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Author Topic: Which tuner for 1500W PEP ?  (Read 2097 times)
AE5RE
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Posts: 14




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« on: December 05, 2009, 12:45:45 PM »

I got my first 1.5KW amp. I need now to find the appropiate tuner to tune my homemade vertical antenna (ZeroFive like)and to be able to use my amp (40m and 20m mainly). Antenna supports 1.5KW, I do not have space for other type of antenna, please focus on the tuner question :-)
I have in mind the Palstar  and Ten Tec 238C. I like more the Ten Tec because the L network configuration and low loss (advertised) but it is more expensive too. I do not really care about the meter on the tuners. Thanks in advance and 73's
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HFRF
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« Reply #1 on: December 05, 2009, 04:22:04 PM »

You answered your own question........Ten Tec.  Buy used and they are much cheaper.  MFJ? Ameritron? Yuk!
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K8AC
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« Reply #2 on: December 05, 2009, 06:53:23 PM »

Maybe hard to believe these days, but you can construct your own tuner for a small fraction of the cost of a commercial one.
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VR2AX
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« Reply #3 on: December 06, 2009, 02:19:23 AM »

At the risk of leading with my chin, I would suggest that with 20 and 40 (lowest) in main focus, you should be better served with a standard T-network tuner than an L-network.

I have had a Ten Tec 238B which is a very nice tuner and well built. You might however find that with an untuned vertical (or rather one impedance-transformed via an unknown length of lossy coax), that  a T-match would suit the bill better than a L-match.

My MFJ 898C even worked fairly ok on those bands even with an alpha amp. The game changes character a bit when you try 160 or certain loads on 80.

If I was in your position, I would save my $ antenna tuner wise. If you are concerned, get an antenna analyzer and measure the input impedance at your shack end of the coax from the vertical (in R +/- jX terms) and report back. Someone here will tell you what you need to match it.
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HFRF
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« Reply #4 on: December 06, 2009, 05:23:20 AM »

Vertical antennas are notorious to have low impedance feed Z.  T and L tuners work more or less equal at the easy to match middle range of Z loads.  But at low Z loads, L tuners are superior with their much lower losses at low Z.
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W8JI
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« Reply #5 on: December 07, 2009, 09:48:09 AM »

I got my first 1.5KW amp. I need now to find the appropiate tuner to tune my homemade vertical antenna (ZeroFive like)and to be able to use my amp (40m and 20m mainly). Antenna supports 1.5KW, I do not have space for other type of antenna, please focus on the tuner question :-)
I have in mind the Palstar  and Ten Tec 238C. I like more the Ten Tec because the L network configuration and low loss (advertised) but it is more expensive too. I do not really care about the meter on the tuners. Thanks in advance and 73's

Since you are worried about loss you really should look at feeline losses in the antenna system you have. On some bands most of the power will be burned up in the feedline (because of the very high feedline SWR). If you are running a long coaxial line with a 10:1 SWR, why worry about tuner losses? The feedline would be the largest problem by far. If you are losing 6-8 dB in the feedline why worry about another 1/2 dB difference?

The PalStar would be fine.

As for tuners in general without consideration of the feedline, you really have to think about what you want to do.

While in general an L network has a little less loss at low impedances, it also has a MUCH narrower matching range. It doesn't do much good to have half the tuner loss (which is small anyway) if you can't match the load. There are many impedances an L simply won't match because of capacitor range, because you almost always cannot switch the cap in series and the L to ground, and because you can't use two components of the same reactance type which some loads would require.

If you can somewhat control the load impedance to a certain range an L is fine, but so is a T!!

I use all T networks here for my tuners because of matching range. If you get one with a lot of capacitance and a big inductor, like the ATR30 (and I think PalStar makes one with a lot of capacitance), you can handle a good bit of power into a very wide load impedance range and losses are very low even at low impedances.

If you buy a T with 200 pF capacitors it won't be so good into very low impedance loads on 160 or 80 meters because the reactance of the caps is too high at maximum capacitance.

But again, losses are really one of the least important things. As little as 50 watts of power loss will make a tuner fail, so the real issue is matching range and handling the power. The L clearly loses on matching range while the T wins, and the L wins on efficiency into a very low load impedance on lower bands. The T does just as well on efficiency into higher load impedances.  

One tuner, no matter what marketing people would have you think, is not superior in every way. Overall if the goal is to match a wide range of load impedances you really need a T. If you can tolerate a limited matching range, the L will do fine.

Tom

« Last Edit: December 07, 2009, 09:52:57 AM by W8JI » Logged
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