I am travelling and unable to post a long message or read everything in
this thread. Comments:
1. The IR 2.8 filter uses STOCK BFO freqs
2. Those 3.1 filters are unique and were offered on eBay a year or two
ago. Use of those filters would absolutely necessitate changing the BFO
freqs, which would then prevent that radio from cascading a second narrower
9MHz filter. Carrier null could also present a problem.
3. Because the receive passband is high pass filtered at ~240hz by the dsp
circuit ALL the time in the Omni6, the use of that uber-wide filter makes
even less sense than the little sense it already was making.
73, Barry N1EU
On Jan 10, 2016 1:18 AM, "Gary J FollettDukes HiFi" <dukeshifi@comcast.net>
wrote:
> It would seem to me that the best use of the Inroad wide filter would be
> to leave the original filter in position one in the first IF. The you could
> easily move a few wires to bypass that filter in receive, and go directly
> to the 2l.8 KHz filter in position 2. This is easy because, in the Omni 6,
> TenTec cascaded the first filter into the second one. If you use the PIN
> diodes to go around the position one filter (2.4 KHz) you would take full
> advantage of the wider filter in position two only in receive. In transmit,
> everything would remain stock.
>
> Omni 6 radios never sounded all that bad in transmit, only in receive
> (tony ears anyway). The above method should improve that sound by quite a
> bit.
>
> BTW: I never observed any significant improvement in Omni 6 audio on
> receive with the so-called audio improvement mod. I have tried it on
> several Omni 6’s and never saw much difference.
>
> I believe the filters in the Omni 6 have more in band ripple than they
> should, and also the positioning of the first OF filter with respect to the
> second IF filter combine to produce the nasal sound of the omni 6
> (non-optimal overlap). No amount of audio chain alteration will correct for
> that.
>
> I have even taken the audio directly from the product detector and passed
> this through to an outboard audio amplifier. No real improvement in audio
> was observed.
>
> This supports the notion that the restricted audio arises in the IF
> combination of filters and their respective center frequencies and overlap.
>
> The only other p=lace where such restricted frequency response could take
> place is in the very first ceramic filter that is used prior to any of the
> 9 MHz roofing filters. I have never tried bypassing this just to see what
> impact it has on the audio response. I will wait for that until I see hows
> the filter arrangement in this particular Omni 6+ sounds.
>
>
> I can’t wait to hear how this Omni sounds tomorrow with the high buck 3.1
> KHz filters in both IF’s. I have high hopes...
>
> Gary
>
>
>
>
> > On Jan 9, 2016, at 10:58 PM, elespe@lisco.com wrote:
> >
> > That is why I asked.
> > I have the 2.8khz INRAD filter and the radio sounds fantastic and gets
> > great audio reports but keeping the carrier supression better than 34 db
> > on both sidebands is impossible without moving the bfo which, without
> > doing the math on the entire radio frequency scheme, seems to have a
> > trickle down effect on screwing something else up along the way. If the
> > bfo is wrong doesn't that reflect in the readout as well?
> > I love the INRAD "wide" filters but am going to change the 1st if down to
> > a 2.4khz model to keep everything else in check.
> > Along the line of sounds great I somehow stumbled across a speaker that
> > fits the original hardware and hole and actually makes the OMNI VI sound
> > better than any external speaker system I have tried on it. Just dumb
> luck
> > and Parts Express---who would know.
> > Paul K0UYA
> >
> >> As I recall, when one purchased the Inroad “wide†SSB filter for the
> >> first IF, one needed to adjust the BFO frequencies in order to get
> proper
> >> positioning of the carrier on the filter slope. I do not (yet) know the
> >> adjustment range for the BFO’s bu I am guessing that the BFO
> adjustments
> >> in this one must have pushed that frequency another 300 Hz, or the BFO
> >> crystal(s) were changed out.
> >>
> >> Anyone who had spent $1000 to have custom filters made up would
> certainly
> >> have taken proper measures to ensure that transmitted SSB was properly
> >> generated.
> >>
> >> I should know the answer tomorrow.
> >>
> >> I have not looked yet, but it is POSSIBLE that the radio may have been
> >> rewired to route the TX 9 mHz IF signal through the position 2 filter.
> >> That is a lot easier to do the one might think, due to the use of diode
> >> switching to select the desired filter, so it is possible.
