Here's the results of a little experiment I did. Recently I acquired a
digital sound level meter and have conducted some very revealing test. My
first experiment was to investigate the effect of cw clicks heard in
certain DSP rigs. I connected identical speakers to the Omni 6+ and IC-
756PROII then placed the level meter equal distance between the speakers.
Across the room, I establised a transmitter, TS-930, and adjusted it's
power output to produce an S9 +20db signal on both the PRO and 6+. A
keyer, sending dits, was connected to the 930. Both the Omni 6+ and PROII
were set for 250hz bandwidth and equal audio output then tuned off
frequency by 500hz.
The S meter on both rigs continued to deflect however
the resulting sound in each speaker was quiet different.
The sound leve meter showed 84 db from the 6+ and 92 db from the PROII.
The clicking sound was very obvious on the PROII but very subdued on the
6+.
Changing the ICOM's DSP's response shape from sharp to soft had no effect
on the click volume.
My conclusion is that ICOM's DSP design tends to produce clicks when
receiving signals that are out of the passband. Turning on the DSP in the
OMNI 6+ did not change the level of these clicks but it does bring up the
overall volume of a cw note which is very helpful since it doesn't
increase the volume of the background noise.
BTW: The ARRL review's on the DSP rigs including the TS-870 mentioned
these clicks but tried to say that the clicks are actually there and just
can't be head on non-dsp receivers because the tone leaks through and
distracts from the clicks. I think this test disproved that theory.
If I still had an Orion here I would certainly want to run the same test.
>From my recollection, I don't think I noticed these clicks on the Orion.
Perhaps someone would care to comment on this.
Steve N4LQ
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|