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MFJ autuner review, was Coax + Ladder Line
Jim Lux wrote:
Mike Coslo wrote: wrote: Sure, there are losses with the balun used in most tuners, but I consider that a price to pay for a multi band antenna. Chiming in late on this one... Mythical attributes aside, I believe the real reason that ladder line has become more popular is: 1. Almost all rigs are All HF band these days. 2. Many people have just one antenna they can put up at any given time. Whether it is space considerations, maintaining a low profile or keeping the XYL happy I remember the discussions with my wife when I wanted to put up the HF vertical. "Why do you need two antennas?" "Are you going to transmit two signals at the same time?". Twasn't easy, and a lot of Hams might lose that argument. So assuming it is a doublet, and I wanted to run 80 to 10 meters, I'd put up much wire as I could, not mess with coax, just run ladder line to a window panel, then into the house, into a tuner that can handle balanced line. And pay attention to the lengths that might make for trouble in matching. Or, put up as much wire as you can, put an autotuner at the feedpoint, and run coax back to the shack. probably a six of one, half dozen of the other, depending on what you already have, what kind of support structures you have (if you are putting up an inverted V, then supporting the weight of the tuner isn't an issue..), etc. Speaking of autotuners, I just got my MFJ933, and have been working with it this last week. MFJ has an interesting reputation, but I have to say they pretty much got this one right. For $224, it is one impressive piece of hardware/programming. I run my window line directly to the tuner, which was a big selling point. NOt many other auto tuners have that feature. Construction was quite acceptable, performance has been fine so far, and appearance good with only one exception. One of the front panel's letters had a little rub mark on it. No biggie, just cleaned it with an eraser. The analog meter is a little small, but the whole unit would have to be made bigger to put in a larger one, so that was a tradeoff. It also has the digital readout, so I find myself looking at the analog meter for initial reference on a frequency, then at the readout after that. It has a lot of other features that I'm still learning. I give the unit an A, at least on my experience so far. - 73 de Mike N3LI |
MFJ autuner review, was Coax + Ladder Line
Michael Coslo wrote in news:h1geb3$do4i$1
@tr22n12.aset.psu.edu: MFJ933 ??? |
MFJ autuner review, was Coax + Ladder Line
On Jun 19, 11:28�am, Michael Coslo wrote:
Jim Lux wrote: Mike Coslo wrote: wrote: Sure, there are losses with the balun used in most tuners, but I consider that a price to pay for a multi band antenna. Chiming in late on this one... Mythical attributes aside, I believe the real reason that ladder line has become more popular is: 1. Almost all rigs are All HF band these days. 2. Many people have just one antenna they can put up at any given time. Whether it is space considerations, �maintaining a low profile or keeping the XYL happy I remember the discussions with my wife when I wanted to put up the HF vertical. "Why do you need two antennas?" "Are you going to transmit two signals at the same time?". Twasn't easy, and a lot of Hams might lose that argument. So assuming it is a doublet, and I wanted to run 80 to 10 meters, I'd put up much wire as I could, not mess with coax, just run ladder line to a window panel, then into the house, into a tuner that can handle balanced line. And pay attention to the lengths that might make for trouble in matching. Or, put up as much wire as you can, put an autotuner at the feedpoint, and run coax back to the shack. probably a six of one, half dozen of the other, depending on what you already have, what kind of support structures you have (if you are putting up an inverted V, then supporting the weight of the tuner isn't an issue..), etc. Speaking of autotuners, �I just got my MFJ933, and have been working with it this last week. MFJ has an interesting reputation, but I have to say they pretty much got this one right. For $224, it is one impressive piece of hardware/programming. I run my window line directly to the tuner, which was a big selling point. NOt many other auto tuners have that feature. Construction was quite acceptable, performance has been fine so far, and appearance good with only one exception. One of the front panel's letters had a little rub mark on it. No biggie, just cleaned it with an eraser. The analog meter is a little small, but the whole unit would have to be made bigger to put in a larger one, so that was a tradeoff. It also has the digital readout, so I find myself looking at the analog meter for initial reference on a frequency, then at the readout after that. It has a lot of other features that I'm still learning. I give the unit an A, at least on my experience so far. � � � � - 73 de Mike N3LI- Hide quoted text - - Show quoted text - The MFJ-933 is a manual loop tuner according to their catalog. Which ever one you are using sounds nice, and is worth a look, but I don't think it is a MFJ-933. Gary N4AST |
