AD9851 output amplitude

Jan Panteltje wrote on 6/6/2017 4:40 AM:
> On a sunny day (Tue, 6 Jun 2017 04:29:31 -0400) it happened rickman
> <gnuarm@gmail.com> wrote in <oh5ove$uro$1@dont-email.me>:
>
>> Jan Panteltje wrote on 6/6/2017 3:42 AM:
>>> On a sunny day (Tue, 6 Jun 2017 07:14:38 +1000) it happened Clifford Heath
>>> <no.spam@please.net> wrote in <wlkZA.60881$zj3.3944@fx15.iad>:
>>>
>>>>>>> I just looked up that AD9851 datasheet.
>>>>>>> You would not happen to be looking at that DAC output?
>>>>>>> It has a 120k or so Rout,
>>>>>> You expected a current source to have a small Rout?
>>>>> I did not expect anyting, do not even have a duino, nevrr used one either AFAIK.
>>>>
>>>> The AVR has nothing to do with the AD9851.
>>>
>>> So why did you blabber about it?
>>
>> The only one blabbering about is you.  He simply described his setup.
>
> No he did not,. no circyuit diagram,, nothing,
> just 'shields' and duinos
>
> Maybe even Dinos come to think of it.
>
> You have no sense wire for humor.

Actually I have a pretty keen sense of humor... when I see it.  Besides, you 
criticized him for his grammar and yours is *always* atrocious, not to 
mention your spelling.

-- 

Rick C

Jan Panteltje wrote on 6/6/2017 4:44 AM:
> On a sunny day (Tue, 6 Jun 2017 04:32:41 -0400) it happened rickman
> <gnuarm@gmail.com> wrote in <oh5p4j$uro$2@dont-email.me>:
>
>> Jan Panteltje wrote on 6/6/2017 4:00 AM:
>>> On a sunny day (Tue, 6 Jun 2017 07:19:11 +1000) it happened Clifford Heath
>>> <no.spam@please.net> wrote in <NpkZA.37030$J83.33061@fx39.iad>:
>>>
>>>>> The 3dB down point varies with load impedance. With a
>>>>> 50ohm load my output is ~500mVpp and the 3dB point is
>>>>> a little under 50MHz. At higher resistance, the 3dB
>>>>> point can be significantly lower.
>>>>
>>>> That must be what's happening. It looks like a buffer is
>>>> needed after the DAC load resistors, before the filter,
>>>> though a buffer afterwards would help. Shame that AD
>>>> didn't show that on their data sheets and eval boards.
>>>
>>> It is just that YOU do not understand the datsheet, as I stated in my fists reply the intention
>>> is not that point as output, but they use a comparator (in the same chip did you notice!!)
>>> to make the varying filter amplitude into two SQUARE WAVE 50 Ohm outputs.
>>> Its a freaking CLOCK generator, not a VFO.
>>> you got the WRONG SHIELD :-) :-) :-) :-)
>>>
>>> loop_the_loop:
>>> hehe
>>> LOL
>>> LMAF
>>>
>>> funny funny funny
>>> bra loop_the_loop
>>>
>>> stack overflow, cosmic ray, FLASH corruption, loop break, Russian hacker succeeded
>>>
>>>
>>> :-)
>>>
>>> LOL
>>>
>>> hahahaha
>>
>> You are in one strange mood.  You also write a *lot* worse than he does.
>> Your sentences often make no sense... if you even use actual sentences.
>
> Apart from the sense-wire for humor you also need in depth No Ledge of the subject to make sense of what I write.
> Else the humor will not even escape you, it won't even ave been be with you,
> as your typing exorcism shows.

Sir, you are one weird dude!

-- 

Rick C

On 07/06/17 10:31, Clifford Heath wrote:
> On 06/06/17 00:01, John Larkin wrote:
>> We use the AD9850 and a couple of other ADI dds parts, and a couple of
>> ADI dacs in home-brew DDS applications, and we've never seen anything
>> like that kind of rolloff. Usually we get a bit of filter rolloff and
>> the usual sinc thing. You should be maybe a dB down at Fclk/3.
>
> I don't think I understand the sinc thing. What should I expect
> to see from it?

Never mind, I found an explanation here:
<https://ez.analog.com/thread/3364>
It doesn't explain my problem, but that's ok.