|
Hi groups,
I finally got some time to troubleshoot a spare 8566 RF section in my junk pile where high bands don’t work. After a lot of hair pulling, it looks like the YTX(YIG tuned harmonic mixer) is dead. The cheapest I could find on eBay is $100.
The 3-pole YIG tuned filter inside the YTX seems good. The problem got to be the mixer diode. I haven’t figure out how to take the YTX out from the RF assembly. And I don’t know once I took the YTX out, if I could disassemble the YTX to gain access to the diode and put it back together.
If I succeed replacing a diode, I could just recalibrate to compensate the conversion gain, right?
Has anyone tried to replace the mixer diode? Is it even worth trying?
Thanks,
Calvin
|
Hi Calvin if you can bye a replacement for
$100 don’t hang back bye it and repair the old one later
Paul B
From:
hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]
Sent: 13 November 2017 00:04
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment]
HP8566 YTX repair
Hi
groups,
I finally got some time to troubleshoot a spare 8566 RF section in my junk pile
where high bands don’t work. After a lot of hair pulling, it looks like the
YTX(YIG tuned harmonic mixer) is dead. The cheapest I could find on eBay is
$100.
The 3-pole YIG tuned filter inside the YTX seems good. The problem got to be
the mixer diode. I haven’t figure out how to take the YTX out from the RF
assembly. And I don’t know once I took the YTX out, if I could disassemble the
YTX to gain access to the diode and put it back together.
If I succeed replacing a diode, I could just recalibrate to compensate the
conversion gain, right?
Has anyone tried to replace the mixer diode? Is it even worth trying?
Thanks,
Calvin
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8013 / Virus Database: 4782/15117 - Release Date: 11/12/17
|
Go to eeblog, there is a video where the diodes we're replaced. Jim h.
Sent from my Verizon 4G LTE Droid
On Nov 12, 2017 4:03 PM, "Calvin Guan guancalvin@... [hp_agilent_equipment]" <hp_agilent_equipment@...> wrote:
Hi groups,
I finally got some time to troubleshoot a spare 8566 RF section in my junk pile where high bands don’t work. After a lot of hair pulling, it looks like the YTX(YIG tuned harmonic mixer) is dead. The cheapest I could find on eBay is $100.
The 3-pole YIG tuned filter inside the YTX seems good. The problem got to be the mixer diode. I haven’t figure out how to take the YTX out from the RF assembly. And I don’t know once I took the YTX out, if I could disassemble the YTX to gain access to the diode and put it back together.
If I succeed replacing a diode, I could just recalibrate to compensate the conversion gain, right?
Has anyone tried to replace the mixer diode? Is it even worth trying?
Thanks,
Calvin
|
Hey Paul,
Yes, i will definitely get a YTX although I already have a fully and beautifully working 8566B. The fact that a tiny blown diode(probably hundredth of a gram) would cripple the 100lb instrument worries me. Time to stock some spare parts when I see them at reasonable price.
I am just thinking out loud to see if I could fix the dead YTX for amateur measurement.
Yes, the diode in the mixer is easy to break. I guess the previous owner of my spare unit wasn't being careful, perhaps connecting the SA directly to an outdoor antenna or such...
Thanks,
Hi Calvin if you can bye a replacement for $100 don’t hang back bye it and repair the old one later Paul B Hi groups,
I finally got some time to troubleshoot a spare 8566 RF section in my junk pile where high bands don’t work. After a lot of hair pulling, it looks like the YTX(YIG tuned harmonic mixer) is dead. The cheapest I could find on eBay is $100.
The 3-pole YIG tuned filter inside the YTX seems good. The problem got to be the mixer diode. I haven’t figure out how to take the YTX out from the RF assembly. And I don’t know once I took the YTX out, if I could disassemble the YTX to gain access to the diode and put it back together.
If I succeed replacing a diode, I could just recalibrate to compensate the conversion gain, right?
Has anyone tried to replace the mixer diode? Is it even worth trying?
