It would be very difficult to measure the out of band noise in the
presence of a 100W PEP multi-tone audio signal. Much of the opposite
sideband noise would be masked by amplifier IMD which measures -29 dB
(3rd order) to -51 dB (9th order) relative to PEP in the ARRL lab (QST,
January, 2009). In addition, one would need some very selective filters
to reduce the 100 W PEP signal to a level that would allow measuring
the out of band (opposite sideband) noise as 100 dB is pushing the range
of many spectrum analyzers. In any case, since the "in band"
pedestal is present with no audio, one can assume any out of band noise
is also generated with no audio.
Don, you can consider my results a sample of two ... although I did not
repeat all the tests, my other K3 looks slightly *better* than the one
I reported on.
Again, the point is that although opposite sideband rejection is
better with the narrow filter, even with the FM filter is it (1) no
worse than a conventional transceiver, (2) better than transmit IMD
from the final amplifier and (3) better than the transmitted phase
noise from many rigs. Note opposite sideband suppression in many
older rigs is in the -65 to -75 dB range (ARRL "Expanded Test Report")
vs. an effective opposite sideband suppression in excess of 100 dB for
the K3.
73,
... Joe, W4TV
On 9/22/2012 6:49 PM, Scott Manthe wrote:
> It might also be interesting to see what happens to the "noise pedestal"
> when audio is added to the equation.
>
> 73,
> Scott, N9AA
>
>
> On 9/22/12 6:31 PM, Don Wilhelm wrote:
>> Gary,
>>
>> Joe did testing on a sample size of one K3. While manufacturing of K3s
>> can produce units that behave close to the average, I think it would be
>> wise to test on a greater number of K3s with different configurations.
>> In addition some testing of K3s under fault conditions should be done too.
>>
>> 73,
>> Don W3FPR
>>
>> On 9/22/2012 6:13 PM, Gary Gregory wrote:
>>> *Joe,
>>>
>>> Thanks for taking the time to conduct the tests.
>>>
>>> Now that I understand what the rationale for the request to Wayne, I am of
>>> the same mind also.
>>>
>>> As I use the FM filter rarely I would also be able to free up a filter slot
>>> and add an additional narrow filter which would be good for me also.
>>>
>>> I hope Wayne will give consideration to your request in light of your
>>> testing and implement it soon.
>>>
>>> Thanks again Joe for the test results and the reasoning for the request.
>>>
>>> 73
>>> *
>>> On 23 September 2012 08:02, Thomas Horsten <[email protected]> wrote:
>>>
>>>> Hi Joe,
>>>>
>>>> Thanks for that analysis! It makes the situation clear to me: The FM filter
>>>> will do just fine for AM and ESSB, and I can free up a filter slot for a
>>>> narrow CW filter.
>>>>
>>
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