An Adequate Preamplifier for the FM band.

I've been trying to focus on cleaning the shack, but keep falling victim to spontaneous construction.

The other night, I fully intended to get some organizing done, so I went down to the shack and fired up my trusty old Crosley 86CR so that I could catch the Tigers game while going about the task at hand.  The 86CR is an interesting old set in a couple ways:  It covers the current FM band (was manufactured in '47), but the dial is calibrated in FCC channel numbers rather than the more familiar frequencies of 88-108 MHz.  It also uses an odd double conversion scheme, 5825 and 167.5 KHz, on the AM and SW bands.  

Apparently, the 86CR wasn't intended to be used from the basement of a home at the fringes of a metropolitan area, as it lacks an RF amplifier ahead of the mixer.  So, as I moved around the shack while listening to the ball game (on FM), the signal would fade in and out.  Irritating.  Gotta fix that, but don't want to put much time, effort or money into it.  

I call the circuit that I whipped up "The Adequate Preamplifier".  It's nothing particularly special or unique, costs about a buck, and gets the job done.

 The circuit uses a pair of J-310 JFETs in cascode.  Some folks like to think of this as being similar to a dual-gate FET, which I suppose it is, but when I look at it, I see a common-source amplifier (Q2) direct coupled to a common gate amp (Q1.)  Tomato, tomahto.  

The input network provides some semblance of a bandpass filter.  The LC network is comprised of L1, C3 and the gate capacitance of Q2.  With the antenna - a couple feet of wire dangling behind the set - connected as shown, there's enough load on the circuit for it to provide gain across the FM dial without retuning.  

The output transformer, made from a broken TV balun, provides balanced outputs to mate to the old Crosley. 

Performance?  I made no effort to quantify anything - it's got gain and doesn't oscillate, and the voices of Jim Price and Dan Dickerson are coming through the speaker loud and clear.  Performance: Adequate.

The next step will be powering it from the Crosley and hiding it below deck.  It doesn't draw beans for current, so maybe I can power it across the cathode resistor of the 6V6...

At this rate, I doubt the shack will ever get cleaned.