What 300 w. does to a "2 kw" LP filter

[Opcom]

Is there, was there, ever a ham tuner that would handle AM from a "1KW DC input" rig of the olde school days? I am not sure the KW Matchbox even would do that.

[K5UJ]

Saw an ad for the KW Matchbox in my 1957 Handbook this morning and the ad copy does say handles 1 KW input.   Doesn't say if that's CW, AM or what.  Since it doesn't limit itself by mode, I guess they claim it can handle 650 or so watts output carrier AM i.e. 4 times that.  So the question is whether or not E.F. Johnson is for real, or like MFJ    Probably more like for real but I guess we don't have to worry on account of the current power limit 

[W3SLK]

Rob said:

Saw an ad for the KW Matchbox in my 1957 Handbook this morning and the ad copy does say handles 1 KW input.   Doesn't say if that's CW, AM or what.

Hmmmm, I thought they were essentially designed to go with the Desk KW. Just like the smaller version was to be (somewhat) mated with the Valiant.

[K5UJ]

Got it right here.  here's what it says (1957):

Viking Kilowatt "Matchbox"--Bandswitching 80, 40, 20, 15, and 10-11 meters -- self-contained.  Use with transmitters up to 1000 watts input--handles unbalanced line impedances from 50 to 1200 ohms and balanced line impedances from 50 to 2000 ohms.  No coils to change, no "tapping down" on the inductor.  Transmit/receive relay grounds receiver antenna terminals in "transmit" position.  Adjustment for matching antenna to receiver input.  Fully shielded.  Provision for RF probe.  Dimensions:  17 1/4" x 12 1/8" x 10 7/8".  Cat. No. 250-30 Wired and tested...Amateur net $124.50

[K5UJ]

Oh yeah this is kind of interesting, the same ad says the small Matchbox handles 275 w. (I always thought it was 250) and the Z range is different, balanced range 25 to 1250 ohms; unbalanced 25 to 3000 ohms.  Other features same as KW model.  $49.85.

[Todd, KA1KAQ]

The big Millen Transmatch (92200) is built like the proverbial brick shithouse inside and looks like it would easily handle a KW input. Can't find the book for it atm, but I seem to recall it says it will handle over 3KW, Can't remember what the class is. I've got one here that I've toyed with selling a few times, but it's just so well made and purty, inside is all shiny copper. Sadly, it only covers 10-80 and is built for coax. That's not a bad thing unless you're using balanced feeders.

[K5UJ]

The big Millen Transmatch (92200) is built like the proverbial brick shithouse inside and looks like it would easily handle a KW input. Can't find the book for it atm, but I seem to recall it says it will handle over 3KW, Can't remember what the class is. I've got one here that I've toyed with selling a few times, but it's just so well made and purty, inside is all shiny copper. Sadly, it only covers 10-80 and is built for coax. That's not a bad thing unless you're using balanced feeders.

Remote it with some motors in a plastic tub out at the vertical feedpoints.

There's one for sale right now on eBay.  I'll see if I can find it.
da da..up to $153 now with one day left.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320431318598

[ke7trp]

I agree that Vectronics is light duty. However, I got that exact same unit at a ham fest for $5.  I ran it for about 6 months at 1500+++.  If the match through the unit is flat, the signal is clean, We are dealing with the connectors and board traces. If you put alot of out of band energy through it or high SWR, You will smoke it.

I dont use TVI filters anymore.  I have a balanced antenna and the transmitter is flat to the tuner. Or I dont key.

C

[ka3zlr]

I like that millen too 


73
Jack.

[Opcom]

I've learned alot about lousy matches and that a decent KW size tuner will tune them, but something may arc even with a 100W radio! I've got one I cobbled together and I am confident it will take 1KW CCS or PEP all day and it has done so into a 1700 ohm load I have cobbled up, but once the load gets too screwy, the voltage ratings are exceeded. I am saying that I get a 3/16" RF arc at 100W because of the rotten little antenna I have. It is depressing. That is the point where some hammies will put an 1:4 transformer in place. I'm not going to bother, it is the antenna that's wrong. great SWL antenna, absolutely wrong cut for any ham band.

Maybe this winter I can put up the Cushcraft 23FT marine vertical I've got, and connect the Sunair autotuner and GSB-900DX and use that. I can just screw the ant. to the roof of the shack, throw up 3 guys of nylon cord, and bolt the tuner to the metal rafters right under it. The shack is an all metal 30x40 building, should make a fine ground plane. I hope.

I'm still going to run a LPF on the outpoot of the NCL2000 leenyar, just an old Johnson one. I want to take the MFJ and shove it squarely where it belongs. The way I see it, I was cheated and stolen from.

[WQ9E]

Patrick,

The output from your NCL-2000 should be quite clean so you shouldn't need to use the lowpass filter.  It is just one more thing to add loss (and go wrong) and you do want to be kind to the 8122 finals since they are a bit pricey.  I doubt that TVI is going to be an issue for you due to the NCL-2000.

You metal building should make a good ground plane and I used a vertical for a while on my metal roofed barn.  One thing you should be cautious about is you are putting a lot of RF into the vicinity of some potentially bad metal to metal contact areas.  If your luck is not good, one or more of these will form little rectifiers and you will get all sorts of RF garbage created that cannot be reduced at the transmitting end (except by reducing your power).  Hopefully this won't be the case for you. 

Rodger WQ9E

[Steve - WB3HUZ]

Agreed. Unless you are operating on 10 meters, that LP filter will do you little or no good.

[K5UJ]

A friend of mine and I were talking about the Millen but as good as it is, you can still do better with some shopping in a few decent (AM, lotsa boat anchors, maulish parts) hamfests.  Get a thick slab of pine or plywood and bolt everything down to it; two big roller inductors and a 1000 pF vacuum variable.   Or roll the coils and tap them manually.   But yeah even the widest range most scrot tuner that matches anything won't help you get out if the antenna stinks.   I learned the hard way that if you can't get a match it is sometimes better to mess with the antenna size and/or feedline length than mess with the tuner.