> >>
> >> The first IF filter that was in the position 2 is marked “48074†and
> >> the second IF filter in position 2 is marked 48058.
> >>
> >> Can anyone tell me if these are the numbers for the “stock†SSB
> >> filters?
> >>
> >> I can measure them fairly easily for bandpass but it would save some
> time
> >> if anyone simply knew the answer to that.
> >>
> >> I will, however, put a frequency counter on the BFO tomorrow and measure
> >> the frequencies on LSB and USB to determine what was done to make this
> >> work. As you know, without adjustment of the BFO down the filter edge,
> >> both carrier suppression and SSB suppression would suffer quite a lot.
> >>
> >> Gary
> >>> On Jan 9, 2016, at 9:54 PM, Paul Kraemer <elespe@lisco.com <mailto:
> elespe@lisco.com>> wrote:
> >>>
> >>> How is that possible?
> >>> The lsb and usb bfo frequencies are only 3khz apart
> >>> Paul K0UYA
> >>>
> >>> -----Original Message----- From: Gary J FollettDukes HiFi
> >>> Sent: Saturday, January 09, 2016 9:05 PM
> >>> To: Discussion of Ten-Tec Equipment
> >>> Subject: Re: [TenTec] 3.1 KHz IF Filter for 2nd IF in Omni 6
> >>>
> >>> I bit the bullet and took the entire bottom cover off.
> >>>
> >>> I found that there is also a custom 3.1 KHz filter in the number 1
> >>> position in the first IF (9 MHz)! This is also an 8 pole filter with
> the
> >>> IF cans on board to tailor response. It is equally well made as the
> >>> second IF filter is well made.
> >>>
> >>> I’ll report tomorrow on how the radio sounds with quiet band
> >>> conditions and also get a transmitted SSB audio report. I may have
> found
> >>> the Omni 6 of my dreams!
> >>>
> >>> I have always hated the SSB sound of the omni 6 (all variations).
> >>>
> >>> I contacted the fellow from whom I got this and he informed me that the
> >>> original owner of this radio had these filters custom made for a cost
> of
> >>> over $1000. I sill do not know what company made them but they are top
> >>> quality all the way.
> >>>
> >>> Apparently that fellow hated the sound of the Omni 6 as much as I doubt
> >>> had the resources to take corrective action.
> >>>
> >>> Hopefully these filters will offer some relief as the overall design of
> >>> the Omni 6 is one of my favorites over any other radio design.
> >>>
> >>> It’s also on of the prettiest radios going.
> >>>
> >>> Gary
> >>>
> >>>
> >>>
> >>>> On Jan 9, 2016, at 8:17 PM, Mark S. Holden <mark@holden-insurance.com
> >
> >>>> wrote:
> >>>>
> >>>> On 1/9/2016 8:32 PM, Gary J FollettDukes HiFi wrote:
> >>>>> I have a 3.1 KHz bandwidth filter in one of my Omni 6+ radios. It
> fits
> >>>>> perfectly into the TenTec socket and was obviously made for the en
> >>>>> Tec. However, it looks unlike any filter I havee ever seen in ANY Ten
> >>>>> Tec product.
> >>>>>
> >>>>> It is an 8 pole filter but it also had four small IF transformers on
> >>>>> it, presumably to tailor the passband shape.
> >>>>>
> >>>>> Has anyone heard of this filter? Does any know who made it? It is too
> >>>>> perfect to have been a home brew job. It is built on thicker board
> >>>>> stock than that used for most Ten Tec filters.
> >>>>>
> >>>>> I would assume that its intent is to improve received audio in SSB. I
> >>>>> am going to try it in a few minutes to see what the radio sounds like
> >>>>> compared with the others.
> >>>>>
> >>>>> Gary
> >>>>> _______________________________________________
> >>>>> TenTec mailing list
> >>>>> TenTec@contesting.com
> >>>>> http://lists.contesting.com/mailman/listinfo/tentec
> >>>>>
> >>>>>
> >>>> I'd expect that to be a fun filter for rag chewing.
> >>>>
> >>>> My Harris RF-550 rx has a 3.24khz crystal filter that's incredible for
> >>>> SWL. I also installed some crystal filters intended for the Racal
> >>>> 6790gm in my AOR 7030+
> >>>> _______________________________________________
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> >>>
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> >>
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> >>
> >
> >
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