Rick Asked: So, what magic wire lengths work well on all bands with the T1 ?
Answer: There are no "magic" wire lengths. Since you understand feed point impedance concerns, the "point" is to choose a wire as close to 1/2 wavelength on the lowest frequency as is convenient and which will still allow a match with the T1. Probably something in the range of 90 to 100 feet or 150 to 175 feet will work FB. As you know, the only real important band where 1/2 wave really helps is the lowest frequency band. Even if you hit an exact multiple of 1/2 wave on the higher frequency bands, the feed point impedance will be a lot lower than it is at the 1/2 wave band, so it should load FB. You are probably aware that as you go up in frequency, the feed point impedance tends to settle down so something in the range of a few hundred ohms which the T1 handles easily. There's nothing "special" about any particular length of antenna as long as it's long enough for the tuner to match on the lowest-frequency band. All tuners have some minimum antenna length that's needed because the impedance of the antenna drops to a very low value as it becomes shorter in terms of wavelength. For example, many high-end commercial tuners required at least 22 feet of radiator at 2 MHz. There's sure to be some minimum length you'll need with the T1 on the lowest band you use but "Longer is Better" still applies, at least up to 1/2 wave. Use "counterpoise" wires, especially on the lower frequency bands; one cut 1/4 wave for each band. Probably one 66 feet, one 33 feet, and maybe one 16 feet. If you want perfection, you might include a 30 meter wire if you use it a lot, but I find little to gain over having the 40/20 meter wires by doing so. ------------------------------------------ Rick Asked: Do I need to use a balun with the endfed wire to make it work or just feed it direct to the T1 ? Answer: No. Used on an end fed wire like that, a balun often makes loading up the antenna easier by introducing some loss. It's sort of a "dummy load" in parallel with the radiator that limits the impedance excursion so the tuner has a better chance of finding a good match. So don't bother to throw away power. Remember that the RF coming out of the BNC connector is "balanced". The currents in the center and shield are equal and opposite. You can feed a balanced load at that point without any concern. There are two useful things a balun can do: 1) Reduce the impedance of some antennas to bring them within range of the tuner and 2) Help isolate common mode currents from the tuner and rig when they are a problem. That's usually when there's a ground problem. --------------------------------------------- Rick wrote: Also, I now find that the T1 requires the push of a button before starting to transmit, so is there no full autotune mode that cause it to tune whenever the swr goes above a certain level ? When changing bands ? If not, kind of messes wit hthe idea of having an utotuner in the first place ! Hmmm ? The "automatic" part is that it finds the best match automatically, once it's been commanded to do so. Since you can destroy the tuner - virtually *any* tuner - by having it tune at full power, the *last* thing you want one to do is tune "automatically" by launching into a tune cycle when the SWR runs above some limit. You can arrange simple external command either with a single two-conductor cable (coax is recommended for RF isolation purposes) or by using the data remote cable with your FT rig. I think you'll find the most comprehensive answers to your questions about this and other issues relating to the T1 manual in the T1 Owner's manual. You can get it at: http://www.elecraft.com/manual/T1%20owners%20man%20rev%20A2.pdf Ron AC7AC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
