Cobra 2000 questions

[tx213]

I just got a Cobra 2000 tonight. How do I tell when it was made? It says it was made in Taiwan but not when. He said the only thing ever done was it was tuned when he bought it. It doesn't have any extra channels or the voicelock opened. It has two speakers and a TUG-8 with the sideband head on it. The mic doesn't work, but he said when I bought it he thought there was a problem with the mic plug. How much is this worth? I am going to try to get pics loaded later from my phone.


What should I do with it? Have it tuned up again? Sell it? Leave it stock? Or have channels added and the clarifier opened? Who would you recommend for the work? :r&r:

Any constructive input would be appreciated.

Thanks, 213

[preacherman]

Box it up and I'll run it for a year...and let you know if you
want to keep it. Seriously...if it works well, it's worth what
the market will bear...which seems to be 200 to 300+ depending
on condition.

Have the mic checked out. Those ssb heads are getting harder
to find.
Preacherman

[Black Lightning]

If you want to do the aforementioned npc/rc with volted final mod, have a look at my site here [Please login or register to view this link] this is a site that documents the mod along with pictures I took myself as I performed the mod on a Cobra 2000. Most of the information you will find on the net deals with the 148GTL, which is good enough, but my page details the mod along with pictures of the 2000 itself, which is just a little bit different in a couple of areas than the 148. I also tweaked the mod a little to make it easily removable if you want to go back for some reason.

This really is the proper way to do that mod. I've done it to mine and I believe that madsage also used it for his 2000.

[madsage]

Yeah nice.. you selling it or what.

you'll want to install an MB8719 pll chip if it doesnt have one, there are lots of cool things to do with the 2000.
dont touch the modulation limiter, they have plenty audio. I run the 601 modulator swing kit (for dk control, 1.5w swings to full power), and the NPC mod on the audio chip.
I wouldnt use a d104 maybe its just me, never thought they worked well with the dynamic. I installed the_mod, gives me -79 thru 108 channels and has a 3 digit chnl display, no extra switches, roadmaps or drilled holes. Also got ikes blue feq counter led and board. colored the meters to match the leds.

here is a crappy cellphone shot,


933 RiffRaff


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[madsage]

I don't see the point in doing the NPC/RC mod if you don't remove (at least) the AM limiter...

Am I missing something?

yes it reduces rfi and splatter when I drive the 2x8 davemade with it.
the modulation control is also wide open, doesnt matter if you are 120% or 180% over modulation, you are still producing negative modulation peaks.
cutting the limiter transistor or its resistor just makes it splatter more. but thats another thread. there are already 4 or 5 on that very topic.
the npc is to negate the negative effects of removing the limiter completly of course. I found I had more than enough modulation with just turning up the control.


933 RiffRaff

[madsage]

I was going to try lowering the resistance on the limiter collector. decided it sounded fine.
did not want to completly eliminate the limiter. i'll experiment with it some more again soon.
i do get over 100% modulation. it kills the internal modulation meter and an external as it is.


arizona 933

[Black Lightning]

FWIW, madsage, your 2000 sounds kick butt out here ... leave it the way you have it set up, there is an argument for doing it the way you did.

[drdx]

Wow, a guy asks a simple question and the tech purses start swinging. I love it. Anyway, get that mic issue worked out and use it a bit before you act too fast. Those are great radios with excellent receive. If you plan to keep it and are the modifying type of personality, have at it, but in the long run you may be wiser to not modify it to death, especially in regard to resale value. It just depends on what you like. I don't think there's a wrong approach as long as you don't just ruin it. In stockish form its value will only increase.

Personally, I'd leave the clarifier locked but that's a whole debate in itself.


If you need a high quality cb base, keep it. If not, sell it off. The speakers are worth money all by themselves and having 2 of them is nice.

-drdx

[TheCBDoctor]

Hi,

I would not do half of the modifications that many older print publications would suggest or what is found on the Internet. Also, the Cobra 2000 GTL never came with an MB 8719 PLL.........ever. The FCC stopped it before it hit production for the USA. The Cobra 148 GTL mobile, which is the exact same radio as a 2000 GTL, came with the MB 8719 because it came first and the FCC did not catch on until after it was already type accepted by them.

