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Re: NPO Capacitor source

Alan McLennan
 

Hi Vince,
I was looking for something similar a couple of weeks ago and I bought these


55 Values 1100PCS 0603 (1pF~1µF) SMD capacitor Assortment kit #U1

from umisky*2014   I paid £13.20, which seems expensive, but it is only about 1p per cap.

This is a general selection; up to 820 pF is NPO/COG.  There is a table with the values and types of cap.
From memory, I searched for something like   NPO capacitor assortment   Other words like kit and range may also be useful.  I know, you can waste a lot of time in these searches.  
Separately I bought a lot of 1 nF NPO.  Above 1 nF, NPO caps become rare and expensive.  Just keep your eye out for the bargains which often come up.
Good luck.
Alan  G7DCF


Re: Can't write to parameters.txt file

N5IB
 

Hi Wayne,

Have you received any of my off-list replies?

Jim, N5IB



---In PHSNA@..., <vk6eh@...> wrote :

Hi all, hoping someone can steer me in the right direction here.


Re: AD9850 DAC output current boost

N5IB
 

I haven't played with R-set. There is a graph in the data sheet showing that the best spurious free dynamic range is at an I-out of 10 mA. Going to 20 mA degrades SFDR by a couple of dB or so. Would only add 5 mA to the average current, so I doubt heating would be an issue. Given the I-supply is around 80 mA, it would be about a 10% increase in dissipation.

Look in the Links area here on the group for an app note about replacing R-set with an FET to amplitude modulate the output (could be the basis of AGC)

Jim, N5IB




---In PHSNA@..., <k5ess.nothdurft@...> wrote :
The AD9850 datasheet says that the max DAC output current is 20mA which can be achieved by reducing the value of the R-SET resistor from 3.9k to 1.95k ohms.  Has anyone tried this and if so were there any deleterious effects? 


AD9850 DAC output current boost

K5ESS
 

The AD9850 datasheet says that the max DAC output current is 20mA which can be achieved by reducing the value of the R-SET resistor from 3.9k to 1.95k ohms.  Has anyone tried this and if so were there any deleterious effects?  I assume it would run hotter.
Mike K5ESS


Can't write to parameters.txt file

Wayne Johnson
 

Hi all, hoping someone can steer me in the right direction here. 

I have completed construction of my PPHSNA, no problems encountered with all that, however when I try to go through the calibration process starting with slope /intercept  measurements all goes well until I try to write the 2 figures back to the parameters.txt file... The 'write' button on the control display when tapped returns with 'can't write to file' or words to that affect and says 'can't find parameters.txt file'

I did rename to parameters file to .txt etc. Both the windows files(.Exe) and parameters.txt files are together in a folder on my desktop and when trying to write to it from PHSNA control screen the path referred to by PHSNA are correct to the word but it will not update the parameters.txt file.

I also tried manually editing the parameters.txt file with notepad++ and it takes the new figures which are saved to the file but restart will not show the new figures being implemented, even DDS type ("0") in my case and COM4 will not be loaded on next restart

The system is clearly working and produces a trace graph (albeit out of cal) but just can't get the parameters file to be written to and consequently loaded.

I suspect it some silly mistake I'm making but it seems so simple that I need to create a folder on desktop, copy the unzipped files (Parameters.txt and PHSNA.exe) and run the program from there.

I even tried deleting everything including the arduino sketch and starting from scratch but same stuff, different day😪

Can anybody see what's wrong....jeez, didn't think I was this thick😀

Regards

Wayne




NPO Capacitor source

vincent coppola
 

Hi, I posted this query on EMFRD but in the past I have gotten good responses for queries from this group: I am trying to stock up my QRP lab with NPO or COG capacitors (I think they are the same thing), in a grab bag form? Maybe grab bag is the wrong term, let's say an assorted collection of common values.  Can someone recommend a site that will accept preferably Paypal or at least Credit cards? I am too lazy in my old age to deal with the inconvenience of money orders, etc. Thanks much, Vince N1VC.



Yahoo

William Kimber
 

Hi All,

I saw something on another Yahoo group that Yahoo was going bust. The
new CEO did well as we all like to hate Yahoo for its "improvements"

However what is the likely final outcome for the groups hosted by Yahoo
for free?

Cheers,
Will
ZL1TAO


Re: AD9851 Pull Up Resistors for communication

Alfredo Mendiola Loyola
 


I want to use my Arduino Uno (Atmega328p chip) with and AD9851 chip, but I don't know if I need Pull up resistors on pins D7, FQ_UD and W_CLK (Communication pins).

