic case of false advertising. By the way the store manager called Icom
to get my questions answered and was put on hold for 10 minutes when I told
him to nevermind... I was not going to buy the radio.
>>
You would think that dealers would have priority channel.
I was curious what DSP on transmit would do to a signal? Take my accent away?
I would like to sound like Rush Limbaugh, that would get me some pileup
going!
Looks like the best buys on the market now are IC781 and TS940, with proper
mods and filters, while having digital interface for the contester, giving
the best performance for the buck. (IC775 might be another one, didn't have a
chance to lay my hands on one.) Signal One is modifying IC781s into MilSpec
1050, that says something.
73 Yuri
--
CQ-Contest on WWW: http://www.contesting.com/_cq-contest/
Administrative requests: cq-contest-REQUEST@contesting.com
|