Sorry but the padding had nothing to do with the filter, I had to pad the
oscillator to get it to it's specified frequency.
73 Fraser G4BJM> From: RMcGraw@Blomand.net> To: tentec@contesting.com> Date:
Tue, 18 Mar 2008 18:31:37 -0500> Subject: Re: [TenTec] Omni VI Plus audio> > I
suspect that you may have a defective filter. The fact that you had to > pad an
oscillator is a clue. Or maybe a BFO crystal is out of tolerance.> > I measured
the audio frequency response of my Omni VI Plus using the > sinewave/power
method. Once I did this, I was able to see the shape of the > filter and take
into account the group delay which affects the "sound" of > the radio. I didn't
do a squarewave response however. I also confirmed > that the DSP artifacts
were present in the RX signal regardless of the NR or > Auto Notch usage.> >
I've found that the mechanical Collins filters used in the Omni VII offer an >
significantly enhanced signal on SSB both in transmit and receive. They are >
clearly different than crystal filters regardless if they are ladder of >
lattice configuration.> > 73> Bob K4TAX> > > ----- Original Message ----- >
From: "Fraser Robertson" <g4bjm@hotmail.com>> To: "Discussion of Ten-Tec
Equipment" <tentec@contesting.com>> Sent: Tuesday, March 18, 2008 6:20 PM>
Subject: Re: [TenTec] Omni VI Plus audio> > > >> > Thanks Bob, yes I'm
referring to the TX signal, although RX is similar of > > course. I agree with
what you say, although the Omni6+ SSB filter is > > worse than that in any
other rig I've used. I did align the oscillators > > as per the manual, in fact
I had to pad one of them as there wasn't enough > > adjustment range. I rarely
use SSB myself so will let someone else worry > > about it! 73 Fraser> From:
RMcGraw@Blomand.net> To: > > tentec@contesting.com> Date: Mon, 17 Mar 2008
20:02:33 -0500> Subject: Re: > > [TenTec] Omni VI Plus audio> > Typical of
filters, the shape factor or > > each side of the slope as measured > from the
-3 dB points is typically > > not identical although we'd like to think > they
are and wish they were. > > Thus a modulated carrier placed on the side of >
the slope, at say the -3 > > dB points, will sound different when listening to
> USB or LSB output > > products of the filter. It is not a common failing, it
is > a law of > > economical filter design and selection of filters that have a
> rea> > sonable or tolerable amount of insertion loss as well as a host of
other > > > factors such as ripple across the top, phase shift, group delay and
etc.> > > > I do not discount that fact that a crystal component within the
filter > > may > fail or may change frequency such that, in either case, the
shape > > factor of > the filter changes. If you have means to measure the
filter > > and its skirts > and insertion loss then you might find a clue as to
why > > it sounds different > on USB and LSB. Otherwise, invest in a new filter
> > and then complete an > alignment of the BFO oscillators. It is important >
> that the alignment be > carried out in the exact sequence as described in > >
the manual. There is > interaction between the adjustments. Even the FSK > >
adjustments need to be > made although you may never intend to operate > >
FSK.> > I trust you are speaking of transmit signal sounding different an > >
not > receive signal sounding different. For receive signal sounding > >
different > that may be caused by and additi> > onal factor being mis-alignment
of the > PassBand tuning oscillator.> > > > 73> Bob, K4TAX> > ----- Original
Message ----- > From: "Fraser Robertson" > > <g4bjm@hotmail.com>> To:
<ken.d.brown@hawaiiantel.net>; "Discussion of > > Ten-Tec Equipment" >
<tentec@contesting.com>> Sent: Monday, March 17, 2008 > > 6:49 PM> Subject: Re:
[TenTec] Omni VI Plus audio> > > >> > Our club's > > Omni6+ option3 sounds very
different on USB and LSB, and it's > > not > > possible to correct it by
adjusting the BFO frequencies, so it must be > > > > down to the filter being
asymetrical. I understood that was a common > > > > failing, but perhaps our
filter is faulty?> >> > 73 Fraser G4BJM> >> Date: > > Sun, 16 Mar 2008 18:37:51
-1000> From: ken.d.brown@hawaiiantel.net> > >> > > To: tentec@contesting.com>
Subject: Re: [TenTec] Omni VI Plus audio> > > > > > >> > Now I don't know why
the higher bands are different on your rig.> > > > > >> Wonder if you have an
antenna problem? > >> > > If the SSB Receive (or > > > >> transmit) audio
sounds differen> > t on 10, 15, 20 > meters than it does on > >> 40, 75 meters,
you should be > > comparing the sound > on USB versus LSB. > >> Your SSB audio
> > characteristic should not change at > all due to changing > >> bands, > >
other than because of the convention of using > USB above 9 MHz > >> and > >
LSB below 9 MHz. The audio characteristics also > should not change > >> > >
very much from USB to LSB. If it does change, that is > an indication > >> > >
that your BFO frequencies are misaligned for one or both > SSB modes. > >> > >
Another possibility, although not nearly as likely, is a > partially > >> > >
failed crystal filter with a non-symmetrical passband shape. > The first > > >
>> thing to do is check the BFO frequencies. If you install new> > > > >
filters, of any brand, without getting the BFO frequencies right, you > > > > >
will still have a problem.> > DE N6KB> > > > > >
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