[Elecraft] AM with FM filter (was: Re: [Elecraft_K3] Re: Close to Ordering)

[Guy Olinger K2AV]

What will happen the most is that the RX bandwidth will be handled
entirely by the DSP filter width, and stuff in the extra bandwidth
will be in the IF when you are listening.  This is the same thing as
listening to CW without a CW roofing filter.  For casual stuff, and
since it is a K3, you may not notice.

On transmit, the bandwidth of the signal is made in the CPU.  The
roofing filter is NOT used to restrict the bandwidth of the
transmitted signal.  That is entirely accomplished in the workings of
firmware, and is all done when the TX digital to analog converter
inserts the fully formed TX signal in the 15 kHz IF.  There is no
analog modulation anywhere in the TX string. Signal generation via
algorithm.

73, Guy.

On Mon, Nov 7, 2011 at 7:16 PM,  <goldtr8 at charter.net> wrote:
> Why not go to the confurgation menue and change the filter setting from
> 13 to 6 khz.   I bet it will work.
>
> I dont have the filter so I can not check it out.
>
> I am not sure what effect this would have on the TX width, maybe someone
> can check it out.
>
>
> ~73
> Don
> KD8NNU
>
>
> On Mon, Nov 7, 2011 at 1:34 PM, Oliver Dröse wrote:
>
>> Hi Joe,
>>
>> interestingly you CAN transmit AM with the FM filter! But it just
>> works for one over. ;-)) Found it out by chance during the last few
>> weeks with the nice 10 m conditions when tuning to the AM portion of
>> the band. I only have the FM filter fitted (besides CW/SSB filters)
>> and running firmware 4.42 beta (not tested with other ones) I can
>> transmit in AM. Just AFTER releasing the PTT I will get an TXFILERR on
>> the VFOB display and will not be able to transmit anymore. You need to
>> power-off and on the radio then to make it work again. As that is no
>> good QSO practice and you probably miss a few sentences from your QSO
>> partner during "K3 reboot" I just did one QSO that way (and
>> furthermore I am not really interested in AM just wanted to try it
>> out). ;-))
>>
>> Just my observations on that topic. Besides I completely agree with
>> you, I do not see why you should not be able (or better "allowed") to
>> transmit AM through the FM filter ...
>>
>> 73, Olli - DH8BQA
>>
>>
>>
>> ----- Original Message ----- From: "Joe Subich, W4TV"
>> <lists at subich.com>
>> To: <Elecraft_K3 at yahoogroups.com>
>> Sent: Monday, November 07, 2011 6:13 PM
>> Subject: Re: [Elecraft_K3] Re: Close to Ordering
>>
>>
>>>
>>>> If you wish to transmit AM, you'll need a 6 kHz filter.
>>>>
>>>> If you wish  to transmit FM, you'll need a 13 kHz FM filter.
>>>
>>> This still bugs me ... *WHY* won't Wayne enable AM transmit
>>> with the FM filter?  I've run multiple tests with a spectrum
>>> analyzer and can find no image when I set the bandwidth of
>>> the FM filter to 6 KHz to enable AM and generate a test signal
>>> with the two-tone generator.
>>>
>>> I don't want to waste one of the limited filter slots for both
>>> AM and FM filters but I want to be able to transmit either mode
>>> if so inclined.
>>>
>>> 73,
>>>
>>>    ... Joe, W4TV
>>>
>>>
>>
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