![\"Indian](\"http:\/\/brainstorms.in\/wp-content\/uploads\/2010\/09\/isdr_reciever_boxed.jpg\" "\\"isdr_reciever_boxed\\"")
<\/a><\/a>OM VU2DEV has also sent\u00a0 me the schematic\u00a0 diagram and component values \u00a0 and\u00a0 permitted me to post the same on my blog.<\/p>\n
The block diagram of the radio is shown below. (Click on the picture for a larger view)<\/p>\n At the heart of\u00a0 ISDR is a 28.224Mhz\u00a0 crystal which is used to create stable\u00a0 oscillations. This frequency is divided by 4\u00a0 using two 74HC74 dual flip flops to produce\u00a0 two\u00a0 90 degree out of phase\u00a0 local oscillator signals for the radio.<\/p>\n On the RF side signals from the antenna are\u00a0 filtered for the 40m band and some\u00a0 RF amplification is given.\u00a0 The RF signal is then mixed with\u00a0 local oscillator signal using two diode ring mixers.\u00a0 The resultant\u00a0 signals\u00a0 are \u00a0 sent to a simple low pass filter to get rid of unnecessary\u00a0 mixer products and then amplified.\u00a0 The\u00a0\u00a0 two quadrature signals are fed to the mic input of\u00a0 a PC sound card.\u00a0 ( You need a sound card with stereo input).<\/p>\n The sound card is used as\u00a0 analog to digital converter. The normal sound card found on your PC will have a sampling rate of 44khz ,with\u00a0 16 bit accuracy.\u00a0 The sampled signals are\u00a0 processed digitally inside the PC using SDR software and you can hear the radio via PC speakers.\u00a0\u00a0 Your tuning range will be half of the PC sound card’s sampling rate.\u00a0 So with\u00a0 44Khz card , you can tune from 7034Khz to 7078Khz. If you have a professional quality sound card,\u00a0 your milage with SDR will be better.<\/p>\n The circuit diagram and\u00a0 component values are\u00a0 given below.<\/p>\n If\u00a0 you want to look at the circuit in finer detail,\u00a0 download this\u00a0 pdf file<\/a>.\u00a0\u00a0 The info sheet provided by vu2dev is here<\/a> .\u00a0 The component values for the circuit can be found here<\/a>.\u00a0 T<\/p>\n I have successfully used\u00a0 Rocky<\/a>,\u00a0 kgksdr<\/a> and winrad <\/a>on my PC running Windows XP ( \ud83d\ude41 , I had to install it at last\u00a0 ).\u00a0 I am yet to test the SDR on linux and will update as and when I am able to do so.<\/p>\n My Intel\u00a0 G35 mother board seems to\u00a0 supports ( I am suspect ) \u00a0 96khz sampling via the onboard Realtech card.\u00a0 Hence , I am able to tune almost the entire 40m band. Here <\/a>is a recording from the\u00a0 radio using\u00a0 Rocky.<\/p>\n Update\u00a0 22-9-2011<\/strong> I have used his\u00a0 JOTA transceiver\u00a0 and reviver . Both are valuable additions to your\u00a0 shack. He has also provided me with PCBs of his new 72 watt linear, I am planning to build them during my next vacation<\/p>\n <\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" I have been\u00a0 playing with the ISDR software defined radio from OM\u00a0 VU2DEV ,\u00a0 Ramaprabhu ( from Bangalore )for the past one week.\u00a0 ISDR is a\u00a0 low cost SDR for\u00a0 40m band.\u00a0 The radio is\u00a0 performing wonderfully.\u00a0\u00a0\u00a0 I bought 2\u00a0 assembled kits from DEV and\u00a0 I recommend the kits\u00a0 to any one who wants\u00a0 to\u00a0… Continue reading ISDR from VU2DEV<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"class_list":["post-644","post","type-post","status-publish","format-standard","hentry","category-ham-radio"],"_links":{"self":[{"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/posts\/644","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/brainstorms.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=644"}],"version-history":[{"count":17,"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/posts\/644\/revisions"}],"predecessor-version":[{"id":664,"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/posts\/644\/revisions\/664"}],"wp:attachment":[{"href":"https:\/\/brainstorms.in\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=644"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/brainstorms.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=644"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/brainstorms.in\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=644"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}<\/a><\/a><\/a>
\nOM VU2DEV\u00a0\u00a0 at his morning QTH M\/s Micronova Impex Pvt Limited\u00a0 is making\u00a0 a large number of\u00a0\u00a0 kits including ISDR for the benefit of the community.\u00a0 You may contact them directly.\u00a0 The contact email id is <vu2dev@yahoo.com<\/a>>.<\/p>\n