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Categories | Antenna Tuners | Dentron MT-3000 Help

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K5YZS  Rating: 3/5 Mar 16, 2013 05:40  Send this review to a friend!
Good on 40 Meters, But......  Time owned: more than 12 months
I bought my MT-3000A in 1980 and used it with Drake TR7 and Heath HA-14 (Kompact Kilowatt) on 80 meters thru 15 meters. So far so good. Then in 1985 I got interested in 160 m band after the noisy LORAN was shut down. I worked 160 meters with TR-7 barefoot as the HA-14 only went down to 80 m band. During years of use, the small flag push-button switch indicator flags quit working. In 1990 I added an Alpha amplifier to the mix and upgraded my antenna to work band end to band end on 160 meters with ladder line feeding the antenna, and the MT-3000A to make 160 meter QSY possible. In working at legal limit on the 160 meter band I used switch position "R" (most of the coil) and at times did arc the caoacitors. I got hold of the TL, and TLW modeling program by Dean Straw nd that inducated the C1 and C2 capacitors were to low in pF values (at 240 pF) to be efficient on 160 meter band. I removed top of case and did some high power transmitting and the the steel mounting plate at the ground end of the coil got too hot to touch (too much circulating current with the too small of pF capacitor values). Read the test article in QST history when natchers have too small of pF values. Very 1nefficient at around 0.8 dB metwork loss. What to do? Running the software indicated that doubling the pF;s for C1 and C2 would make the MT-3000A more efficient on 160 meters. OK !!! Read the latest
MFJ ads, where their high power matchers have now gone to 500 pF and 1000 pF on the output side
on the MFJ-9982. Wow. Its only taken manufactures over 30 years to wake up. Read Fredrick Terman's book chapters on network design and network dissipation. A 0.8 dB loss due to heating in a mis-designed network can heat up a network by almost 120 watts (enough to melt solder connections) when running 100% duty cycle 1500 watts. I added switches to select extra padding capacitors for 80 m and 160 m operating and my coil tap dropped from "R" to "L" tap and that is more efficient as was predicted by the model calculations. Proof ?
My steel mounting bracket no longer over heats on 80 m and 160 m. This unit uses heavy duty parts as noted by others, BUT it is not network efficient on 80 m and 160 m bands without modifications. Get the software OM's and learn like I did. 73 Jim, retired engineer, k5yzs 
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