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I'll wait for a while.? - You? might like to mention the query to any RF designers you know.? It's a very common topology , this phasing choke.? H. Granberg of Motorola used it a lot but he never described how it worked accurately (he says in one appn note that it provides a cntr tap equivalent to the output transformer -that's horse dung).? I have a few suspicions about how reproducable the (OPT)? transformer of this fifty watt class C amplifier is.? Virtually no RF transformers in that power class use a wound primary transformer.? Reasons being - not enough primary inductance compared with a copper tube type and the capacitive shunting that exists in the primary when turns are overwound that simply is not there in a copper tube primary.? In addition if you overwind a secondary on an RF primary (I had a look at the kit instructions and that's what it instructs) then you will get zero net flux in the secondary's flux window at the time the flux is being established (every half cycle) .. until the flux is fully established in the? outer part of the ferrite core - the problem disappears when you use copper tube primaries.? I decided to have look at Motorola AN 762 and An749? as below (the photos for Figure 3 which show transformer construction are very poor but they show braid used for the primary and it is sitting right up high, not in the web of the transformer core.)? The only reproducible design of OPT? I know of in this power class is the Wa2eby amplifier and he used Teflon insulated wire which spreads the windings and reduces the capacitive shunt effect in the primary. He used a pig-nose balun core which for a phasing choke fed application should be basically identical to a dual tubular coil transformer design. (But it is not identical magnetically if the transformer is centre tapped).

I attach a ref to the Motorola PDF on RF transformer design