>> I wonder if a company like Network Sciences did build an improved 8
>> mhz filter how much performance increase we would see. Surely if
>> a 20db jump in IMD dynamic range can be achieved at 70mhz, imagine
>> what the improvement would be at 8mhz! We will never know unless
>> someone tries.
The claimed jump in dynamic range in the FT-2000 with the NS/AC0C
filter is entirely due to the ability of that filter to reduce the
level of the IMD causing signals at +/- 2 KHz (outside the "window").
If you study the AC0C information, you will see the response of the
filter is down about 35 dB at +/- 2KHz. From a theoretical
consideration, reducing the interfering signals by 35 dB should
reduce the IMD by 70 dB!
This performance would indicate that the NS/AC0C filter is probably
protecting the second mixer and second IF but does nothing to solve
the improper (narrow band/reactive) termination of the first mixer
or issues of IMD generated in the noise blanker (even when the NB
is off).
73,
... Joe, W4TV
On 12/31/2010 5:00 PM, juergen wrote:
> Hi Bill
>
> I understand the differences in IF frequencies.
>
> The question still remains, how much extra IMD dynamic could be
> squeezed from the K3 if high performance 8mhz roofing filters were
> used. We have seen no data on the K3 filters that quantified their
> impact on IMD dynamic range.
>
> PA3AKE has shown that careful selection of crystals and building a
> roofing with due care contributes a significant amount to the
> ultimate IMD dynamic range.
>
> http://www.xs4all.nl/~martein/pa3ake/hmode/roofer_intro.html
>
> I wonder if a company like Network Sciences did build an improved 8
> mhz filter how much performance increase we would see. Surely if a
> 20db jump in IMD dynamic range can be achieved at 70mhz, imagine what
> the improvement would be at 8mhz! We will never know unless someone
> tries.
>
> 73 John
>
>
> --- On Fri, 12/31/10, Bil Tippett<btipp...@alum.mit.edu> wrote:
>
>> From: Bil Tippett<btipp...@alum.mit.edu> Subject: Re: [Elecraft]
>> Latest Sherwood table To: elecraft@mailman.qth.net Date: Friday,
>> December 31, 2010, 4:18 AM
>>> I wonder how such a high
>> performance filter would work in the K3? Not that its needed in the
>> K3. However in the interest of science, it might be a worthy
>> pursuit. It also might push the K3 well ahead of the FT5000 in
>> ultimate performance.
>>
>> Not very well since it's at 70 MHz. ;-) The Inrad filters are
>> already better than whatever is in the FT5000 since Sherwood
>> measured ultimate rejection in the K3 at 105 dB vs 90 dB for the
>> 5000.
>>
>> 73, Bill W4ZV
>>
>>
>>
>>
>> ______________________________________________________________
>> Elecraft mailing list Home:
>> http://mailman.qth.net/mailman/listinfo/elecraft Help:
>> http://mailman.qth.net/mmfaq.htm Post:
>> mailto:Elecraft@mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net Please help support this
>> email list: http://www.qsl.net/donate.html
>>
>
>
>
> ______________________________________________________________
> Elecraft mailing list Home:
> http://mailman.qth.net/mailman/listinfo/elecraft Help:
> http://mailman.qth.net/mmfaq.htm Post:
> mailto:Elecraft@mailman.qth.net
>
> This list hosted by: http://www.qsl.net Please help support this
> email list: http://www.qsl.net/donate.html
>
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
