Question about Cobra 148 GTL 120-Channels Base CB Radio

2 Answers

Cobra 148fgtl low power on am/ssb no swing all finals ok

All voltages seem to be right but still will not show more than 1 watt

Posted by on

  • 2 more comments 
  • worldofcb Feb 07, 2009

    when checking tx mixer ic for voltage on pin 2 or 3 voltage is good and transmit is good when probe is on pin 2 or 3 .When probe is removed transmit is back at 1 watt

  • Don Reiman May 11, 2010

    much more information needed. Some one would have to get a meter on it to see whats wrong.

  • Dutyacx May 11, 2010

    I don't have any schematics available to look at the circuitry and verify your measurements . If you place the probe on these pins (whatever the pins are) and you affect the rig's power output, there is something wrong with the driver circuitry before the mixer. Maybe a small transistor got blown up ? Unfortunately at this point I have no insight how the circuit looks like and what kind of mixer you are measuring on. Maybe you can help me with that ?

  • Dutyacx May 11, 2010

    It sounds your end power amplifier is dead. The output you measure is the power driver. Are you sure your antenna is properly setup/connected ?

×

2 Answers

  • Level 1:

    An expert who has achieved level 1.

    Problem Solver:

    An expert who has answered 5 questions.

  • Contributor
  • 4 Answers

Try adjusting the L36,L38 to the highest reading on the external meter and then adjust VR10 TO 4 watts. If this doesn't cure the problem, you have a weak final transistor. Good Luck

Posted on Oct 17, 2009

  • Level 1:

    An expert who has achieved level 1.

    Corporal:

    An expert that hasĀ over 10 points.

    Mayor:

    An expert whose answer gotĀ voted for 2 times.

    Problem Solver:

    An expert who has answered 5 questions.

  • Contributor
  • 13 Answers

Cobra 148 GTL if you do not receive and turn on to the carrier does not transmit or let you change the color

Posted on Oct 31, 2009

  • manhattanlav
    manhattanlav Sep 22, 2014

    hola como puedo comprar un transistor eleflow (cb-20w) y diagrama para hacer ajustes del cobra 148

×

1 Suggested Answer

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi,
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
goodluck!

Posted on Jan 02, 2017

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

2 Answers

Can i use a 10 amp power supply run my cobra 29 and 100 watt linear


I will answer the question. Figuring that 10 amps is continuous not peak. 10 amp multiplied by 12.5 it should be good for 125 watts. But you are on the ragged edge. I do agree you should lower dreaded key but you did not ask that question. But a swing kit will solve that. That is amusing SSB and the 80 watt cobra 29 comments.

Apr 21, 2014 | Cobra 29 LTD CB Radio

1 Answer

Can you turn the rf gain pod up for better receiving


Yes you can turn up VR pot inside to recieve max level but will cause noise to be max too. I don't rightfully remember which one does it but I'll refer you to Defcom cb radio mods for a spec sheet
or Snakedoctors cb radio mods google site. Go to these radio mods sites on Google search and type in radio model. It will tell you what Vr inside to turn up RX of RF gain. Turn up modulation and written instruction if you are handy with solder gun how to change a resistor or cap to make it more sensitive recieve. How to replace final stage and resistors to 1/2 watt size for 6 more watts output and spread coils 1/8 inch apart like a comb for 100% microphone loudness or swing output. say 3 watts to 40 watts output. More windshield wiper swing in meter makes loud voice and extends range with Power final boost. Most people prefer to keep a mobile at around 11 watts swing to 45 watts.(but on generic radio meter will show 2 to 5 watts-its not accurate just a cheap indicator you are forward swing). Even though factory says 4 watts FCC hogwash. They come tuned from Cobra with 11 watts to 14-22 watts.Cobra really peaks them babies so competition doesn't beat them out like new louder radios made by Galaxy 55. Even though law says blah blah (corporations bend it)sales pitch Galaxy very heated with Cobra on the game(rich can do what they want)Galaxy is 20 watts factory with big promise to 40 watts dual finals. So Cobra updated and said "screw it we will break the law too" Now Cobra is loud as ever and offering their own super mod versions and dual final radios with 45 to 65 watts output with ranges on SSB & USB of 1500 miles on a strong good outdoor antenna.