The Cobra 148 GTL also came with a 11.3258 MHz crystal, unlike the 2000, which came with a 11.3250 MHz crystal. It is not a big deal unless you intend to unlock the Voice-Lock and align the USB so the control is top dead center. Replace the PLL and put in an 11.3258 MHz loop mixer crystal and you have the same radio as a Cobra 148 GTL.

Respectfully,

[Foxhunter]

I just got a Cobra 2000 tonight. How do I tell when it was made? It says it was made in Taiwan but not when. He said the only thing ever done was it was tuned when he bought it. It doesn't have any extra channels or the voicelock opened. It has two speakers and a TUG-8 with the sideband head on it. The mic doesn't work, but he said when I bought it he thought there was a problem with the mic plug. How much is this worth? I am going to try to get pics loaded later from my phone.

What should I do with it? Have it tuned up again? Sell it? Leave it stock? Or have channels added and the clarifier opened? Who would you recommend for the work? :r&r:

Any constructive input would be appreciated.

Thanks, 213

Hey I see others have given you some advice to choose from already so I won't very much. Can I ask what you paid for it and how you got it ? (I like to hear these kind of stories)

Which Astatic SSB mic do you have 10-C, 10-D, 10-DA, which? Hopefully it's just the plug on the mic and not the element or you'll have problems getting the right replacement. From what I read, (it must've been a fad at one time) but many of these style mics had their elements get holes poked into them with pins or ice picks by guys trying to alter their sound.

Now this is just me, but if it is a bone-stock Cobra 2000GTL I'd leave it fairly close to staying that way. If I had it to do over again, I'd have left my first one all-original with just a basic tune-up being done. Maybe just have done a straightforward tuneup and SSB alignment etc which is sometimes needed on older sideband radios over time (unless it's been in the shop for service already recently already).

For servicing it maybe try one of our Sponsors, a Cobra 2000GTL specialist Rick The CB Doctor. Sounds like he knows this particular radio inside out, it's all he does day in and day out (well, I'm sure there are a few other models too).



Foxhunter 351 NJ

[madsage]

Hi,

The Cobra 148 GTL also came with a 11.3258 MHz crystal, unlike the 2000, which came with a 11.3250 MHz crystal. It is not a big deal unless you intend to unlock the Voice-Lock and align the USB so the control is top dead center. Replace the PLL and put in an 11.3258 MHz loop mixer crystal and you have the same radio as a Cobra 148 GTL.

Respectfully,

you can also use an 11.1125 i think it is. and chop 40channels off the bottom and add them to the top, putting its upper limit around 28.800 -15 thru 179. it does require some additional broadbanding of the radio, i've yet to perform this so i just left it at -79 thru 108 for now.

thanks for the flowers there Black Lightning, its mostly just a stock 2000 with purdy lights. They just sound great even without modding them. not big on power for sure, it is a single final radio, but the audio makes up for it easily. the pll bcd counter and channel led driver is done by another great bunch of guys keepin the radio alive.

Anyways thats a nice find that Cobra 2000, and the fact that its not been modified by somebody else does make it even more special.
I hope it serves you well, and that you got some ideas from the discussion.

933 RiffRaff
in the stickers

[TheCBDoctor]

Hi madsage

If you put an 11.1125 MHz crystal and leave the MB 8734 in place the radio will go lower in frequency. You would need to put in an MB 8719 and ground pin 10 to get it back to the normal CB frequencies. If you ground pin 10 on an MB 8734 the chip will pop. Most conversions require putting in the MB 8719 and uses pins 10 and 11 for the standard conversion. This conversion misses too many channels 41,42,43,44,46,49.

The other option is to use a 6 pole rotary switch to avoid missing these channels. I would never drill a hole in a Cobra 2000 GTL. They are worth more unconverted. If you choose to substitute the loop crystals the values are 11.1758 MHz for 40 below CB-1 and 11.4758 MHz for 40 above CB-40. I also would take the 11.325 MHz out and install an 11.3258 MHz for the normal CB frequencies. This will allow everything to align nicely. If the voice-lock is opened you must use the 11.3258 MHz crystal to get upper side band to go to to dead center, otherwise every time you use USB you would have to move the voice-lock to 11o'clock.

