Re: Tuner? Well Sure!
¿ªÔÆÌåÓýGlenn.? Welcome aboard and hope to work with you more¡ ? Yes I see you have been working at this project for a while now.? You have developed some very nice boards.? I¡¯ve used the AD8307 on a lot of projects too and they are wonderful for power resolution since they are native logarithmic/ decade devices, but they are not necessary for an inexpensive a tuner.? It also tells me that you are using a straight linear hunting algorithm to find the lowest SWR calculated from forward and reverse power. ?I did that with the first tuner I built, but moved to using Phase and Magnitude measurements instead¡ as they give you more information (add L, add C, etc.)¡ and then just calculate power using math routines now available in the processor libraries.? If you make a revision to those boards, I strongly suggest you add two additional relays to put the capacitor network on either side of the inductor.? That completes the transform space needed to be covered for both hi-Z and low-Z antennas.? Again all subjects covered in Sabin¡¯s book¡ ? You are very right.? The relays make and break the project.? Been there, done that and suffered in between.? ? I do like the caps you use¡? I¡¯ll see if I can source those here¡ don¡¯t see why not, but they seem to be high current density devices¡ needed for RF designs like this. ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? ? email:? bill@... ? From: [email protected] [mailto:[email protected]] On Behalf Of Glenn ? My 1st post. Have a look at the K3NG ATU (Google K3NG TUNER). While he designed it as a balanced tuner, I have built an unbalanced version for around 20W or so. Using standard footprint 'cheap' relays. Actually the relays are the bugbear of an ATU, finding the right type and rating and low cost, since in this example there are 18 relays. From what I can see, latched relays are very expensive especially when you need 18. The trade-off is current draw, as per some posts here. |
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