[Elecraft] [K3] Unanswered Questions ...

[Joe Subich, W4TV]

> Elecraft does not recommend using the FM filter in transmit 
> for anything other than  FM.  For ESSB, you will need to use 
> the AM filter. 

Why is that, does the DSP modulation process require additional 
filtering to make it acceptable on transmit?  If so, how "bad" 
is the unfiltered signal?  

Since the KFL3B-FM is not likely to be any wider than the 
typical four pole "roofing filter" in most of the "modern" 
transceivers, one would think that AM receive performance 
would be good to excellent with just the DSP filtering.  In 
that case it would seem to be silly to "waste" one filter 
filter slot if one wanted to configure a K3 for both FM and 
AM (or ESSB) transmission.  

If both the KFL3B-FM and KFL3A-6K are required, it means the 
user must make a choice between equipping the receiver with 
normal and narrow roofing (first IF) filters for both SSB and 
CW or "all mode" (FM, AM, and ESSB) operation.   

73, 

   ... Joe, W4TV 
 


> -----Original Message-----
> From: Greg - AB7R [mailto:ab7r at cablespeed.com] 
> Sent: Wednesday, October 24, 2007 4:53 PM
> To: Elecraft at mailman.qth.net; 'Joe; Subich; W4TV'
> Subject: Re: [Elecraft] [K3] Unanswered Questions ...
> 
> 
> Joe,  Those measurements are not yet available for the FM 
> filter.  I believe a plot will  be posted on the website when 
> the testing is done.  If not, I'll put the data on  the FAQ.  
> Elecraft does not recommend using the FM filter in transmit 
> for anything other than  FM.  For ESSB, you will need to use 
> the AM filter.  There will also be a config  menu item for 
> ESSB to select the final TX BW when the AM filter is used.    
>  ------------------------- 73, Greg - AB7R Whidbey Island WA 
> NA-065 K3#0009  On Wed Oct 24 16:21 , "Joe Subich, W4TV"  
> sent:  > >I have not been able to find answers to these two 
> questions  >in the archives, in the K3 FAQ or on the Elecraft 
> web site.  > >1) What is the bandwidth of the KFL3B-FM filter 
> at -6 dB  >   and -60 dB?   > >2) If the KFL3B-FM is 
> installed in a K3 (when available) is  >   a separate AM 
> filter required for AM and/or ESSB transmit?  >   In other 
> words, is the requirement simply that one roofing  >   filter 
> be of sufficient bandwidth to pass the AM/ESSB or  >   is the 
> "proper" bandwidth required to clean up artifacts  >   from 
> the DSP modulation process?  > >73,  > >   ... Joe, W4TV