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N3DRB The Derb
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« on: January 06, 2008, 09:43:53 PM » |
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After looking at some inside pictures of the small matchbox, it impresses me that it should be able to take more power under fairly well matched conditions than a 275 watt input rating. How much more ?
Has anyone here run more RF into these units than this rating and what was the result? Kilowatt matchboxes are pretty much into the realm of unobtainum for me now. The small ones without the coupler and meter can still be had where I can afford them.
Anyone got any knowledge on this? how about a pep rating guess?
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Ed-VA3ES
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« Reply #1 on: January 06, 2008, 10:27:49 PM » |
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Derb, remember that the Matchboxes were originally rated for the specified power level in AM service. Guide yourself accordingly. I suspect that the 275W Matchbox can probably handle a lot more.
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"There ain't a slaw-bukit inna worl, that kin jam me!!"
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KD6VXI
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« Reply #2 on: January 06, 2008, 11:31:00 PM » |
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After looking at some inside pictures of the small matchbox, it impresses me that it should be able to take more power under fairly well matched conditions than a 275 watt input rating. How much more ?
Has anyone here run more RF into these units than this rating and what was the result? Kilowatt matchboxes are pretty much into the realm of unobtainum for me now. The small ones without the coupler and meter can still be had where I can afford them.
Anyone got any knowledge on this? how about a pep rating guess?
My last matchbox that I used was a simple pair of ceramic variables, and a simple L between them. I kid you not, I shoved 750 PEP into it. This was years ago, (before the MFJs), so I couldn't tell you what the real mismatch was, but I saw about a 1.7 SWR into the antenna. YMMV, but a matchbox rated at 275 watts, if it uses real caps, is probably rated at 275 watts of carrier. 1Kw PEP. --Shane |
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KA7WOC
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« Reply #3 on: January 07, 2008, 12:19:00 AM » |
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I used my little matchbox during the HMR. I was running 400 watts nearly 100% modulated the entire evening. I expected to hear or smell some protests but the box took it in stride. The antenna is a full wave 75 meter loop fed with open wire.
I probably won't try 500 watts though.
I'll be using it until I build a bigger tuner or a kw box comes my way.
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Bob (aka Boatyard)
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N3DRB The Derb
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« Reply #4 on: January 07, 2008, 02:16:43 AM » |
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Just to clarify, I'm referring to the "small" E.F. Johnson Matchbox.
I was thinking 200++ watts carrier power, but me and some gangsters observed on a scope that my FT-101 is capable of 200% positive modulation. That would up the ante a bit.
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KA7WOC
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« Reply #5 on: January 07, 2008, 08:12:58 PM » |
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Get one. Use it. If you fry it, sell it on ebay. You are a gangster aren't you?
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Bob (aka Boatyard)
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Steve - WB3HUZ
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« Reply #6 on: January 07, 2008, 08:21:58 PM » |
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Should be good for 1 kW PEP and/or at least 200 watts on AM. You will be within those limits.
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K1DEU
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« Reply #7 on: January 07, 2008, 09:11:14 PM » |
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In the 60's I ran 1200 watts PeP SlopBucket on 80, 40 and 20 Meters with my 3 paralleled 813's and 250 Carrier out on AM. Lotsa extra bias in AM linear mode with more zenier diodes and lotsa air cooling! John
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N3DRB The Derb
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« Reply #8 on: January 07, 2008, 09:51:39 PM » |
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I'll be picking up 2 of them then soon as I can afford it. Truck needs new tires.  |
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KD6VXI
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« Reply #9 on: January 07, 2008, 11:03:42 PM » |
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I'll be picking up 2 of them then soon as I can afford it. Truck needs new tires. I feel for you. 1200 dollars later, my truck is back on the road. --Shane |
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N3DRB The Derb
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« Reply #10 on: January 08, 2008, 02:27:19 PM » |
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2004 Dodge Ram 1500 here. We've had to put it off twice because of no $$$. Plus lotsa other medical folk buggin fer money.  We got 81K out of the Michelin ETX's that came on it. |
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W1DAN
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« Reply #11 on: January 08, 2008, 05:59:00 PM » |
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Derb:
A friend ran SSB with the Collins 30S1 floor amp. I think he ran 1500w PEP SSB through one with no problems.
Dan
W1DAN
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N3DRB The Derb
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« Reply #12 on: January 08, 2008, 07:34:21 PM » |
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wow that seals it for me. I'll be in the small matchbox buying dept. when I get some spare bux. You look at the inside of one and it's HD compared to the tunas of today.
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w3jn
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« Reply #13 on: January 08, 2008, 07:37:01 PM » |
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You can always keep an eye peeled for a KW matchbox. That ugly mofo that you have now cost me $20 or 30 as I recall.
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W9GT
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« Reply #14 on: January 08, 2008, 07:58:44 PM » |
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It depends somewhat on what you are trying to match. Under some tuning conditions you can end up with some pretty high voltages in that box and arc things a bit. I got away with running 300 watts of AM through a 275 watt box for quite a while, but then started having some problems with it. I eventually replaced the 275 watt job with a KW Matchbox...no problems since. The 275 watt rating is POWER INPUT to the final, which probably equates to 200 watts carrier output to the tuner. Of course, there was a significant safety factor built in to the design and they seem to work at up to 1 KW PEP quite nicely. If you are planning to run full strap, however, you might have problems. YMMV   73, Jack, W9GT |
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Tubes and Black Wrinkle Rule!!
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KD6VXI
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« Reply #15 on: January 08, 2008, 08:31:10 PM » |
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2004 Dodge Ram 1500 here. We've had to put it off twice because of no $$$. Plus lotsa other medical folk buggin fer money. We got 81K out of the Michelin ETX's that came on it. I WISH I could get that kind of mileage off mine. Duallys and rotating tires = not good for it, supposedly. I got 35K out of my fronts, and 55K out of the back. HOWEVER, most of that was towing a 50 foot trailer, and usually loaded. The front tires have problems with the IRS... (I HATE IRS on a tow vehicle)... When I load the rear down, the camber goes all out of wack, wearing the outer groove on the tires. I'm going to throw a couple thousand pounds of sandbags in it the next time I get an alignment done. Gotta help with those tires. 1200 dollars is a new plate transformer!!!! --Shane |
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N3DRB The Derb
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« Reply #16 on: January 08, 2008, 11:14:48 PM » |
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The most I'll be able to run with the ft 101 - gsb 201 combo I've decided to standardize on is around a 200 watt carrier. I think I'll be ok fine.
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WD8BIL
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« Reply #17 on: January 09, 2008, 01:17:10 PM » |
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The most I'll be able to run with the ft 101 - gsb 201 combo I've decided to standardize on is around a 200 watt carrier. I think I'll be ok fine. YUP! |
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