[JMS] WTB: Millen 90700 Vari-Arm Coupling Unit

[TOM SNEED]

Here are a couple pictures of the coupler for the Millen 90711:

Tom N0ZK


> On 03/16/2026 1:46 PM CDT JAMES HANLON via James_Millen_Society <james_millen_society at mailman.qth.net> wrote:
> 
>  
> I made a coupler to match my 90711 vfo to my 90800 transmitter.  It is simply a parallel-tuned circuit in a mini box with a 5-pin plug to connect to the 90800.  The line from the vfo is link-coupled to the tuned circuit, and the tuned circuit connects to the grid of the 6L6 oscillator where the crystal would normally be attached.  The other side of the tuned circuit goes to ground.  And you run with the switch on the 90800 shorting out the cathode coil.  Mine has two tuned circuits, one for 80 and the other for 40, and I switch between them depending what vfo output frequency I happen to be using.  It works just fine.
> 
> Jim, W8KGI
> 
> -----Original Message-----
> From: james_millen_society-bounces at mailman.qth.net <james_millen_society-bounces at mailman.qth.net> On Behalf Of Robert Nickels via James_Millen_Society
> Sent: Monday, March 16, 2026 10:36 AM
> To: james_millen_society at mailman.qth.net
> Subject: Re: [JMS] WTB: Millen 90700 Vari-Arm Coupling Unit
> 
> My understanding is the Variarm VFO originated with an article in QST in January 1941 by Henry B Rice W9YZH, "The "Variarm 150" - A simple ECO Exciter and it's Power Supply".    It was the cover article and I presume Millen picked up the design and offered it commercially.   The resemblance to Rice's original is very strong.     A few years ago I picked up a homebrew clone that was quite nicely done including an output coupler mounted in a small tin can that used a 4-pin plug-in coil.  The one that I have was for 80 meters but is identical in design to the schematic:
> 
> It  should be simple enough to wind up a coil and make a homebrew clone of the output coupler, although since the output of the 25L6 amplifier already has an identical tuned circuit, I don't really see the need for it.  Recall that back then it was a bit of a challenge to put a stable VFO signal on the higher bands, so it was common to run the oscillator at a low frequency and multiply up to the desired band.   Hams were expected to figure these things out and most transmitters were homebrew so a typical setup might be to make a 7 MHz output from the VFO and mulitiply in the transmitter to reach 10 meters, for example.     Most "modern" transmitters should be happy with the up-to-2 watts from the Variarm VFO.
> 
> 73, Bob W9RAN
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