Thanks,
Calvin No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8013 / Virus Database: 4782/15117 - Release Date: 11/12/17
|
Hmmm, I think you meant the one posted by “feedback loop” for a 8590A. That’s a NICE video. However, the 8566’s YTX is very different and I’m afraid it’s not repairable. The diode is somewhere under the blue thingy as I can see the diode bias fed in. There are very fine gold wire bond on top. There is a gold plated pillbox housing the 3 YIG spheres and the ceramic rods. To access the diode(s), I would need to remove the gold bonding wires and perhaps removing the YIG ball housing. I’m suspecting it’s some sort of thin film diode. I guess I will let the harmonic mixing function RIP and see if I could use it as a 2-22Ghz YIG tuned filter — 3 YIG spheres — WOW, that’s gonna kick ass...
Here are the two pictures of the inside beautiful YTX(not mine). What a piece of engineering marvel!!!!
Cheers! Calvin
Go to eeblog, there is a video where the diodes we're replaced. Jim h.
Sent from my Verizon 4G LTE Droid On Nov 12, 2017 4:03 PM, "Calvin Guan guancalvin@... [hp_agilent_equipment]" < hp_agilent_equipment@...> wrote: Hi groups,
I finally got some time to troubleshoot a spare 8566 RF section in my junk pile where high bands don’t work. After a lot of hair pulling, it looks like the YTX(YIG tuned harmonic mixer) is dead. The cheapest I could find on eBay is $100.
The 3-pole YIG tuned filter inside the YTX seems good. The problem got to be the mixer diode. I haven’t figure out how to take the YTX out from the RF assembly. And I don’t know once I took the YTX out, if I could disassemble the YTX to gain access to the diode and put it back together.
If I succeed replacing a diode, I could just recalibrate to compensate the conversion gain, right?
Has anyone tried to replace the mixer diode? Is it even worth trying?
Thanks,
Calvin
|
I was just hoping that your construction was like that of the microstrip board from the video, where some smd diodes were used to replace two other discrete schottky diodes. In my earlier days I used to repair hot wire anemometers. Typically the students would poke around and break one of the .0005" platinum wires, part of the sensor. I would perform the surgery in the morning before coffee, done under a microscope. Another time, they broke the bonding wire to a bolometer thermistor inside a waveguide, I couldn't get enough heat in the area to melt the solder, sent that one back to HP for repair. Nothing like trying, Jim H.
------ Original Message ------
Sent: 11/13/2017 11:10:25 AM
Subject: Re: [hp_agilent_equipment] HP8566 YTX repair
Hmmm, I think you meant the one posted by “feedback loop” for a 8590A. That’s a NICE video. However, the 8566’s YTX is very different and I’m afraid it’s not repairable. The diode is somewhere under the blue thingy as I can see the diode bias fed in. There are very fine gold wire bond on top. There is a gold plated pillbox housing the 3 YIG spheres and the ceramic rods. To access the diode(s), I would need to remove the gold bonding wires and perhaps removing the YIG ball housing. I’m suspecting it’s some sort of thin film diode. I guess I will let the harmonic mixing function RIP and see if I could use it as a 2-22Ghz YIG tuned filter — 3 YIG spheres — WOW, that’s gonna kick ass...
Here are the two pictures of the inside beautiful YTX(not mine). What a piece of engineering marvel!!!!
Cheers! Calvin
Go to eeblog, there is a video where the diodes we're replaced. Jim h.
Sent from my Verizon 4G LTE Droid On Nov 12, 2017 4:03 PM, "Calvin Guan guancalvin@... [hp_agilent_equipment]" < hp_agilent_equipment@...> wrote: Hi groups,
I finally got some time to troubleshoot a spare 8566 RF section in my junk pile where high bands don’t work. After a lot of hair pulling, it looks like the YTX(YIG tuned harmonic mixer) is dead. The cheapest I could find on eBay is $100.
The 3-pole YIG tuned filter inside the YTX seems good. The problem got to be the mixer diode. I haven’t figure out how to take the YTX out from the RF assembly. And I don’t know once I took the YTX out, if I could disassemble the YTX to gain access to the diode and put it back together.
If I succeed replacing a diode, I could just recalibrate to compensate the conversion gain, right?
Has anyone tried to replace the mixer diode? Is it even worth trying?
Thanks,
Calvin
|
In one of the HP Journals there's a write up on the YTX. The reason the mixer/diode is inside the pre-filter (YIG assembly) is so the components are no further apart than 1/4 wavelength of the instruments highest frequency. Being under 1/4 wavelength helps reduce SWR in the path between the pre-filter and the mixer and obviates a 3dB to 6dB pad that would normally be used to reduce reflection.
