K3: Poor sound on FM

[DL5OCD]

Hello, from my point of view the K3 is one of the best sounding radios on AM and SSB. But i observed a lack of quality on FM-the sound is very thin compared to AM and SSB. It seems that the DSP cuts out the range from 400 to 2700Hz (uuh!). Measured with my analyzer, i can send those graphs to anyone who may concern. No matter how the EQ is adjusted. Any ideas are welcome 73 Michael

[Bruce Beford-2]

Hello Michael.
Two things come to mind-
1.- I assume you have the 13 KHz FM filter installed, and that is the one
you have selected for FM mode.
2.- Have you checked the FM deviation setting in the CONFIG: FM DEV menu
item? It defaults to 5 KHz deviation, which is standard in the USA. I
believe much (or all) of Europe uses a narrow channel spacing, requiring a
lower deviation?

Perhaps one of these suggestions may help you.

Here, my FM receive audio is fine.
73,
Bruce, N1RX



> Hello,
> from my point of view the K3 is one of the best sounding radios on AM and
> SSB.
> But i observed a lack of quality on FM-the sound is very thin compared to
> AM and SSB.
> It seems that the DSP cuts out the range from 400 to 2700Hz (uuh!).
> Measured with my analyzer, i can send those graphs to anyone who may
> concern.
> No matter how the EQ is adjusted.

> Any ideas are welcome

> 73
> Michael




______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[DL5OCD]

Hello Bruce,
tnx for answer my call, hi !
This behaviour is also in RX-Mode, after a while it is a real pain to listen to. Especially i miss the lows.

73
Michael

[KK7P]

Michael,

Standard CTCSS tones used on FM can range up to 254 Hz.  So, on Tx we
have to block microphone energy below about 300 Hz.  Likewise, on Rx, we
have to suppress things below about 300 Hz so you won't hear continuous
CTCSS tones in the audio.

The DSP filters have some slope, so the audio filter corner frequencies
must be a bit higher than this.

I'll look into the firmware and see if there is a way to reduce the low
frequency corner frequency without degrading CTCSS.

Thank you for bringing this to our attention.

73,

Lyle KK7P

> But i observed a lack of quality on FM-the sound is very thin compared to AM
> and SSB.
> It seems that the DSP cuts out the range from 400 to 2700Hz (uuh!).

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[DL5OCD]

Hello Lyle,
 
that makes sense. Here in Germany CTCSS is not so important, we use the 1750Hz Tone to key up our repeaters. It would be a nice feature if the user could decide by himself if he want to hear down to 0Hz on FM. Maybe a switch in the menu could solve this. Or adjustable bw like in other modes. I really miss the warm sound of my analog gear.
Many thanks for your answer !

73
Michael

[Bruce Beford-2]

Thanks for offering insight in on this, Lyle.
I was just going to suggest that either you or Wayne could perhaps chime in
with some info as to why it is the way it is.

Perhaps in a truly DSP-centric radio like the K3 limitations are different
than in a more traditional analog rig, like the typical VHF/UHF FM mobile
radio.

I generally refer to CTCSS tones as "subaudible" tones as the level is
usually kept low enough as to not be noticeable to the listener except in
the quietest of environs, or if the transmitting station has the subtone
deviation set too high.

Actually, being able to receive down to 100 Hz can be quite helpful. On more
than one occasion, I have been able to assist other operators with
identifying power supply issues by the noticeably 120Hz (60 Hz full wave
rectified) hum on their transmitted signal.

73,
Bruce, N1RX


______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[DL5OCD]

Funny point Bruce !

73

[Ken G Kopp]

       
As a career two-way radio tech, I'll say that's "just
the way it is".  CTCSS tones must be filtered out of
both the TX and RX audio path, or the user would
quickly tire of listening to the "hum".  

The TX deviation is set to about 600 Hz, with 750 Hz
considered to be the maximum that should be used.

CTCSS is almost a necessity on today's multi-user
FM channels, where different user groups are stacked
10+ deep on channels in busy metropolitan areas.

73! Ken Kopp - K0PP
 
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Jim Brown-10]

On 8/22/2011 3:25 PM, DL5OCD wrote:
> It would be a nice feature if the user
> could decide by himself if he want to hear down to 0Hz on FM.

Audio down to 0 Hz for speech makes no sense.  The lowest frequencies in
the human voice are in the 100-200 Hz range (depending on the
individual), and frequencies below about 500 Hz make almost no
contribution to communications. There are often noise components below
500 Hz, like power supply hum, noise in the shack (or in the car,
including wind noise and road noise) microphone handling noise, and
breath popping. Not only that, but directional mics EMPHASIZE low
frequency sounds very close to the sound source (like the mouth, where
pops are generated).

For all of these reasons, Elecraft's low frequency rolloff is a good
thing, and there are no good reasons not to do it.  If Elecraft were to
decide to do a setting for hams in areas that don't use low frequency
tones, my recommendation would be to move the rolloff down to 150 or 200
Hz.  Also, Lyle's suggestion to tweak the rolloff to a steeper slope
could be a good idea.

73, Jim K9YC
Fellow, Audio Engineering Society
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[DL5OCD]

Anything of this would be nice, 100-3200Hz is my prefered "armchair bandwidth" for FM.

73
Michael