Right now, with the dollar tanking, the price of radios on eBay are falling. A fine or mint Cobra 2000 GTL with two matching original factory speakers is worth about $400. That is what that set up wholesaled for back around 1990. There was a time just 3 years ago you could have gotten $550 or more. No one is buying right now.

I like the Cobra 2000 GTL stock just like it comes from the factory. If you want channels, and not have any roll off, I suggest a Uniden HR 2510.

Respectfully,

[tx213]

Thanks for the suggestions guys.

Foxhunter how do I tell which head it is? I got very luck on it. Guy saw my 10k antenna yesterday and asked what it was for. He said he used to be into CB back in the 80's and still had his base up in his closet and wanted to know if I would be interested in it. When he told me what it was and that he wanted $50 for it I almost passed out. It looks good to me. The man said he bought it used it for a couple years then got married, moved and never hooked it back up. It has been in his bedroom closet boxed up since the mid 80's. It seems to be working good. Looks stock. DK 5 swings to 15 on my meters. Everyone says it is loud with an old stock mic on it. The one thing wrong is that when you put the voice lock at 12 the counter shows 27.1848. Other than that the counter/clock works great.

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[721HACKSAW]

$50??? I will give you $100 for it and pay shipping!!! You are a lucky person, listen to the Doc he is the man on those from what I know. I am still looking for one that hasn't been hacked to death.

[drdx]

That's a great find. That goes to show that even way after the fad, there is stuff like that out there yet to be discovered. People are packrats and some never throw anything away. If you got it with the original box, keep it too.

-drdx

[Foxhunter]

Good story and $50 boy that's sick . You hit the jackpot my friend, unmodified and with TWO speakers? You got everything for the cost of one single speaker alone. I never get deals like that, never had that kind of luck. Yeah I wouldn't touch that puppy for all the modifications etc if it were mine, no way. I'd rather buy one already modified or trade someone (me lol) who has the extra channels etc in theirs already and do a swap.

Now they say those "10-D" type mics are best used for sideband. Although I have one, I can't personally attest to that yet. There are several different versions of this mic and they all look nearly/completely identical. There should be a black & silver Astatic ID tag below the mic head on the front that tells you what model it is. Like on many Astatic mics, unfortunately over a period of time the label gets damaged or removed at some point. I've tried to post for help in this area myself, with little help given in reply. I have a "10-D". Many seem to have "10-DA" mic's. Mine sounds good in a Dalcomm MTC-101 mic tester, but haven't tried in on-air.

I've found twice now by buying Cobra 2000GTL's that have been sitting unused that the meters end up sticking at some point in the first hour or two of use. I'd leave the radio plugged in and on sitting idle for a day or two before using it. Not absolutley critical, but I would. It's usually a good policy for equipment that's sat in storage for years.



Foxhunter 351 NJ

[TheCBDoctor]

Hi Guys

The worst thing you could do to Cobra 2000 GTL is not use it. The meters have a tendency to get stuck if it sits unused for a while. There is a trick to fixing the meters. You need a steady hand, just the exact size screwdriver with a good grip handle, and some scotch tape. Remove the cover off the meter, make sure you do not touch the decal or you will leave a finger print. Turn the adjustment slightly to the left until the meter is free. There is usually some lock-tite on the set screw. You may have to scrape it off.

Never ever use contact cleaner. The most important thing is the exact size screw driver with a good size hand grip. A jeweler's screwdriver will not cut it. Don't press down while turning. Once the screw is botched forget about repairing the meter. That is the trade secret to fixing them. Some times you may have to ruin a couple to get the hang of it, but it wasn't working anyway.

Never touch the adjustment on the back of the meter and when you are finished put some nail polish on the set screw, just a little so it can be repaired again if need be. Put the tape back on the front cover and you are done.

It is an inherent design flaw. The radio was designed for an external 13.8 volts DC, but if you put it in a vehicle the needles will fall off the movement from the vibration. Some free advice from The CB Doctor. Use it wisely and pass it on. I can't take the knowledge with me so someone should be there to carry on.

