Wider bandwidth while listening to AM SW on the KX3?

[Andrew Robertson-2]

While I do enjoy the AM SWL capabilities of the KX3, I would really like to be able to appreciate a more hi-fi sound from the unit.  I do know that that roofing filter XFIL1 is probably the ultimate limiter (I believe it’s 15 KHz?  or 10?) but I think the DSP filter in software is actually what is reducing my bandwidth to 4.2 KHz.  Since it is in software, I am hopeful that, perhaps, a future software update could provide a wider bandwidth or even shut off the DSP filter completely (pass-through mode).

I’m sure I’m not alone in using my KX3 as a SWL rig, and I hope that consideration could be given to this suggestion.  Thanks Wayne and Eric and the rest of the gang at Elecraft for a superb product!

-Andy KE7TMA
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[Andrew Robertson-2]

It’s true that, in the USA, the sidebands will be 5 KHz, at the absolute maximum, which means that I am missing at most about .8 KHz of audio at the very most.  However, in the shortwave bands (above MW BCB) there are many broadcasters using 12 to even 15 KHz of spectrum these days.  China, Cuba, Russia, and others have all adopted a very hi-fi sounding very wide bandwidth in the past few years.

I use the same speakers for all my listening with different radios so it’s not likely that this is the issue.

Thanks.

-Andy KE7TMA

On Nov 1, 2013, at 7:31 AM, dave <[hidden email]> wrote:

>
> The audio bandwidth of an AM radio station is something less than half the separation between stations on the dial. In the EU that separation is 9 kHz and in the US that is 10 kHz. So the max bandwidth one can hear on AM - at absolute most - is 5 kHz. Remember that AM is double sideband. The audio energy is both above and below the carrier (USB and LSB). The audio passband is approx half the RF bandwidth used.
>
> If the KX3 has an audio passband of ~ 4.2 kHz then you are effectively missing nothing in terms of bandwidth.
>
> If some other radio 'sounds' better that is likely due to listening to a different speaker with different freq response.
>
> 73 de dave
> ab9ca/4
>
>
>
> On 11/1/13 5:25 AM, Andrew Robertson wrote:
>> While I do enjoy the AM SWL capabilities of the KX3, I would really
> like to be able to appreciate a more hi-fi sound from the unit.  I
> do know that that roofing filter XFIL1 is probably the ultimate
> limiter (I believe it’s 15 KHz?  or 10?) but I think the DSP
> filter in software is actually what is reducing my bandwidth
> to 4.2 KHz.  Since it is in software, I am hopeful that, perhaps,
> a future software update could provide a wider bandwidth or even
> shut off the DSP filter completely (pass-through mode).
>>
>> I’m sure I’m not alone in using my KX3 as a SWL rig, and I hope
> that consideration could be given to this suggestion.  Thanks
> Wayne and Eric and the rest of the gang at Elecraft for a
> superb product!
>>
>> -Andy KE7TMA
>> ______________________________________________________________
>> Elecraft mailing list
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>>
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>

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[Raymond Sills]

Hi Guys:

Well, it is quite true that EU AM broadcast stations are spaced 9 KHz  
apart, and US stations are 10KHz apart, it's not true that the audio  
bandpass for those stations is about 5 KHz.  AM stations may very well  
modulate their transmitters so that audio frequencies up to 10 KHz (or  
more) are transmitted.  It simply depends on the design of the  
transmitter and the audio chain that feeds it.  Yes, this makes their  
signals broader, but the FCC rules for AM stations provide (in effect)  
that stations will be located far enough apart from one another that  
the "wide" sidebands are not interfering with other stations.  Or, the  
stations will need to use a directional pattern for their signals, so  
as to "protect" the other stations from interference.

In fact, at one time, many US AM stations would use high quality phone  
lines that were certified to pass up to 15 KHz, for their connection  
from a studio to a transmitter site, for those stations that had  
studios "in town" and a transmitter elsewhere.  If dedicated phone  
lines were not used, then often a microwave link of equivalent quality  
(or better) would be used.  Back when AM stations were part of a major  
network, like ABC, NBC, CBS, or Mutual, the phone lines used for the  
network programs would only be rated to 5KHz.  That's because of the  
cost per mile for the high grade lines was so much more.  Easy enough  
to justify for a mile or ten, but not hundreds or thousands of miles.

Since many AM stations now primarily have talk programming, some  
stations will deliberately limit audio response to 5K, so as to try to  
pack more "talk power" into the signal, just as hams do with AM and  
SSB rigs.  SSB, after all is AM, too.

