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Reviews Categories | Antenna Tuners | Kenwood AT-300 Help

Reviews Summary for Kenwood AT-300
Kenwood AT-300 Reviews: 3 Average rating: 4.7/5 MSRP: $(missing—add MSRP)
Description: Longwire ATU for TS-50, etc
Product is in production.
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IK5WQO Rating: 5/5 Jun 24, 2005 11:45 Send this review to a friend
A good antenna tuner!  Time owned: 0 to 3 months
Hello, i recently have blind-bought a used AT-300 (from Spain), after looking a lot to buy one of this devices, very rare to find. I received this antenna tuner, i cleaned, disassembled and checked it, and i tested it with my long wire antenna falling from the apartment window to the garden downstairs, with about 20/25 meters of thin (almost invisible!!!) copper wire. I used as counterpoise the metallic water drop pipe... Well, this system is working perfectly, and now i am able to use also lower bands. The tuner is very fast, the SWR obtained on my 870 is everytime less than 1,5:1, and no RFI problems anymore. AT-300 is definitely an old but still very good device.
K3ICH Rating: 5/5 Apr 7, 2005 05:25 Send this review to a friend
Works great for portable operation  Time owned: more than 12 months
I have used most all of the current remote auto-tuners, , Kenwood AT-300, the Alinco EDX-2, a couple different Icom & SGC versions, all with about the same results. I find that with a typical 2 foot piece of copper water pipe as a ground, and 45 feet of wire to one of those German 30 foot fiberglass zip-up masts, it will outperform any antenna short of a full size, resonant dipole or 1/4 wave vertical. Just clamp the light weight mast to anything handy, a fence post, short tree etc. and run a piece of #24 magnet wire up at an angle to near the top of the mast. Pound in the ground rod and you're all set. In one installation, I had a Cush-Craft R-5 at about 15 feet and was able to switch between it and the auto-tuned wire. Only on ten meters were signals the same. On all other bands, the wire was better. I have used this wire/tuner combo on all bands from 160 to 10 with very good results. The only item of concern is to make sure the length of wire you choose is NOT a half wave *, or muliple of it, on any frequency you plan to use. It turns out that 45 feet meets that requirement and makes for a convenient length for a sloping wire to the 30 foot mast.

* An end fed half wave presents a very high impedance and therefore a very high Voltage at the feed point which could be damaging to the tuner as well as making it near impossible to obtain a match.
M0ADR Rating: 4/5 Aug 17, 2003 17:39 Send this review to a friend
Working well now  Time owned: more than 12 months
I bought an AT-300 and TS-50 together, shortly followed by an AT-50 coaxial ATU. For years the AT-300 seemed to have a problem in that it did not always respond to the commands sent to it by the TS50, and eventually this problem got more and more prevalent until it stopped working altogether. I stuck it to one side for a long time and eventually decided to have a bash at it.

The problem turned out to be that a 10uf capacitor rather than 2.2uf had been fitted in the C38 position at the time of manufacture, causing the AT-300's internal reset phase to be much longer than it was supposed to be and holding the processor in the reset state while the TS-50 was trying to send commands to it. I know manufacturers sometimes change components for a reason during a unit's run but all the timing diagrams in the service manual were telling me that the reset pulse should be 25ms long, not 80ms as it was.

Since I caught and shot this problem, the unit has behaved impeccably. I don't imagine anyone else will have had this problem, but if your unit doesn't respond to a tune command first time every time, it may be worth checking out.

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