Feb 15, 2013 | Cobra 29 LTD CB Radio

2 Answers

Cobra 2000 with a d 104 mic and a palomor tx100 bi linear amp...how can if possible make the amp key up with less than one watt on the ssb side..Radio has a 4 watt dead key on am and i have ajusted the...


Hi, my name is John. Adjust the radio to key 1 watt, then switch to SSB on radio,then switch to SSB on amp, key down and adjust to 1 watt on amp. enjoy !!!!!! ...hope this was very helpful....

Aug 31, 2010 | Cobra 148 GTL 120-Channels Base CB Radio

2 Answers

I have a 77 that has got hardly any swing anymore.it keys 3-4 watts and won't swing past about 8 watts.i used to get 25 watts plus swing out of it. i have replaced the finals and it did not help.any ideas?


Is this just on the AM side or also on SSB?
If you type in 77HML or Galaxy 77HML in your Search Block,you should have a listing for cbtricks.com. and it should say Manual.This will give you Schematics,Transistor Voltages,Parts Placement and Specifications anything you would need is on this page.There are 3 Transistors on the Back Right Corner of the Radio looking at the part side,TR-49 is a predriver for TR-50 and TR-51,which are your AM Modulation Transistors.Hope this helps you out.

Jan 24, 2010 | Galaxy Radios DX 77HML Base CB Radio

1 Answer

Cobra 29 modulation modification


did you make sure the caps stripe is facing the back of the radio? If not, its the wrong way.

Also, don't use a 1/4 watt resistor because it will get too hot for it to last. use 1/8th.

changing the cap size will not change output, however it will change the tone. Bigger the cap, the deeper the tone of audio.

to be honest with you, high output mods are worthless in these radios. they are fine with out them. mosfets are unstable and are very dirty transmit finals. As well if you are planning to use a linear you may hit it too hard unless its a high drive, in which case you will need more then 35 watts swing to drive it fully. A stock cobra 29 that has been peaked and tuned, then the swing mod put in, 220uf e cap and 100 ohm resistor, which should give you about 2 watts, should swing to about 27 watts, and kick an amp in the pants.

I run a cobra 29 in my blazer with a dave made 5 pill, and I key on 6 pills and I near keyed on a 2x8. very close. All that I have done to the radio is peak and tune, (of course I have a few tricks with that up my sleave which I don't usually share with just any one.) and variable power, wich will control the dead key, which is basically a varible swing kit. I run it just under 2 watts, just enoug to get a 125 watt dead key out of the amp. The amps swings over 920 watts.

any more swing from the radio will beat up the pills in the amp.

