[minima] Re: minima with dds (from Wire.h )
- From: farhanbox@xxxxxxxxx
- To: minima@xxxxxxxxxxxxx
- Date: Thu, 23 Jan 2014 07:49:40 +0000
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-----Original Message-----
From: Sandeep Lohia <sandeeplohia12@xxxxxxxxx>
Sender: minima-bounce@xxxxxxxxxxxxx
Date: Thu, 23 Jan 2014 13:13:24
To: <minima@xxxxxxxxxxxxx>
Reply-To: minima@xxxxxxxxxxxxx
Subject: [minima] Re: minima with dds (from Wire.h )
Thank you Farhan Sir...
On 23/01/2014, farhanbox@xxxxxxxxx <farhanbox@xxxxxxxxx> wrote:
> You can upload to www.hfsignals.org
> Sent from BlackBerry® on Airtel
>
> -----Original Message-----
> From: Sandeep Lohia <sandeeplohia12@xxxxxxxxx>
> Sender: minima-bounce@xxxxxxxxxxxxx
> Date: Thu, 23 Jan 2014 13:00:15
> To: <minima@xxxxxxxxxxxxx>
> Reply-To: minima@xxxxxxxxxxxxx
> Subject: [minima] Re: minima with dds (from Wire.h )
>
> Hi, Rick
>
> Plzz check your direct mail (.Pdf attached something about image) ,
> for others download from:
> http://www.hamradio.in/circuits/dds.php
>
> I use this:
> http://www.hamradio.in/forum/viewtopic.php?t=857
>
>
> I don't have costly visual set up like spectrum-analyzer here in my
> workshop, what I simply do is analyze spurs (image + harmonics) in
> nearby radio-receiver, here connecting a radiating wire to output of
> DDS, & listening/observing signal strength in another Radio RX or in
> SDR.
>
> And as Steve already said, this might also be useful:
> http://designtools.analog.com/dtDDSWeb/dtDDSMain.aspx
>
> ---------------------------------------------------------------------
>
> Many of us already knows this, but still for others who don't...
> Harmonics are always even & odd that of class A amp (if used with DDS)
> where as image of DDS is different, it keeps 1:1 ratio relation with
> the fundamental frequency.
> If fundamental frequency increases 1 Hz then the image frequency also
> shifts by 1 Hz.
>
> Calculating Image is easy, if study diagram by VU3CNS.
> It is better to use highest possible MCLK (reference clock oscillator)
> and not enable x6 multiplier.
> Sometime I also over clocked & it worked.
>
> Suppose system clock is 100Mhz and the output frequency set to 20 Mhz.
> then we have image = (100+20), (100-20) & they keep adding,
> subtracting, multiplying, etc.
>
> On 23/01/2014, Sandeep Lohia <sandeeplohia12@xxxxxxxxx> wrote:
>> Quick reapply :
>> Rick please wait till morning, half asleep now, softcopy in my desktop.
>>
>> Or google 'VU3CNS' his .Pdf covers good info + diagram on unwanted
>> image / spurs generated from DDS (AD9850).
>>
>> U can also use his freeware design with Chinese module (+ PIC16F628A)
>> DDS verson 3 or 4.
>> Other PIC for switching USB/LSB or CW, band relay etc
>> U will need to boost AD9XXX output for KISS MIXER, now we also have
>> harmonics.
>>
>> DDS currently used by me has scan feature, memory save - one touch
>> frequency recall, SWR read etc.
>>
>> There's also a 'Hans Summer' work on diffrence between DDS vs Si570.
>>
>> (mailed from mobile)
>>
>> On 23/01/2014, Ricardo Suarez <eleu9da@xxxxxxxxxxxxx> wrote:
>>> Hi, Sandeep
>>>
>>> No problem for me to modify the sketch, I only need know if the DDS
>>> degrades too many the signal purity...
>>>
>>> Tomorrow I go to the electronic provider and buy the components for
>>> minima with dds...
>>>
>>> Thanks
>>>
>>> Rick LU9DA
>>>
>>>
>>> El 22/01/2014 21:21, Sandeep Lohia escribió:
>>>> Hi Rick,
>>>>
>>>> You can use any controller including DDS, (here I was using same :
>>>> DDS-V3, Shaji's DDS, also AD9833)
>>>>
>>>> but DDS (AD9850 or more with 'X6' AD9851) has unwanted images & spurs
>>>> (will add little unwanted noise).
>>>> I will mail you direct, about DDS image (PDF by VU3CNS) in morning
>>>> after approx 6~7 hours...
>>>>
>
>
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