New input coil for the KW Matchbox - need ideas and input

[N3DRB The Derb]

I have just finished dremeling out new RF input coil supports for the KW Matchbox to replace the coil that hammy hambone wound (the one that was shorting to the primary)  out of brown bakelite and I'll be damned if I dont finish this before I go to bed tonight. So far it's looking good. 

it will be #8 solid copper spaced about 3/4" from the main coil. I also figured out where the factory coil taps were that Hammy Hambone all cutoff to make his demon spawn from hell mods. I have to resolder them back to where they should be.

Question: is this coil rf connection tapped down on the RF input end at all or is it a end connection? I assume it would be tapped down more toward the center as the freq increases and go towards the end as it decreases, like a roller inductor would. I could install a ceramic switch for fixed micas or a air variable as well, since he holes are already drilled in the front. 

 Also, is there any advantage to using coax internally for various connections such as input and output? I have dozens and dozens of 18 to 22" lengths of rgs 400 (silver/teflon rg 58 sized) with female N connectors. I'd like to use these things since I have extra holes in the back, maybe I could take advantage of them thar holez. I have 4 N connectors out the back and a bnc which I plan to use as a scope pickup.

Ideas??? Coil? Coax? 

[WA1GFZ]

Derb,
I think the primary was about 4 or 5turns and stock it was tapped down a turn or 2  but you could change it to the full coil to move the tuning range.  The instructions told about it. I have the instructions at home somewhere and can look if you need me to. I would think #8 will be fine. Go with a few extra turns to make it more flexable. Maybe an extra switch to allow more range by selectable taps. Heck you could even series tune it since the panel has eatra holes???

[W8EJO]

I have a stock KW matchbox link coil here.

It's 5" OS diameter, 1/4" edgewound stock, about 2.5" shy of 5 full turns (doesn't bridge the gap between the mounting insulators on the 5th turn), tapped down about 1.2 turns.

[N3DRB The Derb]

yeah  lemme post this image. Might explain what I am thinking about doing since the holes are there. Just a matter of best implementation. I like the hive mind method because someone always comes up with a good idea or way to do something I never would have thought of.

I want the input to be more like the one on the left and I want to add 160 using Fixed C switched into place, one set on the left air variable, and one on the right. i got good ceramics.

Hammy Hambone destroyed the balance of the tuna and his mods were in place all the time no matter what band he was on. I want the bandswitch to work as factory but use the other 2 holes next to it to switch in the fixed caps only when the main switch is set to 80.

160 is going to become real important so I may wind the input coil for 8 to 10 turns. I'll upload a photo in a few hours.

EJO. Thank You, that helps a lot. I'll tap it down a bit.

[WA1GFZ]

Derb,
put the input cap on the low side so you can reference it to ground.

[N3DRB The Derb]

I'm soldering up the main bandswitch now. It took me 2 weeks to figure out where the factory taps on the coil were. Hambone removed most of them and clipped the STRAP flush with the coil in different spots, then used the excess strap to hook up his abortions.

Next, drilling and mounting the new input coil supports. We are cooking with gas today. Then we wind new coil and reassemble and hook it up without the case on it. See how she tunas. Maybe a couple more hours.

Frank, I'm not sure I have good cap for that. I'll find one at Timonium for sure, and I can run it as is until then.

I wanna get on TONITE.

[WA1GFZ]

Check fair radio for a cap.

[N3DRB The Derb]

body is giving out for today. gonna do it again in the morning.

big signals from HUZ, Buddly, and Jay at the moment; been listening while working. drugs takin over. 

[Steve - WB3HUZ]

Ah... too bad you couldn't get on. The conditions were very good.

[N3DRB The Derb]

yh vryon was strqpping. i hink you were op dog followed by budly.

obsrvtions were mde about yer "clank" when ou get don on the maw. nd how wide yer clank was. 

 o 3 supports made outa bakelite, gotta drill hem and mount em up wind coil, hook up he in ans out's.

I still cant figure out one tap on he main coil  I think it's for 10 meters but I dont see a matching tap on the other side of center of the coil.

80 should be all coil with no positions shorted, then 40 wih one shorted and 1 tap in on both sides, hn 20 with 2 shorted going towards center of coil, hn 15 hen 10. But there is no 2nd tap for 10 and it looks like there never was one. I dont get it and it bugs me.

I'll be able o mount the supports and wind he coil by PM tomorow.

csan anyone confirm number of taps of main coil o me? Ther should be 2 for each band, right? Freq goes p as yo move into middle of coil, correct?

too doped out to tpe thanks read answes tomorrow.

[Steve - WB3HUZ]

Hope you get the tuna fixed. Can't help you on the turns. Don't have a MB here.

Here's my key up thunk!

[N3DRB The Derb]

listenin to you and bert. big sigs once again and getting bigger. I got the MB about 75% re asssembled. Gonna JS it and try to fire up with my 15 large.

[WA1GFZ]

Derb I seem to remember only 1 tap for 10 meters. All others have 2.
the other pole of the switch was connected to the 15 meter tap if I remember

[N3DRB The Derb]

ok I could have a go at it that way,  it's not like I wanna get on 10. The 80 and 40 are the only ones I care about, along with a tasteful conversion to 160, but if you can make it all work FB, why not do it?

gonna be scouting for the big brown fixed transmitting micas with the brass studs at the fester coming up, 300, 400, 500 pf.

I got the caps remounted and hooked back up and gonna play with some clips to try to find out which is the best for 80 and 40. The only sure way to do it is to have rf ammeters in each lead an tap and tune for maximum feeder current combined with even balance between the 2 feeders. I 'll probably have the input coil mounted back on and wound by the morning, it's proving to be more difficult than I thought it would be. It's hard to wind a good coil evenly spaced with one good hand.

[WA1GFZ]

Derb,
Lay the wire out across the floor or table and roll it up over something round like a hunk of PVC pipe. RF amp meters will work great if you don't have any way to measure swr.

[W7SOE]

Derb
  Mr Hambone strikes again.  I finally scored my KW matchbox and he has struck here as well, though not nearly as bad as on yours.  A EFJ SWR bridge was kludged into the back panel.  Relay is AWOL.

Looking at the schematic for this tuner it appears that in the transmit position the primary side of the input transformer is just one coil and in receive it is four coils.

How important is this?  In it's present state it is using just one coil for both.

It is amazing to me that an air wound transformer such as this does not suffer huge losses!

Rich

[WA1GFZ]

The same primary is used for RX and TX. There is an option to move the primary tap to go to the whole coil but I never moved mine. What a hack job mounting the coupler inside.

[N3DRB The Derb]

yeh, the coil is tapped for both 50 ohm and 300 ohms o feeding the station receiver. The tap closer to the ground end is the 50 ohm one. The other is the 300 ohm. Not having a model coil to work with, I guessed and wound mine 6 turns and am using the entire coil. Since I use the Yaesu, it's not a factor. I should take a current pic of mine as it is now.

that coupler job is double fugly.