[Today’s run: nothing.\u00a0 Yesterday 1 mile]<\/p>\n
I looked up my calculations for that low pass filter (LPF) that I am using with my “first transmitter”\u00a0 (see previous blog posting.)<\/p>\n
I have been measuring the transmitter output with my O-scope. When I run into a dummy load the waveform looks really nice.\u00a0 When I run into my antenna tuner\/antenna, it doesn’t look so nice.<\/p>\n
I reviewed my notes on the LPF.\u00a0 Then I sent an email to the author of the article in QEX last December from which I derived my LPF design.\u00a0 He was very gracious and confirmed my design.\u00a0 Also, he suggested that maybe I am seeing some other signals on the antenna when I measure things that way.<\/p>\n
That prompted me to have a couple of ideas. 1) I would do the same measurements with another signal source other than the transmitter.\u00a0 and 2) I could make a specific antenna (dipole) so that I could make a measurement without the antenna tuner in the circuit.<\/p>\n
So, I got a bit of a start on number 1.\u00a0 I used my TenTec Century 21<\/a> transmitter and the same frequencies as the “first transmitter” and measured into the dummy load and into the antenna.\u00a0 I see the same effect!\u00a0 So it is not the fault of the transmitter at all, or most likely not.<\/p>\n My antenna tuner is an open breadboard construction.\u00a0 I think maybe the RF is getting back into my measurement connection somehow and messing things up.\u00a0 I tried measuring with a regular o-scope lead and I tried using a coupler and a bnc cable.\u00a0 Both show the same effect.<\/p>\n So I am not yet sure what the problem is, but I am now more confident that my LPF is working ok and I can use my little transmitter without splattering my signal all over the place.<\/p>\n I still think it would be useful to build a 40-meter dipole antenna so that I can test without the tuner in line. Stay tuned for that.<\/p>\n As I typed this entry, I’m wondering if my antenna tuner is set up as a low-pass configuration or high pass.\u00a0 I think it is low-pass.\u00a0 I will have to check.\u00a0 (didn’t I post about that awhile ago?\u00a0 found it<\/a>)<\/p>\n","protected":false},"excerpt":{"rendered":" [Today’s run: nothing.\u00a0 Yesterday 1 mile] I looked up my calculations for that low pass filter (LPF) that I am using with my “first transmitter”\u00a0 (see previous blog posting.) I have been measuring the transmitter output with my O-scope. When I run into a dummy load the waveform looks really nice.\u00a0 When I run into […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-1961","post","type-post","status-publish","format-standard","hentry","category-ham-radio"],"_links":{"self":[{"href":"http:\/\/w0ep.us\/OM\/index.php?rest_route=\/wp\/v2\/posts\/1961","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/w0ep.us\/OM\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/w0ep.us\/OM\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/w0ep.us\/OM\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/w0ep.us\/OM\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1961"}],"version-history":[{"count":4,"href":"http:\/\/w0ep.us\/OM\/index.php?rest_route=\/wp\/v2\/posts\/1961\/revisions"}],"predecessor-version":[{"id":1965,"href":"http:\/\/w0ep.us\/OM\/index.php?rest_route=\/wp\/v2\/posts\/1961\/revisions\/1965"}],"wp:attachment":[{"href":"http:\/\/w0ep.us\/OM\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1961"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/w0ep.us\/OM\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1961"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/w0ep.us\/OM\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1961"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}