73 de Ray
K2ULR

On Nov 1, 2013, at 4:21 PM, Andrew Robertson wrote:

> It’s true that, in the USA, the sidebands will be 5 KHz, at the  
> absolute maximum, which means that I am missing at most about .8 KHz  
> of audio at the very most.  However, in the shortwave bands (above  
> MW BCB) there are many broadcasters using 12 to even 15 KHz of  
> spectrum these days.  China, Cuba, Russia, and others have all  
> adopted a very hi-fi sounding very wide bandwidth in the past few  
> years.
>
> I use the same speakers for all my listening with different radios  
> so it’s not likely that this is the issue.
>
> Thanks.
>
> -Andy KE7TMA
>
> On Nov 1, 2013, at 7:31 AM, dave <[hidden email]> wrote:
>
>>
>> The audio bandwidth of an AM radio station is something less than  
>> half the separation between stations on the dial. In the EU that  
>> separation is 9 kHz and in the US that is 10 kHz. So the max  
>> bandwidth one can hear on AM - at absolute most - is 5 kHz.  
>> Remember that AM is double sideband. The audio energy is both above  
>> and below the carrier (USB and LSB). The audio passband is approx  
>> half the RF bandwidth used.
>>
>> If the KX3 has an audio passband of ~ 4.2 kHz then you are  
>> effectively missing nothing in terms of bandwidth.
>>
>> If some other radio 'sounds' better that is likely due to listening  
>> to a different speaker with different freq response.
>>
>> 73 de dave
>> ab9ca/4
>>
>>
>>
>> On 11/1/13 5:25 AM, Andrew Robertson wrote:
>>> While I do enjoy the AM SWL capabilities of the KX3, I would really
>> like to be able to appreciate a more hi-fi sound from the unit.  I
>> do know that that roofing filter XFIL1 is probably the ultimate
>> limiter (I believe it’s 15 KHz?  or 10?) but I think the DSP
>> filter in software is actually what is reducing my bandwidth
>> to 4.2 KHz.  Since it is in software, I am hopeful that, perhaps,
>> a future software update could provide a wider bandwidth or even
>> shut off the DSP filter completely (pass-through mode).
>>>
>>> I’m sure I’m not alone in using my KX3 as a SWL rig, and I hope
>> that consideration could be given to this suggestion.  Thanks
>> Wayne and Eric and the rest of the gang at Elecraft for a
>> superb product!
>>>
>>> -Andy KE7TMA
>>> ______________________________________________________________
>>> 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
>>>
>>
>
> ______________________________________________________________
> Elecraft mailing list
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[Don Wilhelm-4]

The KX3 is designed as a Ham Band receiver as the primary
consideration.  It includes filtering that is practical for Ham Band
operation.
Yes, it does provide full general coverage receive,  but the design
parameters are not primarily for SWL wideband audio response.  The
general coverage aspects are a nice add-on, but are not the primary
focus of the KX3.

73,
Don W3FPR

On 11/1/2013 4:21 PM, Andrew Robertson wrote:
> It’s true that, in the USA, the sidebands will be 5 KHz, at the absolute maximum, which means that I am missing at most about .8 KHz of audio at the very most.  However, in the shortwave bands (above MW BCB) there are many broadcasters using 12 to even 15 KHz of spectrum these days.  China, Cuba, Russia, and others have all adopted a very hi-fi sounding very wide bandwidth in the past few years.
>
> I use the same speakers for all my listening with different radios so it’s not likely that this is the issue.
>
>

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[alorona]

Ray Sills, very simply, is correct.
 
I know because my senior project was building a wide bandwidth "hi-fi" AM receiver. It had audio response out to 10 kHz and it sounded awesome.
 
My senior advisor came into the room to sign off on the project, and when I finished the demo he simply got up to leave and said, "But you'll never hear out to 10 kHz because all stations cut off at 5 kHz or less."
 
I sat there in disbelief. He waited until the last day to tell me this? "If I can prove to you that stations do indeed transmit wideband audio, will you accept my work?", I asked.
 
"No way can you prove it, because it's not true." This guy could be a real jerk when he wanted to. He gave me an hour.
 
With a six-year college career on the line, I then got on the phone and actually reached the chief engineers of two major radio stations in the Los Angeles area, KFI and KNX. Each of them told me, "Oh, yes, we absolutely transmit out to at least 12 kHz." The chief of KFI even said, "We apply pre-emphasis out to 15 kHz to partially counteract the rolloff in the typical receiver." This was in 1985.
 
I went back to the prof to report the happy news, he didn't even make eye contact with me, just grunted, and gave me a "D" -- barely passing.
 
My college professors were such a joy.
 
Anyway, listen in good health. You may have to search for it, but there's some pretty good audio still remaining in the AM bands. Not sure if it's worth it on noisy shortwave, though.
 
 
Al  W6LX
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[vk2rq]

[George Danner]

Guys,
AM Broadcasting isn't your grandmother's AM radio of old.
Many years ago, along came NRSC and it's 10kHz brick-wall filter & modified
preemphsis. NRSC recommendations do not include a requirement for the audio
be flat to the limits of the filter but encourage the broadcaster to use the
bandpass that is necessary for the program material - Best Engineering
Practices. Possibly limiting the audio to 5 kHz or even lower for voice only
programming (talk radio).
The FCC has adopted the NRSC specifications for the audio chain; but
retained the occupied RF bandpass requirements.

I'm fully confident that Elecraft could create a mode that complies with the
NRSC's recommend AM receiver practices to include limiting the bandpass,
premphsis & the 10 kHz notch filter curves.
Those of us that do not use an Elecraft transceiver for AM Broadcast can
probably find other firmware features that we would like to have higher on
the software enhancement list.

