I am much more comfortable in the conceptual virtual world than I am in the physical world where what is built (by me) frequently disappoints my vision of how things will function.
I'm currently experiencing this with my attempts to have a great antenna in operation at my QTH, an apartment complex. I started off with an Alpha Delta DX-CC arranged as a sloper with center point at about 30 feet strung between trees and negotiated with apartment management. I got reasonably good results on 20m but that was all, even though this is a multiband antenna. I then overlayed a mystery antenna onto this with separate coax feed lines. This combination seems to give somewhat good performance on 20m 40m and 80m but my intuition tells me that I am not getting the best performance I can. Trouble is, I can't get a low SWR match using the flex 5000a ATU on 80m. I have the minimum transmit SWR set to 3 and thus I can't transmit on 80m. There is (to me) an astounding article on the ARRL web site called "Another Look at Reflections" by M. Walter Maxwell, a silent key who designed antenna systems for spacecraft. I'm still digesting his material, but if I understand him correctly, SWR is simply not important as long as the feed line losses are minimal which is the case for coax and ladder line operating in the 10m to 80m range. Login to the ARRL web site and search the articles for "reflections" and you'll find this. He states that impedance mismatch, not SWR, is the cause of transmitter failure. Given this statement, what protection exists in the flex 5000 to protect the transmitter from failure? Is it irrelevant what swr I operate at and thus I can go ahead and bump up the max SWR limit for tuning so I can transmit on 80m? Is there failsafe protection built-in to the flex so that I can't do something stupid and destroy the transmitter? Would it be better to use an external tuner rather than the internal flex 5000A ATU in order to better match the transmitter impedance to the antenna/feedline impedance? i.e. what are the limitations of the internal ATU compared to commercially available external ATUs. Does an ATU affect reception in a positive way or is it simply used to ensure maximum transmitted power transfer? Signed, Lot's to learn Jim WD7W _______________________________________________ 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/ Message delivered to arch...@mail-archive.com
