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Bob_p
Advanced Member
Username: Bob_p

Post Number: 550
Registered: 7-2004
Posted on Thursday, December 02, 2004 - 8:36 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Tech 833 I just bought a Kenwood TS 480HX and have been planning on buying a G5RV to use for awhile until I can afford a decent muti-band HF antenna.

My Question is after playing around with the I-Max and a MFJ-949E antenna tuner and can tune 17 to 40 meters with a flat 1.1.1 SWR. It doesn't even need the tuner on 15 meters, and at 17 meters I get a usable SWR without the tuner. But just to be safe I've used the tuner just to be sure.

Now I've talked on 15 and 17 meters and the I-Max seems to do pretty well but I have to wonder if it's safe to use the antenna on 17, 20 and 40 meters?

Your help will be greatly appreciated as always
Bob
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Tech833
Moderator
Username: Tech833

Post Number: 903
Registered: 8-2002
Posted on Friday, December 03, 2004 - 3:14 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Hi Bob.

If your tuner tunes it and your power does not exceed 100 watts or so, then it is perfectly safe.

On 40 meters, the Imax will have a VERY low feedpoint impedance, so a tuner is vital. The performance will be poor but useable.
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Bob_p
Advanced Member
Username: Bob_p

Post Number: 551
Registered: 7-2004
Posted on Friday, December 03, 2004 - 3:47 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Thanks Paul, my radio does 200 watts so would it be safe to use the 200 watts on 17 and 20 meters? or should I keep it down to 100 watts on those two as well?
I actually get a moderate but usable SWR on 17 meters, but have been using the tuner just to be sure it's not going to cause any problems.

Thank you very much and I doubt that you really know how much help you've been to myself and others on the board.

Thanks again

Bob
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Bob_p
Advanced Member
Username: Bob_p

Post Number: 552
Registered: 7-2004
Posted on Friday, December 03, 2004 - 6:24 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I'm sorry I need to clarify something. When I said a moderate SWR on 17 meters. I'm getting a 1.5.1 or under without the tuner, so I guess that's actually a good SWR, but of course with the tuner I can get it flat. In this case on 17 meters with an SWR of 1.5.1 I am guessing that I could run all 200 watts without the tuner, but I am being cautious.
By the way the MFJ 949 shows an SWR of 1.3.1 without the tuner and the radio shows just a hair under 1.5.1.

On 20 meters I need the tuner to get a usable SWR but I can still get a 1.1.1 with no problem, but there is a lot of white noise. So I guess I need to keeep it at or under 100 watts on 20 meters.

Sorry to drag this out, but after I looked at my last posts I realized I didn't make myself clear, and the Kenwood being my first HF rig, I want to know that I'm not going to create any problems or hurt the radio.

Again thank you in advance

Bob
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Tech833
Moderator
Username: Tech833

Post Number: 906
Registered: 8-2002
Posted on Saturday, December 04, 2004 - 2:50 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Hi Bob.

Running 200 watts PEP will not be a problem either. Especially on 17m. You should be able to run up to full legal power on 17 with no trouble.

What you are trying to avoid is getting a voltage potential in the tuning network high enough to arc across windings or connections and leave a carbon trace.
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Bob_p
Advanced Member
Username: Bob_p

Post Number: 553
Registered: 7-2004
Posted on Saturday, December 04, 2004 - 7:02 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Thanks Paul I'll plan on using up to 200 watts on 10 through 17 meters, and will probably run less on 20 and 40 meters. I'm not sure if I want to even run the radio on 40 meters because I've heard that even though the I-Max will tune on 40 meters it is not very effective.

Thank you very much for your patience and assistance
Bob

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