[Premium-Rx] What's in a WJ-8716 front end preselector?

[stephous]

See the discussion about tracking preselectors and options here:
http://watkins-johnson.terryo.org/WJ-Receivers/WJ-8716.htm

8718 data sheet here:
http://watkins-johnson.terryo.org/Documents/data%20sheets/WJ-8718A-data-sheet.pdf

----- Original Message ----- 
From: "James A. (Andy) Moorer" <jamminpower at earthlink.net>
To: <premium-rx at mailman.qth.net>
Sent: Wednesday, November 28, 2007 10:35 AM
Subject: Re: [Premium-Rx] What's in a WJ-8716 front end preselector?


> Isn't what you mean by the "preselector" really the RF Filter, part number
> 280093, shown in figure 6-1a of the 8716 manual as "Type 791616 RF
Filter"?
> It is numbered page 6-1a. It is exactly as you describe - one BIG
> featureless box. There are no controls, no band select wire or shaft -
> nothing going in except the RF from the antenna. No digital nothing on the
> inside. No motors - no active components. If you open it up, you will find
> inductors and capacitors and a couple of zeners.
>
> There is a thing called the WJ-9073-2 "Tracking Preselector", but that is
a
> separate 1U unit that goes with the "B" model of the 8716. It takes a
serial
> data input from connector J5 on the back of the 8716B. It has all sorts of
> good stuff on the inside - five separate RF filters, all precisely tuned
by
> banks of varactors.
>
> James A. (Andy) Moorer
> www.jamminpower.com
>
> ----- Original Message ----- 
>
> > I've got a WJ-8716 that has a front end preselector in it. It's a big
> > metal box with obvious coax in, coax out, and some presumably digital
> > and power wiring going into it too.
> >
> > I'm familiar with, say, the R-390A's front end preselection: a bunch
> > of octave-wide tunable LC narrow filters, with mechanical coupling
> > between the main tuning and the slugs that tune the L's. Pretty
> > nifty and perfectly obvious to me how iwoks.
> >
> > Is this how a WJ-8716 preselector works too? Are there little motors
> > moving slugs up and down inside as I tune, and banks of slugs
> > for each octave? Or does it work on some entirely different mechanism?
> >
> > Tim N3QE
>
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