MFJ Enterprises Original MFJ-945E 1.6~60 MHz Mobile Antenna Tuner w/Watt Meter & Antenna Bypass Switch. 300 Watts

Will match thin air !

Great antenna tuner for what I needed.

Works well and really helps get the swr down to a reasonable level, protecting the finals in your transmitter. Small and compact. Good for the Go kit. This price is more than double than the MSRP.

MFJ-945E - had this for several years. Its junk. But it works. The bypass switch is responsible for missing receive side audio. If your receive side cuts out, check that switch. I need to replace mine. I think. I touch it [bypass] with a finger, receive side audio comes back. Still investigating this. sidebar: TUNE - BPS (top switch; push in/pop out type switch action: bypass. Setup for a new antenna Ive found it instructive to keep receive audio loud enough to hear clearly, while working on adjusting the indoor antenna to near resonance. The background noise (or any signals) come up in amplitude, when the antenna is closer to resonance, than before. I do a lot of makeshift indoor antenna work, using cup hooks into the woodwork, nylon string, copper wire -- anything on hand. I also have the Buddipole antenna system, with the center feedpoint insulator screwed to the woodwork, well above eye level. The Buddipole usually works better when fed well off-center, to match the impedance of a ground floor indoor dipole near resonance (468/F in MHz = 1/2 wave dipole antenna length, in feet). Ex. 468 / 28.400 = 16.478 feet So, receive audio comes up (gets louder) when the antenna is trimmed closer to resonance. This match box works the same way - when one of the [A through L] inductor taps are selected, one of them is louder in the receive audio. Thats either the right one to be working with, or nearby (one or two clicks, either side). When you get it all working great, you can then try a different inductor tap [A through L] since your knowledge of the match is much better, by then; and youll have a direct comparison, to the best match youve found so far, to work with. Chances are good that the inductor tap [A through L] will be near the same position, for that band, no matter what else you do. Maybe a very different antenna design would change it more, but havent seen that, so cannot speculate. It is usually within two clicks for any given band and antenna. Limited experience on other bands (with longer dipoles) as of late, so may have something misunderstood. ;) Use a QRP transmitter, to test new antenna installations For the other two controls on the MFJ-945E, a small amount of RF put through the system will expose the correct settings, but again, you can bring up the receive audio as a preliminary - there should be a distinct peak in receive amplitude in at least one of the controls. When either one of them gives a distinctive peak, leave it near that setting and try to peak the other one. You may have to slightly de-tune the one or the other, to optimize. Make sure you have a low power transmitter available to test, without putting a lot of RF through the tuner, while seeking the sweet spot(s) in the tuning range of this match box. The cross-needle scales have red curved paths which show where the intersection of the two needles lies, for that particular standing wave ratio. When the thing is off-the-charts wrong, the left needle will peg (swinging counter-clockwise) and thats really bad for your radio, so if you see it peg like that, immediately either retune the match box control that caused it to peg, or let up on the key (stop transmitting) as you just went to infinite SWR (very bad). ;) hi hi The left needle (pivot lower left) is Reflected Power, on the MFJ-945E. On very low power, the two needles make a shape where they cross; one shape should be dominant. When that shape is not dominant, itll feel reversed to you .. something is wrong; you can feel it - the needles are crossing, biased the wrong way. Instead of having lots of forward power, you find you have lots of reflected power. So its like a mirror image of where its supposed to be trending towards, and its wrong. Since you were running very low power, thats all good. Your transmitter was designed to put out more power than that, so you arent challenging it very much, by making short transmissions with a poor match. It can handle the extra heat of too much reflected power. Just dont overdo it. Keep in mind that once you get it tuned, you can swap in your expensive rig. You dont have to subject your good transceiver to this initial, exploratory antenna tuning session, at all. Thats why you bought the junk radio, for days like this, right? ;) To test sketchy antennas and your .. incomplete .. understanding of this MFJ match box. There are better and worse matches possible with these boxes; it takes some experience to develop the intuition that youve found a secondary resonant match that will work but isnt quite ideal. You want to learn which side of the null to skew towards; one of them is better and one of them is .. soft. The sharper null is usually the more resonant point. You can bring the forward power needle up a bit, by sacrificing a tiny extra bit of flatness on the reflected needle, but this technique is mostly used to find which side of the null is sharpest (they are asymmetrical). Keep in mind that the length of the coax between transmitter and match box/SWR meter is critical. Too long is no good, since youre now out on the line, a distance from a node. You want to be on the node. So keep that coax jumper as short as you can. Its inconvenient; physics does not care that its a nuisance to do it with a short coax jumper.

very good

Works excellent!

***

As always, great service. Highly recommend.

The unit does work but it did arc a few times at 200 watts PEP which is max power for my transmitter. Would not buy again.

good tuner but very touchy. could be better, I did expect more from MFJ but overall rating 8 out of 10