Cobra 148 gtl channel mods

The same board was used in the Cobra GTL. These chassis are remarkably stable after the clarifiers are opened and expanded. Although they do drift until warm, it's not much compared to the DX radios that have the same clarifier capabilities. The following instructions will expand the clarifier range after it is unlocked:.

cobra 148 gtl channel mods

With a frequency counter connected to TP1 and clarifier control in the 12 O'clock position adjust the following:. Remove the blue and brown wires from the fine clarifier control.

Add a 2K resistor from the empty end terminal of the fine clarifier potentiometer. Set both clarifier controls to 12 O'clock and adjust as above. The dual controls on the are easy to deal with for the fun range of the clarifier. All that's needed to drop 5 KHz or 10 KHz is to get close with the coarse and trim in with the or assistant control.

The single controls are more difficult but the schemes listed above make them fairly easy to tune at the center slot position. A dual potentiometer can be added to most radios.

The only limiting factor is the space available in the front panel. Radios with the controls mounted flush to a circuit board behind them would take more work than it would be worth. These could be two separate controls Fine Coarse but one dual potentiometer would be best. The 2K resistor can be larger or smaller depending on the range you prefer from your fine control.

Save my name, email, and website in this browser for the next time I comment. The following will unlock and keep the standard clarifier range: 1. Remove D58 2. The following instructions will expand the clarifier range after it is unlocked: 3.Cobra has really shot themselves in the foot with this new radio, why you ask?

Their Sideband radios such as thegtl and were superb, they were stable and a radio you could be proud of. The first thing that happened to Cobra was that Uniden wanted to raise the price on there PC boards, Cobra did not like this so they got some other company to make there boards cheeper! Of course this is all history, they fixed that problem.

I had a customer send me a NW ST for peaking and tuning for better receive and transmit. So before doing anything else, I hooked it up to my antenna to get some radio checks, well, AM was OK, nothing to write hone about but clear and clean.

So I really got concerned! After checking the oscilator frequencies I find that they change when I modulate! What the Hell! I placed a volt meter on several test points and found that the voltage to the oscillators is changing with modulation!

So I start looking for the reason for this and ran into the cause right away.

Cobra 148GTL Channel Mod

To my knowledge it could be inproved with some additional filtering and RF bypassing. Cobra HH34 Basic handheld with charging jack and lighter plug.

This is a typical example of mis-information, the resistor changes listed below will not produce more power, they will make the radio sound crappie. Change R76 3. Change R43 10 Ohm to a 2. Change R 1 Ohm to a. Replace stock final with a 2SC transistor. Re-tune coils L10,L9,L8 for maximum forward Power.

1978 COBRA 148 GTL REFRESH AND MODS FOR DAVID TX

Modification: Change stock final to a 2SC Change C71 to a 33uf 16volt polarized electrolytic capacitor. Two, Install a k ohm pot between these two points. The smaller the value, the more the receive is boosted.

Look for the collector of TR, you should read about 4. If you find that this voltage is not present, check on the opposite side of R for 6. Most likely this voltage will not be present; if this is the case, C18 has shorted and needs to be replaced.

This is a uf, 10V electrolytic capacitor beside L Transmit Audio normal. The newer units may have corrected this problem.

Output level uV. Set Squelch Maximum. Adjust VR-3 so that squelch just breaks. Adjust VR-1 for s9 on signal meter.Author cannot verify these modifications to work.

All mods on this page are representing the last Grant XL pc board before being discontinued. Always check radio operation in all modes and settings after performing any modification. PLL Modifications. Information for image above. Locate pin 14 of the chip on the bottom of the circuit board. Cut the trace for pin carefully. Solder a 4. Obtain 3 micro spst switches and find a suitable mounting area on the radio and install. Switch 2 requires wiring to pin 10 and the board ground.

Switch 3 requires wiring to pin 9 across from 10 and to the chip side of the cut trace on pin Cut the Trace on pin 14 of PLL and place 4. Next, solder the anode end of a 1N diode to pin 11 of PLL.

Next, solder the cathode banded end of a 1N diode to pin Next, solder the remaining diodes as shown and wire them on the switch just like the diagram shows.

And finally, you will have to put the wires on the switch. A5 to pin 10 A1 to pin B to pin 9. B3 to pin A to GND. Ground pin 16 using a SPST switch. No cut to the PLL is necessary. Pulling pin 16 low will cause it to jump down 10Kc. This will not work on all channels. Clarifier Mods Slider. Some info may be repeating, but with some differences. Different variations on the same operation- you choose which is best. Find R and jump it. Take this wire andsolder it to Ground. Then solder it to pin 3 of the mb ic.

