Date   
Re: PHSNA for DDS-60 and NANO checkout

Nick Kennedy
 

Well, it's kind of "dealers choice" where to set your power output. But once you've set it you calibrate the system based on that.

Many people go with -10 dBm output from the DDS so they can drive crystals without fear of over-driving them.  Others want more maximum output and will just use attenuators as needed or desired when testing crystals.

Remember that when you measure 2 Vpp open circuit, that's not actually a power level since the DDS is not putting out power. True, 2 Vpp into 50 ohms would be +10 dBm and 1 Vpp is 6 dB less than that.

I looked at Jim's schematic for a PHSNA with a DDS-60 and he has an additional 10 dB attenuator after the DDS-60 board. That will allow you to get down to -10 dBm if desired or have a bit more output if you wish, using your adjustment pot. The attenuator also makes the DDS look more like a constant 50 ohm source, so it has that value in addition to reducing output.

73-

Nick, WA5BDU


On Mon, Dec 28, 2015 at 11:28 AM, km5ht@... [PHSNA] <PHSNA@...> wrote:
 

Nick;

    Thanks for the quick reply.  Just wondering how I should proceed then, set the power meter for 4 dBm, and/or crank up the output of the DDS60 for 10 dBm?

73 Steve, KM5HT


---In PHSNA@..., wrote :

That sounds normal to me. Your first test was the open circuit output. In the second test, you have a voltage divider between the 50 source resistance of the DDS-60 and the 50 ohm input resistance of the log power meter.

73-

Nick, WA5BDU

On Mon, Dec 28, 2015 at 9:55 AM, km5ht@... [PHSNA] <PHSNA@...> wrote:
 

I have built the PHSNA for DDS-60 and NANO version of the PHSNA.  I am just starting checkout.  I set the output of the DDS60 module for 2V P-P at J8 BNC on the scope with no load at 10 Mhz.  


If I scope J8 BNC and tie this to the power meter with a short jumper cable, the output at J8 drops to about 1V P-P.  Is this signal loading normal, or do I have something wrong with my power meter?


The DDS60 was built from a kit.  All other surface mount parts came from Mouser.  The through hole parts came from my junk box, but all resistors and caps were tested with meters before installing them including the surface mount stuff.


73 Steve, KM5HT



Re: PHSNA for DDS-60 and NANO checkout

km5ht@...
 

Nick;
    Thanks for the quick reply.  Just wondering how I should proceed then, set the power meter for 4 dBm, and/or crank up the output of the DDS60 for 10 dBm?

73 Steve, KM5HT


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

That sounds normal to me. Your first test was the open circuit output. In the second test, you have a voltage divider between the 50 source resistance of the DDS-60 and the 50 ohm input resistance of the log power meter.

73-

Nick, WA5BDU

On Mon, Dec 28, 2015 at 9:55 AM, km5ht@... [PHSNA] <PHSNA@...> wrote:
 

I have built the PHSNA for DDS-60 and NANO version of the PHSNA.  I am just starting checkout.  I set the output of the DDS60 module for 2V P-P at J8 BNC on the scope with no load at 10 Mhz.  


If I scope J8 BNC and tie this to the power meter with a short jumper cable, the output at J8 drops to about 1V P-P.  Is this signal loading normal, or do I have something wrong with my power meter?


The DDS60 was built from a kit.  All other surface mount parts came from Mouser.  The through hole parts came from my junk box, but all resistors and caps were tested with meters before installing them including the surface mount stuff.


73 Steve, KM5HT


Re: Transformer T1-1T Output Impedance

Alfredo Mendiola Loyola
 

I understand that at 80 Mhz, I will not get an output impedance of 50 Ohm at the output of the T1-1T Transformer.

How Can I know the exact transformer output impedance at 80 mhz with a source with 50 ohm of output impedance.


How can I transform the 10db of return loss to impedances?

Thank you for the information.

Regards.
Alfredo Mendiola Loyola

Re: PHSNA for DDS-60 and NANO checkout

Nick Kennedy
 

That sounds normal to me. Your first test was the open circuit output. In the second test, you have a voltage divider between the 50 source resistance of the DDS-60 and the 50 ohm input resistance of the log power meter.

73-

Nick, WA5BDU

On Mon, Dec 28, 2015 at 9:55 AM, km5ht@... [PHSNA] <PHSNA@...> wrote:
 

I have built the PHSNA for DDS-60 and NANO version of the PHSNA.  I am just starting checkout.  I set the output of the DDS60 module for 2V P-P at J8 BNC on the scope with no load at 10 Mhz.  


