949-E tuner for a SSB amplifier of 800+ watts?

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949-E tuner for a SSB amplifier of 800+ watts?	Reply
by K6TC on February 3, 2004	Mail this to a friend!
I recently bought a Kenwood 922-A amplifier and was told that the former owner used a 250 watt Johnson matchbox with it on a loop dipole, usually on 17 meters...amp. is in perfect condition and I am anxious to use it on the air BUT? will the 300 watt rated 949-E MFJ tuner be o.k. to use for fine tune? K6TC

RE: 949-E tuner for a SSB amplifier of 800+ watts?	Reply
by KD5ZBV on February 3, 2004	Mail this to a friend!
Let it suffice to say those old Johnson matchboxes were built like tanks. You decide if the MFJ is similarly constructed...

RE: 949-E tuner for a SSB amplifier of 800+ watts?	Reply
by WT0A on February 3, 2004	Mail this to a friend!
If your antenna is near resonance (under 2:1 swr) the 922 will load into it just fine.

RE: 949-E tuner for a SSB amplifier of 800+ watts?	Reply
by KT8K on February 3, 2004	Mail this to a friend!
Using the MFJ tuner with 800+ watts is asking for a bad smell in the shack. The Johnson matchbox was built like a shick brithouse, quite unlike the MFJ. Oh, the MFJ might survive for a little while if the antenna is already pretty well matched, but if that's the case, as WT0A says, why do you need a tuner? If you need a tuner, you're better off getting one rated for use with your amplifier. 73 de kt8k - Tim

RE: 949-E tuner for a SSB amplifier of 800+ watts?	Reply
by WB2WIK on February 3, 2004	Mail this to a friend!
My guess is the 949-E will go up in a puff of smoke fairly quickly, but of course you're welcome to experiment! The Johnson Matchbox's power rating was actually 275 Watts, and that was an "AM" rating (predominant mode in the 1950's when it was built). PEP for an AM signal is 4x carrier power, so the Matchbox was actually good for 275*4 = 1100W PEP. The MFJ isn't. I agree that the TL-922A shouldn't need any sort of tuner at all for coaxially fed antennas, under most conditions. If you can get a plate current "dip" and an output power "peak" within the tuning ranges of the plate TUNE and LOAD controls for the band you're operating, the 922A's internal pi-net is matching the load. If you can't, then you'd need an external tuner, and one rated for 1500W PEP. WB2WIK/6

RE: 949-E tuner for a SSB amplifier of 800+ watts?	Reply
by K5LXP on February 3, 2004	Mail this to a friend!
IF the SWR is 2:1 or less you don't need a tuner anyway, the pi network on the amp should tune that just fine. Any higher mismatch than that and your voltages or currents will go up in a hurry. The 300W rating on the '949 is probably a stretch at it's matching extremes. I've melted baluns and arced over caps and switches in various tuners with just 100W, when you play in the kW game you can't fudge it. You should also be running RG-8 sized coax, RG-58 cannot safely handle some of the voltages developed at these power levels. Mark K5LXP Albuquerque, NM k5lxp@arrl.net

RE: 949-E tuner for a SSB amplifier of 800+ watts?	Reply
by WA2JJH on February 3, 2004	Mail this to a friend!
I reduced the power on my HL-2200 to 300W. The 300W MFJ went poof! Even the 300W dummy load got fried with 300W for 10 seconds! The MFJ is good for 300W only if a 1:1 match is present. Yup, mine really was a "smoker"(hi-hi) I really doubt the 300W rating on tose series of MFJ's. People have even had problems with their 1KW designs. The MFJ's are great with your typical 100 watt rig. Where MFJ got a 300W rating is a joke! 73 MIKE

RE: 949-E tuner for a SSB amplifier of 800+ watts?	Reply
by K6TC on February 3, 2004	Mail this to a friend!
I want to thank everyone that answered my question about the tuner and what I should use for the 922-A...I am using a Sommers 7 band untrapped beam that I'll be doggoned if I can get at or below the 2.5.1 match...we've had it on the ground three times to make sure that nothing was missed in the assembly, the last comment we had was to use the very best coax available and 9913 from the transciever to the antenna balum is in place, did make a difference but not enough for me to try the 922-A amp. on...I am scrapping the idea of the little MFJ tuner and have been looking for a Johnson Matchbox as was used by the former owner of this amplifier. Thank you all again and 73 Tom, K6TC***

RE: 949-E tuner for a SSB amplifier of 800+ watts?	Reply
by RobertKoernerExAE7G on February 3, 2004	Mail this to a friend!
Have you tried your swr meter into a dummy load? Bob

RE: 949-E tuner for a SSB amplifier of 800+ watts?	Reply
by K6TC on February 3, 2004	Mail this to a friend!
*Yes I sure have, the Bird wattmeter us usually pretty good but your right, you never know do you?*

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