MFJ autuner review, was Coax + Ladder Line
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MFJ autuner review, was Coax + Ladder Line
J. Mc Laughlin wrote:
Dear N3LI: Might the MFJ model be 993? Sorry, Germs, I typo'd. It is indeed a 993. - 73 de Mike N3LI - |
lightning protection Coax + Ladder Line
Jim Lux wrote in
: Dave Oldridge wrote: "Kash J. Rangan" wrote in If your antenna is balanced, it would probably be better to simply split the ladder line onto the center conducters of two identical short coaxes and then run ladder line inside to your tuner. If you MUST ground the shields that's OK and you can use lightning arrestors on both coaxes. But remember, no lighning arrestor is as good for protecting equipment as a foot or two of air. Disconnecting during thunderstorms is solid policy! If you have a direct hit, a one foot air gap isn't necessarily going to do you much good, unless the antenna end of the gap is on the ground surface. (i.e. the wire going from where the coax ends to your lightning dissipation ground has some non-zero inductance/resistance) If you're worried about induced voltages from adjacent strikes, then a good transient suppressor will help, but almost all suppressors have "let through" voltage that is above the damage threshold for, say, a FET front end. Depends on what your equipment sensitivity is. Shorting the input of the radio and tying it to chassis ground.. that WILL protect the radio. I have been through some VERY violent storms. I always disconnected all antenna and power leads from the radio. Outside arrestors will help keep it out of the house but you need airspace to protect receiver front ends. Also disconnect any ethernet runs. Surge protection can only do so much. I learned the hard way about disconnecting stuff. My neighbour across the street had a direct hit and it danced across the phone lines into my equipment. I lost several modems, a couple of ethernet cards and a monitor and considered myself lucky that none of the computers was totalled. But my radios were disconnected and unscathed. Now the coast station I worked for had a direct hit on our Nautel 500khz transmitter's tower. Blew out half the solid state final modules but the damn thing kept right on ticking on the others! -- Dave Oldridge+ ICQ 454777283 VA7CZ |
lightning protection Coax + Ladder Line
MUST ground the shields that's OK and you can use lightning arrestors on both coaxes. This is probably not going to work in most cases. Remember an open wire feedline can have rather high voltages on it compared to a matched coax liine. This is because they are often mismatched at the antenna. If a voltage peak should happen to occur at the place where you have the arrestor, it can fire the gas tube because of the rf voltage. For example, a gas tube arrestor made for legal limit typically has a firing voltage of about 800 volts. In a matched 50 ohm system, even with a full 1500 watts into 50 ohms the peak rf voltage is in the neighborhood of 600 volts. But even a moderate power into a high impedance open line could be enough to fire the gas tubes. Neither the transmitter nor the gas tube would be happy with this situation. Rick K2XT |
lightning protection Coax + Ladder Line
"Rick" wrote in
: MUST ground the shields that's OK and you can use lightning arrestors on both coaxes. This is probably not going to work in most cases. Remember an open wire feedline can have rather high voltages on it compared to a matched coax liine. This is because they are often mismatched at the antenna. If a voltage peak should happen to occur at the place where you have the arrestor, it can fire the gas tube because of the rf voltage. For example, a gas tube arrestor made for legal limit typically has a firing voltage of about 800 volts. In a matched 50 ohm system, even with a full 1500 watts into 50 ohms the peak rf voltage is in the neighborhood of 600 volts. But even a moderate power into a high impedance open line could be enough to fire the gas tubes. Neither the transmitter nor the gas tube would be happy with this situation. That's true. You would probably need air-gap arrestors that can be adjusted to not arc on normal transmitted voltages. Still, the only really effective way of feeding a non-trap wire system on several bands that I've encountered is to use open wire. -- Dave Oldridge+ ICQ 454777283 |
lightning protection Coax + Ladder Line
In article ,
Dave Oldridge wrote: That's true. You would probably need air-gap arrestors that can be adjusted to not arc on normal transmitted voltages. Still, the only really effective way of feeding a non-trap wire system on several bands that I've encountered is to use open wire. -- Dave Oldridge+ ICQ 454777283 One of the best "air-gap arrestors" of the home-brew variety I have seen, was made with a couple of Wide Gapped Spark-Plugs, threaded into a 1/4 Steel Plate that was bonded to a very deep Grounding System. The fellow used GTO15000 to connect the spark-plugs to the Wire-Feeders. Worked very well....... -- Bruce in alaska add path after fast to reply |
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