[TenTec] TT Synthesizer Accuracy (Orion 2)

Thu Nov 12 23:21:23 EST 2015

Jim:

I can tell you for certain that it's not in the Orion product line since
mine generally stays within +- 5 Hz from the broadcast band to 10 meters.
In the old days when there were two separate oscillators that determined the
frequency, tracking errors you described can occur, but unless my memory is
getting foggy, the entire frequency routine of the Orion is determined from
a single oscillator module.  In that case, if you're off 5 Hz on 5 MHz WWV,
you would be off 10 Hz at 10 MHz, 15 Hz at 15.  On ten meters, you would be
30 Hz off, all in the same direction, either plus or minus.  IOW a linear
deviation.  

If you calibrate the radio exactly on at 15 MHz WWV, how far off is 10 MHz
and 5 MHz WWV?  Also check 2.5 MHz WWV if you can hear it, and in the day if
propagation is good, check 20 MHz WWV.  If you continue to get the same
result, there may be something else wrong that the factory needs to look at.

          Ron Castro
           N6IE
    www.N6IE.com

Member:
                  ARRL
     Redwood Empire DX Assn.
 Northern California Contest Club
Northern California DX Foundation
  Society of Broadcast Engineers

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of N4BE_Jim---
via TenTec
Sent: November 12, 2015 7:42 PM
To: ronc at sonic.net
Cc: N4BE_Jim at yahoo.com; Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] TT Synthesizer Accuracy (Orion 2)

Hi Ron,

I thought I was following your procedure but it's still off at each end of
the HF spectrum.  I know it's probably within the advertised specs but it
just seems excessive.  Below are the O2 frequency readouts and the actual
tuned frequencies across the bands.  I used a known frequency source at each
of 9 frequencies, rather than rely on WWV at one frequency.  The WWV
reference alignment assumes that once you calibrate at one frequency, the
synthesizer will track linearly at all other frequencies.  In my case, it
doesn't.  I haven't tried a reset yet, that's tomorrow.  I have listed the
O2 readout frequencies along side the actual tuned frequency below.  In this
case, I calibrated the TCXO at 20 meter frequencies and it tracks dead on
within that band, but error creeps in on bands above and below.  I used an
Icom IC775 aligned to WWV as a reference, in addition to an HP8640 sig gen.

If this same synthesizer design is used in other TT radios, which I suspect,
then this may be a problem throughout the product line.  I'm hoping it is an
operator error.  Here are the numbers:

O2 Freq Readout.       True tuned freq.        Error
4.000.000.                   4.000.074.                 +74 Hz
7.000.000.                    7.000.052.                 +52 Hz
10.090.000.                 10.090.032.                +32 Hz
14.050.000.                 14.050.000.                 0 Hz
14.300.000.                 14.300.000.                 0 Hz
18.120.000.                  18.119.973.                 -27 Hz
21.100.000.                  21.099.950.               -50 Hz
25.000.000.                 24.999.919.              -81 Hz
28.100.000.                 28.099.900.              -100 Hz

jim N4BE

Sent from my iPad

> On Nov 12, 2015, at 9:55 PM, Ron Castro <ronc at sonic.net> wrote:
> 
> Jim:
> 
> The only accurate way to calibrate is to use the main VFO and WWV,
preferably 15 or 20 MHz.  Follow the directions for tuning the master
oscillator found on my website:
> 
> http://n6ie.com/TXCO%20Calibration.htm
> 
> The fan mod helps too, but it's not 100% necessary.
> 
>          Ron Castro
>           N6IE
>    www.N6IE.com
> 
> Member:
>                  ARRL
>     Redwood Empire DX Assn.
> Northern California Contest Club
> Northern California DX Foundation
>  Society of Broadcast Engineers
> 
> 
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Jim M.
via TenTec
> Sent: November 12, 2015 1:51 PM
> To: tentec at contesting.com
> Cc: Jim M.
> Subject: [TenTec] TT Synthesizer Accuracy (Orion 2)
> 
> I suspect this has already been hashed over in the past, but I need some
guidance.  I use the TCXO calbration procedure found on the wiki, i.e. use
SubRx, tune to WWV, adjust TCXO for same tone on USB and LSB.  But
afterwards, the Main RX seems to be off by 30-50 Hz depending on the
frequency/band.  I also use a known calibrated signal source (an Icom TCVR)
at various freqs to confirm.  Conversely, if I modify the procedure and
instead listen to the known signal source on the Main Rx set for say 14Mhz,
all is well for that band but then the Sub RX is off.  Then lets say I use
the known source to set the Tcxo when receiving 28Mhz on the O2, then tune
the O2 down to a lower band, it will be off by 30-70 Hz depending on how far
from 28Mhz I go.  Seems like the O2 synth tracking is amiss.  Is this normal
behavior?  My conslusion, unless something is malfunctioning, is DON'T
adjust the Tcxo using the Sub RX, but rather using the Main Rx with a
calibrated source.  Then maybe cali
 brate it close to the middle of the HF frequency range, like 14.4 Mhz.
> 
> Thanks, Jim N4BE
> _______________________________________________
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