| Author |
Message |
    
Canon5218
Junior Member
Username: Canon5218
Post Number: 15
Registered: 8-2006
| | Posted on Friday, August 25, 2006 - 7:20 am: | 
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Alright here is the issue I am having. When the radio is first fired up I am transmitting up freq about 1kHz and Tx audio is garggled. Audio almost sounds like mic gain is overdriving it. Thats the "cold" report I am getting from my uncle and here is the "warm" report.. Once warmed up I am on freq (actually a hair low) and audio is great.
Anyone have a clue why there is so much drift here and what can be done to help correct. |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1339
Registered: 6-2004
| | Posted on Friday, August 25, 2006 - 9:02 pm: |
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Drift from cold to warm is normal. Most SSB CBs I've used typically drift from 300Hz to 400Hz, but 1kHz isn't uncommon especially if the clarifier circuit has been modified for greater swing. Is the 1kHz a guestimate, or is there a reference being used?
When your signal is clarified, is the audio still distorted? |
Oldpirate
Member
Username: Oldpirate
Post Number: 96
Registered: 11-2003
| | Posted on Saturday, August 26, 2006 - 4:35 am: |
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These newer Cobra radios drift like Crazy. I bought a new Cobra 148NWST and this would drift all over the place. Anything up to 300hz off frequency was normal and that was hot and cold. I have an older Uniden Grant and that thing is rock solid on frequency hot or cold, no drifting at all.
Quality control went out the window when Cobra stopped making their radio's in the Philippines and went to China. The last good cb's were the Uniden Grants and the TR296 from Texas Ranger. |
Canon5218
Junior Member
Username: Canon5218
Post Number: 16
Registered: 8-2006
| | Posted on Saturday, August 26, 2006 - 9:19 am: |
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The reference being used to determine the amount of upward drift is when communicating with my uncles base station he can't clarify me until he gets up the band approx. 1kHz.
No mod's to the radio what so ever...no clarifier...nothing modified. Straight out of the Chinese Box.
If I was do do an alignment on the thing it would be WAY off when at full operating temp and right on when first turned on and cold....right?
Anything that would be checked to further determine the problem and come to a solution? |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1688
Registered: 1-2005
| | Posted on Saturday, August 26, 2006 - 1:56 pm: |
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Canon, An alighnment of the new GTL models is a must. Of all the 148 GTL's I know of not one had exceptable SSB performance out of box! After a tuneup my 148 gets flowers from everyone. Drift is just something we all have to deal with especially in the mobile when temps are always changing. Even my Connex drifts until a stable temp is made. Once you get a reliable tech to tuneup your 148 things should be OK. Gonna drift a little, you can't help that. Too many nit pickers these days on SSB to let you know your off a little. Those guys are not there to have fun and DX. |
Unit199
Intermediate Member
Username: Unit199
Post Number: 312
Registered: 8-2003
| | Posted on Saturday, August 26, 2006 - 6:37 pm: |
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THE COBRA RADIOS THAT I HAVE HAD EXPERIENCE WITH THAT HAVE FRONT MIC CONNECTORS ARE THE ONES THAT HAVE ALL THE ISSUES. SINCE THEY HAVE WENT AWAY FROM THE SIDE MIC CONNECTOR AND RANGER STARTED MAKING THEM FOR COBRA, MY EXPERIENCES ARE THAT THEY ARE NOT THE BEST RADIOS ON THE MARKET. IN MY EXPERIENCE THE LAST DECENT 148 WAS MADE IN MALAYSIA AND NONE COMPARE TO THE PHILLIPINE MADE 148. PERSONALLY I WOULD NOT WASTE MY MONEY ON ONE MADE NOW. I HAVE TWO THAT ARE NOT WORKING AND I WONT WASTE MY TIME FIXING THEM. I USE THEM FOR PARTS RADIOS. MY PHILLIPINE AND MALAYSIA MADE 148s BOTH WORK GREAT. JUST MY EXPERIENCE IN REPAIRING RADIOS.
HARVE
UNIT199 |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1341
Registered: 6-2004
| | Posted on Saturday, August 26, 2006 - 7:29 pm: |
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ALL CBs DRIFT FROM COLD TO WARM!!!!! 300kHz is not uncommon - it's typical. CBs don't have temperature compensating crystal oscillators or crystal ovens which are the only ways I know of to keep a radio from drifting from cold to warm.
When you align a SSB rig you let it warm up with the covers on for 30 minutes or so, and check the frequency. Then you take the covers off and let it sit for 30 minutes to let the frequency stabilize and check the frequency again. Then you adjust the frequency with the difference in mind so when it warms back up it'll be close to on frequency. The radio will still drift a small amount with use, and if it's an export or has an expanded clarifier it'll drift even more.
Canon5218 - What is your Uncle using to measure the drift? Is it a frequency counter installed in his radio, or is he using an HF rig?
If he's using a frequency counter just let me say that none of the counters that are made for CB use are very accurate, and may be drifting quite a bit themselves. Frequency counters are only as good as their design, and for $50 you can't expect them to be rock solid.
