On Sun, Mar 14, 2010 at 11:53 AM, Lazy Senior <lazysen...@verizon.net> wrote:
> 2. Flex advertises their Flex 5000 ATU to work with a 10:1 SWR. This is > false advertising as the Flex ATU struggles with 2:1 SWRs. 10:1 SWR would be > a wet noodle antenna. It actually *will* match a 10:1 mismatch. Try connecting a 500Ω or a 5Ω load and it will match it. But that is not the real story. A "tuner" actually does two things: 1. "tunes out" (cancels) whatever reactance is present; 2. provides an impedance transformation from whatever is at the input to 50 ohms. For most tuners, the available reactive and resistive ranges are interdependent. The more reactive the antenna, the more limited the tuner is in matching the resistive component. It would be much better if tuners were spec'd by the reactance and resistance ranges that they will tune. Sounds like something the ARRL might do in their labs. As for tuning a "wet noodle," an end-fed 1/2 wave antenna has an impedance of about 8000Ω or an SWR of about 160:1. There are precious few tuners that can handle that mismatch. That might actually be worse than a "wet noodle." :-) > 3. On bands like 75, 15, and 10 mtrs, an antenna will not have a low SWR > over the whole band. An internal antenna will "help" the radio work the > whole band. It depends on the 'Q' of the antenna. It is common to increase the bandwidth of a monopole by increasing its diameter or by switching to a folded monopole so that a tuner isn't required over the whole band. > 5. Every internal tuner I have had in a radio works on 3:1 SWRs. My last > radio, the Icom Pro III worked perfectly with my antennas. The Flex ATU does > not. I do not expect the Flex ATU to load up a wet noodle. I DO expect it to > work as well as other internal tuners. Well, Gerald did say they were aware of the limitations and that they are improving the code. So far, other than the time it takes to get things done, Flex has been very good about keeping its promises. Getting back to my original comment about comparing tuners, it would be nice to know what the inductance and capacitance ranges are so that it can be compared to other tuners. If you look at the block diagram you will see that it is an 'L' network but that the shunt capacitance can be switched to either side of the series inductance. Knowing the minimum and maximum inductance and capacitance will tell you what the matching range is. -- 73 de Brian, WB6RQN/J79BPL _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
