Date   

Re: Bandpass filter measurement anomalies - problem identified

Steven Dick
 

Problem has been isolated on my Type II PHSNA. The ERA-3+ is causing the harmonic distortion. I first tried reducing the amplitude of the input signal to ther ERA-3+ by crude tests - jumpering the output of the first attenuator at R3 with various resistors. I realize it was mismatched, but ok for this crude test. The amplitude of harmonics went down a bit but they were still there.  Then, I eliminated the ERA-3+ in  the signal path by the following crude method: I soldered a jumper across R2 to increase the amplitude, removed the jumper at pins 2-3 on P102 just after the anti-alias low pass filter, and took the output directly from pins 1 and 3 to a coax to BNC jumper to drive my filters.  This gave me about -7dbM of output power, albeit mismatched all over the place. The response was beautiful!! - no more jiggles due to harmonics on the left slop of the bandpass filter responses. 

The harmonics don't show up if you are testing lowpass filters.  The harmonics don't show up if you are testing narrowband crystal filters. The harmonics are quite obvious when you are testing LC bandpass filters on their left edge.

For the Type II PHSNA, if you remove the first attenuator and drive the antialias filter directly from the push-pull transformer, you have 6dB more power output than the Type 1 as it is no longer doubly terminate.  This is permissible per the AD9851 data sheet.  My recommended fix is to eliminate the first attenuator, take the output from the antialias filter, and use it to drive the final 6dB output attenuator from the output of the antialias filter after removing the components in and out of the ERA-3+.  I'll do a write-up on this AFTER field day.

Regards,
"Digital Steve", K1RF

 


Re: Bandpass filter measurement anomalies

Steven Dick
 

Yup, the file "BRARC BPF Sweeps 17 Dec 2013.pdf" in the Files area shows the same effect I was posting about - the weird duplicated filter shape on the left side of the bandpass filter plots.

"Digital Steve" K1RF


Re: Bandpass filter measurement anomalies

N5IB
 

A recent check with a spectrum analyzer on a Type-2 DDS module, whose on-board LPF had been removed, mounted on an Experimenter Board with the "push-pull" output transformer and a 50 ohm termination, showed the 2nd harmonic (of 10 MHz) down about 30 dB from the fundamental. This board does not include the wide band amp.

I'll see about pulling out another Type-2 DDS on a Type-2 PHSNA board with the MMIC amp and see what contribution the amp makes.

I saw the same effect when testing a bunch of our club's BPFs a couple of years ago with a Type-1 PHSNA. See the file "BRARC BPF Sweeps 17 Dec 2013.pdf" in the Files area. On those plots it looks like the 2nd harmonic was 28 dB or so down.

This is one of the few places where the interchangeable LPFs on the Type-2 PHSNA could be a useful feature. You can have a selection of them to use when testing filters at frequencies well below their pass band, where harmonics will give ghost responses. You can usually get another 20 dB or so of harmonic suppression.

Jim, N5IB



---In PHSNA@..., <sbdick@...> wrote :
Hi all. Have any of you observed any strange wiggles on the left edge of bandpass filter measurements?  This had been bugging me for awhile and I had attributed it to bad cabling, non-linearities in toroids, etc but I think I found the cause.  See writeup in the K1RF folder, file "bandpass Filter Measurementr Anomalies".  I think harmonics generated in the ERA-3+ output stane are causing wiggles and jiggles I see on the left side of a bandpass filter response. Has anyone else seen a similar problem?
Regards,
"Digital Steve", K1RF



Re: Bandpass filter measurement anomalies

Steven Dick
 

Thanks Rudolf. Good info.

Regards,
"Digital Steve", K1RF


Re: Bandpass filter measurement anomalies

Rudolf Reuter
 

Hello Steve,

Thank you for the very interesting post.

Because I did not like a wide band amplifier because of the
lack of qualified measuring equipment, I designed a passive
output filter for the DDS generator. Please look at:
http://www.rudiswiki.de/wiki9/AmateurRadioDDSgenerator#Filter_AD9850_from_DL5FA

With a symmetric transformer I reach about -3 dBm output level.
If I increase the DDS DAC output current within a allowed range,
0 dBm output level is achievable.
http://www.rudiswiki.de/wiki9/AmateurRadioDDSgenerator#Output_level_0_dBm

73, Rudolf DL5FA


FRA capabilities for the PicoScope instruments from Pico Technology

Peter Andersson
 

Those of you who happens to own a PicoScope PC oscilloscope might be aware of Aaron Hexamers application FRA4PicoScope, hexamer / FRA4PicoScope / wiki / Home — Bitbucket ,

The app provides Frequency Response Analysis (FRA) capabilities for the PicoScope. 