If I scope J8 BNC and tie this to the power meter with a short jumper cable, the output at J8 drops to about 1V P-P.  Is this signal loading normal, or do I have something wrong with my power meter?


The DDS60 was built from a kit.  All other surface mount parts came from Mouser.  The through hole parts came from my junk box, but all resistors and caps were tested with meters before installing them including the surface mount stuff.


73 Steve, KM5HT


PHSNA for DDS-60 and NANO checkout

km5ht@...
 

I have built the PHSNA for DDS-60 and NANO version of the PHSNA.  I am just starting checkout.  I set the output of the DDS60 module for 2V P-P at J8 BNC on the scope with no load at 10 Mhz.  


If I scope J8 BNC and tie this to the power meter with a short jumper cable, the output at J8 drops to about 1V P-P.  Is this signal loading normal, or do I have something wrong with my power meter?


The DDS60 was built from a kit.  All other surface mount parts came from Mouser.  The through hole parts came from my junk box, but all resistors and caps were tested with meters before installing them including the surface mount stuff.


73 Steve, KM5HT

Re: Transformer T1-1T Output Impedance [1 Attachment]

K5ESS
 

Correction:  The radius isn’t 1.92 it’s the distance between the normalized resistance point 1.0 and normalized resistance of 1.92.

Mike K5ESS

 

From: PHSNA@... [mailto:PHSNA@...]
Sent: Sunday, December 27, 2015 10:11 PM
To: PHSNA@...
Subject: RE: [PHSNA] Transformer T1-1T Output Impedance [1 Attachment]

 

 

[Attachment(s) from K5ESS included below]

Well I’ll take a shot at answering this and welcome any comments/corrections to my reply.  The T1-1T is a transformer with a one-to-one turns ratio, so within limits its output impedance should be equal to that of the source its connected to.  IF it were a perfect transformer which it isn’t.  The Input Return Loss gives a measure of how imperfect it is.  Let’s take the Return Loss figure for 80 Mhz.  and call it 10 dB.  So, if you connect the T1-1T to a device with a 50 ohm source impedance the output impedance of the T1-1T at 80 MHz. will be somewhere between purely resistive impedances of 96.2 and 26 ohms.  To see all the possible impedances presented for the 10 dB return loss you can draw a circle on a Smith Chart centered on 50 ohms normalized to one with a radius of 1.92.  See attached PDF. 

Mike K5ESS

 

From: PHSNA@... [mailto:PHSNA@...]
Sent: Sunday, December 27, 2015 3:18 PM
To: PHSNA@...
Subject: [PHSNA] Transformer T1-1T Output Impedance

 

 

Dear All:

 

Does the Transformer T1:1T has an output impedance of 50 ohm through all the transformer bandwidth?

Does the transformer output impedance change on high frequencies?

 

Bandwidth: 0.08 to 200 Mhz

Branch. Mini Circuits

 

Regards

Alfredo Mendiola Loyola

Lima, Peru

Re: Transformer T1-1T Output Impedance

K5ESS
 

Well I’ll take a shot at answering this and welcome any comments/corrections to my reply.  The T1-1T is a transformer with a one-to-one turns ratio, so within limits its output impedance should be equal to that of the source its connected to.  IF it were a perfect transformer which it isn’t.  The Input Return Loss gives a measure of how imperfect it is.  Let’s take the Return Loss figure for 80 Mhz.  and call it 10 dB.  So, if you connect the T1-1T to a device with a 50 ohm source impedance the output impedance of the T1-1T at 80 MHz. will be somewhere between purely resistive impedances of 96.2 and 26 ohms.  To see all the possible impedances presented for the 10 dB return loss you can draw a circle on a Smith Chart centered on 50 ohms normalized to one with a radius of 1.92.  See attached PDF. 

Mike K5ESS

 

From: PHSNA@... [mailto:PHSNA@...]
Sent: Sunday, December 27, 2015 3:18 PM
To: PHSNA@...
Subject: [PHSNA] Transformer T1-1T Output Impedance

 

 

Dear All:

 

Does the Transformer T1:1T has an output impedance of 50 ohm through all the transformer bandwidth?

Does the transformer output impedance change on high frequencies?

 

Bandwidth: 0.08 to 200 Mhz

Branch. Mini Circuits

 

Regards

Alfredo Mendiola Loyola

Lima, Peru

Transformer T1-1T Output Impedance

Alfredo Mendiola Loyola
 

Dear All:


Does the Transformer T1:1T has an output impedance of 50 ohm through all the transformer bandwidth?

