[hpsdr] Alex update?

[John Ackermann N8UR]

The attachment was too large for the mailing list, so you can find the 
sample Alex old vs. new toroid comparison referenced below at 
http://www.febo.com/pages/alex/alex_9_combined.png

John
----
John Ackermann N8UR said the following on 03/06/2010 09:00 AM:
> 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
> ----
> 
> Henry Vredegoor said the following on 03/06/2010 05:27 AM:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> Hi John, All,
>>
>> Thank you for your explanations!
>> Will these informations and measurements be made available somewhere? 
>> (Alex Wiki)
>>
>> Thanks again for all your good work.
>>
>> 73's
>>
>>
>> Henry.
>>
>>
>> John Ackermann N8UR schreef:
>>> Henry, for the most part the toroids had somewhat different 
>>> inductance than specified but other than that performed OK.  So the 
>>> main work has been changing the turns count to get the correct 
>>> inductance, and in a couple of cases changing the associated 
>>> capacitance to optimize the filter performance.
>>>
>>> After adjusting for the changed changed inductance, the stopband 
>>> loss, insertion loss, and power handling weren't much different 
>>> between the spec'd and actual toroids.
>>>
>>> (We did network analyzer measurements of each filter with both the 
>>> spec'd Amidon toroids and the Chinese ones -- over 40 captured data 
>>> sets in all -- as well as 100W saturation tests of the transmit 
>>> filters to measure both heating and spurious generation.  These 
>>> filters are *well* characterized!)
>>>
>>> John
>>> ----
>>>
>>> Henry Vredegoor wrote:
>>>> ***** High Performance Software Defined Radio Discussion List *****
>>>>
>>>> Hi Scotty, Graham, All,
>>>>
>>>> I have a few technical questions about the changes for Alex; could 
>>>> you please explain a little bit more?
>>>>
>>>> - I understand that the currently used cores are manufactured in 
>>>> China, a lower price beïng the main reason for doing so, but that 
>>>> they initially did not meet the quality standards of TAPR; where/why 
>>>> more exactly didn't they meet the spec?
>>>> - The circuits of the filters had to be changed to accommodate the 
>>>> China manufactured cores.
>>>>   Are the quality or spec's  of the filters on the Alex boards 
>>>> compromised by this change and if yes what are the resulting 
>>>> differences/new specs/consquences?
>>>> - Would it still be possible to use the original cores (for maybe 
>>>> better quality or  tighter specs) ?
>>>>
>>>> I hope I am not bugging you too much with my questions, I highly 
>>>> appreciate the outstanding job you are doing for us all.
>>>> But "Ham-Radio minds" want to know.......................    :-)
>>>>
>>>> 73's,
>>>>
>>>> Henry.
>>
>> _______________________________________________
>> HPSDR Discussion List
>> To post msg: hpsdr at openhpsdr.org
>> Subscription help: 
>> http://lists.openhpsdr.org/listinfo.cgi/hpsdr-openhpsdr.org
>> HPSDR web page: http://openhpsdr.org
>> Archives: http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/
> 
> ------------------------------------------------------------------------
> 

 1267909053.0