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[TenTec] How to read specs.

To: <tentec@contesting.com>
Subject: [TenTec] How to read specs.
From: W8JI@contesting.com (Tom Rauch)
Date: Thu, 28 Oct 1999 09:57:59 -0400
Hi Scott,

If everything is measured the same way, and a USEFUL way, rig X 
is better.

> rig X= MDS at 80 meters-128, MDS at 20 meters-139,
>        Blocking DR at 80 meters 115, Blocking DR at 20 meters 125
>        IMD DR at 80 meters 94, IMD at 20 meters 90
> rig Y= MDS at 80 meters-127, MDS at 20 meters-124,
>        Blocking DR at 80 meters 117, Blocking DR at 20 meters - (?),
>        IMD DR at 80 meters 84, IMD DR at 20 meters 80

Rig X has less "gain" on 80 meters, that's a good thing since site 
noise is virtually always higher on lower bands. Rig Y has less 
"gain" on 20, that's a bad thing.

Rig X has much better IMD performance, which is what usually 
causes problems we notice in normal operation on crowded bands.

Rig Y has better blocking performance, would be better if you had a 
neighbor who operated the same band as you on a clear band.

The problem is how these things are measured. For example, the 
ARRL uses a wide test signal spacing which puts one or both 
signals outside the passband of roofing filters in the first IF of most 
rigs. That makes their IMD related tests (dynamic range and third 
order intercept) about as useful as a frog-hair wig.

73, Tom W8JI

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