> The only reason I had for putting the FM filter in the 2nd receiver
> was to be able to hear more of the split in a broad pileup situation
> (like the extremely large split widths that we saw a few months ago
> with 7O6T),
The width of the roofing filter has nothing at all to do with hearing
more of the pile-up (unless you're talking about literally "listening"
to all the signals at one time like a pile-up tape). The P3's pick-
up point is ahead of any roofing filter - it can "see" up to 200 KHz
at a time. The K3 transmitter and receiver can be split anywhere in
the band and if the KRX3 is used with a separate antenna the K3 and
KRX3 can literally transmit on one band and listen on another.
73,
... Joe, W4TV
On 9/26/2012 8:58 PM, Dale Boresz wrote:
> Joe,
>
> Good observations, all. I agree that 4.2 KHz is certainly good enough
> for communications audio.
>
> The only reason I had for putting the FM filter in the 2nd receiver was
> to be able to hear more of the split in a broad pileup situation (like
> the extremely large split widths that we saw a few months ago with
> 7O6T), figuring that being able to simultaneously hear the wider
> bandwidth and see it on the P3 would be a great combination. I'll just
> have to be a bit quicker with the VFO-B knob ;-)
>
> 73, Dale
> WA8SRA
>
>
> On 9/26/2012 8:10 PM, Joe Subich, W4TV wrote:
>> The limit occurs several places ... adjust the "HI" setting and one
>> will find 4.20 is the maximum available. There is also an analog
>> lowpass filter in the audio (headphone and speaker) between the DAC
>> and the headphone/speaker amplifiers.
>>
>> I'm sure this limitation derives from the roughly 10 KHz clock/sample
>> rate used for the DAC ... Nyquist says the maximum frequency can not
>> be more than half the sample (clock) rate. 4.2 KHz is plenty good
>> enough for communications audio ... and not bad for AM with fading,
>> noise, and interference typical of medium and high frequencies.
>>
>> The FM filter still provides noticeably better double sideband AM
>> response (4.2 - 4.5 KHz with DSP/LPF skirts) than the AM filter
>> (3.0-3.3 KHz depending on the IF filter response).
>>
>> 73,
>>
>> ... Joe, W4TV
>>
>>
>> On 9/26/2012 7:23 PM, Don Wilhelm wrote:
>>> Sorry, but yes, the K3 audio is limited at 4 kHz, no matter whether it
>>> is to the headphones or to the speaker. Please do not "shoot the
>>> messenger". but that information is in the archives of this reflector in
>>> several places - it has been discussed periodically.
>>>
>>> If you want to lobby for extended audio response, that is fine, but I am
>>> just saying what the limits are today. Whether those can be extended or
>>> not is for the DSP designer to answer.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>> On 9/26/2012 7:11 PM, Dale Boresz wrote:
>>>> On 9/26/2012 1:35 PM, Edward R Cole wrote:
>>>>> ... But I learned that audio is limited to 4-KHz
>>>>> regardless of IF filter so I ended up selling the extra 13-KHz filter.
>>>>>
>>>>> ...
>>>>>
>>>>> 73, Ed - KL7UW
>>>> I really hope that this does not apply to received audio to the
>>>> headphones or loudspeaker! I just purchased two FM filters (one for
>>>> sub-receiver to monitor wide splits) specifically to open up the receive
>>>> passband (audio included) for SWL and BCB reception. I have no intention
>>>> of actually transmitting FM or AM for that matter -- just want the wider
>>>> audio bandwidth for receive.
>>>>
>>>> So... is the received audio bandwidth *really* limited to 4 KHz?
>>>>
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>
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