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'[EE]: What am I doing wrong? (RF amp)'
2002\09\03@103116 by Dale Botkin

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Damn, you're right.

On Tue, 3 Sep 2002, Jochen Feldhaar wrote:

> even when maybe sounding a bit OLINish, the tag is not correct, it
> should be [EE]:, and not [EE:]....

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2002\09\05@050745 by Jochen Feldhaar

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Hi Jim and Nate,

even if this might seem like nitpicking, I would like to add a tidbit
that is definitely intermodulation.
A manufacturer of N series RF connectors with gold metallization for the
inner contact areas (... a better quality grade...!!) they had to test
for incredible -160 dBc !!!! of intermodulation. As it seems, the gold
layer created something a bit similar to a schottky diode on the metal
surface.
So as improbable as it might seem, it is not only rusty TX towers, but
also cabling and connectors can add to your difficulties in a dense RF
populated environment.....

Greetings
Jochen Feldhaar DH6FAZ


Jim schrieb:
>
> {Original Message removed}

2002\09\05@115748 by Jim

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Try dissimilar metal contact too. Like Brass and steel.

A guranteed RF "noise maker" ...

There is a reson DB Products tests all their cellular antennna
designs with mnay carriers and lotsa watts ... to insure
'clean' designs ...

The cardinal rule to live by: ONLY combine/attach materials that are
next to each other in the *galvanic series* ...

I have measured coax noise on old coax before - in a full duplex
system - when the coax was moved ... the sound was a kind
of swishing sound, and at a level of around -140 dBc ...

RF Jim

(I have MUCH more to write this subj but, so far, no time to do so.)

   "Our ability to manufacture fraud has exceeded
    our  ability to detect it."

    - Al Pacino as Viktor Taransky in the movie 'Simone'


{Original Message removed}

2002\09\05@135019 by Peter L. Peres

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>A manufacturer of N series RF connectors with gold metallization for the
>inner contact areas (... a better quality grade...!!) they had to test
>for incredible -160 dBc !!!! of intermodulation. As it seems, the gold
>layer created something a bit similar to a schottky diode on the metal
>surface.

This I do not believe until I see it, although you may be right. I have
done some testing on metal oxide semiconductor junctions and gold/gold was
the one that did NOT do that. All the others did though. Tin with anything
else is in the 'worse than bad' category. Including tin/tin, especially
after dry heating (forms pure tin oxide layer - a well known
semiconductor). Tin/steel is good enough to make galena radios and even
transmitters out of (negative resistance type oscillators). Electroplated
tin on steel was the 'best' (for making junctions - what was that singing
tower made of again ?). The 'highest activity' voltage was almost always
between 0.8 and 14V. Ouch. None of the gold/gold contacts suffered any of
these problems, but I did not test to -160dB.

Peter

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2002\09\05@140532 by Jim

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Let's see: Assume two 100 Watt carriers (+50 dBm each) are
combined in a 50 Ohm system and any 'products' are measured.

A 'spec' of -160dBc (related to one carrier) then works out to
be:

 +50 dBm +(-160 dBc) ==> -110 dBm

(where 1 microvolt in a 50 Ohm system equals -113 dBm. Contemporary
 commercial receivers are capable of .25 uV for 12 dB SINAD)

A figure of -160dBc is not so unreasonable ...

RF Jim

{Original Message removed}

2002\09\05@163409 by Peter L. Peres

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On Thu, 5 Sep 2002, Jim wrote:

>A figure of -160dBc is not so unreasonable ...

At that level (0.25uV) even a thermocouple can compete as a mixer imho. I
assume that dBc is specced against the weaker carrier to make things
harder, no ? Anyway my testing was at low frequency (<1MHz) even so I got
some contact samples to produce parametric oscillation with the test
cables alone.

Peter

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