[Elecraft] [K3] Tunijng the Radio

[goldtr8 at charter.net]

Hi Jack,

So I think what you are telling me is that the IPA is after the DSP and 
that obvioulsy any inperfections in this circuit and the final amp are 
what creates the IMD products.

Is that another reason that the tx filter is 2.7 or 2.8 wide at the 
skirts to act as a wall to prevent this from getting out on the air 
compared to using a 3.0 wide filter.

Thanks
Don

~73
Don
KD8NNU


On Sun, Jul 15, 2012 at 8:51 AM, Jack Smith wrote:

> Don:
>
> Not so at all - whilst the low level SSB generated by the K3's DSP may 
> be close to theoretically perfect, intermodulation products produced 
> by the K3's IPA and final amplifier stages are present in quantity and 
> are the limiting factor.
>
> Jack K8ZOA
>
>
> On 7/15/2012 8:02 AM, goldtr8 at charter.net wrote:
>> Being a SDR there is really no suppressed carrier as the carrier is
>> never created only the sideband for the mode selected.   So unless 
>> you
>> have signficant splatter there should not be an IMD problem with a 
>> K3.
>>
>> Again assuming no splatter and a properly functioning radio.
>>
>> This is no analog radio and all TX is based on the DSP first and then
>> the TX filter last.
>>
>> ~73
>> Don
>> KD8NNU
>>
>>
>> On Sun, Jul 15, 2012 at 7:34 AM, Geoffrey Mackenzie-Kennedy wrote:
>>
>>> Dave,
>>>
>>> To add to the replies which you have received, the width of your USB
>>> signal should also include those intermodulation products which 
>>> appear
>>> at frequencies less than that of the suppressed carrier frequency,
>>> i.e. in the LSB region.  If you tuned your K3 to 14.225 MHz, these 
>>> IMD
>>> products would fall outside of your General Class portion of the 
>>> band
>>> and could create interference.  To be safe I would suggest that you 
>>> do
>>> not operate your K3 in USB mode below 14.228 kHz.
>>>
>>> In Europe the top end of our 80m allocation is 3.800 MHz, and some
>>> European hams operate LSB on or very close to 3.800 MHz.  This
>>> practice has caused some non-amateur users operating just above 
>>> 3.800
>>> MHz to complain about interference from amateur IMD products.
>>> Fortunately those complaints which I have heard are still at the
>>> "muttering" stage.
>>>
>>> 73,
>>> Geoff
>>> LX2AO
>>>
>>>
>>> On July 14, 2012 at 10:39 PM, David Guernsey wrote:
>>>
>>>
>>>> If I tune my K3 to 14.225 MHz will I be in the General Class 
>>>> portion
>>>> of the 20 meter band, or do I have to allow for the width of my USB
>>>> signal when I transmit?
>>>
>>>
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