Copper Talk » Ask The Tech » Modifications » Need Help with Cobra 148 / PDC-256 Freq Counter « Previous Next »

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The_Grand_Pooh
Posted on Thursday, September 12, 2002 - 5:15 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Im trying to hook a Para Dynamics PDC-256 Frequency counter to my Cobra 148GTL. It requires me to connect a 15 pf cap, 51 ohm resistor and PDC-256 cable to the VCO/Output Transformer in the radio. Then is says to solder the ground of the cable to a ground point adjacent to the VCO output transformer. I have taken some pictures of the inside of the radio and want to know if Im connecting to the right locations. Can I ground the cable to the case of the transformer?(2nd photo)

Thanks
The Grand Pooh-Bah

Links to photos
http://nagca.com/cb/transformer.jpg
http://nagca.com/cb/transformertop.jpg
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3ew29
Posted on Saturday, January 11, 2003 - 10:25 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

That is NOT the VCO output transformer...you are showing the AUDIO output transformer..
The VCO transformer is located behind the BIG Brown Thingy in the front left hand corner behind the Pll IC..
it is 2.30am now and i don't have a schematic with me...sorry 'bout that
Rick
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Gunship
Posted on Wednesday, August 20, 2003 - 6:23 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

There should be a test point right behind L59. That is where you connect the lead.
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Adshar64
Posted on Wednesday, August 20, 2003 - 3:44 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

TP 9 is the vco output testpoint tuned by L20 rf output. L19 is the vco lockrange tune.You can ground to the cans on these id you can solder ok. Too much heat will damage the slug casing. look for a trace that meters 0 ohms to a can casing instead if your not confident.
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Adshar64
Posted on Wednesday, August 20, 2003 - 3:45 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

TP 9 is the vco output testpoint tuned by L20 rf output. L19 is the vco lockrange tune.You can ground to the cans on these if you can solder ok. Too much heat will damage the slug casing. look for a trace that meters 0 ohms to a can casing instead if your not confident.

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