[TenTec] TenTec Digest, Vol 202, Issue 18

wes Bolin k5apl41 at gmail.com
Thu Oct 24 13:14:35 EDT 2019 

The OMNI VI is a piece of cake and you don't have to open the case.  In the
software menu you can actually adjust the Oscillator frequency from the
front panel.  Its in the manual.  I have done it years agoso
don't remember the details.  The OMNI V requires you to open the cover.
The OMNI V did not have a TCXO, but the OMNI VI does, so you need to give
it time to stabilize the frequency before you do any
adjustments.  Some guys have disabled the TCXO to minimize the drift after
turn-on and stabilization.  At any rate you have options to get it on
frequency.  BTW the best way to get it on the proper frequency is to have a
frequency standard, not the other guy's comments.  On 20M, the net on
14.300 is always very close to 14.300.  Have fun.
Wes

On Thu, Oct 24, 2019 at 11:00 AM <tentec-request at contesting.com> wrote:

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> Today's Topics:
>
>    1. frequency adj. (wt4t at reagan.com)
>    2. Re: frequency adj. (Bob McGraw K4TAX)
>    3. Re: frequency adj. (Gary Follett)
>    4. Re: frequency adj. (Ken Brown)
>    5. Re: frequency adj. (wt4t at reagan.com)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 23 Oct 2019 15:13:25 -0500 (CDT)
> From: wt4t at reagan.com
> To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
> Subject: [TenTec] frequency adj.
> Message-ID: <1571861605.226246652 at webmail.reagan.com>
> Content-Type: text/plain; charset="UTF-8"
>
>
> Have a OMNI VI+ ,started to set up a position for the rig today and
> noticed the frequency  readout was off about .22 hz. I remember my old
> omni V  had a simple adjustment point to tweek the readout. Same on the + ?
> if so what board and location would I find it?
>  The older I get  the more I for get. 73
> dale wt4t
>
> ------------------------------
>
> Message: 2
> Date: Wed, 23 Oct 2019 16:56:07 -0500
> From: Bob McGraw K4TAX <rmcgraw at blomand.net>
> To: dale via TenTec <tentec at contesting.com>
> Subject: Re: [TenTec] frequency adj.
> Message-ID: <147bdd2c-2540-5db0-8b5c-9c3862e2856d at blomand.net>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> Dale:
>
> The spec as I recall is +/- 50 Hz.? Looks as though you are well within
> that spec.? Oh by the way,?? .22 Hz is ~1/4 of one Hertz. I think you
> mean 22 Hz.
>
> You should check all bands and determine the error on each one. Each one
> has a crystal oscillator operating in a Phase Lock Loop based on the
> reference frequency.?? Earlier radios had a crystal oven which required
> time to reach operating temperature.? It was not at uncommon for that
> oven to fail and there was no temperature control.?? Also, if you turn
> off the DC power to the radio, you should wait about 1 hr for the oven
> to heat and stabilize.? Later radios had a TCXO which had a trimmer
> accessed through a small hole in the top of the device.? They are about
> the size of a postage stamp located on the Logic Board.?? Also you will
> find that the BFO oscillators are not temperature stabilized.? Any error
> or drift due to temperature change will cause an error in absolute
> frequency.?? For these reasons, the spec is +/- 50Hz.
>
> Yes, you can correct the read-out but what frequency is the radio on???
> Remember the digital read-out is just that, and is not a frequency
> measurement.
>
> My advice, don't tamper with it.? You'll like come away frustrated and
> maybe worse off than 22 Hz.
>
> 73
>
> Bob, K4TAX
>
> On 10/23/2019 3:13 PM, dale via TenTec wrote:
> > Have a OMNI VI+ ,started to set up a position for the rig today and
> noticed the frequency  readout was off about .22 hz. I remember my old
> omni V  had a simple adjustment point to tweek the readout. Same on the + ?
> if so what board and location would I find it?
> >   The older I get  the more I for get. 73
> > dale wt4t
> > _______________________________________________
> > TenTec mailing list
> > TenTec at contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
> >
>
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 23 Oct 2019 17:02:48 -0500
> From: Gary Follett <dukeshifi at comcast.net>
> To: Discussion of Ten-Tec Equipment <tentec at contesting.com>
> Cc: wt4t at reagan.com
> Subject: Re: [TenTec] frequency adj.
> Message-ID: <397421D8-7678-4F1F-B742-F84126145274 at comcast.net>
> Content-Type: text/plain;       charset=utf-8
>
> I suspect you MEAN off by 0.22 KHz not 0.22 Hz?
>
> Is it off by the same amount on all bands?
>
> Frequency calibration of the crystal board on an Omni VI is quite
> different due to the PLL used for the crystal oscillator board compared
> with the open loop operation of the Omni V. Alignment of frequency of this
> board simply involves adjustment of the reference oscillator on the logic
> board. It should be 20 MHz dead on.
>
> If it?s off by the same amount on all bands, it could also be the BFO.
> However, this error in frequency should depend upon mode.  LSB and USB
> should show different errors and CW yet another. Alignment of the BFO is in
> the TX Audio section for the manual. There are separate trim capacitors for
> each mode.
>
> It is quite common for the trimmer caps in the BFO to become ?dirty? just
> like a potentiometer or switch can get ?dirty?. Cleaning is a simple matter
> of lightly spraying with non-residue contact cleaner, rotate full range
> several times, let dry overnight at least, then calibrate the BFO trimmers.
>
> Sometimes you can get lucky and clean the trimmers by dry operating
> through full range several times without the cleaner. Then you can
> calibrate immediately since there would be no trapped solvent to evaporate
> out of crannies.
>
>
> Gary
>
> W0DVN
>
>
