Need info on Globe King 500 L6

[wb4nkl]

I am trying to rebuild 2 Globe King 500's. One is a 500 and the other is a 500B. Both have L6 missing. This is the 2.5 inch dia. coil under the rf chassis in the final tank circuit. I need to know how many turns are on it and are they close wound or spaced. Is the wire #16 like that is on the coil above chassis?

Thanks
WB4NKL

Cliff Hensley

[nq5t]

I am trying to rebuild 2 Globe King 500's. One is a 500 and the other is a 500B. Both have L6 missing. This is the 2.5 inch dia. coil under the rf chassis in the final tank circuit. I need to know how many turns are on it and are they close wound or spaced. Is the wire #16 like that is on the coil above chassis?

Thanks
WB4NKL

This must be a fairly common problem.  My GK 500B is missing that coil.

It provides series inductance to enable the radio to match 160M to a 300 ohm output Z.  I never bothered to put something in there since I don't operate on 160 (no space for wire), and it isn't used on any other band.  Figured if it came to it at some point, a small rotary inductor in series with the output would make a reasonable sub.

Grant/NQ5T

[Jim, W5JO]

L6 is 12 turns of #16 enameled wire (same as that on the forms above the chassis) on a 2.5 inch diameter form.  The spacing is 12 turns per inch.  Most of them are probably gone because no one could run that kind of power on 160 after the war and that coil just took up space.

[Jim, W5JO]

I forgot to mention, the output impedance for 160 meters is 300 ohms.  You may know that, but many people miss that little gem and you can tell because the bottom of the vertical coil on top of the chassis may be burned.  Mine wasn't because the guy that owned it before me didn't try to operate on 160. 

Getting it to work into a 50 ohm load is a bit of a challenge.  Have fun.

[w4fms]

Cliff...if you do put the coil back to stock, matching the 300 ohms is an easy fix with an external L network.   A 9.3uH coil and 600pf to gnd will do it just like K0Eoo's ER article.   Works great..see my photo.  160m is about the only place I use my 500.

Frank, W4FMS

[ke7trp]

My 500C has the coil.   I posted a pic of the bottom of my RF deck.  You can kind of see the coil.  Its next to the huge Bypass jennings cap.  I was experimenting with modulating the screen with a Dropper from the modulated plate supply. This made a HUGE difference in sound and power output.  Later, I put the rig back to the factory screen supply and left it alone.  Its been running now for 2 years. I used it today for several hours.

I really wish I had more pictures of this thing apart. 

Also. Search around on this forum for Globe king 500 under my name.  I have mine on 160 with the addition of one loading cap.  You really dont need the inductance. At least on mine, I did not.  Some guys here helped me with measuring each band with the MFJ259B analyzer, You back feed it into the RF deck with a plate load resistor. THen you can simply tune around and see if each band is in fact going down to 1.0 and 50 ohms.  Several of my bands where off, This turned out to be the loading caps where out of value.  On 160, I tacked Caps on, and bingo.  160 Dropped right down.  I do make a bit less power then I do on 75.. But not by a huge margin.   Ever since I did this mod, 4 or 5 other GK owners have read my article and contacted me that, this was a cheap and easy solution for 160.

The outboard matching network to me is pointless. It uses a 50 ohm coax to feed it.  Lots of guys have done various things to try to make this work on 160. Some just use a tuner inline on the coax and tune it so the GK is up at 300 MA and then they go on. 

Clark