{"id":374,"date":"2009-05-03T23:17:11","date_gmt":"2009-05-03T17:47:11","guid":{"rendered":"http:\/\/brainstorms.in\/?p=374"},"modified":"2009-05-03T23:17:11","modified_gmt":"2009-05-03T17:47:11","slug":"bitx-20-update-the-band-pass-filter","status":"publish","type":"post","link":"https:\/\/brainstorms.in\/?p=374","title":{"rendered":"Bitx 20 update: The band pass filter."},"content":{"rendered":"

The\u00a0 bitx, I\u00a0 built using the ugly construction method was too ugly to look at.\u00a0\u00a0 The board\u00a0 was rebuilt using Manhattan style construction last week end . Now the board looks tidy and neat. The added advantage is that\u00a0 I can plug and play with any section.\u00a0 Individual sections are built on smaller PCBs and all sections are\u00a0 glued to a larger copper clad sheet.<\/p>\n

\"Bitx
Bitx Rebuilt in Manhattan Style<\/figcaption><\/figure>\n

However, the power output in transmit mode was very low.\u00a0 Up on investigation , it was noticed\u00a0 that the band pas filter was not performing well.<\/p>\n

\"Bitx
Bitx version 3 band pass filter<\/figcaption><\/figure>\n

This morning, I decided to\u00a0 experiment with the band pass filter.\u00a0 My board is based on version 3 schematic of the bitx and the band pass filter was built from old IFTs recovered from a junk radio reviver.\u00a0 The filter was\u00a0 not tuning properly. The output at the end of the filter was very low ( 100 mv)\u00a0 May be the ferrite\u00a0 used\u00a0 in the IFT is of inferior quality.<\/p>\n

\"The
The band pass filter that was built with IFT<\/figcaption><\/figure>\n

I looked around my junk box and found out some small resistor looking\u00a0 inductors. I decided to try the\u00a0 band pass filter\u00a0 from the original design. This design uses 2 ?h inductors wound on tap washers. Fortunately, I had a few 1?h<\/p>\n

\"Bitx
Bitx version 1 band pass filter<\/figcaption><\/figure>\n

I built the circuit as shown below and soldered it to the board.\u00a0 Oops. The performance went down. I was getting only 50mv\u00a0 on transmit and the receiver performance also suffered.\u00a0 Again ,I suspect the\u00a0 junk box components. I thought of rewinding the coil using tap washer. \u00a0 Ferrite slugs and torrid cores\u00a0 are not easily available in this part of the world.<\/p>\n

\"Bitx
Bitx Version 1 bandpass filter <\/figcaption><\/figure>\n

. I looked around the junk box again and found out a set of coils used for 3 band broadcast radio.\u00a0 I decided to rebuild the\u00a0 version 3 band pass filter again<\/p>\n

\"The
The radio coil rewound <\/figcaption><\/figure>\n

The coils were rewound .\u00a0 I\u00a0 used 11 turns for the main winding and 3 turns for coupling winding The coil inductance was varying form 2.7 to 1.65 micro henries.\u00a0 The completed filter was installed and bitx powered up . Now I was\u00a0 getting around 700mv RF\u00a0 from the filter stage.\u00a0 I am yet to test the power amplifier section . I hope I will get 5 watts as advertised.\u00a0\u00a0 With the new filter in place the receiver performance has improved tremendously. I can hear lot of stations both on CW and\u00a0 SSB.<\/p>\n

\"Bitx
Bitx with the new front end filter<\/figcaption><\/figure>\n

The signal I got while whistling to the mic is also shown below.<\/p>\n

\"Scope
Scope waveform after filter<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"

The\u00a0 bitx, I\u00a0 built using the ugly construction method was too ugly to look at.\u00a0\u00a0 The board\u00a0 was rebuilt using Manhattan style construction last week end . Now the board looks tidy and neat. The added advantage is that\u00a0 I can plug and play with any section.\u00a0 Individual sections are built on smaller PCBs and… Continue reading Bitx 20 update: The band pass filter.<\/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":[33],"class_list":["post-374","post","type-post","status-publish","format-standard","hentry","category-ham-radio","tag-bitx-trifilar-transformer-winding"],"_links":{"self":[{"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/posts\/374","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=374"}],"version-history":[{"count":6,"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/posts\/374\/revisions"}],"predecessor-version":[{"id":388,"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/posts\/374\/revisions\/388"}],"wp:attachment":[{"href":"https:\/\/brainstorms.in\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=374"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/brainstorms.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=374"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/brainstorms.in\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=374"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}