FW: [Elecraft] SSB Filters

Tue Feb 26 10:50:01 2002

All other doc bitches aside, you gotta love the PDF's. If you can't find =
a part on the schematic, or in the text, the FIND function can. I wish =
I'd had my HW-101 doc on PDF back in the 70's. (Of course, my TRS-80 =
didn't have Adobe, darn).

Dan

-----Original Message-----
From: Ron D' Eau Claire [mailto:[email protected]]
Sent: Tuesday, February 26, 2002 10:38 AM
To: Dan Barker
Subject: RE: [Elecraft] SSB Filters

Y'know. that's a GOOD point, Dan.

Your question got me to go take a look at the documentation.

The Elecraft Application Note dated 1 June, 2000 "Eliminating the =
Frequency
Roll-Off On One End of the K2 SSB Filter" does say that one way to =
"flatten
out" the apparent response of the SSB Option filter is to, "Adjust L34 =
until
the passband of the filter appears to be more uniform..." and then it =
goes
on to say, "Unfortunately...the overall signal-to-noise ratio of the K2
receiver will be compromised."

HOWEVER... that is with C-180 still in the circuit. The mod involving =
the
transistor switch removes C-180 from the circuit (as you did) and adds =
120
pf in parallel with C182 only during SSB operation. Does simply removing
C-180 without using the transistor switch to add the 120 pf capacitor to =
the
circuit work as well? Perhaps. I've not see a peep about it on the
reflector. So I can't say whether the procedure Gary gave you would have =
the
same negative effect on the S/N that the Application Note predicts.

But you can check it. Just try setting L34 for best Signal-to-Noise =
ratio in
CW mode on a weak signal and see if that is a DIFFERENT setting from =
where
it is now. To do that the instructions (in the above application note) =
say
to remove the antenna from the rig and turn on the pre-amp, then tune in =
the
'birdie' they all have at 7 MHz. (This spurious signal is normally only
audible with the antenna disconnected.) Then the procedure says, "While
listening to the weak signal at 7000 kHz, adjust L34 for the best signal
strength and lowest noise. The best overall setting typically occurs at =
1-2
turns below the top of the can."

You can do that to see if the setting on L34 is different from where you
have it now.

I think I will post a question about whether the 120 pf cap is still =
needed
on the reflector.

I am a writer by trade, and have been becoming increasingly frustrated =
by
the morass of documents relating to MY particular K2 - option manuals,
application notes AND all the various changes to all of those that have
occurred over the past two years. Have a fat envelope of documents and =
it's
getting impossible to keep track of them.

And then they leave important stuff out of the documents. Case in point =
was
the issue of the tuning rate actually slowing down as one turns the K2
tuning knob faster that I brought up on the reflector recently. It =
turned
out that is "normal", if counter-intuitive, with the Rev. 2 firmware. It =
is
a performance compromise they accepted in order to get more accurate =
dial
calibration across the tuning range. But they forgot to mention it in =
the
documentation.

It's a very small team at Elecraft, and the sheer volume of material is
starting to overwhelm them too, from the looks of it.