If he's using an HF rig I'd be more inclined to believe him, but only if the display has been recently calibrated to WWV's frequency. |
Ck29
Junior Member
Username: Ck29
Post Number: 18
Registered: 3-2006
| | Posted on Sunday, August 27, 2006 - 2:44 am: |
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Hollpoint 445, Don't you mean 300hz drift because that would be 300 cycles.
and 300khz would be 300,000hz. |
Canon5218
Junior Member
Username: Canon5218
Post Number: 17
Registered: 8-2006
| | Posted on Sunday, August 27, 2006 - 10:32 am: |
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I understand all CB's drift from cold to warm. This issue seems to be more then a typical drift issue though. The "garggled" audio output when cold almost like it is being overdriven or something makes me beleive there is more going on. |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1344
Registered: 6-2004
| | Posted on Sunday, August 27, 2006 - 8:00 pm: |
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Yep - you're right Ck29! I meant 300Hz, not 300kHz. 300kHz is about 30 channels, and even Galaxies don't drift that much! I normally read over a post first, but I was in a hurry. Thanks for pointing out my mistake. |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1345
Registered: 6-2004
| | Posted on Sunday, August 27, 2006 - 8:23 pm: |
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Canon5218 - Can you stop the audio distortion by varying the microphone gain or clarifying the signal? How long does it last? What size power supply are you using for the radio? Is it warm and ready to go when you turn the radio on, or is it also cold? Are there any sound problems on AM? |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2010
Registered: 9-2004
| | Posted on Sunday, August 27, 2006 - 11:13 pm: |
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from what i have heard, the new front mic style 148's have poor voltage regulation from the factory.
i think there is a fix for that, and i think hotwire's tech did that to his. i could be wrong here.
also, crystals are very expensive to make these days, and you can bet that cobra was cutting every corner they could when building this radio.
the 11.3258 crystal just to the right of the PLL is the one im speaking of.
if you were to replace it with a very high quality crystal, i think it would help your problem alot.
good luck finding someplace to make you just one.
i think your best bet is to have an alignment done, (NOT a peak and tune!) and just let the radio warm up before you talk.
good luck,
matt |
Canon5218
Junior Member
Username: Canon5218
Post Number: 18
Registered: 8-2006
| | Posted on Monday, August 28, 2006 - 7:53 pm: |
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Okay shoot me.....Seems as if my problem wasn't at all related to temperature. Don't know what it seemed that way really but I guess that was the only thing I had to blame it on. Problem seemed to be my poor grounding. Dumb Dumb Attack on my part. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2017
Registered: 9-2004
| | Posted on Tuesday, August 29, 2006 - 10:45 pm: |
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the good news about "dumb dumb" mistakes is that they are usually very easy to fix.
last week i single handedly stalled the show i work at for 11 minutes troubleshooting a bad device, when it turned out to be a breaker that has gotten switched off.
this breaker is right within my line of sight right now.
emabrrassing? yes.
easily fixed? YES! thank goodness.
glad to hear the radio is working,
matt |
Oldpirate
Member
Username: Oldpirate
Post Number: 99
Registered: 11-2003
| | Posted on Monday, September 25, 2006 - 8:24 pm: |
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Canon, these later model cobra's do have a notorious reputation for drifting. I bought a cobra 148NWST (same basic radio) brand new and it was the most frustrating radio I have ever owned. Hot or cold it would drift off by as much as 300hz. I got it fixed by a tech that knew what he was doing and it was very good after that.
Annoying to pay $200 for a radio and then have to pay another $100 to get it to work properly.
Would I buy Cobra again? Definitely not!. I bought it on the reputation that Cobra had when they were being made in the Philippines, not knowing that there quality contrrol had gone out the window. I eventually bought a second hand Uniden Grant and that is one rock solid radio,hot or cold stays right on frequency.
Pirate |
Hyperno_1979
Intermediate Member
Username: Hyperno_1979
Post Number: 180
Registered: 12-2005
| | Posted on Saturday, September 30, 2006 - 10:10 am: |
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I agree with Muzz, the new 148 and the 200 seem to have some serious issues attached to them. In times gone by the 146 & 148 were held in the same high esteem as the Uniden Grant & AX144 over here but looks like that has gone by the wayside. I was thinking about buying a new 148 for nostalgia's sake but after all the reports i have read......NO.
CEFFFCEF
Bob CEF703. |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1827
Registered: 1-2005
| | Posted on Saturday, September 30, 2006 - 2:08 pm: |
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I have never had the chance to use the new cobra 10 meter rigs but I can comment on the new China made 148's. I have owned 2 of the 148 soundtracker models and 2 of the 148GTL models.
All 4 radios needed alignment out of box very badly. All 4 had very unaceptable SSB performance. After major upgrades and alignments by a highly respected tech the 2 soundtracker models performed exceptionally well for 3 years on AM and average on SSB (for a type accepted cb). After daily use of 3 years( base only) one was retired and still sits on a shelf in good working condition. The other ST model used daily for 3 years (mobile) developed some problems. For one it seemed to detune and just did'nt sound like it once did another was the knobs produced a scrathy sound in the speaker when used and the on off volume knob started to mal function. I would turn it on and it would light up but I would get no recieve. Funny thing is that it was not recieving and transmitting on the desired channel but on some other freq unknown causing only distortion to a recieving radio. After turning the rig off and on repeatadly real fast it would eventually return to normal operation. I thought that maybe I had worn out the on off knob. Not so, I believe it was a factory defect caused by cheap componets.
Of the 2 GTL models I used both radios were upgraded for modulation and aligned by the same tech as before. They worked fine just like the others but being brand new BOTH rigs started having the same on off knob problem! Just ridiculous and I feel that the problem with these new 148's is the qaulity of the componets used to build them. You might get a good radio you might not. They have the potential to be really good radios its just that they are so cheaply made. I always got good reports AM and SSB. Sure they drifted around but what can you do? Like any SSB cb without a counter and course clarifier your gonna get drift. Thats what a clarifier is for. I hear all the fuss about radios drifting but thats just the nature of the SSB radio. May take a long time AM mode user to get over it. ANy serious SSB operator should have a rig with counter and dual clarifier to monitor his radios freq. Whenever I make a contact and he is a little off compared to the last contact I just tune without even thinking. I'm to concerned with the QSO to worry about perfection anyway. |
