[Elecraft] K3 Filter Question

Thu Jul 9 11:35:19 EDT 2009


> > 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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> >
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