Cobra 148 GTL: Unlocking the Clarifier

Discussions on CB Radio Modifications
Post Reply
User avatar
Shadow
Dead Key
Dead Key
Posts: 39
Joined: Wednesday 26th Mar 2008, 20:07
Location: SF Bay Area, California

Cobra 148 GTL: Unlocking the Clarifier

Post by Shadow » Tuesday 11th Nov 2008, 10:26

A few days ago I ran into a great deal. Someone was selling a virgin Filipino 148 in great condition and with all the accessories for $50 so I picked it up and started modifying it right away.

Talkback, frequency conversion (hi and low), 10khz switch, variable dead-key and modulation, and now im trying to unlock the clarifier. I've got another 148 that came with the clarifier already unlocked and the center is at 12 o'clock. Last night I did the clarifier mod on my new 148 but there are a few problems.

The center is at 9:30 and when i key up, it takes a second for it to settle on frequency. For example: When keyed up, it will go from 27.1152 to 27.1150 in about 1 second. I read somewhere that after this mod is done, the radio needs to settle for a while. One page said 2 hours, another said 2 days. Im a little confused, anyhow this is what I did to unlock the clarifier:

1. Cut R44
2. Cut D52
3. Solder a jumper wire across R 174 (or remove it and put a jumper in its place)
4. Remove red wire that comes from the Fine tune pot from the board and hook it to the + side of C84
5. Change R175 to a 1KOhm

Is this a solid mod or does anyone know of a better way to unlock it and maybe get more slide?

thanks :D

User avatar
marveylus22
Light User
Light User
Posts: 109
Joined: Saturday 19th May 2007, 11:03
Location: Las Vegas Nevada

Cobra 148 GTL: Unlocking the Clarifier

Post by marveylus22 » Wednesday 12th Nov 2008, 5:39

Varctor is D35. Adding a 5.6uh choke to the anode will also increase slide range further.
When the Boogeyman goes to sleep every night he checks his closet for Chuck Norris.

User avatar
hijacker
Newbie
Newbie
Posts: 5
Joined: Monday 10th Nov 2008, 7:20
Location: Michigan

Cobra 148 GTL: Unlocking the Clarifier

Post by hijacker » Thursday 13th Nov 2008, 1:50

Hello,
After you did the mod, you need to do an alignment of the frequencies on am, usb and lsb with the clarifier set to center slot, I hope you have a good frequency counter to do this. or have someone do it for you. 73.
Hijacker :)

hamguy2
Light User
Light User
Posts: 101
Joined: Monday 20th Oct 2008, 22:16
Location: sydney australia
Contact:

Cobra 148 GTL: Unlocking the Clarifier

Post by hamguy2 » Thursday 13th Nov 2008, 6:15

hi shadow, i know that mod in the cobra 148gtl the one that has the mb8719 and the left mounted mic it has a big loop crystal up the front. you cant miss it the crystal is like 2 to 3 times bigger than the normal crystal ,the slide will slide 30khz down and 10 khz up which is quite good so if you were on channel 22am you could move your voicelock and your back on 19am but your channel still says 22 you can reduce the slider range by tuning the cans but 30khz is quite handy ,regards david from australia. :D

User avatar
Rick
Technical Helper
Technical Helper
Posts: 1041
Joined: Sunday 4th Jun 2006, 12:52
Location: UK

Re: Cobra 148 GTL: Unlocking the Clarifier

Post by Rick » Thursday 13th Nov 2008, 7:09

There is no way you can get a crystal to move 30KHz or even 10KHz.
Rick.

Dodgem250
Dead Key
Dead Key
Posts: 23
Joined: Tuesday 16th Sep 2008, 9:55
Location: Indian Head, Maryland
Contact:

Cobra 148 GTL: Unlocking the Clarifier

Post by Dodgem250 » Friday 28th Nov 2008, 16:27

I have to tell you this from experience... Unlocking the clarifier in any side band unit is just not a good thing to do.

BUMP-BUMP !
Dodgem

RedEye
Light User
Light User
Posts: 140
Joined: Wednesday 29th Nov 2006, 15:38
Location: Clermont, Florida

Cobra 148 GTL: Unlocking the Clarifier

Post by RedEye » Friday 28th Nov 2008, 17:01

Dogem250, did you have too much coffee?!?!!? Heh Heh.... Your adding posts to just about every topic in here..... and to be honest, (well, in my opinion) many of them are very strange or incorrect answers. Many of them go against what most techs and long time users say or recommend....

No disrespect, just wondering what it going on with you tonite?!?!?