Ron AC7AC

> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Dan Barker
> Sent: Tuesday, February 26, 2002 4:10 AM
> To: Elecraft
> Subject: [Elecraft] SSB Filters
>
>
> Ron: Now you've got me wondering what damage I might have done to
> CW. Any way to measure the S/N at my current setting? I could
> then peak it and see what I'd lost. If it's just db between that
> birdie at 7mhz and the noise floor, I can take that number off
> Spectrogram. Might need a little amplification to get a good reading.
>
> I'd like to know what the SSB audio cost me on CW.
>
> Dan
>
> -----Original Message-----
> From: Ron D' Eau Claire [mailto:[email protected]]
> Sent: Monday, February 25, 2002 10:33 PM
> To: Dan Barker
> Subject: RE: [Elecraft] SSB Filters
>
>
> True enough, Dan.
>
> The "flattening mod" was more for receive than transmit. My K2 sounded
> absolutely tinny on one sideband and bassy on the other until I
> put it in. I
> was able to get it "flat" by adjusting the coil, but that really
> compromised
> the signal/noise ratio on CW. That's when Wayne or Eric came up with =
the
> transistor switch mod.
>
> I suspect the need for it varies a bit with each radio, since
> these filters
> are made up of discrete xtals.
>
> I wanted to know because next time someone asks about the weird
> SSB audio on
> the reflector, I'll suggest that they consider doing what you did as =
well.
>
> Thanks,
>
> Ron AC7AC
>
> > -----Original Message-----
> > From: [email protected]
> > [mailto:[email protected]]On Behalf Of Dan Barker
> > Sent: Monday, February 25, 2002 7:15 PM
> > To: Elecraft
> > Subject: [Elecraft] SSB Filters
> >
> >
> > Ron:
> >
> > You are absolutely right, it's just build the thing, and remove
> > the 10 pf cap, and twist some knobs (one LARGE, several small). I
> > read about the "flattening mod", but the Spectrogram came out so
> > nice without it, I don't really see the need. The guys on the
> > receiving end don't seem to hear the need either<g>.
> >
> > My rig is stock except for the sidetone cleanups (not very clean,
> > but at least better) and C180 being pulled. The "trick" was not
> > to worry that my numbers were so very far from the examples (like
> > 400-600 Hz) in the book and in diddling L34 by eye, not ear.
> >
> > Dan / WG4S / K2 #2456
> >
> > -----Original Message-----
> > From: Ron D' Eau Claire [mailto:[email protected]]
> > Sent: Monday, February 25, 2002 8:20 PM
> > To: Dan Barker
> > Subject: RE: [Elecraft] SSB Filters
> >
> >
> > Hi Dan:
> >
> > By your description of removing C180, I take it you did not put
> > the "filter
> > flattening" mod in that is provided as an Application Note on
> the Elecraft
> > Reflector.
> >
> > Just curious, because you managed to get a very nice looking =
response
> > without it if that's so.
> >
> > Wayne/Eric announced almost two years ago that the mod would
> > become part of
> > the r-f board in future releases, but I've not yet seen it hit
> the street.
> > They may have re-thought the idea.
> >
> > Ron AC7AC
> > K2 # 1289
> >
> > > -----Original Message-----
> > > From: [email protected]
> > > [mailto:[email protected]]On Behalf Of Dan Barker
> > > Sent: Monday, February 25, 2002 2:40 PM
> > > To: Elecraft
> > > Cc: Steve & Anne Ray
> > > Subject: [Elecraft] SSB Filters
> > >
> > >
> > > Failing miserably to get my K2 sounding right on my own, I
> > > grabbed the telephone and called Elecraft. I had LSB sounding OK,
> > > and USB off in left field. None of my numbers were within 400 Hz
> > > of the "book" values. Gary said that was fine.
> > >
> > > Gary talked me through the procedure for a K2 with recent
> > > firmware and the KSB2 adapter installed.
> > >
> > >  a) Bend C180 back and forth until it breaks off, and discard.
> > >  b) Fire up Spectrogram; and set a marker at 400 and 2200 Hz.
> > >  c) Move the FL1 BFO freq. until it's balanced between the marks.
> > >  d) Repeat for the other sideband.
> > >  e) Diddle L34 to flatten the top of the USB response, but not so
> > > far as to screw up the LSB response.
> > >  f) Repeat centering the response curves if necessary.
> > >
> > > My results below:
> > >
> > >       USB
> > >
> > >   Picture suppressed on reflector, see
> http://www.visioncomm.net/ssb.html
> >
> >       LSB
> >
> >   Picture suppressed on reflector, see
> http://www.visioncomm.net/ssb.html
> >
> > I just spend about an hour on SSB with Steve in GA, and he says
> > both Sidebands sound FB, and the same. Cool!
> >
> > So, what's this about a flattening mod? Doesn't really look like
> > one is needed.
> >
> > Dan / WG4S / K2 #2456, KAT2, K160RX, KIO2, KSB2
> >
> > PS: Now, How do I get on PSK? The MH2 ain't gonna cut it! I'm a
> > gonna need some WIRE! (who ever called this hobby wireless? -
> > They're nuts!).
> >
> > _______________________________________________
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> >
>
>
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>
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