So theoretical it should be possible to attach a comparable mixer module and attenuator pad outside of the YIG once the damaged mixer is adequately bypassed. The trade off of adding the 3 to 6 dB pad is loosing comparable sensitivity.
Thanks for sharing the pictures. It's always worth cracking open these components to see what's inside. You never know if it's kluge-able. I think I remember seeing where someone using a wire bonder was repairing some of the hybrid RF modules on the HP 8753's.
-rastro
On Monday, November 13, 2017 1:10 PM, "Calvin Guan guancalvin@... [hp_agilent_equipment]" wrote:
Hmmm, I think you meant the one posted by “feedback loop” for a 8590A. That’s a NICE video. However, the 8566’s YTX is very different and I’m afraid it’s not repairable. The diode is somewhere under the blue thingy as I can see the diode bias fed in. There are very fine gold wire bond on top. There is a gold plated pillbox housing the 3 YIG spheres and the ceramic rods. To access the diode(s), I would need to remove the gold bonding wires and perhaps removing the YIG ball housing. I’m suspecting it’s some sort of thin film diode. I guess I will let the harmonic mixing function RIP and see if I could use it as a 2-22Ghz YIG tuned filter — 3 YIG spheres — WOW, that’s gonna kick ass...
Here are the two pictures of the inside beautiful YTX(not mine). What a piece of engineering marvel!!!!
Cheers! Calvin
Go to eeblog, there is a video where the diodes we're replaced. Jim h.
Sent from my Verizon 4G LTE Droid On Nov 12, 2017 4:03 PM, "Calvin Guan guancalvin@... [hp_agilent_equipment]" < hp_agilent_equipment@...> wrote: Hi groups,
I finally got some time to troubleshoot a spare 8566 RF section in my junk pile where high bands don’t work. After a lot of hair pulling, it looks like the YTX(YIG tuned harmonic mixer) is dead. The cheapest I could find on eBay is $100.
The 3-pole YIG tuned filter inside the YTX seems good. The problem got to be the mixer diode. I haven’t figure out how to take the YTX out from the RF assembly. And I don’t know once I took the YTX out, if I could disassemble the YTX to gain access to the diode and put it back together.
If I succeed replacing a diode, I could just recalibrate to compensate the conversion gain, right?
Has anyone tried to replace the mixer diode? Is it even worth trying?
Thanks,
Calvin
|
Calvin,
How did you verify that it's a bad diode?
The YTX is generally not repairable unless you have a lot of information and equipment. However, if you feel the urge to open yours, mark the rotational positions of the two pole pieces. They are intentionally ground at a slight angle to allow for alignment. Again, I would not open it unless you are 100% sure that it has a bad diode and you no longer care what happens to the thing.
Vladan
|
Also I think it's mentioned in the manual that the diode and YTX is very static sensitive. It may be a good idea to to cover the SMA connection with a 50-ohm load when it's unhooked from the system. -rastro
On Monday, November 13, 2017 2:40 PM, "pianovt@... [hp_agilent_equipment]" wrote:
Calvin,
How did you verify that it's a bad diode?
The YTX is generally not repairable unless you have a lot of information and equipment. However, if you feel the urge to open yours, mark the rotational positions of the two pole pieces. They are intentionally ground at a slight angle to allow for alignment. Again, I would not open it unless you are 100% sure that it has a bad diode and you no longer care what happens to the thing.
Vladan
|
Hmmm, I think you meant the one posted by “feedback loop” for a 8590A. That’s a NICE video. However, the 8566’s YTX is very different and I’m afraid it’s not repairable.
|
Hi Vladan,
First I traced through the LO and signal paths to the YTX to rule out problems in RF switch and various couplers. I measured the LO(between ALCU and YTX) and the test tone(between hi-band swtich and the YTX LO in) input to the YTX, they looked good to me. Then I tried to pick up the 321Mhz IF, and there is absolutely nothing(or below the noise floor of my SA). I only saw the test tone and LO. Because of the inherent non-linearity of components, if the diode is not completely open, I would at least see tiny bit of mixing product even it’s not, or improperly biased so I figured the diode is just dead.
I can definitively confirm it but swapping the YTX to my working 8566 or the other way, but it seems quite a bit of work the take out the it off and RF assembly and put it back on both units.