Does the transformer output impedance change on high frequencies?


Bandwidth: 0.08 to 200 Mhz

Branch. Mini Circuits


Regards

Alfredo Mendiola Loyola

Lima, Peru

Re: AD9851 Type II DDS module questions

N5IB
 

I've updated the schematics and BOMs for the Type I and Type II PHSNA to reflect use of a 1 W or 2 W resistor for the ERA-3+ bias. Now available in the Files area.

Also added the LPF filter component data to the Type II schematic for use with these newly found AD-9851 Type II modules.

Jim, N5IB

---In PHSNA@..., <n5ib@...> wrote :
Thanks for catching that, Steve.
The nominal current is 35 mA, for around 300 mW, but there surely ought to be a 4x or so de-rating.
I need to update the BOMs and make sure the schematics call out a 1 or 2 W part.
I've been using the 2 W metal oxide resistors that are about the size of the old 1 W carbon comps.
I like to mount them with a little air gap between the body and the PCB
The first one I made used a pair of 560 ohm 1/2W in parallel.
Jim, N5IB


---In PHSNA@..., <sbdick@...> wrote :
For new builders, on the PHSNA board, R7, the dropping resistor to the ERA-3+ amp, is a 1/2 watt resistor called out in the parts list (660-MF1/4DCT52R2700F). This is same part on Type 1 or 2 boards.  This has inadequate de-rating . There is a comment in the notes in the BOM that 1 watt might be better.  A good choice might be the dropping resistor used on the xtal test fixture, a 2W resistor, Mouser P/N 660-MO2CT631R271J whose size should fit and cost 14 cents.  The resistor really wants to be at least 1 watt.
"Digital Steve", K1RF

Re: AD9851 Type II DDS module questions

Steven Dick
 

For new builders, on the PHSNA board, R7, the dropping resistor to the ERA-3+ amp, is a 1/2 watt resistor called out in the parts list (660-MF1/4DCT52R2700F). This is same part on Type 1 or 2 boards.  This has inadequate de-rating . There is a comment in the notes in the BOM that 1 watt might be better.  A good choice might be the dropping resistor used on the xtal test fixture, a 2W resistor, Moouser P/N 660-MO2CT631R271J whose size should fit and cost 14 cents.  The resistor really wants to be at least 1 watt.

"Digital Steve", K1RF

Re: AD9851 Type II DDS module questions

Steven Dick
 

Glen and Will thanks for the info. I'm on my way!!  It's a shame the on-board filter can't be used (not sure how bad the performance is with an AD9851 but you can't use it with the two outputs for the transformer anyway)

"Digital Steve", K1RF

Re: AD9851 Type II DDS module questions

gtennys54@...
 


Steve,

I just built up a PHSNA using a Type II 9851 module.  I can answer three of your questions. 

Question 1 and 3 -- In the files section of the PHSNA group on Yahoo, there is a folder entitled 'Type II PHSNA - version using Type 2 DDS module.' In that folder is a file entitled 'PHSNA Type II DDS info.pdf.'  This file has the schematic of the module, the filter elements to remove, and where to connect a jumper once the elements are removed.  The file deals with a 9850 module, but everything is the same.

Question 2 -- Also in the files section of the PHSNA group on Yahoo, there is a folder entitled 'Type I PHSNA - version using Type 1 DDS module.'  In that folder there is a file entitled 'PHSNA ERA-3+ Type 1 DDS rev6r10.pdf.'  In that file is a schematic.  The schematic has the filter components for both a 9850 and a 9851.

I can't answer your question #4. 

Good luck,

Gary
KO4CY

Re: AD9851 Type II DDS module questions

William Kimber
 

Hi,

As you say most of info is in files some where. Try the AD9850  directory for the Type II AD9850.  I believe AF9851 is the same just that the oscillator is multiplied by 6 internally.

The only difference between Nano and Uno is pinout.  You would need to change the defines at the start.

Cheers,
Will

On 24/12/15 12:54, sbdick@... [PHSNA] wrote:
 

Hi All. I am finishing up a Type II PHSNA and have a AD9851 Type II DDS module. They are not that common, but there are a few ebay sellers that offer it such as this one: AD9851 DDS Signal Generator Module 0-70MHz 2 Sine Wave and 2 Square Wave

 


I have several questions:

1. Does anyone know where I can get the schematic for a type II DDS module of this type? or even for the AD9850 type?

2. Can someone point me to what the required filter values are for the LPF-components on the PHSNA for the AD9851?  I plan to use this up to about 50 MHz as I need to test some 45 MHz filters.

