[hpsdr] Alex update?

[John Ackermann N8UR]

We haven't done true IP3 tests, but did do a transmit test at high power 
  with the new cores to measure the core heating, and whether there were 
any noticeable spurs created by the filters.  We didn't any signs of 
core saturation.

John
----

Henry Vredegoor said the following on 03/06/2010 11:16 AM:
> ***** High Performance Software Defined Radio Discussion List *****
> 
> Hi John, All,
> 
> Thank you John for the example diagram.
> Of course I didn't mean to have "all" the data in comparison be 
> availlable, just enough to get some idea/illustration of the problems 
> you were having during the developement of "Alex-With-The-Chinese-Cores" 
> (  ;-)  )
> The example diagram of  the 80M LPF section gives a good idea.
> 
> After refreshing my knowledge a little by re-reading the Wiki pages for 
> Alex etc., I was wondering if an IP3 check/measurement was/will be done 
> with the combined boards of Mercury and "Alex-With-The-Chinese-Cores" (I 
> read on the Wiki that this was done by Phil - VK3APH with good results 
> for the original Alex)
> I could imagine cores fabricated by different manufacturers having 
> impact on this figure?
> Or is this somehow obvious (for the people with the appropriate 
> knowledge anyway.... ;-)  ) from your measurements-data?
> 
> 73's,
> 
> Henry.
> 
> John Ackermann N8UR schreef:
>> The measurements on the original alpha board with Amidon toroids are 
>> on my website at http://www.febo.com/pages/alex/index.html .
>>
>> I'm not sure how useful the comparative data are, since Graham has 
>> made a number of circuit changes based on those results and therefore 
>> they don't really bear resemblance to the production version.
>>
>> Just to give an example, though, attached is a plot comparing the 
>> original ("old") and Chinese ("new") toroids in the 80M LPF section.  
>> In this case the old and new cores track quite closely, but some of 
>> the other filters showed more substantial discrepancy, and as a result 
>> of these tests Graham has made significant further adjustments to some 
>> of the filters.  (The data is from an Agilent 8712ES network analyzer.)
>>
>> We'll plan to do the same tests on the production units, but the fly 
>> in the ointment is that we may get those in hand just as I'm packing 
>> up my basement for a move to another city, so I can't guarantee the 
>> timing.
>>
>> John
>> ----
> 
> 
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