[TenTec] Re: ARRL Rcvr 3rd and 2nd IPs Test Methods

[Jim Reid]

Aloha to all following this topic,

Ed Hare has written a very detailed and well presented
reply to my posts and concerns,  thank you Ed.  And I
accept your criticism of my "low blow";  was not intended
as such,  but on re-reading can certainly see your point.
I apologize for over stepping in my comment.

Comments on only a couple of Ed's comments.  He has
made an excellent presentation of the facts about the
ARRL Lab test methods and use,  well worth reading
by all.

> The article in question is available for download at:

http://www.arrl.org/tis/info/pdf/020708qex046.pdf

Thank you ,  that will be helpful to others.

I am now going to cut out a bunch of Ed's great material,
and skip on down near to the end.

Ed's concluding paragraph:

> "In this post, I have outlined some of the reasons that ARRL is 
> making the testing choices it is using. I believe them to be the 
> correct choices, offering a reasonable level of standardization 
> in testing and reporting on receivers with a wide range of 
> capabilities and "real-world" receiver performance. There are 
> improvements in the works, but they are not going to make 
> a night and day difference in results, because the test methods 
> used give good results for the test conditions employed, and 
> most improvements I can think of will serve only to tighten up 
> a bit on the test conditions."

Again,  I greatly appreciate the time Ed has taken to prepare this
thourouh discussion of the ARRL lab methods and the reasons for
their use.

Now,  I would like to understand why the great difference in IP's
reported by the Lab for the Ten Tec Argo V from the "claimed"
IP's for that radio by Ten Tec.

The ARRL lab came out with IP's well below the
Ten Tec specs.  TT spec is +4 dBm for
the third order IM intercept point,  at least that is what
the ARRL lab test reports TT has specified.
 
At 3.5 MHz, 20 kHz  signal spacing,  the ARRL  Lab
measured only -4.5 dBm;  and at 14.2 MHz,  only -3.4 dBm.

Those are really significantly lower numbers than the 
Ten Tec claimed spec.  And,  for 5 kHz signal spacing,  the
deltas are even greater:  3.5 MHz,  ARRL says -30 dBm;
and for 14.2 MHz,  -29 dBm.  Those are huge differences IF
TT really specs +4 dBm IP3 for 5 kHz two signal spacing;
I do not know if Ten Tec specs this spacing for the Argo V.
  
 Also,  TT specs the second order IP to be +66 dBm.
But the ARRL lab reports only +47 dBm.  Again,  a very large
difference.

Certainly nothing in the QEX piece,  downloadable as above, is
there any reason given to explain such large deltas between
what the engineers at Ten Tec measured, probably several
times to come up with  "typical" IP2 and IP3 specs for the new
Argo V and the alarmingly lower numbers reported by ARRL.

These differences between TT claims and the ARRL Lab report
are what initiated my posts about this topic.  I still do not
understand why the great deltas,  and worry about the future
tests on the new Ten Tec Orion!  It seems to me it is imperative
to identify why the differences in numbers,  and to provide some
assurance about what we will read next.

Thanks again,  Ed.  And also,  thank you again for your visit
out here to Hawaii a few years ago. And yes,  I did have an
opportunity to work the Tuna Tin II you left with the Hilo QRP
gang.  Had a very good signal up here to Kauai,  some 350
miles away and through the Mauna Kea Volcano to boot!
And I enjoyed our across the table visit over dinner at the
concluding convention event.  You will have to visit us again!

73,  Jim  KH7M