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Cobra 150GTL-DX

Now this really sucks.

Got the sack of TDA2005 audio power chips. Changed the one in the radio. Not for the faint of heart, that.

Fire it up and SAME PROBLEM ! !

Bummer. Sounds, modulates just fine on a "AAAAAAAH". But on a "HEEEEELLOOOO" the modulation cuts out for bursts of 20 mSec or so, and drops to half-level for bursts of 200-300 mSec. Slack off, take a breath and it's okay so long as you don't say the wrong thing. Nutty. No way it's smart enough to tell what I'm saying, computer or no computer.

Still, it goes nuts on some syllables and not on others. Gotta be RF getting in somewhere it doesn't belong. The TDA2005 has more 'protection' and 'shutdown' circuits in there than you can shake a stick at. Best (educated) guess for now is that RF is leaking into one of those protection circuits and "bleeding" it like a neighbor's $7.95 Walgreens' telephone.

AAAAARRRRRGGGGHHHH ! ! !

So, not only did Cobra design this thing without asking anybody what they want on the front (Variable key, anyone?) but they forgot to try it with the modulation limiter disabled. Nice.



73
 
its ok before when i had my antenna closer to the house everytime someone would call i would have to shut everything down because if i keyed the mic it would be like i was talking on phone. :) But it sounds like a nice radio .
 
The +10 switch is puzzling and from the pictures I have seen of the 200, it too includes a +10 switch. It is always nice to have a spare front panel switch. I just wonder if it was done on purpose maybe to include 4 more positions on the ABCD band switch?

Nomad, looking forward to reading the rest of the 150 review, also hoping you do the same type of review for the 200 when it is available. I am very curious how the receive on these radios stacks up against the other current offerings. Nice to see factual real world data presented with your unique style.

Keep up the good work (play) Nomad! :-)

73

riq165
 
"Fire it up and SAME PROBLEM ! ! "

try re-enabling the amc by restoring Q64. there was nothing
wrong with the 2005. you created the problem.

"but they forgot to try it with the modulation limiter disabled."
yeah, right.

low power: 4 Watts Carrier, 35 Watts PEP
high power: 15 Watts Carrier, 60 Watts PEP
 
Nice try, Freecell. Does it with AND without AMC. Both.

The point is that their market is populated with users who want it to work with the AMC clipped. You may not approve. I may not approve. Doesn't affect the behavior of that market.

Ignoring what a particular market's participants VOTE for over and over is irresponsible business practice, whether you're a drug dealer, a "dual-use" radio supplier, or General Motors. Same rules apply.

73
 
"Nice try, Freecell. Does it with AND without AMC. Both."

sure, but would the problem exist if the amc was never disabled in the first place? haven't seen it in a dozen of them so far.

"Ignoring what a particular market's participants VOTE for over and over is irresponsible business practice,........blah blah blah, blah blah blah blah."

you're right, that would require someone along the line to have some scruples and to adhere to some standards. if you think that accomodating a bunch of morons by facilitating the destruction of circuitry constitutes responsible business practice, that's your opinion and you're welcome to it.
 
Well, if you're up to a dozen of them, that's 11 more units' worth of statistical knowledge than I can claim.

At one level, it's relief to hear that a string of 12 units do NOT exhibit this bad habit. That would be genuinely unpleasant.

Another (one) unit is on the way, at least to compare and decide what to do next. That's why I've had no more to say on the subject this week. Need more data.

On the other hand, if you have twelve customers who have no desire for a carrier-power control, that's borderline astonishing. Pleased to hear that you only accept customers who fully abide the law and run the radio barefoot.

And all of them on 10 meters, with legit ham licenses.

Naturally, you're free to turn away users who don't walk the straight and narrow, every time. And you're free to characterize that business policy as "intelligent", should you choose.

Besides, you're also free to pretend you're still in fifth-grade recess and make personal characterizations, all with NO first-hand evidence from which to judge.

One good thing about this radio. You can't just use Vice-Grips (r) to rip out the AMC transistor by its roots.
 
"On the other hand, if you have twelve customers who have no desire for a carrier-power control, that's borderline astonishing."

not really, once you understand that an am transmitter (or same driving an amplifier) is fully modulated once the peak-to-carrier reaches 4:1 and all of this "swing" crap is just exactly that, crap.

at 4 & 35 it drives a small 250 in the medium power position to almost exactly 4:1, wiith peak-to-carrier just slightly higher with the amp in the low power position and just slightly lower in the high power position, assuming three available power levels.

with respect to the two power levels provided on the front panel of the radio, carrier power is controlled by the pre-sets on the board. so the user has the option of either operating the radio in the high power position without the amplifier or selecting the low power position and another 3 power levels at the amp, without destroying the amc circuit or the addition of any other modifications.

as to the 10 meter comments, no one will be operating any of these radios above 27.995 unless they present the required license. with all due respect to the amateur community, that's what i call a "pro-active & responsible business practice."

as to your current dilemma, you may want to consider the possibility that the disabling of the amc (Q64) may have caused some other component damage in the surrounding associated circuitry that cannot now be compensated for by re-enabling it.. since we are not in the habit of disabling amc you may want to leave it intact when you receive your next 150, at least until you have an opportunity to check it out thoroughly after conversion before repeating the same procedure again. i have no doubt that we will see our share of 150's in the same condition as your first test rig and we'll worry about it then. when we do you can count on further input.
 
I for one have to applaud cobra for bring a SMT radio to the market. Now lets hope the quality is their. I think the performance is gonna be fairly good on tx and rx on these. But Joe Blow CbShop can't service them.
 
OK guy,s heres the fix for the audio cliping that we have expereinced,,,,
I got another 150GTL-DX in today,,,,out of the box ,,opened the Freq.'s up,,,and didnt touch the audio limiting,,,and it also had the same problem....So as far as i can see,,,there is just not enough care being taken when building these things....or they just dont have the time to make the correct adjustments before they shove them into a box,,,which is probibly the case,,,and i can understand that....anyway,,I would say to do this to all of these radio's and it should be fine,(or at least the ones i have seen needed this to correct the problem).

Vr-9 adjust for NO More than 4 watts,,This is the low carrier adjust...

next

Vr-4 adjust this for NO MORE than 96%modulation,,I adjusted to about 95% and all was still ok,,,over that and its back to choppy audio....

next

Vr-12 also set to no more than 96% modulation....I also set about 95%....

after this the audio sounds fine,,,and low power peaks were around 35watts,,,and high power peaks were around 55watts..

I will post a diagram later,(as soon as i get a chance to put one togather) should be later tonight...

I hope this helps some of you not have the problem at all,,,if you do this out of the box,,,before trying to adjust coils and the 27mhz peaking coil,,,ya should have nice clean audio....
As far as those of you wanting that Ripping LOUD Raspy audio,,,,Sorry....dont buy this radio,,,,it aint gonna happen!!

I'm sure Nomad will get started on the swing module very soon..

One more thing,,,if i've misspelled anything or used the wrong grammer,,,,please excuse me,,,cause my fingers move faster than my brain....lol


:edit:
No need for diagram...Nomad has all the info ya need in this thread,,,look at pic's



rfpowerman 8)
 
good call, rfpower. your findings coincide with what we have found here with one "conditional" exception.

"before trying to adjust coils and the 27mhz peaking coil........"

if you intend to operate the radio outside the 27 mhz. band i would strongly recommend that you also leave these adjustments alone to maintain uniform power throughout the full frequency range of the radio.
 

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