Are you sure that applies to transmit bandpass? Every Flex I've
heard has been excessively wide.
By the way, the Elecraft K3 has an optional post modulator filter
for AFSK (CONFIG:AFSK TX). Its steep sided bandpass eliminates
both low-frequency hum and harmonics before they can be amplified
and reach the antenna.
73,
... Joe, W4TV
On 2/6/2012 6:25 PM, Jerry Flanders wrote:
> Just a FIY: Flex radios allow easy adjustment of the tx bandpass. I
> routinely use a narrow tx bandpass with AFSK just to avoid problems
> such as Joe describes below. It is a click/drag adjustment, with
> visual feedback on the bandpass adjustments.
>
> Jerry W4UK
>
> At 05:03 PM 2/6/2012, Joe Subich, W4TV wrote:
>
>> > Someone sent me this comment when the subject of FSK readouts came up.
>> > Any thoughts on his plan?
>>
>> The only problem with using 915/1015 (1 KHz) or any other "low" audio
>> tones with AFSK is the chance that over driving the microphone input
>> of the transceiver will produce harmonics that will get transmitted.
>> The problem is particularly a problem with tones 1 KHz and below since
>> the 3 KHz harmonic content *will* make it through the IF filter in most
>> rigs. 3 KHz is right on the "knee" of the response of most modern
>> rigs.
>>
>> 73,
>>
>> ... Joe, W4TV
>
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