Jan 06, 2010 | Cobra 29 LTD CB Radio

2 Answers

How to adjust frequency on transmit??? Galaxy


hELLO THERE
hERE IS SOME MODIFICATIONS FOR THIS RADIO
Galaxy Mods DX 2527 - VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR11...Driver Bias, VR12...SSB ALC, VR13...Hi Power, VR14...AMC, VR15...AM Low Power, VR16...SSB Low Power, VC 1....10.240, VC 2....10.240. DX 2517- VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 5....FM Deviation, VR 6....SSB Carrier Balance, VR 7....TX Offset, VR 8....CW Beep Level, VR 9....RF Meter, VR10...Final Bias, VR11...Final Bias, VR12...Driver Bias, VR13...SSB ALC, VR14...AM/FM High Power, VR15...AM Modulation Meter, VR16...AM Modulation, VR17...SSB Power, VR18...AM/FM Low Power, VR601..13.8 Volt Power Supply. DX 22B- VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR11...Driver Bias, VR12...SSB ALC, VR13...High Power, VR14...AMC, VR15...AM Low Power, VR16...SSB Low Power, VR21...TX Offset, VC 1....10.240, VC 2....10.240. DX 11B- VR 1....AM/FM S-Meter, VR 2....SSB/CW S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 5.....FM Deviation, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR10...Final Bias, VR11...Driver Bias, VR12...SSB ALC, VR13...AM/FM High Power, VR14...AM Modulation, VR16...CW Tone Level, VR20...Final Bias, VR21...TX Offset, VR601..13.8 Volt Power Supply, VR803..AM/FM Low Power. DX 77HML, DX 88HL, and DX 99V- VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 5.....FM Deviation, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR10...Final Bias, VR11...Driver Bias, VR12...SSB ALC, VR13...AM/FM High Power, VR14...AM Modulation, VR16...AM/FM Low Power, VR20...Final Bias, VR21...TX Offset.
Unmarked VR in R189..AM/FM Medium Power for DX 77HML only. DX 33HML, DX 44V, DX 55V, DX 66V, and DX 73V- VR 1....AM/FM S-Meter, VR 4....AM/FM Squelch Range, VR 5.....FM Deviation, VR 8....RF Meter, VR12...Low Power AM Modulation, VR13...AM/FM High Power, VR14...High Power AM Modulation, VR16...AM/FM Low Power.
Unmarked VR in R188..AM/FM Medium Power (DX 33HML only)
Unmarked VR in C139..Med Power AM modulation (DX 33HML only) DX 949,DX 959- VR 1....AM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM Squelch Range, VR 6.....SSB Carrier Balance, VR 7....TX Offset, VR 9....RF Meter, VR10...Final Bias, VR12...Driver Bias, VR13...SSB ALC, VR14...AM High Power, VR15...AM Modulation Meter, VR16...AM Modulation, VR17...SSB Power, VR18...AM Low Power, VC1....10.240. DX 2517 and DX 2527-
Symptom:Buzzing or motorboating sound in either the transmit or receive.
Problem: TR602 is oscillating
Cure: Replace C602 with a .01uF cap {Cap is located in the power supply board}.
RG 66,99,DX2517 Replace Q54 2SB754 60watt 7A with a higher power 2SB817 100 Watt 12A. Derating of this component will cool operation, provide better voltage stability,decrease wobble, allow voltage increase to 14.5 volts comfortably. (replace 10 volt caps in this section of the radio to a minimum of 16 volts before increasing supply voltage to this level)and provide faster swing rise time, Replace Q37 2SA473 to a 2SA1012-0 or ECG153 this will improve the clarity and volume of the modulation and it will also run a lot cooler.

Nov 12, 2009 | Galaxy Radios DX-949 40-Channels Base CB...

1 Answer

Tunring up a cobra 150 gtl/dx


Um... What?? This is hooked to a switch? CB radio by FCC regulations is only supposed to have a max of 4 watts total output. If you can flip it to 7 watts dead key, you are doing really good. It won't do much more then that. It sounds like its set up to run on a linear amplifier, which cannot have more then 3 watts dead key transmitting into it.

Dead key, and modulation are different. You may have a meter that only reads dead key, and won't see the modulation. This radio is probably swinging close to 15-20 watts. you need a meter that can read PEP, Peak envelope power. Cheap meters only read AVG, or average power, witch will only show your dead key.

7 watts dead key is really good for that radio.especially since stock only has 4 watts. you cannot get any higher then that without changing finals.

at 3 watt dead key, or 7 watt dead key, your modulation wattage is still swinging much higher.

Also, you will get more swing with a lower dead key any way, which is better if you want it to be loud.

Leave it alone. its probably set just right.

May 12, 2009 | Cobra 150 GTL DX Base CB Radio

1 Answer

148gtl, Taiwan when you modulate the meter swings backwards


In the back is where power mods have been added...It sounds like a swing kit 1/2 watt deadkey to 25 watts which is a powerful modulation exceeding 100%. Its a 220uf capacitor in place of a jumper J1 or J(x) J something in some radios. if you replace the jumper and remove the capacitor 220uf or 470uf one.(near finals it will return to around 4 watt dead key) The result of 4 watts is modulation is flat;where if you adjust it to 2 1/4 watt to say 20 watts it will be very loud and modulation is at 100%.

Dec 07, 2008 | Cobra 148 GTL 120-Channels Base CB Radio

2 Answers

142 GTL Good AM Carrier Weak Modulation????


you may have to scope the finals circuit on the modulation to see if all the "inline" caps are installed correctly... be sure your pc board is grounded in all areas as required by specs in your manual. Make sure there is no bleedover and you are sheilding your crystals from the modulation platform. al

Mar 24, 2007 | Cobra 148 GTL 120-Channels Base CB Radio

Not finding what you are looking for?
Cobra 148 GTL 120-Channels Base CB Radio Logo

896 people viewed this question

Ask a Question

Usually answered in minutes!

Top Cobra Radio Communications Experts

AnyMHz.com
AnyMHz.com

Level 2 Expert

489 Answers

Iron
Iron

Level 3 Expert

3018 Answers

Brad Brown

Level 3 Expert

13751 Answers

Are you a Cobra Radio Communication Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...