Having just repaired an Omni 6+ 5.0 to 5.5 MHz PLL, I can see why many might
like a simpler DDS offering.
However, there is a dark side.
Many of these do not use enough bits to draw the sine wave from the lookup
table in ROM to provide anything nearly as good as what the Omni 5 and 6 PLL’s
provide.
You end up with some really odd looking distortion products that are only down
from the full output by the bit resolution of the DAC. Thus, a 16 bit DAC can
only offer 96 dB local oscillator purity below full output, even worse (84 dB)
for the more common 14 bit D to A devices in low cost DDS circuits.
I had thought of putting one of these into myParagon and even bought one. I
decided that the performance was not even as good as the relatively poor PLL
synthesizer in the original Paragon.
One COULD put the DDS synthesizer at high frequency and divide it down like Ten
Tec did in the late Omni’s.
I am not sure if these low cost devices work at 200 MHz. If they were
available, then one could simply use the simple divider/filter that Ten Tec
used.
Gary
> On Nov 25, 2016, at 6:45 AM, Barry N1EU <barry.n1eu@gmail.com> wrote:
>
> It should have mode inputs as well as a CAT port and the logic to set the
> freqs of both VFOs from the CAT port
>
> Barry N1EU
>
> On Fri, Nov 25, 2016 at 7:28 AM, Steve Ellington <steven4lq@gmail.com>
> wrote:
>
>> For sure this would be a great product.
>> It would also need inputs for the T-R voltage and a couple of offset
>> voltages as are used to correct the readout in the Corsair.
>>
>> I've had Corairs readout failure and one was so unfixable that I ended up
>> installing a new frequency counter with a beautiful LED readout I found on
>> on Ebay from China. However it lacked these offsets and a cheat sheet had
>> to be created for mentally calculating the offsets. I suppose this could be
>> easily handled with the outboard processor we're talking about.
>>
>> Steve N4LQ
>>
>> On Thu, Nov 24, 2016 at 10:27 PM, Ron Notarius W3WN <wn3vaw@verizon.net>
>> wrote:
>>
>>> As prevalent as 5 MHz and 9 MHz based VFO/PTO circuits have been over the
>>> years in so many different analog transmitters and transceivers, I'm
>>> surprised that no one has done just this -- marketed a DDS VFO in an
>>> external enclosure. You'd think it'd be relatively simple enough to do.
>>>
>>> Just think -- a simple, relatively inexpensive device that would greatly
>>> improve any of these old rigs, without requiring any significant (or even
>>> any) modifications or adjustments.
>>>
>>> 73, ron w3wn
>>>
>>> -----Original Message-----
>>> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Al
>>> Gulseth
>>> Sent: Thursday, November 24, 2016 9:06 PM
>>> To: gerd Groos; Discussion of Ten-Tec Equipment
>>> Subject: [TenTec] "Semi-CAT" for analog* TT rigs (was Re: Corsair II
>>> PCInterface)
>>>
>>> Since we're doing some "what-if" here:
>>>
>>> Instead of a frequency counter, how about using a DDS VFO in an
>> _external_
>>> enclosure - set up along the lines of the 301/302 remote tuning knob ?
>> The
>>> VFO jumper on the back panel provides a very convenient input point for
>> the
>>> DDS signal. If implemented properly, in conjunction with the band data
>>> outputs the DDS VFO could output rig frequency to the control program as
>>> well as possibly allowing computer controlled tuning within the selected
>>> band. If the mode switch was also tied into the system as Gerd suggested,
>>> "semi-CAT"
>>> operation would seem to be possible with minimum modifications to the
>> rig.
>>> Returning the rig to its normal operational state would simply require
>>> unplugging a couple of data connectors (along with an RCA cable to the
>>> accessory 12V output on the back of the rig if powering the DDS VFO that
>>> way) and switching back to the VFO jumper on the back panel.
>>>
>>> As stated previously, this one's "above my pay grade" so I'll let someone
>>> else run with this if it's deemed to be a viable possibility.
>>>
>>> * "analog" here refers to early Omnis, Corsairs, etc. with remote VFO
>>> input.
>>>
>>> 73, Al
>>>
>>> On Thu November 24 2016 3:09:51 pm gerd Groos wrote:
>>>> *> For a "black box", as cheap as RasPI's are that might be an option
>>>> to
>>>> consider*
>>>>
>>>> Raspberry will be fine.
>>>>
>>>> Hardware:
>>>> - Use Raspberry
>>>> - Add dd frequency counter interface, along idea here
>>>> http://www.swharden.com/wp/2016-10-10-raspberry-pi-rf-frequency-counte
>>>> r/
>>>> - Add bad data lines, plus SSB/CW mode line interface
>>>> - Add shielding / EMI measures as required
>>>>
>>>> Software:
>>>> CAT command implementation can be based based on hamlib or Juma TRX-2
>>>> firmware (source code available for the Jumma TRX, see firmware on
>>>> their
>>>> website)
>>>>
>>>> Link from Corsair to PC could be by WLAN
>>>>
>>>> 73
>>>>
>>>> Gerd.
>>>>
>>>> 2016-11-24 20:19 GMT+01:00 Al Gulseth <wb5jnc@centurytel.net>:
>>>>> I didn't look at the C II but the Omni B/C and Corsair 560 all
>>>>> appear to have a dedicated (isolated) bandswitch wafer tied to the
>>>>> "linear" socket on the back panel. If' I'm reading the schematics
>>>>> right the individual bandswitch positions and the common terminal
>>>>> all come out to the connector, so the voltage/logic level used could
>>>>> be anything reasonable within the switch rating. The only reason I
>>>>> could see needing diodes would be to encode it down to a binary
>>>>> sequence instead of dealing with 9 individual lines.
>>>>>
>>>>> That being said, the C II may be different.
>>>>>
>>>>> For a "black box", as cheap as RasPI's are that might be an option
>>>>> to consider (speaking out of school here as I'm not up to speed on
>>>>> them.)
>>>>>
>>>>> 73, Al
>>>>>
>>>>> On Thu November 24 2016 9:01:45 am Steve Ellington wrote:
>>>>>> Corsair II and older TTs.
>>>>>>
>>>>>> The band information (+13.8v) is easily available from the
>>>>>> bandswitch
>>>>>
>>>>> with
>>>>>
>>>>>> just the addition of a few diodes on SW4 or SW5.
>>>>>>
>>>>>> The frequency information is available via the VFO jack.
>>>>>>
>>>>>> A black box is needed to convert this info to interface via a USB
>>>>>> port to the pc and emulate some rig. That's beyond my pay scale.
>>>>>>
>>>>>> Is there anyone out there willing to tackle such a project?
>>>>>>
>>>>>>
>>>>>> Steve N4LQ
>>>>>> _______________________________________________
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>>>>>> TenTec@contesting.com
>>>>>> http://lists.contesting.com/mailman/listinfo/tentec
>>>>>
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