Regards, Calvin
Calvin,
How did you verify that it's a bad diode?
The YTX is generally not repairable unless you have a lot of information and equipment. However, if you feel the urge to open yours, mark the rotational positions of the two pole pieces. They are intentionally ground at a slight angle to allow for alignment. Again, I would not open it unless you are 100% sure that it has a bad diode and you no longer care what happens to the thing.
Vladan
|
Wow, the RYTHM is a 4-ball YIG filter which is even more complex:)
Hmmm, I think you meant the one posted by “feedback loop” for a 8590A. That’s a NICE video. However, the 8566’s YTX is very different and I’m afraid it’s not repairable.
|
Wow, the RYTHM is a 4-ball YIG filter which is even more complex:)
So you're shopping for a wedge bonder now?
|
Calvin,
The best way to test the diode is by measuring the forward drop and the reverse leakage current. Fortunately, the diode is directly accessible through the IF/LO connector. The diode’s cathode is grounded through the loop of the last YIG filter stage. The anode is connected to the IF/LO SMA connector.
If you do this test, make sure you don’t blow up the diode with static or an excessive test voltage. Diode leakage is tested at 2.8V reverse bias and should be under 10uA. The forward voltage drop is measured at 18mA current and it should be under 1V. Make sure you have the ground lead of the test source connected to the YTX body before you touch the SMA center pin. Also, make sure there is no chance that spikes will be emitted from the test source. Limit its voltage and current.
Another possibility is that the YTF is not tuned to the correct RF frequency. That will very effectively stop the RF signal from getting to the mixer diode. This could happen if YTX the coil driver is not working correctly or is severely mistuned.
You can also measure the d.c. resistance into the RF port of the YTX. The RF signal passes through the first YIG loop which has its far end grounded. So, you should read zero Ohms to ground.
Vladan
|
Hey Vladan,
I was about to report my finding and fix and saw you email:))….
I was suspecting the YIG is mistuned as I only saw LO feedthrough from the IF port but not test signal as I mentioned earlier this afternoon. I measured the voltage drop on the power resistor bank (25 ohm)which reflecting the tuning current on the YIG coil. It's 10.57V constant regardless of the center frequency that I tuned to. Big red flag to me. Then I swapped YTX driver board from my working unit, measure the voltage drop again, it changes as I tune the CF. Sure enough, I see the IF as expect. Close the IF jumper, wow — it works for all high band now!!!
So the YTX has one diode? I was trying to measure the diode but I don’t know how the mixer is implemented internally. Your info is extremely useful! Did you working on the YTX by any chance?
I just ordered a YTX before I found the problem in the YTX driver. I guess I can use it as another spare part if it works.
Thank you! Calvin
Calvin,
The best way to test the diode is by measuring the forward drop and the reverse leakage current. Fortunately, the diode is directly accessible through the IF/LO connector. The diode’s cathode is grounded through the loop of the last YIG filter stage. The anode is connected to the IF/LO SMA connector.
If you do this test, make sure you don’t blow up the diode with static or an excessive test voltage. Diode leakage is tested at 2.8V reverse bias and should be under 10uA. The forward voltage drop is measured at 18mA current and it should be under 1V. Make sure you have the ground lead of the test source connected to the YTX body before you touch the SMA center pin. Also, make sure there is no chance that spikes will be emitted from the test source. Limit its voltage and current.
Another possibility is that the YTF is not tuned to the correct RF frequency. That will very effectively stop the RF signal from getting to the mixer diode. This could happen if YTX the coil driver is not working correctly or is severely mistuned.
You can also measure the d.c. resistance into the RF port of the YTX. The RF signal passes through the first YIG loop which has its far end grounded. So, you should read zero Ohms to ground.
Vladan
|
Now that I fixed the YTO loop unlock (YTO went into “spread spectrum” mode while pre-tund to anything > 4.5~5Ghz) and identified the broken hi-band issue so that entire RF and PLLs are working fine for my spare unit.
The next problem is the CPU board won’t boot:), both red leds on. I have very little idea as what to look:( All digital cables and connections look good to me.
I have done all the RF/PLL test/fix on my good 8566 so far.
Regards,
Hey Vladan,
I was about to report my finding and fix and saw you email:))….