LOL!
Redeye - Clermont Florida
Cobra 142 GTL, D104 Eagle,
Gonset GSB 201 MkIII
27.385 LSB
Cobra 200 modded w/2SC2879 Finals
Astatic D104 Hand mic

_______________________________________
How about coming up a few Kc's and join the rest of us?!?

User avatar
frogman296
Heavy User
Heavy User
Posts: 228
Joined: Monday 12th Nov 2007, 0:47
Location: canada

Re: Cobra 148 GTL: Unlocking the Clarifier

Post by frogman296 » Saturday 14th Feb 2009, 12:46

marveylus22 wrote:Varctor is D35. Adding a 5.6uh choke to the anode will also increase slide range further.
just curious... this choke you speak of... is there any certain style i should get??

i see some on ebay... 5.6uh axial choke....
Image
Image
or should i go with the coil style??

help please... in need of more slide

thanks in advance fellas

User avatar
The Defpom
Site Admin
Site Admin
Posts: 435
Joined: Friday 20th Aug 2004, 18:06
Location: New Zealand
Contact:

Re: Cobra 148 GTL: Unlocking the Clarifier

Post by The Defpom » Saturday 14th Feb 2009, 14:21

Those green axial type are the ones you would want.

A warning though, adding a inductor to the varactor has some tradeoffs, firstly, it gives you more down slide than up slide, and it also then requires you to re-align the loop oscillator section, it can also increase LSB instability and cause more drift.

User avatar
frogman296
Heavy User
Heavy User
Posts: 228
Joined: Monday 12th Nov 2007, 0:47
Location: canada

Re: Cobra 148 GTL: Unlocking the Clarifier

Post by frogman296 » Saturday 14th Feb 2009, 15:23

The Defpom wrote:Those green axial type are the ones you would want.

A warning though, adding a inductor to the varactor has some tradeoffs, firstly, it gives you more down slide than up slide, and it also then requires you to re-align the loop oscillator section, it can also increase LSB instability and cause more drift.
wow

doesn't sound like the plan at all

thanks for the info

User avatar
frogman296
Heavy User
Heavy User
Posts: 228
Joined: Monday 12th Nov 2007, 0:47
Location: canada

Re: Cobra 148 GTL: Unlocking the Clarifier

Post by frogman296 » Sunday 22nd Feb 2009, 9:56

this mod intrigues me... i have been trying on and off to get "channel 44"

i want 10kHz slide down...

1. Remove D51 and put in a jumper.
2. Install a "super-diode" in place of the stock varactor D35.
3. Add a 4.7uh to 10uh choke to the banded-end of the stock varactor.

here are the 3 steps i have found to follow...

what exactly is a super diode??

also... does both the super diode and the choke go in the location for d35??

User avatar
The Defpom
Site Admin
Site Admin
Posts: 435
Joined: Friday 20th Aug 2004, 18:06
Location: New Zealand
Contact:

Re: Cobra 148 GTL: Unlocking the Clarifier

Post by The Defpom » Tuesday 24th Feb 2009, 21:48

I would definitely keep what is done to a minimum, the more slide range you give, the more it will drift, AM would be OK, but SSB will really suffer for it.

As far as a super diode goes, I have no idea, someone once used to market them as such, but as far a an actual part number goes, I do not know, all they would be is a varicap diode which has a large capacitance range.

User avatar
frogman296
Heavy User
Heavy User
Posts: 228
Joined: Monday 12th Nov 2007, 0:47
Location: canada

Re: Cobra 148 GTL: Unlocking the Clarifier

Post by frogman296 » Wednesday 25th Feb 2009, 17:09

defpom...thanks

reason i am so intrigued by this mod... a local had a 148 that would slide a full 10khz down... was having issues with it on ssb... i suspect this is the reason why it was acting so goofy on ssb

once again thanks for setting me straight.

User avatar
The Defpom
Site Admin
Site Admin
Posts: 435
Joined: Friday 20th Aug 2004, 18:06
Location: New Zealand
Contact:

Re: Cobra 148 GTL: Unlocking the Clarifier

Post by The Defpom » Wednesday 25th Feb 2009, 22:35

If you think about it you will understand that you only need to slide by about 6K down, as the upwards slide from the channel below it would cover the gap, giving full coverage.

User avatar
frogman296
Heavy User
Heavy User
Posts: 228
Joined: Monday 12th Nov 2007, 0:47
Location: canada

Re: Cobra 148 GTL: Unlocking the Clarifier

Post by frogman296 » Thursday 26th Feb 2009, 8:41

you know...i never thought of it in that aspect...makes sense...stupid me

violator
Newbie
Newbie
Posts: 9
Joined: Tuesday 19th May 2009, 3:46
First Name: Lee
Location: WI

Re: Cobra 148 GTL: Unlocking the Clarifier

Post by violator » Tuesday 19th May 2009, 3:59

I like the clarifier to slide further than 6 kz because then I can get to the "A" channels between 3&4, 7&8, 11&12, and 19&20. JMO.
146 GTL
D104 M6B
2/2290's in a box
Wilson 1000

hotshot
Dead Key
Dead Key
Posts: 37
Joined: Tuesday 10th Apr 2007, 7:44
Location: ireland

Re: Cobra 148 GTL: Unlocking the Clarifier

Post by hotshot » Saturday 23rd May 2009, 10:20

well then you should add a 10 kc shift mod and a 10kc slide that's not the proper mod and will upset your good radio for sure
info found on you tube for the 10kc mod
you will always miss the shot you don't take.

Post Reply

Return to “CB Radio Modifications”