6k7 vs. 6k6

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What is the reason for the differente in test Resultat measured by Rob Sherwood?
Rolf
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DJ1WT

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Posted 4 weeks ago

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Johan / SE3X

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Use Google, read some reports. And you will be enlightened. 
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HCampbell WB4IVF

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Rolf -

Here is a discussion including comments from Rob and Flex:

https://groups.io/g/FlexRadioSmartSDR/topic/19203177?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,19203177

Howard






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DJ1WT

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Thank you, Howard! For several month I tried to find it out talking with the two German dealers. And 'googling' here in Germany was not successful.
A nice monday for all,
Rolf
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kjave63@yahoo.com

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Glad that you got help from a gentleman! Good luck and 73!
KJ8DO
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Matt NQ6N

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In reading the information on the Sherwood ranking difference, it seems that the difference is attributed to variance in actual specs across multiple samples of the ADC part. 

I also read that there is not actually a need for a heat sink on the ADC chip, and that the heat sink was added in the first place to help with temperature stability, to make the calibration of the routine that uses the ADC more stable across varying temperatures. 

It was also mentioned that the calibration routine runs when the rig boots.

So my question is this:  Does the calibration routine run again once the rig is up to temperature, or periodically to adjust to shifts in ambient temperature which may effect the amount of residual heat on the ADC?

It would seem that since the ADC has constant heat dissipation, that if the rig was booted from room temperature and calibrated immediately, that the calibration result would be different than if the rig had been powered on for a few hours and then was simply rebooted/recalibrated. 

In the reboot case the ADC would already be very close to actual operating temperature when calibrated, whereas in the cold boot case the heatsink would be relatively cool and thus the calibration would run when the chip was a bit cooler than it would be after the rig had been running for a while. 

I ask this just out of curiosity because it has been something I've wondered about that I don't think has been covered on the forum posts I've read.  It seems logical that if the purpose of the heat sink is to stabilize the ADC thermally, that calibration would need to occur again after the heat in the system had stabilized, and that during a cold boot the sink and chip would be a lot cooler than they will be a few minutes later. 

73,
Matt NQ6N


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Bill -VA3WTB

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Mat, the ADC used in the flex is also used in other ways in many kinds of devices. In almost all these aplications a heat sink is not needed as the temp is not critical and the range for the ADC is wider. the chip will never be damaged from from not having a heat sink how ever.

But when this chip is used in the Flex radio, the chip must stay with in a critical range in order to perform as the Flex needs. If the heat sinks are removed in the radio many things go south, a very high noise floor is one of them.

As for how the radio makes adjustments from cold to warm I don't know, but it must.
Perhaps Steve will talk about this some time when he has time?
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DJ1WT

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Would an 'traditional' temperature compensation be an improvement?

As this community has accumulated a lot of knowledge and experience I have another question being interesting perhaps to all:
in the production process of chips, the output is not uniform in quality. I've been told that those chips of lower quality (matching the specs more or less) are sold at lower prices. Can this be a reason for the variance in test data of rigs Rob has measured?
Rolf
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Bill -VA3WTB

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It is clear not clear to me that a cool chip performs differently than a warm one, and by how much? We do know that once the chip gets to warm, the Flex does not perform well.  When we start up our radios do we notice a performance difference at startup compaired to 15 minuts warmup? If you can, you would notice a higher noise floor at startup then as is warms up the noise floor decreases.

It is also important to understand that the differences in numbers make no difference in real world operation of the radio. in other words to us they would both perform the same.
Rob would need to test several radios to see how much difference there is between them instead of a one off that he does per test.

When Flex was in the designe stage they shopped around for the parts they needed that would perform to the standereds they set. This is why they were able to make 4 new radios very competitive in price where no one has been able to match.

It seems unlikely that by selecting components much more expensive performance would improve. Unless we are talking about processors. In that case Flex waits till a processor comes down in price before considering using it. Some new processors cost so much that they can not be considerd.
(Edited)
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DJ1WT

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I think FRS should help to clarify these things, it's their business.
Rolf
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Bill -VA3WTB

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Here is a very good talk by Steve Hicks
https://www.youtube.com/watch?v=DvI7a1ka0TM
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DJ1WT

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Matt, I'll try to find out how professional receiver (e.g. R&S) handle this problem.
For me it is unsatisfying to buy a rig which is 'by luck' an excellent one. Average equipment I can buy cheaper...
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Ken - NM9P, Elmer

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It isn't by luck, but the ADC chips used in the SCU must be cooled by a heat sink.  This is not because they would get so hot that they risk damage to the component, but because if the chip temperature rises above a certain temperature the noise figure and other performance stats of the chip will be affected.  

Some of the early 6400 & 6600 rigs were supplied by the chip manufacturer with heat sinks whose adhesive failed.  When the chips dislodged, their performance was affected.

The fix required new heat sinks to be attached to the other side of the board with new adhesive.  These new heat sinks now keep the ADC chips well in their proper operating zone and this is no longer an issue.  Period.

Production problem solved.  Early rigs have been repaired.  No luck involved.
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DJ1WT

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As I've understand Rob tested updated versions of the rig, so why is the 6k7 so much better?
Or do we have to live with such variances? And we would see them in a test of another 6k7-sample too?
And are those variances accepted in professional equipment too?
Ok, I accept that a receiver which costs 1/10 of the price of a professional one is not of the same quality. But I would like to see this in the specs.

And thank you Rob for your work!! These data make such discussions possible.
Rolf
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AA0KM

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Bill Roberts

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BTW, the Icom 7610 had a similar heatsink detachment issue.  Because there is no vendor sponsored community, this was not immediately reported or dealt with.  As a 6600 owner since May 12th (manufactured after the defect was uncovered and resolved in production), I remain thankful that Flex provides this Community.
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Bill -VA3WTB

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Yes here on this community you can see people post in real time and reply in real time, unlike an email based product group. This community helped put Flex on the map.
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Alester How

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For the issue or the problem related that which can also be solved from the guidance which you need to be taken with the help of the Canon support for the guidance of that.
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Bill -VA3WTB

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Lookout,,Scam
Unrelated to Flex radio.
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