I was suspecting the YIG is mistuned as I only saw LO feedthrough from the IF port but not test signal as I mentioned earlier this afternoon. I measured the voltage drop on the power resistor bank (25 ohm)which reflecting the tuning current on the YIG coil. It's 10.57V constant regardless of the center frequency that I tuned to. Big red flag to me. Then I swapped YTX driver board from my working unit, measure the voltage drop again, it changes as I tune the CF. Sure enough, I see the IF as expect. Close the IF jumper, wow — it works for all high band now!!!
So the YTX has one diode? I was trying to measure the diode but I don’t know how the mixer is implemented internally. Your info is extremely useful! Did you working on the YTX by any chance?
I just ordered a YTX before I found the problem in the YTX driver. I guess I can use it as another spare part if it works.
Thank you! Calvin
Calvin,
The best way to test the diode is by measuring the forward drop and the reverse leakage current. Fortunately, the diode is directly accessible through the IF/LO connector. The diode’s cathode is grounded through the loop of the last YIG filter stage. The anode is connected to the IF/LO SMA connector.
If you do this test, make sure you don’t blow up the diode with static or an excessive test voltage. Diode leakage is tested at 2.8V reverse bias and should be under 10uA. The forward voltage drop is measured at 18mA current and it should be under 1V. Make sure you have the ground lead of the test source connected to the YTX body before you touch the SMA center pin. Also, make sure there is no chance that spikes will be emitted from the test source. Limit its voltage and current.
Another possibility is that the YTF is not tuned to the correct RF frequency. That will very effectively stop the RF signal from getting to the mixer diode. This could happen if YTX the coil driver is not working correctly or is severely mistuned.
You can also measure the d.c. resistance into the RF port of the YTX. The RF signal passes through the first YIG loop which has its far end grounded. So, you should read zero Ohms to ground.
Vladan
|
Hello Calvin,
I suck at analog, but hunting CPU errors is something I like.
Lets start:
( ) Are all voltages OK? DONT ADJUST ANYTHING JUST MEASURE NOW!!!
Some ancient CPUs need really odd voltages.
( ) Is the clock generator farting out a stable rectangular wave?
( ) How are the reset pins configured?
( ) Do we see bus activity after powerup?
Tam
On 14.11.2017 08:41, Calvin Guan
guancalvin@... [hp_agilent_equipment] wrote:
toggle quoted message
Show quoted text
Now that I fixed the YTO loop unlock (YTO went into
“spread spectrum” mode while pre-tund to anything >
4.5~5Ghz) and identified the broken hi-band issue so that
entire RF and PLLs are working fine for my spare unit.
The next problem is the CPU board won’t
boot:), both red leds on. I have very little idea as what
to look:( All digital cables and connections look good to
me.
I have done all the RF/PLL test/fix on my
good 8566 so far.
Regards,
Calvin
Hey
Vladan,
I was about to report my
finding and fix and saw you email:))….
I was suspecting the YIG
is mistuned as I only saw LO
feedthrough from the IF port but not
test signal as I mentioned earlier
this afternoon. I measured the voltage
drop on the power resistor bank (25
ohm)which reflecting the tuning
current on the YIG coil. It's 10.57V
constant regardless of the center
frequency that I tuned to. Big red
flag to me. Then I swapped YTX driver
board from my working unit, measure
the voltage drop again, it changes as
I tune the CF. Sure enough, I see the
IF as expect. Close the IF jumper, wow
— it works for all high band now!!!
So the YTX has one diode?
I was trying to measure the diode but
I don’t know how the mixer is
implemented internally. Your info is
extremely useful! Did you working on
the YTX by any chance?
I just ordered a YTX
before I found the problem in the YTX
driver. I guess I can use it as
another spare part if it works.
Thank you!
Calvin
Calvin,
The best way to test
the diode is by
measuring the forward
drop and the reverse
leakage current.
Fortunately, the diode
is directly accessible
through the IF/LO
connector. The diode’s
cathode is grounded
through the loop of
the last YIG filter
stage. The anode is
connected to the IF/LO
SMA connector.
If you do this test,
make sure you don’t
blow up the diode with
static or an excessive
test voltage. Diode
leakage is tested at
2.8V reverse bias and
should be under 10uA.
The forward voltage
drop is measured at
18mA current and it
should be under 1V.