This should give you about 6khz of slide. Unlocking the Clarifier. You should see about 5 khz of slide. Find D52, R44 and R and remove them.

Solder a jumper from where you removed R NOTE: Some radios have different colored wires on the clarifier control. The Tx will track exactly with the Rx. Make sure to retune again after radio has been on for many hours.Privacy Terms.

cobra 148 gtl channel mods

Skip to content. Quick links. Ad blocker detected: Our website is made possible by displaying online advertisements to our visitors. Please consider supporting us by disabling your ad blocker on our website. The place to talk about specific radios, equipment and accessories. Do you prefer the latest generation of rigs and antennas or do you like the classics? Discuss it here! My brother has a mk1 cobra gtl dx and has asked me to do the channel expansion mod for him.

Firstly,how shall I explain,I am licensed for other bands at the full powr limit here in the uk,so I'm pretty use to getting the soldring iron out. With that,this mk1 cobra is at the moment standard with 3 bands low,mid,high. My brother wants the six band conversion doing ie super super low,super low,low,mid high,and uk 40 muppet with the appropiate eprom conversion,this will be sourched from Tony at spectrum.

Is this what a standard six band conversion covers?

COBRA CB RADIOS MODIFICATIONS

A new six band switch will be going in. From what I can fathom expansion is done by pulling the codes high via 1n diodes via the adder ICs. My question is ,does any forum member have the conversion data ie which pins to pull. I would like the conversion data for the MK1 and MK2.

I have some conversion data for the mk2,but this only shows how to get the low low,and high high. Nothing shown for the other bands,I understand its about interrupting the code and presenting a new code. I have in the shack a fair amount of test gear including various sig gens,scopes, deviation meter,freq counter,sinad meter,the trusty avo and DMM to name but a few.

So hopefully the correct alignment shouldn't be a problem. Please help if you can,many thanks for your kind advice,in advance. The very best regards. Never, ever, ever Far too many radio's to list here. But I do own a legal one You'll either need to replace the PLL and add adders or an eprom to drive it, or switch in another crystal for the extra banks. You'll probably have fun making the VCO track that range too. I would think your brother would be better off buying a SuperStar and adding UK FM to that if he's really after that band coverage.

Im not talking a colossal freq range channels max not even that due to the overspill from high to the muppet 40,max span at max is around 2mhz. I remember many moons ago when I was young I had a mk1 with the 6 band conversion,so it can be done,but as you say its just reaching and getting advice from the right person to achieve this.

Oh and many thanks for welcoming me to the forum,it's very much appreciated. Best regards-Roger.We invite you to JOIN today so that you can post and interact with our members.

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When I asked him why, he told me that they don't make extra channel kits for Cobra's anymore, so he told me if I ever want to buy another Cobra to have the channel kit taken out and put in the new one, because if not I'll have to buy a Stryker, Ranger, or Galaxy DX radio.

Just figured I'd let everyone know. Mad Electronics is an awsome store to do buisness with, the guys name is Miketell em i sent you. What freqs does this give me? The guy that did it for me is long ago passed and the guys that I used to chat with are far away.

Remember Me? Page 1 of 2 1 2 Last Jump to page: Results 1 to 10 of Thread: Cobra Extra Channel Kits. Thread Tools Show Printable Version. Will a cobra 29LX do the extra channels mod?? I have this in my old Where can I get upper and lower channels for a cobra 29?

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Please consider supporting us by disabling your ad blocker on our website. Need some help with a radio mod? Pop in and ask away. Extra channels on a Cobra GTL? How is this possible and what frequency does it put you on? But the modification needed should only be attempted by a qualified tech.

Hi Turbo-T I would use caution if the radio was made in China. If it is a Philippine style radio, then grounding pins 11 and 10 in various combination will provide channels from There are skipped channels between 40 and 45 plus 46 and 48, as well as others.

There are no parts to replace. To get the skipped channels you only need to apply 8 volts to the binary pins 16 through to 10 or ground them. There is a little more to it if you go that route. You may need to cut the trace to the pins and put a 4. Then you can make the pins go high and low without damaging the 8 volt regulator chip and get the channels you want. I am sure the mod is on cbtricks. When in doubt? Ship it out. Good luck.

Best Regards, Rick. Nope it's a Taiwan model. Considering if I want to have this done or sell it for a EDX. Turbo-T wrote: Nope it's a Taiwan model. Ignorance can be fixed. Stupid will present a special challenge!Read more From all of us here at CB World, we wish you the very best. Contact CB World! We strive to carry all of the parts you might need for your equipment. We carry replacement parts such as transistors, knobs, switches, controls, and much more.

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cobra 148 gtl channel mods

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