In order to work past the frequency limitation of the 100 kHz generator built-in to my PS2205, I added the possibility to use an AD9850 or AD9851 DDS module controlled by an Arduino-based

microcontroller over a serial port. 

See peter_andersson_ / FRA4PicoScopeExtSigGen — Bitbucket .


73

Peter, OH2PA



Re: Bandpass filter measurement anomalies

Steven Dick
 

Thanks Nick. The Type II PHSNA design drives the ERA-3+ slightly more than the Type I PHSNA so it may show up the effect more. About 2.5dB more drive, which will increase the harmonics in the Type II design.
 
“Digital Steve”, K1RF
 

Sent: Monday, June 20, 2016 9:12 AM
Subject: Re: [PHSNA] Bandpass filter measurement anomalies
 
 

That's a very interesting observation, Steve. 
 
I've not done a good job of keeping plots I've made where I can find them, nor having them properly labeled. Also, most filter plots were done only wide enough to see the shape down to a certain floor, so the half-frequency point wasn't covered.
 
However!  I do have one plot of a 14 MHz filter that goes below 7 MHz and I see the effect you mention. I see a "mini-me" response in the half frequency area.
 
It's interesting to try to quantify the harmonic output with this. My peak at 14 MHz is at about -3 dBm and my 7 MHz peak is at about -45 dBm so it looks like my 2nd harmonic at 7 MHz is 42 dB down.
 
This plot is also wide enough for me to view the 1/3 frequency point, but I don't see evidence of any 3rd harmonic content.
 
73-
 
Nick, WA5BDU
 
On Mon, Jun 20, 2016 at 7:15 AM, sbdick@... [PHSNA] <PHSNA@...> wrote:
 

Hi all. Have any of you observed any strange wiggles on the left edge of bandpass filter measurements?  This had been bugging me for awhile and I had attributed it to bad cabling, non-linearities in toroids, etc but I think I found the cause.  See writeup in the K1RF folder, file "bandpass Filter Measurementr Anomalies".  I think harmonics generated in the ERA-3+ output stane are causing wiggles and jiggles I see on the left side of a bandpass filter response. Has anyone else seen a similar problem?

Also see, in the writeup how the output amplifier is not needed if the type II DDS with its push-pull transformer drives the antialias filter directly with no attenuator, providing a 6dB power increase compared to ther single ended version as shown in the AD9851 data sheet, page 11. With the antialias filter driven directly bu the transformer output and a single 6dB attenuator, you can get anout -9dBm output with no amplifier, eliminating any harmonics created in the output stage. I will try this and report back.

Regards,
"Digital Steve", K1RF


 

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Re: Bandpass filter measurement anomalies

Nick Kennedy
 

That's a very interesting observation, Steve.  

I've not done a good job of keeping plots I've made where I can find them, nor having them properly labeled. Also, most filter plots were done only wide enough to see the shape down to a certain floor, so the half-frequency point wasn't covered.

However!  I do have one plot of a 14 MHz filter that goes below 7 MHz and I see the effect you mention. I see a "mini-me" response in the half frequency area.

It's interesting to try to quantify the harmonic output with this. My peak at 14 MHz is at about -3 dBm and my 7 MHz peak is at about -45 dBm so it looks like my 2nd harmonic at 7 MHz is 42 dB down.

This plot is also wide enough for me to view the 1/3 frequency point, but I don't see evidence of any 3rd harmonic content.

73-

Nick, WA5BDU

On Mon, Jun 20, 2016 at 7:15 AM, sbdick@... [PHSNA] <PHSNA@...> wrote:
 

Hi all. Have any of you observed any strange wiggles on the left edge of bandpass filter measurements?  This had been bugging me for awhile and I had attributed it to bad cabling, non-linearities in toroids, etc but I think I found the cause.  See writeup in the K1RF folder, file "bandpass Filter Measurementr Anomalies".  I think harmonics generated in the ERA-3+ output stane are causing wiggles and jiggles I see on the left side of a bandpass filter response. Has anyone else seen a similar problem?

Also see, in the writeup how the output amplifier is not needed if the type II DDS with its push-pull transformer drives the antialias filter directly with no attenuator, providing a 6dB power increase compared to ther single ended version as shown in the AD9851 data sheet, page 11. With the antialias filter driven directly bu the transformer output and a single 6dB attenuator, you can get anout -9dBm output with no amplifier, eliminating any harmonics created in the output stage. I will try this and report back.

Regards,
"Digital Steve", K1RF




Bandpass filter measurement anomalies

Steven Dick
 

Hi all. Have any of you observed any strange wiggles on the left edge of bandpass filter measurements?  This had been bugging me for awhile and I had attributed it to bad cabling, non-linearities in toroids, etc but I think I found the cause.  See writeup in the K1RF folder, file "bandpass Filter Measurementr Anomalies".  I think harmonics generated in the ERA-3+ output stane are causing wiggles and jiggles I see on the left side of a bandpass filter response. Has anyone else seen a similar problem?

