I often use a Timewave DSP 599zx on my receivers (I have two of those
units) with good results. First, I like the high-pass and low-pass
frequency cut off filters, as they are fairly (not completely) effective
at cutting high and low noise - i.e. that which is outside the main
speech intelligibility frequency range.
Second, with varying success, I use the random noise filter coupled with
the DSP-599zx AGC feature turned on, or off, depending.... it can
matter either way sometimes yes, sometimes no; and it can help with
noisy signals. I especially like it with my older Kenwood R5000
receiver.
I sometimes run the final audio through a stereo graphic equalizer, with
the high and low frequency ranges cut as much as possible, and with some
of the mid-range frequency bands set up a bit; and this combination can
be an effective way of tailoring the audio to the speech frequency
spectrum, while cutting out noise above and below that.
Unfortunately, these have their limitations and cannot, of course, make
a purse out of a sow's ear, for which I would have paid triple the cost
of all my accessories ! Like... who wouldn't ?
MOST of the time... I do not need these accessories, but they have
occasionally made the difference between making the contact or not.
But, as in the case of microphone input accessories (equalizers,
compressors, noise gates, etc.) a little can be good, too much can be
bad, and judicious use thereof is always the order for the day.
Just MY take, anyway...
PS = I think making Jerry's filter sounds like a fun weekend DIY project
and will likely enlist my local Elmer/radio engineer genius to look over
my shoulder as I proceed. I am in the process of developing a
switch-box - patch breakout box to route all my audio to various
external audio devices, including the computer, amplified studio
speakers, the equalizer, DSP filters, and the like. I may get
ambitious enough to incorporate Dr J's audio filter right inside the
box, and kick it in or out with a switch. Nothing like being able to
select various different tools from the tool box immediately while
operating.
Happy Trails.
======================= Richards / K8JHR =========================
On 2/26/2011 8:55 PM, Dr. Gerald N. Johnson wrote:
I have also used a Timewave DSP59+ but its not clean from HF hiss. The
DSP in my FT-857D is pretty good about filtering high frequency hiss.
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