> > On Oct 23, 2019, at 3:13 PM, dale via TenTec <tentec at contesting.com>
> wrote:
> >
> >
> > Have a OMNI VI+ ,started to set up a position for the rig today and
> noticed the frequency  readout was off about .22 hz. I remember my old
> omni V  had a simple adjustment point to tweek the readout. Same on the + ?
> if so what board and location would I find it?
> > The older I get  the more I for get. 73
> > dale wt4t
> > _______________________________________________
> > TenTec mailing list
> > TenTec at contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
>
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 23 Oct 2019 15:00:55 -1000
> From: Ken Brown <kenradiobrown at gmail.com>
> To: Discussion of Ten-Tec Equipment <tentec at contesting.com>
> Subject: Re: [TenTec] frequency adj.
> Message-ID:
>         <CAGnjFfnmpGhnX+HSLjgrih8E=2z9ctYwGJ=
> O3kkpbkyMej0f5Q at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> If you really mean 0.22 Hz you should consider yourself fortunate and not
> mess with it. If it is 0.22 kHz off you can make it better, but not much.
> I agree with Bob that you should check it on all bands. I expect you will
> find it better one some bands and worse on others.
>
> My experience with two Omni VIs is that even when you get the BFO
> frequencies as perfect as possible, say less than 1 Hz beat with a known
> accurate reference synthesizer, and get the 20 MHz reference similarly
> correct, the readout will still not be perfect. Off by tens of Hertz on
> some bands. And this is the case even after confirming that the band select
> crystal oscillators are locked to the reference.
>
> I have found that the offset is not necessarily proportionate to the
> operating frequency, which is what you would expect if only the 20 MHz
> reference was slightly off and the PLL system divide by numbers were
> exactly correct. My theory is that the PLL system does not have high enough
> resolution divide by numbers to really get the exact correct frequency on
> every band. I think Ten-Tec rounded the numbers off to make the PLL work
> faster and quieter, while still maintaining the specified +/- 50 Hz
> accuracy.
>
> I would love to hear from someone who knows about the PLL program running
> in the Omni VI, and knows what numeric values are in the ROM.
>
> DE N6KB
>
>
> On Wed, Oct 23, 2019 at 10:25 AM dale via TenTec <tentec at contesting.com>
> wrote:
>
> >
> > Have a OMNI VI+ ,started to set up a position for the rig today and
> > noticed the frequency  readout was off about .22 hz. I remember my old
> > omni V  had a simple adjustment point to tweek the readout. Same on the
> + ?
> > if so what board and location would I find it?
> >  The older I get  the more I for get. 73
> > dale wt4t
> > _______________________________________________
> > TenTec mailing list
> > TenTec at contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
> >
>
>
> ------------------------------
>
> Message: 5
> Date: Thu, 24 Oct 2019 07:56:47 -0500 (CDT)
> From: wt4t at reagan.com
> To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
> Subject: Re: [TenTec] frequency adj.
> Message-ID: <1571921807.142530004 at webmail.reagan.com>
> Content-Type: text/plain; charset="UTF-8"
>
>
> Bob
>  thanks for your info. your right , I guess if it really is not broke ,
> don't fix it.
> dale
> -----Original Message-----
> From: "Bob McGraw K4TAX" <rmcgraw at blomand.net>
> Sent: Wednesday, October 23, 2019 4:56pm
> To: "dale via TenTec" <tentec at contesting.com>
> Subject: Re: [TenTec] frequency adj.
>
>
>
> Dale:
>
> The spec as I recall is +/- 50 Hz.  Looks as though you are well within
> that spec.  Oh by the way,   .22 Hz is ~1/4 of one Hertz. I think you
> mean 22 Hz.
>
> You should check all bands and determine the error on each one. Each one
> has a crystal oscillator operating in a Phase Lock Loop based on the
> reference frequency.   Earlier radios had a crystal oven which required
> time to reach operating temperature.  It was not at uncommon for that
> oven to fail and there was no temperature control.   Also, if you turn
> off the DC power to the radio, you should wait about 1 hr for the oven
> to heat and stabilize.  Later radios had a TCXO which had a trimmer
> accessed through a small hole in the top of the device.  They are about
> the size of a postage stamp located on the Logic Board.   Also you will
> find that the BFO oscillators are not temperature stabilized.  Any error
> or drift due to temperature change will cause an error in absolute
> frequency.   For these reasons, the spec is +/- 50Hz.
>
> Yes, you can correct the read-out but what frequency is the radio on?
> Remember the digital read-out is just that, and is not a frequency
> measurement.
>
> My advice, don't tamper with it.  You'll like come away frustrated and
> maybe worse off than 22 Hz.
>
> 73
>
> Bob, K4TAX
>
> On 10/23/2019 3:13 PM, dale via TenTec wrote:
> > Have a OMNI VI+ ,started to set up a position for the rig today and
> noticed the frequency readout was off about .22 hz. I remember my old omni
> V had a simple adjustment point to tweek the readout. Same on the + ? if so
> what board and location would I find it?
> > The older I get the more I for get. 73
> > dale wt4t
> > _______________________________________________
> > TenTec mailing list
> > TenTec at contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
> >
>
> _______________________________________________
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> TenTec at contesting.com
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> ------------------------------
>
> End of TenTec Digest, Vol 202, Issue 18
> ***************************************
>

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