[Elecraft] K3 Filter Question

Brett Howard brett at livecomputers.com
Thu Jul 9 23:56:31 EDT 2009 

Looks like buying the FM filter and lying to the rig gives me the
maximum flexibility with a minor inconvenience.  Being that I won't be
TXing in those modes all that often I'm not too worred but I just want
to have a true All mode tranceiver.  

~Brett  

On Thu, 2009-07-09 at 11:35 -0400, Joe Subich, W4TV wrote:
> 
> > > This is as expected since the FM filter should be at least -60
> > > dB at +/-23 (2:1 shape factor) with an ultimate attenuation
> > > of at least -100 dB.
> 
> Correction ... +/- 26 KHz or a 2:1 shape factor.  However 
> for comparison, Inrad's six pole front end filters for 40 
> meters are 15 KHz wide (+/- 7.5 KHz) at 1 dB and 32 KHz 
> (+/- 16 KHz) at - 60 dB or 20 KHz ((+/- 10 KHz) at -1 dB 
> and 45 KHz (+/- 22.5 KHz) at - 60 dB.  Converting to a 6:60 
> framework makes the shape factor around 1.8:1.   
> 
> 73, 
> 
>    ... Joe, W4TV 
>  
> 
> 
> 
> > -----Original Message-----
> > From: Stewart Baker [mailto:stewart at baker.nildram.co.uk] 
> > Sent: Thursday, July 09, 2009 10:35 AM
> > To: lists at subich.com; 'Brett Howard'; 'Bob Cunnings'
> > Cc: elecraft at mailman.qth.net
> > Subject: Re: [Elecraft] K3 Filter Question
> > 
> > 
> > I agree.
> > The cost of the K3 filters is now so high in the UK, that I 
> > want to get away with the minimum number necessary.
> > 
> > 73
> > Stewart G3RXQ
> > On Thu, 9 Jul 2009 10:00:42 -0400, Joe Subich, W4TV wrote:
> > >
> > >> I wonder if there is any possibility of allowing AM TX and/or ESSB 
> > >> via the FM filter...
> > >
> > > It is theoretically possible to transmit AM and ESSB through the FM 
> > > filter but the K3 is currently configured to prohibit AM and ESSB 
> > > transmit unless the 6 KHz filter is used.  I have transmitted using 
> > > the FM filter by setting the K3 as if the FM filter was an 
> > AM filter 
> > > but then I can not transmit FM without resetting the filter set-up.
> > >
> > > Elecraft will argue that the 6 KHz filter is necessary to prevent 
> > > transmitted images (the DSP IF is 15 KHz, the image is 30 KHz away 
> > > from the transmit frequency).  However, I can not measure 
> > any image - 
> > > to -120 dB from the CW level - when looking at the 
> > transmitter output 
> > > with a directional coupler using the SDR-IQ as a spectrum 
> > analyzer.  
> > > This is as expected since the FM filter should be at least -60
> > > dB at +/-23 (2:1 shape factor) with an ultimate attenuation
> > > of at least -100 dB.
> > >
> > > It would certainly be nice if the "6 KHz" restriction was removed.
> > >
> > > 73,
> > >
> > >   ... Joe, W4TV
> > >
> > >
> > >> -----Original Message-----
> > >> From: elecraft-bounces at mailman.qth.net 
> > >> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Brett Howard
> > >> Sent: Thursday, July 09, 2009 2:21 AM
> > >> To: Bob Cunnings
> > >> Cc: elecraft at mailman.qth.net
> > >> Subject: Re: [Elecraft] K3 Filter Question
> > >>
> > >>
> > >> I forgot to go back to that...  I was thrown off by the comment on 
> > >> the order page that said you only need one of each filter for 
> > >> transmit.  I know that doesn't fully say what I was hoping for 
> > >> though....
> > >>
> > >> I wonder if there is any possibility of allowing AM TX and/or ESSB 
> > >> via the FM filter...  As I'd like to have maximum flexibility but 
> > >> only have one slot left because of the way I have setup 
> > the radio for 
> > >> what I spend most of my time doing.
> > >>
> > >> Thanks for the assistance gentlemen.
> > >>
> > >> ~Brett
> > >>
> > >> On Thu, 2009-07-09 at 00:13 -0600, Bob Cunnings wrote:
> > >> > Manual, pg 74:
> > >> >
> > >> > "Rule #1: If you plan to use a particular filter for both
> > >> transmitting
> > >> > and receiving (main receiver), you'll need to install it 
> > on the RF 
> > >> > board. You can optionally install a filter of the same 
> > or similar 
> > >> > bandwidth on the sub receiver for receive-only use. (This is 
> > >> > recommended since it will keep the receivers identical.)"
> > >> >
> > >> > Bob NW8L
> > >> >
> > >> > On Wed, Jul 8, 2009 at 11:31 PM, Brett
> > >> Howard<brett at livecomputers.com>
> > >> > wrote:
> > >> > > Ok so I'm curious if I'll be able to do what I'd like.
> > >> I'd like to
> > >> > > setup my K3 for maximum flexibility.  At the moment I 
> > have these 
> > >> > > filters.
> > >> > >
> > >> > > 2.8Khz
> > >> > > 1.8Khz
> > >> > > 1Khz
> > >> > > 250Hz
> > >> > >
> > >> > > These 4 filters are duplicated in the lower 4 slots of both 
> > >> > > receivers. I'd like to have the ability to do AM and FM
> > >> both TX and
> > >> > > RX in this radio.  Can I add the AM filter and KBPF into
> > >> the main RX
> > >> > > and then put the FM filter into the KRX3?
> > >> > >
> > >> > > I'm hoping that I can then use the MainRX for broad frequency 
> > >> > > coverage and AM broadcast receive.  Then if I ever 
> > want to do FM 
> > >> > > work I simply have to use the sub receiver to do so.  Will TX 
> > >> > > through the FM filter work with it in the sub RX...  To
> > >> the best of
> > >> > > my knowledge it appears that I can set the rig up in 
> > this fashion 
> > >> > > but that doesn't always mean it will work how I expect it to.
> > >> > >
> > >> > > Am I all wet here?
> > >> > >
> > >> > > Thanks
> > >> > >
> > >> > > ~Brett
> > >> > >
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