Cobra 148 GTL: Unlocking the Clarifier

[Shadow]

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

[marveylus22]

Varctor is D35. Adding a 5.6uh choke to the anode will also increase slide range further.

[hijacker]

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]

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.

[Rick]

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

[Dodgem250]

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]

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!

[frogman296]

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....


or should i go with the coil style??

help please... in need of more slide

thanks in advance fellas

[The Defpom]

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.

[frogman296]

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

[frogman296]

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??

[The Defpom]

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.

[frogman296]

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.

[The Defpom]

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.

[frogman296]

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

[violator]

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.

[hotshot]

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