73
George
AI4VZ

-----Original Message-----
From: Matt VK2RQ wrote:
This is quite true Don, however it should also be noted that the design
parameters of interest to this discussion largely lie in software, which
provides considerable flexibility in meeting the goals of both ham band and
general coverage reception. This is of course one of the big advantages of
adopting a Software Defined Radio architecture.

73, Matt VK2RQ

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[Martin AA6E-3]

You get up to 48 kHz bandwidth out of the KX3 I/Q outputs, but you need to supply
your own I/Q demodulator - like Quisk, PowerSDR, etc.

73 Martin AA6E


On 11/01/2013 05:33 PM, Don Wilhelm wrote:

> The KX3 is designed as a Ham Band receiver as the primary consideration.  It
> includes filtering that is practical for Ham Band operation.
> Yes, it does provide full general coverage receive,  but the design parameters are
> not primarily for SWL wideband audio response.  The general coverage aspects are a
> nice add-on, but are not the primary focus of the KX3.
>
> 73,
> Don W3FPR
>
> On 11/1/2013 4:21 PM, Andrew Robertson wrote:
>> It’s true that, in the USA, the sidebands will be 5 KHz, at the absolute maximum,
>> which means that I am missing at most about .8 KHz of audio at the very most.
>> However, in the shortwave bands (above MW BCB) there are many broadcasters using
>> 12 to even 15 KHz of spectrum these days. China, Cuba, Russia, and others have all
>> adopted a very hi-fi sounding very wide bandwidth in the past few years.
>>
>> I use the same speakers for all my listening with different radios so it’s not
>> likely that this is the issue.
>>
>>
>
> ______________________________________________________________
> 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

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[Andrew Robertson-2]

> Guys,
> AM Broadcasting isn't your grandmother's AM radio of old.
> Many years ago, along came NRSC and it's 10kHz brick-wall filter & modified
> preemphsis. NRSC recommendations do not include a requirement for the audio
> be flat to the limits of the filter but encourage the broadcaster to use the
> bandpass that is necessary for the program material - Best Engineering
> Practices. Possibly limiting the audio to 5 kHz or even lower for voice only
> programming (talk radio).
> The FCC has adopted the NRSC specifications for the audio chain; but
> retained the occupied RF bandpass requirements.
>
> I'm fully confident that Elecraft could create a mode that complies with the
> NRSC's recommend AM receiver practices to include limiting the bandpass,
> premphsis & the 10 kHz notch filter curves.
> Those of us that do not use an Elecraft transceiver for AM Broadcast can
> probably find other firmware features that we would like to have higher on
> the software enhancement list.
>
> 73
> George
> AI4VZ

Yes, I’m sure this is true, George.  I do hope that my little bug in the ear reaches the right people, and if time and resources permit wider DSP filter bandwidths become possible.  I suspect many people who own a KX3 have a little list of features they would like to see added, but I don’t want to try to sounds like I’m complaining.  The KX3 is the best radio I ever owned and I love it just how it is, but I would like it even more if my wish came true!

Thanks to all the others for their input as well.  It was interesting to hear from Al and his experience in college, and many thanks to Martin for his suggestion as well.  So far I have only used my iPad and iSDR to provide panadapter functionality for the KX3, preferring to take the audio straight out of the KX3 instead of iSDR because I do really like the filters and noise reduction.

Thanks also to Don, I do realize that the KX3 is primarily a ham band radio and I do notice sensitivity suffers a bit outside the ham bands, but it is still excellent by any standard even when compared to top-dollar commercial and military communications receivers, let alone consumer grade shortwave radios.

Contrary to real life (heh) when it comes to the radio I tend to listen more than talk or send, and I listen to the shortwave segments more than the ham bands, still being a bit of a shortwave buff at heart.

Thanks again and happy radioing!

-Andy KE7TMA
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[Alan Bloom]

On 11/01/2013 05:02 PM, George Danner wrote:
> Guys,
> AM Broadcasting isn't your grandmother's AM radio of old.
> Many years ago, along came NRSC and it's 10kHz brick-wall filter

FCC regulations [73.44 (b)] for AM broadcast stations require the
emissions to be at least 25 dB down from the un-modulated carrier at
frequencies greater than 10.2 kHz from the carrier.  Back in the days of
analog filters it was difficult to get much more than 5 kHz bandwidth
and still guarantee at least -25 dB at 10.2 kHz.  Now with digital
filtering you can get out to almost 10 kHz and still meet the spec.

For comparison, the audio bandwidth of FM stations is 15 kHz and the
audio tends to have much less distortion (which is generated mainly in
the receiver's AM detector).

Since AM stations in the US are spaced 10 kHz apart, a station whose
modulation extends +/- 10 kHz from the carrier will heavily interfere
with the channels above and below it.  Supposedly the FCC assigns
channels in such a way that stations in the same area are not adjacent,
in order to reduce interference.  But of course that does not work at
night due to long-distance skip propagation.

Alan N1AL
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