Make sure you have the
ground lead of the
test source connected
to the YTX body before
you touch the SMA
center pin. Also, make
sure there is no
chance that spikes
will be emitted from
the test source. Limit
its voltage and
current.
Another possibility is
that the YTF is not
tuned to the correct
RF frequency. That
will very effectively
stop the RF signal
from getting to the
mixer diode. This
could happen if YTX
the coil driver is not
working correctly or
is severely mistuned.
You can also measure
the d.c. resistance
into the RF port of
the YTX. The RF signal
passes through the
first YIG loop which
has its far end
grounded. So, you
should read zero Ohms
to ground.
Vladan
|
I’m curious what the typical 3dB bandwidth of the 3-sphere YIG preselect filter and how fast it rolls off.
In the process of aligning the DAC pretune to best YTO loop capturing range, I adjusted the pretune DAC output voltage, and adjust YO free run frequency at the two frequencies(2.3Ghz and 6.15 Ghz) to spec. But now YTX seems out of track, the measurement is 20~30 dB lower than expected.
Calvin,
The best way to test the diode is by measuring the forward drop and the reverse leakage current. Fortunately, the diode is directly accessible through the IF/LO connector. The diode’s cathode is grounded through the loop of the last YIG filter stage. The anode is connected to the IF/LO SMA connector.
If you do this test, make sure you don’t blow up the diode with static or an excessive test voltage. Diode leakage is tested at 2.8V reverse bias and should be under 10uA. The forward voltage drop is measured at 18mA current and it should be under 1V. Make sure you have the ground lead of the test source connected to the YTX body before you touch the SMA center pin. Also, make sure there is no chance that spikes will be emitted from the test source. Limit its voltage and current.
Another possibility is that the YTF is not tuned to the correct RF frequency. That will very effectively stop the RF signal from getting to the mixer diode. This could happen if YTX the coil driver is not working correctly or is severely mistuned.
You can also measure the d.c. resistance into the RF port of the YTX. The RF signal passes through the first YIG loop which has its far end grounded. So, you should read zero Ohms to ground.
Vladan
|
They are all a little different, but as I recall, most 3-ball YTFs will have about 6 dB insertion loss (over low to mid-band, and a little more toward the high end), about 20 MHz BW, and the skirts should drop about 60-80 dB by the time you're about 100 MHz away from center. There can also be some spurious responses farther out, and sometimes on the skirts, but should be pretty far down.
The 8566 has a peaking routine to get maximum accuracy at a specific frequency. I forget the name, but it's in the marker section of the controls. When you have the desired frequency centered, you push the button, and it tweaks the YTF tuning up and down a little bit, looking for the maximum value, then sets it for that. Unfortunately, that also can make the other frequency levels lower, so for best accuracy, you'd want to read each spur with the same process.
So, the better you can tweak up the YTF control during calibration, the better overall accuracy and flatness you'll get. The frequency tracking and overall amplitude response are both tweaked to compensate for the various errors. If in doubt, always use the peaking process for any critical measurements. Good luck.
Ed
|
Thanks for the info, Ed. Yes, I tried peaking it but it’s still low even in the low band. I am thinking not only YTX is off track, the Last converter slope gain and slope generator need to be adjust too.
Another weekend project.
Thanks,
On Nov 15, 2017, at 4:14 PM, edbreya@... [hp_agilent_equipment] < hp_agilent_equipment@...> wrote:
They are all a little different, but as I recall, most 3-ball YTFs will have about 6 dB insertion loss (over low to mid-band, and a little more toward the high end), about 20 MHz BW, and the skirts should drop about 60-80 dB by the time you're about 100 MHz away from center. There can also be some spurious responses farther out, and sometimes on the skirts, but should be pretty far down.
The 8566 has a peaking routine to get maximum accuracy at a specific frequency. I forget the name, but it's in the marker section of the controls. When you have the desired frequency centered, you push the button, and it tweaks the YTF tuning up and down a little bit, looking for the maximum value, then sets it for that. Unfortunately, that also can make the other frequency levels lower, so for best accuracy, you'd want to read each spur with the same process.
So, the better you can tweak up the YTF control during calibration, the better overall accuracy and flatness you'll get. The frequency tracking and overall amplitude response are both tweaked to compensate for the various errors. If in doubt, always use the peaking process for any critical measurements. Good luck.
Ed
|
Paul Bicknell