Globe King 275 RF Output

[WB6NVH]

The Globe King 275 seems to be rather rare compared to the other models.  I recently acquired one in very nice condition, which I am getting in shape to go back on the air.  I have a question for other 275 owners, namely, how does your output RF terminate at the rear of the PA deck?  The manual has a vague reference to "binding posts."

This one has the swinging link connected to a set of porcelain stand-offs but from there, two pieces of hook-up wire come out about 6 inches and are terminated in banana plugs by the previous owner.  I would think there should have been an antenna connection on a plate attached to the rear apron with a set of feed-thru insulators, but there is nothing.  See photo below.  If you have a 275, how is your antenna line connected to the swinging link lines?

This one does not have the factory cabinet and there would be no way to run open wire line in without leaving the door open, so I am thinking of putting a couple of feed-thru insulators either at the side of or above the door.

[KC4VWU]

Wonder what value that added fixed capacitor is?  If you're going to run coax, it would probably be best to add a bracket and SO 239 to the rear apron, and you'll have to play with some shunt capacitance to get it to play nice. GK 400 has the link coupled output too.

73, Phil

[WB6NVH]

At the moment that added fixed capacitor is not connected to anything.  I was thinking I should have asked whether it was stock, although I presumed not,  and also what the more common GK's such as the 400 do for the RF output termination when using open wire line since it is probably the same.

I wasn't planning on modifying to use coax / unbalanced output but that might be an idea.  I will have to see where I put my General Radio bridge and measure the plug-in fixed capacitor in the photo.

EDIT:  Fixed air cap that has been added is 100 mmfd.

[KC2ZFA]

that fixed capacitor doesn't look like it was ever connected to anything.

I may be wrong but that jackbar and link coil look like they are of the TVL series. In my 812A push-pull xmtr I found the standard TVL link coil has insufficient turns to properly load the stage to 250mA at 1250 VDC. So I modified the swing arm with plugs and made my own 4/3/2-turn plug-in link coils to experiment. A 5-turn link doesn't fit between the 2 halves of the TVL tank coil. With the 4-turn link I can load up to 300 mA when fully meshed with the coil (which is too much so I pull out to 250 mA).

Since it's a swinging link you can ground one side of it and terminate the other side with an SO-239 to feed you power/swr metering setup and the antenna tuner (if you use one). The swing of the link is like the loading control on the pi-network if your transmission line is flat.

The female/male plugs are from junk TVL coils/jackbars I get cheap off ebay. I also used the ceramic hardware to make my own TVL coils using appropriate B&W coil stock and strips of bakelite to support the coils. In the pic, both link and tank coil are made like this.

[WB6NVH]

Yes, that is an 80 TVL tank coil.  The link there now is a three turn with slightly closer spacing than the turns of the coil itself.  It looks like I could easily get a 5-turn in there but that may be because there is some deterioration and cracking of the plastic support ribs on the TVL coil part that is making the halves be farther apart.

I see now that the previous owner has ground some paint off the rear apron and crudely soldered a banana jack to the chassis so that one of those lines from the coupling link would be grounded.  I was thinking that link would not match 50 Ohms unbalanced but maybe it can? 

[KC2ZFA]

I was thinking that link would not match 50 Ohms unbalanced but maybe it can? 

yes.

[Detroit47]

I wound a 4 to 1 balun and mounted in the rf deck. I added a so239 on a angle bracket it worked great.

N8QPC