Also see, in the writeup how the output amplifier is not needed if the type II DDS with its push-pull transformer drives the antialias filter directly with no attenuator, providing a 6dB power increase compared to ther single ended version as shown in the AD9851 data sheet, page 11. With the antialias filter driven directly bu the transformer output and a single 6dB attenuator, you can get anout -9dBm output with no amplifier, eliminating any harmonics created in the output stage. I will try this and report back.

Regards,
"Digital Steve", K1RF



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 : /K1RF/Bandpass Filter measurent anomalies.pdf
Uploaded by : k1rf_digital_steve <sbdick@optonline.net>
Description : Explanation for some LC bandpass filter sweep measurement anomalies


You can access this file at the URL:
https://groups.yahoo.com/neo/groups/PHSNA/files/K1RF/Bandpass%20Filter%20measurent%20anomalies.pdf


To learn more about file sharing for your group, please visit:
https://help.yahoo.com/kb/index?page=content&y=PROD_GRPS&locale=en_US&id=SLN15398


Regards,


k1rf_digital_steve <sbdick@optonline.net>


Re: XTAL parameters for measurement receiver

Steven Dick
 

Hi Nick.
I have measured many a crystal with the PHSNA and crystal test fixture including samples of 12MHz(q=92000 to 135,000), 20MHz (Q=15,000-31,000), and 40 MHz (Q=2534 to 58,000). Most of them are not very good. The Q's are not too bad for the posted data on the 3.28 MHz crystals at around 120,000.  I posted a schematic in the K1RF folder for a narrow band CW crystal filter using the 3.28 MHz crystals.  It is about 410 Hz at 3dB down, 502Hz at 6dB down.  I may just build it. Simulated in LT Spice. I also posted the LT SPICE file
 


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 : /K1RF/3.3MHz qer 5 xtal cw xtal filter.asc
Uploaded by : k1rf_digital_steve <sbdick@optonline.net>
Description : LT SPICE file for 3.3 MHz 5 pole equiripple CW filter. Note: Subtract the crystal leads to case capacitance frim the shunt caps shown. The two end crystals flatten the response. The LC-s on the ends are for impedance match.


You can access this file at the URL:
https://groups.yahoo.com/neo/groups/PHSNA/files/K1RF/3.3MHz%20qer%205%20xtal%20cw%20xtal%20filter.asc


To learn more about file sharing for your group, please visit:
https://help.yahoo.com/kb/index?page=content&y=PROD_GRPS&locale=en_US&id=SLN15398


Regards,


k1rf_digital_steve <sbdick@optonline.net>


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 : /K1RF/3.28MHz QER equiripple CW crystal filter.jpg
Uploaded by : k1rf_digital_steve <sbdick@optonline.net>
Description : narrow CW QER equiripple crystal filter. The paralled end crystals flatten the response. For shunt caps, subtract crystal leads to cfase capacitance from the values shown. The LC-s at end are for impedance match. 400Hz at 3dB, 502 Hz at 6dB down


You can access this file at the URL:
https://groups.yahoo.com/neo/groups/PHSNA/files/K1RF/3.28MHz%20QER%20equiripple%20CW%20crystal%20filter.jpg


To learn more about file sharing for your group, please visit:
https://help.yahoo.com/kb/index?page=content&y=PROD_GRPS&locale=en_US&id=SLN15398


Regards,


k1rf_digital_steve <sbdick@optonline.net>


Re: XTAL parameters for measurement receiver

Nick Kennedy
 

​In order to use things I had on hand, I used crystals at around 5.2 MHz for my measurement receiver. The actual frequency chosen isn't really critical.

73-

Nick, WA5BDU​

 

Hi,

I forgot to mention that the crystals were really cheap when I bought them in a local store which is not very well supplied.

I don't know why this frequency was selected for the MS but it might be due to its abundance.  I don't know for what they are supposed to be.

73 de Ignacio EB4APL




Re: XTAL parameters for measurement receiver

EB4APL
 

Hi,

I forgot to mention that the crystals were really cheap when I bought them in a local store which is not very well supplied.

I don't know why this frequency was selected for the MS but it might be due to its abundance.  I don't know for what they are supposed to be.

73 de Ignacio EB4APL


El 06/06/2016 a las 2:55, 'Steve Dick' sbdick@... [PHSNA] escribió:
 

Thanks very much Ignacio. Really appreciate the data.
“Digital Steve”, K1RF
 
Sent: Sunday, June 05, 2016 2:02 PM
Subject: Re: [PHSNA] XTAL parameters for measurement receiver [1 Attachment]
 
 

Hi,

I have measured a bunch of 12 crystals that I bought for the MR, I attach the results.

