Message-ID: <3A18459F.3757@infoave.net>
To: <tentec@contesting.com>
Date: Sun, 19 Nov 2000 13:26:55 -0800
From: "Bob & Linda McGraw (K4TAX)" <RMcGraw@infoave.net>
Reply-To: RMcGraw@infoave.net
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To: George W5YR <w5yr@att.net>
Subject: Re: [TenTec] early morning questions
References: <B63D56B2.1406%vbbond@ix.netcom.com> <3A181E1E.9578F4E5@att.net>
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I think George is correct. My experience, professionally, says that
audio transducers which have very restricted response typically generate
a level of un-needed or un-desired distortion.
As to the Tentec Omni VI+, the LP filter at 600, 800 or 1000 Hz does the
bandpass limiting quite well.
As to "The headphones do not and cannot introduce anything since they
are a passive device." Absolutely correct. I think the HF noise is
mostly distortion products generated in the transducers.
73
Bob K4TAX
George W5YR wrote:
>
> I also use the ProSet and have for some time now. I use it with an
> IC-765, a Kachina 505DSP and an IC-756PRO. I have not observed the hiss
> that Vince mentions with any of these radios.
>
> I think it is off the mark to assert that the Proset "introduces a white
> noise type of low level hiss . . ." The headphones do not and cannot
> introduce anything since they are a passive device.
>
> I think that what Vince is observing is that the high-frequency response
> of the ProSet is such that he is able to hear the "white noise" coming
> from his receiver. As he mentions, another headphone with a more
> restricted frequency response does not allow him to hear the noise.
> Evidently, the TenTec has an extended high-frequency audio response
> which Vince is able to hear with his ProSet.
>
> So, my point is that the ProSet should not be faulted as a contributor
> of unnecessary noise; rather it merely reproduces the noise which is
> coming from the signal source.
>
> I have not observed this hiss effect with any of the three radios I
> mentioned above. This is due partly due to my hearing loss at the higher
> audio frequencies and partly due to my use of external audio filtering
> most of the time. Nonetheless, I have no difficulty hearing and
> understanding speech even under adverse conditions.
>
> I find that the comfort and convenience (boom HC-5 mic) of the ProSet
> are outstanding; it is my only headphone now. I highly recommend it. I
> have not used the Yaesu headset that Vince recommends, but from his
> comment, I am sure that it is a very good one, especially for CW.
>
> My approach to hearing CW is to do the necessary filtering in the radio,
> etc. and not rely upon the headset to contribute its own response
> function. The problem with headsets that have a relatively narrow
> response is that they can tend to introduce ringing and other aural
> artifacts. This also applies to speakers with sharply peaked response.
> These factors can be controlled properly with modern filters such as the
> DSP filters, but are seldom dealt with correctly in audio transducer
> design.
>
> 72/73, George W5YR - the Yellow Rose of Texas NETXQRP 6
> Fairview, TX 30 mi NE Dallas in Collin county QRP-L 1373
> Amateur Radio W5YR, in the 55th year and it just keeps getting better!
> Icom IC-756 PRO #02121 (9/00) Kachina #91900556 (12/99) IC-765 (6/90)
>
> Vince & Betty wrote:
> >
> > In my experience, I have found that the Heil Pro Set introduces a
> > white noise type of low level hiss when operating CW with narrow filters in
> > line (use of the LP or NR DSP facilities reduces or deletes this situation).
> > Perhaps this additional internally generated noise is due to the wider audio
> > pass band of the Pro Set headset.
> > I currently use the Yaesu YH-55 headset which, because it is very
> > sensitive and requires little audio gain to produce adequate volume, does
> > not introduce any hiss when using CW filters. It's chief advantage to me is
> > that it appears to have a limited audio passband which peaks around 700-800
> > Hz, perfect for CW reception. Although not quite as comfortable as the Pro
> > Set, the YH-55 has been an excellent CW headset over the years.
>
> --
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