Cobra 148gtl dx only 3kc shift PB010

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MARKASTERIX
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Cobra 148gtl dx only 3kc shift PB010

Post by MARKASTERIX » 19 Dec 2017, 23:02

Any ideas why this one only has 3kc slide each side?
Faulty 15mhz crystal? Varicap?

speeddemon

Re: Cobra 148gtl dx only 3kc shift PB010

Post by speeddemon » 19 Dec 2017, 23:45

Hi markasterix yes could it be or bad disk cap or bad inductor .etc . Check all vco components and all voltages. Gd luck n cheers.
Last edited by speeddemon on 20 Dec 2017, 23:28, edited 1 time in total.

Tim
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Re: Cobra 148gtl dx only 3kc shift PB010

Post by Tim » 20 Dec 2017, 22:54

What mods has the radio had?

MARKASTERIX
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Re: Cobra 148gtl dx only 3kc shift PB010

Post by MARKASTERIX » 22 Dec 2017, 09:23

Hi Tim none but the crystal has been changed

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13EL121
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Re: Cobra 148gtl dx only 3kc shift PB010

Post by 13EL121 » 22 Dec 2017, 10:41

This can happen if the oscilators are not set up correctly. With a frequency counter you should read the main oscillator and BFO frequency at the test points inside the radio. Had the same issue years ago with a SS360FM. Service manual helps.

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Re: Cobra 148gtl dx only 3kc shift PB010

Post by cb4ever104 » 22 Dec 2017, 11:35

MARKASTERIX wrote:
22 Dec 2017, 09:23
Hi Tim none but the crystal has been changed
Is the replacement a Uniden crystal ? I think I remember someone (probably Nick) saying that the Unidens have a wider "Q" than others . I would definitely start there if it isn't .

S.
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Re: Cobra 148gtl dx only 3kc shift PB010

Post by astradyne » 22 Dec 2017, 14:39

cb4ever104 wrote:
22 Dec 2017, 11:35
MARKASTERIX wrote:
22 Dec 2017, 09:23
Hi Tim none but the crystal has been changed
Is the replacement a Uniden crystal ? I think I remember someone (probably Nick) saying that the Unidens have a wider "Q" than others . I would definitely start there if it isn't .

S.
You're correct Sammy. The aftermarket Crystals are very narrow compared to the original and will top out at around 3Khz. That would make sense in this case.
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MARKASTERIX
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Re: Cobra 148gtl dx only 3kc shift PB010

Post by MARKASTERIX » 22 Dec 2017, 22:58

Originals are like hens teeth

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