3. I know all the DDS module filter components should be removed in order to be able to use the two outputs with transformer coupling.  What is the minimum number of components that need to be removed and where is a jumper required?  The info is probably in the files section somewhere but I haven't found it.

4. Can the "Hotrod phsna software" by WB6OGD be used on an Arduino Uno instead of the Nano?  Has anyone modified the code for use on an Uno?


Thanks,

"Digital Steve", K1RF


AD9851 Type II DDS module questions

Steven Dick
 

Hi All. I am finishing up a Type II PHSNA and have a AD9851 Type II DDS module. They are not that common, but there are a few ebay sellers that offer it such as this one: AD9851 DDS Signal Generator Module 0-70MHz 2 Sine Wave and 2 Square Wave

 


I have several questions:

1. Does anyone know where I can get the schematic for a type II DDS module of this type? or even for the AD9850 type?

2. Can someone point me to what the required filter values are for the LPF-components on the PHSNA for the AD9851?  I plan to use this up to about 50 MHz as I need to test some 45 MHz filters.

3. I know all the DDS module filter components should be removed in order to be able to use the two outputs with transformer coupling.  What is the minimum number of components that need to be removed and where is a jumper required?  The info is probably in the files section somewhere but I haven't found it.

4. Can the "Hotrod phsna software" by WB6OGD be used on an Arduino Uno instead of the Nano?  Has anyone modified the code for use on an Uno?


Thanks,

"Digital Steve", K1RF

Re: Differential Transformer Coupled Output 1:1

Alfredo Mendiola Loyola
 

Can I use a 2:1 center tap transformer to get 1 volt peak 2 peak.

Primary: 50 + 50 = 100 ohm
Secondary: 50 ohm

73
Alfredo
OA4AJP

Re: Differential Transformer Coupled Output 1:1

N5IB
 

Both the "Type II PHSNA" and the "Experimenter Board" are set up to use a center-tapped broadband transformer to utilize both sine wave outputs of the AD9850/51. Schematics are in the Files area. It works very well and does give some increased output, but not enough to reach the +10 dBm level without additional amplification. The push-pull approach also provides some cancellation of even harmonics.

N5IB




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

Dear All:

Have you used Differential Transformer 1:1 to get more voltage peak 2 peak from the AD9851?

The datasheet has a diagram showing a Differential Transformer 1:1 connected to the two AD9851 differential outputs.

Is it better to use transformers instead of opamps amplifiers?

I will work from 1 Mhz to 30 Mhz.

Actually my Ad9851 modules is giving 250 mv peak 2 peak with a 50 ohm resistor load.

73s.

Alfredo Mendiola Loyola

Lima, Peru



 

Re: Use 3.3 volts oscillator with AD9851

Andy
 

This question (interfacing between voltage domains) is one I frequently had to deal with.

I have seen ICs (not this one) powered by 5V where all the inputs were compatible with 3.3V or even 2.5V signals ... EXCEPT for the clock input which required a full 5V rail-to-rail swing.  That's not very common, but it can happen.  Always consult the datasheet.

In this case the AD9851 datasheet apparently shows the input must swing between 1.5V and 3.5V at minimum.  So yes, I think you could bias a sine or square wave around 2.5V, and as long as its swing exceeds 2Vp-p, it should work.  Be careful if the source pulsewidth isn't symmetrical.

Become intimately familiar with the datasheet, and if in doubt, consulting an ADI field engineer might be a good idea.

Active converters (amplifiers) are OK but not always needed and IMHO you are better off without them if you don't need them.

Andy


New file uploaded to PHSNA

PHSNA@...
 

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New file uploaded to PHSNA

PHSNA@...
 

Hello,


This email message is a notification to let you know that
a file has been uploaded to the Files area of the PHSNA
group.


File : /AD9851/12404630_10207026261447270_367793225_n.jpg
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To learn more about file sharing for your group, please visit:
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mendiola_loyola <mendiola_loyola@...>

Differential Transformer Coupled Output 1:1

Alfredo Mendiola Loyola
 

Dear All:


Have you used Differential Transformer 1:1 to get more voltage peak 2 peak from the AD9851?


The datasheet has a diagram showing a Differential Transformer 1:1 connected to the two AD9851 differential outputs.


Is it better to use transformers instead of opamps amplifiers?


I will work from 1 Mhz to 30 Mhz.


Actually my Ad9851 modules is giving 250 mv peak 2 peak with a 50 ohm resistor load.


73s.

Alfredo Mendiola Loyola

Lima, Peru