73 de Ignacio EB4APL


El 05/06/2016 a las 13:47, sbdick@... [PHSNA] escribió:
 

If anyone has measured crystal parameters for the 3276.8 KHz crystals used in the measurement receiver (ECS part number ECS-32-17-1X) I would appreciate it (Rs, Lm, Cm, Q). I was thinking of buying a bunch of extras for making some experimental filters. I'm particularly interested in the Rs or Q that people are seeing.  The Rs looks fairly high from the data sheet at 120 ohms which is typical for low cost crystals.  Have your crystals been running at the high end for the ESR or are they really much better?  (or if you have Q values that would be helpful)

Thanks,
"Digital Steve", K1RF



Posted by: sbdick@...



Re: XTAL parameters for measurement receiver [1 Attachment]

Steven Dick
 

Thanks very much Ignacio. Really appreciate the data.
“Digital Steve”, K1RF
 

Sent: Sunday, June 05, 2016 2:02 PM
Subject: Re: [PHSNA] XTAL parameters for measurement receiver [1 Attachment]
 
 

Hi,

I have measured a bunch of 12 crystals that I bought for the MR, I attach the results.

73 de Ignacio EB4APL


El 05/06/2016 a las 13:47, sbdick@... [PHSNA] escribió:
 

If anyone has measured crystal parameters for the 3276.8 KHz crystals used in the measurement receiver (ECS part number ECS-32-17-1X) I would appreciate it (Rs, Lm, Cm, Q). I was thinking of buying a bunch of extras for making some experimental filters. I'm particularly interested in the Rs or Q that people are seeing.  The Rs looks fairly high from the data sheet at 120 ohms which is typical for low cost crystals.  Have your crystals been running at the high end for the ESR or are they really much better?  (or if you have Q values that would be helpful)

Thanks,
"Digital Steve", K1RF



Posted by: sbdick@...



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Re: XTAL parameters for measurement receiver

EB4APL
 

Hi,

I have measured a bunch of 12 crystals that I bought for the MR, I attach the results.

73 de Ignacio EB4APL


El 05/06/2016 a las 13:47, sbdick@... [PHSNA] escribió:
 

If anyone has measured crystal parameters for the 3276.8 KHz crystals used in the measurement receiver (ECS part number ECS-32-17-1X) I would appreciate it (Rs, Lm, Cm, Q). I was thinking of buying a bunch of extras for making some experimental filters. I'm particularly interested in the Rs or Q that people are seeing.  The Rs looks fairly high from the data sheet at 120 ohms which is typical for low cost crystals.  Have your crystals been running at the high end for the ESR or are they really much better?  (or if you have Q values that would be helpful)

Thanks,
"Digital Steve", K1RF



Posted by: sbdick@...



XTAL parameters for measurement receiver

Steven Dick
 

If anyone has measured crystal parameters for the 3276.8 KHz crystals used in the measurement receiver (ECS part number ECS-32-17-1X) I would appreciate it (Rs, Lm, Cm, Q). I was thinking of buying a bunch of extras for making some experimental filters. I'm particularly interested in the Rs or Q that people are seeing.  The Rs looks fairly high from the data sheet at 120 ohms which is typical for low cost crystals.  Have your crystals been running at the high end for the ESR or are they really much better?  (or if you have Q values that would be helpful)

Thanks,
"Digital Steve", K1RF



Bright ideas for thinkering

Jon EA2SN / AE2SN
 

Folks
Frank, PA3CNO, while working on the Sweeperino by Farhan, found a couple of tricks to
get levelled, sinusoidal signals from 0 to 30 MHz out of a Si570, by using a down conversion
from a filtered 80-110 MHz signal and a TL026C video amp with AGC.
Even better, he has written down the whole thing in English too on his Club bulletin for all to
Kudos to Frank for his work.
Share and enjoy.
jon, ea2sn


Re: Problem with PHSNA.exe

N5IB
 

Glad to hear you got it going, Tony.
I was confident there were folks in the group who could point the way. We sure do have a wide spectrum of expertise lurking here.  I'm sure you'll enjoy using Nick's program.

I'd invite you to write up a short summary of what the initial symptom was and what you had to do to overcome it, and also any comments about using the PHSNA on a "legacy"  system. You can post it here in the Files area and I'll make sure a copy gets put in the Windows PHSNA folder.

Now I'm off to install .net on my sister's old desktop    :^))

73
Jim, N5IB



---In PHSNA@..., <anthonyjaques94@...> wrote :
 I reported that I have tried .net V4 and it would not install ..... I had collected V4.5, and that won't run on XP. Yesterday I found V4. That does install and I can now run any version of PHSNA.exe.

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