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Re: [TenTec] Omni VI Plus audio

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] Omni VI Plus audio
From: Fraser Robertson <g4bjm@hotmail.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sat, 29 Mar 2008 21:42:19 +0000
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
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> > > ----- Origin
 al 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 > i
 nteraction 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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