cobra 146 GTL mod ?

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mec131
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cobra 146 GTL mod ?

Postby mec131 » Friday 13th May 2011, 22:23

can the cobra 146 gtl be moded for extra channels

lbcomms
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Re: cobra 146 GTL mod ?

Postby lbcomms » Saturday 14th May 2011, 0:51

Yes, but it's not a mod for a newbie. Either buy an easier to mod radio, or take it to someone who knows what they are doing.
It involves rewiring the clarifier and either changing the PLL or changing the downmix tripler into oscillator(s).

Google "upd2824" and you should get all the info you need.

zodiac
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Re: cobra 146 GTL mod ?

Postby zodiac » Tuesday 24th May 2011, 12:54

Take a look on transmission1 in the Uk at Clint's post, "converting my AR144 to 555"
http://www.transmission1.co.uk/forum/vi ... 35&t=16811
They are the same board and the information is very good with phots.
How far is it.
Twice it's length from halfway.

lbcomms
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Re: cobra 146 GTL mod ?

Postby lbcomms » Wednesday 25th May 2011, 23:27

This might let you hit 555, but your clarifier range will be lousy and you'll also have problems centring LSB and USB at the same position of the clarifier.

A PLL swap with EPROM addressing (i.e. a MC145106 PLL with a 27C64 EPROM) will solve these issues and give unbroken 5K steps, but like I said before, neither option is practical for those "newbies" without both experience and the right tools for the job.

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Re: cobra 146 GTL mod ?

Postby wikkans » Monday 27th Jun 2011, 23:52

thanks for good post +1
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perrym1962
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Re: cobra 146 GTL mod ?

Postby perrym1962 » Thursday 15th Dec 2011, 14:43

If you can find one, a galaxy A kit will work in them. Also a expo 100 "N" kit will work in it. But the problem is finding them.

lbcomms
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Re: cobra 146 GTL mod ?

Postby lbcomms » Friday 16th Dec 2011, 20:59

a galaxy A kit will work in them. Also a expo 100 "N" kit will work

Depends on your definition of "work" :)

The '2824 PLL clarifies and does the SSB offsets by varying the 10.240 frequency slightly.
This is halved and then tripled to 15.360 and mixed with the VCO.
The offsets are preserved by this math stuff and the radio operates at the correct frequency for AM, USB, and LSB.

These "expansion kits" inject a new signal around 15 to 17 Mhz to trick the PLL into going to places it wasn't intended to go.
The problem is they have a fixed offset that can only be set for one of the 3 modes, and most don't have a clarifier offset.

This reduces the clarifier range by about 75% and means it's impossible to center the clarifier at 12'o'clock on all the modes.

Like I said before, these kits might let you hit 555, but your clarifier range will be lousy and you'll also have problems centering LSB and USB at the same position of the clarifier.

Of course, you can add 2 more offsets and a clarifier circuit to the kit, but it's not worth the trouble.
Better to change the PLL if you have the patience / knowledge, or buy an "export" radio if you don't.

Sue

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perrym1962
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Re: cobra 146 GTL mod ?

Postby perrym1962 » Saturday 17th Dec 2011, 14:58

All I know is I put a galaxy a kit in a 146 that I had. It yielded 40 low channels and 40 upper channels. The instructions came with it and was fairly simple.. I did not try ssb, but on the am side worked perfectly..

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Re: cobra 146 GTL mod ?

Postby lbcomms » Monday 19th Dec 2011, 13:11

the am side worked perfectly

:lol: That would be like putting skinny bald tires on a Mustang and saying "That's OK, because only use it to drop the kids off to school"

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perrym1962
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Re: cobra 146 GTL mod ?

Postby perrym1962 » Monday 19th Dec 2011, 13:15

I did it to suit me. I don't really care if anyone else "approves"...


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