Fifty dollars for 2 speakers and a unmodified Cobra 2000 GTL? Boy, did you step in some lucky $hi...............................t

Respectfully,

[tx213]

Fifty dollars for 2 speakers and a unmodified Cobra 2000 GTL? Boy, did you step in some lucky $hi...............................t.

Don't I know it. I was in the right place at the right time. I was in a town about 20 miles from where I live that I never go to. I was meeting a guy there to do some trading and after that stopped to get gas. That is where the guy saw my antenna.

I'm sending a PM too.

Thanks, 213

P.S. The trade was a Cobra 21 for a new Wilson 5000 magnet mount without a whip. A guy bought it from a whole sale place online and did not know there was not a whip with it so he put it on Craigslist for trade. I am going to try a spare 10k whip on it tomorrow if I get the chance.

[Foxhunter]

Rick the CB Doctor thank you very much for sharing that. I think some will find that valuable advice and if they are at that point have little more to lose and everything to gain. Thank you, just wanted to say that and not let that go without a reply.

Foxhunter 351 NJ

[madsage]

Hi madsage

If you put an 11.1125 MHz crystal and leave the MB 8734 in place the radio will go lower in frequency. You would need to put in an MB 8719 and ground pin 10 to get it back to the normal CB frequencies. If you ground pin 10 on an MB 8734 the chip will pop. Most conversions require putting in the MB 8719 and uses pins 10 and 11 for the standard conversion. This conversion misses too many channels 41,42,43,44,46,49.

The other option is to use a 6 pole rotary switch to avoid missing these channels. I would never drill a hole in a Cobra 2000 GTL. They are worth more unconverted. If you choose to substitute the loop crystals the values are 11.1758 MHz for 40 below CB-1 and 11.4758 MHz for 40 above CB-40. I also would take the 11.325 MHz out and install an 11.3258 MHz for the normal CB frequencies. This will allow everything to align nicely. If the voice-lock is opened you must use the 11.3258 MHz crystal to get upper side band to go to to dead center, otherwise every time you use USB you would have to move the voice-lock to 11o'clock.

Right now, with the dollar tanking, the price of radios on eBay are falling. A fine or mint Cobra 2000 GTL with two matching original factory speakers is worth about $400. That is what that set up wholesaled for back around 1990. There was a time just 3 years ago you could have gotten $550 or more. No one is buying right now.

I like the Cobra 2000 GTL stock just like it comes from the factory. If you want channels, and not have any roll off, I suggest a Uniden HR 2510.

Respectfully,

Cb Doctor,

I do not skip any channels. infact I also have the alpha channels, 3A, 7A,11A,15A,19A it currently goes channel -79 thru 108 with a 3 digit channel display. 26.1750 - 28.0850.. If you use the 11.1125 crystal nothing changes except now you are -15 thru 179. Putting the radio up fully into teh 10meter band plus Cb and everything between. Its very cool mod. It interfaces to the PLL and provides binary bit counter via its own small processor and 3 channel led driver.

There are no hacks or holes for rotoray switches, no hacked switches for channel banks, no roadmaps, You just turn the dial. Even your 2510 your have to switch banks. If i'm not mistaken. .. here you should check this out. [Please login or register to view this link] I can also add if desired, a channel up and down button, and a home channel button and scanning. imagine that. channel scanner on a damn 2000! I did not want to drill or cut, so i left those features out for now.

By the way, the board version in that URL is very old. they are not even close to that size today, everything or on a pic (single prom and cpu) now.

933 Arizona
in the supes

[TheCBDoctor]

Hi madsage

You may noticed I said a "standard conversion" this involves using 2 switches. You will skip 41, 42 ,43, 44, 46, and 49. What you have is a kit that uses a EEPROM to utilize the entire radio's capability without skips. it requires replacing the display and is very labor intensive.

I see no reason to do that to a Cobra 2000 GTL. The problem is that even if you manage to get all the channels the total amount that can be used without a drastic roll off is 100 channels. After that the radio must be broad-banded, which causes cross talk and bleed over. If you want a radio to do 26 to 29.999 MHz you should buy a radio that is designed for that purpose. The Cobra 2000 was designed for 40 channels and has the ability to go about 20 channel above CB channel 40 and 20 channels below CB channel 1. After that the radio's performance drops off drastically.

