Cobra 148 GTL ST DDS Deluxe SS

by 303

Here you will find an adventure that you can follow along with or make fun of. The choice is yours!

This specimen is a hacked up $20 ebay find. Bought it with lots of squeals. Several modifications had been done to it, for example an echo board, unlocked clairifier, talkback, other mods im unsure the funtions.

This is a run down of objectives for this build:

• Frequency ocillator replacement. (Primary objective) Expand frequency range from the stock 26.965Mhz to 27.405Mhz to a freebanded 24Mhz to 30Mhz VFO 10, 11, 12 meter ham radio.
• Talkback enhancment (adding volume and disable controls).
• MCU controls, (amp remote power, amp auto keyer, aux expansion)
• Full cosmetic graphical dyesubbed wrap of case and bezel. Faceplate replace.
• Digitization of front panel controls. (secondary objective)
• Direct injection (wideband audio .25" phono jack with bypass switch.

When hookd up and keyed, there was a squeal that i messed with and messed with and couldn't get it out of my TX. Ended up pulling out the echo board and the squeal was gone. So now with a clear sounding TX, it can go to the chopping block for serious upgrades. Not worring about the RF section, or audio for that matter, other than to inject processed audio beyond the bandwidth narrowing filters of the stock audio chain. The focus of this build is digital frequency manipulationwith some automation controls. Then last but not least, the themed graphical make over. This is the merging of 3 of my hobbies into one single project.

First thing I did was study everything i could about the inside of the radio. Locate the ocillator, follow the audio lines, etc.

So one of the first steps is to remove to current channel selector, display and oscillator. This model has the Sound Tracker tech in it and this board is on the part we have to remove, so i will need to bypass this audio compression feature for transmittion. It also enhances the recieve as well, so to bypass that is next or isolate the sound tracker part and keep that put it elsewhere in the chassis. Need more research on that route.