TopBand:What Is Bad SMD Devices or MMICs?

[James R. Duffey]

I am somewhat confused by this thread.

Consider the following quotes from recent posts;

1."I saw a note from Carl, KM1H talking about how bad surface mount devices
can be for intermodulation products."

2."Many small signal SMD devices are completely useless outside of a lab
enviroment."

3."I'd be careful using MMIC's, since the intercept ratings can sometimes
be misleading."

Is it Surface Mount Devices (SMDs) that have poor intercept and
intermodulation performance or MMICs?

Quotes 1 and 2 seem to indicate that there is something inherent in the
surface mount packaging that deteriotes intermodulation performance. I
don't see why the mounting package type, SMD, should determine the
intermodulation performance at all. Several devices are available in both
conventional packages and SMDs. The ubiquitous 2n2222 is such a beast. Is
the intermodulation performance of this deevice in the TO-22 package really
better than in the Surface Mount package? If so why? I am not suggesting
using a 2222 as a high performance front end, just using it as an example.

On the other hand, MMICs are available in other packaging than surface
mount packaging. Do these have better intermodulation performance than
those in surface mount packaging? If so why??

My guess is that the MMIC with its preordained gain and circuit
configuration is not as good as a strong signal amplifier as one made from
discrete components, even if those components are SMDs.

Tom's suggestion of using CATV devices for a robust front end is a good
one. - Duffey KK6MC/5

James R. Duffey      KK6MC/5  DM65   <jamesd1@flash.net>
30 Casa Loma Road
Cedar Crest NM 87008



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