73s.
Alfredo Mendiola Loyola
Lima, Peru


Re: AD9851 Pull Up Resistors for communication

Alfredo Mendiola Loyola
 

I want to use the DDS-60 Module with my Arduino Uno (Atmega328P).

Regards.
Alfredo


Re: AD9851 Pull Up Resistors for communication

N5IB
 

I'm not sure I understand your question, Alfredo.

If the DDS-60 module is used with the DDS60/NANO PHSNA board, no additional pullups are needed.

Are you planning to use a DDS module with a PHSNA board other than the one designed for it?

Or are you planning to use a Type II DDS with a 9851 chip, and the new Experimenter Board?

Jim, N5IB


AD9851 Pull Up Resistors for communication

Alfredo Mendiola Loyola
 

Dear All:


I have seen the DDS60 schematic and I saw three Pull Up resistors for the Pins D7, FQ_UD and W_CLK (Communication pins).


If I use a AD9851 chip do I have to add those pull up resistors?


http://midnightdesignsolutions.com/dds60/#Schematic


Regards.

Alfredo Mendiola Loyola



Re: Experimenter Board build notes

Ian
 

Hi Jim and Group

After building my unit I have wondered if mounting the Arduino module under the experimenters PCB instead of on top of it would allow the filter segment to remain attached without obstructing the USB port. It may require the extended length pins to be used on the sockets for the DDS module and it would hide the reset button but that is not a major problem. There are alternatives that are provided. It would also allow straight or 90 degree pins to be used above the board if required as well for the breakout pins.

Ian VK3LA

 


Re: Experimenter Board build notes

DuWayne Schmidlkofer
 

For most of my projects that use the Arduino Nano I use 40 pin low profile IC sockets cut down to 30 pins.  On the Nano I install the regular header pins down through the top of the board.  This is gives a nearly flush fit with the IC socket.  After everything is checked for fit I cut the short pins off flush with the top of the header plastic retainer strip.  If you do not need the A4-A7 pins on a Pro mini they fit directly in a 24 pin IC socket.
DuWayne


Experimenter Board build notes

N5IB
 

After playing around with a few different kinds of pins, headers, and socket strips I had in the junque boxe, I decided to revise my earlier recommendations on how to mount the header strip for the DDS. I posted an updated document in the Experimenter Board folder in the Files area. Not really anything radically different. Has to do with how much the socket strip needs to be elevated above the board. DRY FIT TEST is essential in any case.

Wouldn't hurt to read it over before beginning parts collection and building.

73
Jim, N5IB




Re: preset pot on AD9850

Terry VK5TM
 

Just a word of caution.

Certain settings of that pot can add garbage to the sine signal.
Best to remove the resistor coupling the sine output to the comparator if not using it.

Terry VK5TM


Re: preset pot on AD9850

Wayne Johnson
 

Cheers, thanks fellas, I guess we can ignore it for our application, construction is coming along fine with the generator section finished, now working on the power meter (Det.), my PHSNA is self contained with an analogue meter included in the PM.
73
Wayne
VK6EH


Re: preset pot on AD9850

N5IB
 

Look at either one of the square wave outputs on a scope while turning that pot. You'll see the duty cycle change. It has no effect on either sine wave output. On my Type II DDS (little blue pot) I could just barely get to 50%

Jim, N5IB


---In PHSNA@..., <vk6eh@...> wrote :

I'm sure it's written here but can anybody tell me what the preset on an AD9850 is for? Tried to tweak it while watching the output level but NG, mind you I only shifted it a few degrees either way


Regards

Wayne VK6EH


Re: preset pot on AD9850

Mvs Sarma
 

the sine wave output can be sent to a comparator to convert it to square wave.
 while so, the mark to space ratio can be adjusted by the said pot  as it sends a ref dc to the other input of comparator.
 Hope I could clarify it.


preset pot on AD9850

Wayne Johnson
 

I'm sure it's written here but can anybody tell me what the preset on an AD9850 is for? Tried to tweak it while watching the output level but NG, mind you I only shifted it a few degrees either way


Regards

Wayne VK6EH


Re: Arduino Library for AD9852

HAM-Radio
 

I belive you could program it in the same way as AD9851 on a serial programmer, looking at the

FUNCTIONAL BLOCK DIAGRAM - not much difference i pin-assignment.

de OZ6YM