You can not just put in an 11.1125 loop mixer crystal in place of the 11.325. The frequency will be below the CB band. Since the MB 8734 can not have Pin 10 grounded without being destroyed. You must replace the PLL with a Fujitsu MB 8719 and gound Pin 10 to get back to the CB band.

If you put an 11.325 MHz loop crystal in a Cobra 142 GTL you will be at 27.6050 MHz on Channel 1. You must cut away the ground from Pin 10 on the MB 8719 PLL to go back to the CB band. Originally the Cobra 142 GTL grounded pin 10 of the MB 8719 PLL and used an 11.1125 MHz loop mixer crystal. It was done because pin 10 of the MB 8719 determines if the radio will use an 11,1125 or an 11,3250 MHz crystal as a loop frequency. When the Cobra 148 GTL came out, Cobra decided to use an 11.3258 Mhz crystal and leave pin 10 ungrounded. They knew what they were doing, but the FCC caught on and required the PLL to not have the Pin 10 option on the Cobra 2000 GTL, so the MB 8734 was designed and installed.

Your radio has an MB 8719 PLL and the EEprom is doing the binary count to get the radio to cover above and below the CB band with the "A" channels included. Your radio is worth less than a mint untouched Cobra 2000 GTL because it has been modified. it is the same as if you have a mint untouched Ford Mustang. It is worth more than one that has been modified or restored.

The performance of you radio can not be good below say 26.7150 and is just as bad at 27.7150. The radio was not designed for that range. Most Expo kits will allow the radio to go from 26.5150 MHz to 27.8150 Mhz. but the performance range is less than the channel coverage. A standard Conversion will allow the radio to go from 26.8150 to 28.0045, but the performance does not extend to that range as well. Your EEprom conversion with the 3 digit display looks nice but the radio can only do 100 channels tops at best. Trust me when it comes to the Cobra 2000 GTL I have seen it all.

A good investment is buying a mint 2000 GTL with the original factory speaker that came with the radio. Any modifications has decreased the value of the radio. As for the HR 2510, the UPC 1250 microprocessor adjusts the varactor diodes in the tuned circuits to compensate for the band coverage. It will perform just as well at 26 MHz as it does at 29.695 MHz because it was designed to. The Yaesu 101 uses relays to do the same job.

I may be in error on some things, and I make mistakes as does anyone else, but when it comes to the Cobra 2000 GTL and the MB 8719 Uniden chassis I know of what I speak.

Respectfully as always, The CB Doctor where advice is always free.

[Circuit Breaker]

To each his own opinion but the whole purpose of the NPC/RC (negative peak COMPRESSION) allows you to have greater than 100% positive peaks while keeping the negative peaks in check. I don't think you gained anything by using that mod if your positive peaks are under 100%...

But that isn't really possible. When you go past 100% on positive peaks, you cause splatter.

[madsage]

Cb Doctor,

Yep you are right. I think i have my crystals backwards. 11.11325 for upper and 11.1125 for the lower capabilities.
And roger on the broadbanding, mine started dropping out quickly at about 27.75, removing R95 gave me a little more. I thought i mentioned 8719 pll installed.
its usable on 28mhz but easily less than half power of center, same with the receive. There is more I can do yet, but like you said, the right radio for the job.
a ts-450 works 10meter much nicer on ssb. Its been a fun radio to modify and I certainly dont regret it. I believe you are wrong that my radio is worth less now. Maybe to a vintage collector, but they go for much more on ebay with the_mod. But i didnt build it for that, I wanted it for me.

933 Arizona

[Black Lightning]

To each his own opinion but the whole purpose of the NPC/RC (negative peak COMPRESSION) allows you to have greater than 100% positive peaks while keeping the negative peaks in check. I don't think you gained anything by using that mod if your positive peaks are under 100%...

But that isn't really possible. When you go past 100% on positive peaks, you cause splatter.

What determines 100% on the positive peaks? It's the negative peaks that run you into trouble. It's when they wrap around that you get distortion and it's this distortion that causes splatter. Increase your positive peaks without increasing your negative peaks and the net result is you increase your power. This is the theory behind this mod - that average power along with carrier power actually increases with the modulation of the transmitter.