I have been messing around with different turns and I found the more turns on the secondary, it gives you more signal amplitude . Well I found a calculator on line for matching
transformers , I have included the web site for everyone . I made two of them . Since I am using 75 ohm cable , I used the numbers that It gave me for seventy five ohms on the primary and secondary one with , two hundred ohms and one with five hundred ohms . I found that the one with higher number of turns works even better about 3 " S " unites higher . Now this is what I am seeing . The other thing that I am finding is that the capacitors being bypassed or not makes no deference in performance .
Since I have written my first post I have found that Mini-Circuits makes RF transformers . After looking at all the electrical specifications I found a matching transformer that is about the size of the T37-43 toroid with all the winding on it , so it does fit in side the dongle . The Mini-Circuits RF transformers is about 1/2 of a " S " unite better that the hand wound Toroid at 500 ohms on the secondary and their is no winding it . The Mini-Circuits RF transformer part is T16-6T-kk81 . Now I live in Pensacola FL. and I can hear Hams well into Europe and to the west , Hawaii . Now for the people that don't know about direct sampling , you need a preselector and RF amp. I found one that is all in one package , I use a MFJ-1020C . Let's hear back from people as to what you think about what I have written .
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