View Full Version : 148GTL SSB Transmit and Recieve

08-18-2018, 02:04 AM
148GTL is acting strange on trans. and rec. Bought it from shop year ago and just now hooked it up. Charlie's Airwaves in Houston had it on a shelf. Clarifier is unlocked (slides 16 KHz, about 8 KHz both ways). Testing it I was told I sounded off freq., had to adjust clarifier. On trans. On receive I have to adjust clarifier to keep from hearing the space aliens :alien: on helium. Knob setting for rec. is about 11 o'clock. Knob setting for trans. is almost 1 o'clock. My co-conspirator in test was only a few miles away. Knob Jockeying is not my idea of fun to communicate. Anyone have an idea what can be done to remedy this 148 ailment?:300 (119):

08-18-2018, 08:30 PM
Never mind that.....this thing has been modified by a golden screwdriver. Has some kind of channel mod installed. NB/ANL, HI/LOW, and BRT/DIM change frequencies. The different positions seem to only change the freq from what is shown on LED display. NB/ANL-LOW-BRT changes Chl. 29 to 27.935(10M). NB/ANL-HI-DIM changes chl. 23 to 26.935(LSB 38). Some positions duplicate freq. This thing is F'd up. Screws holding board down are all soldiered. The Ext. speaker and PA have been jumped over to create Talk Back. Guess I'll build a Road Map from Hell for all chl. configurations. Thinking this may be some form of Enigma Machine. Three switches change chl. freq's- the Enigma had three wheels in it that changed key output. Any help would be greatly appreciated.

08-18-2018, 11:03 PM
Found this online at Anglefire:

1. Replace 11.1125 crystal with an 11.3258 crystal.
2. Isolate the ground pin 10 of the MB8719 PLL by cutting the PC trace.
3. At this point, turn your radio on and check to verify that all channelsare locked in and working. If it is not, adjust these in the following order:
a. CT3 for USB.
b. L20 for LSB.
c. L19 for AM.
4. Install a SPST switch between pins 11 and 12 of the MB8719 PLL
5. Install a SPST switch across the cut you made to isolate pin 10.
SW1 UP / SW2 DOWN (NB/ANL-HI-DIM): (ch.15-27) 26.815 to 26.955
1= 27.605 6= 27.505 11= 27.565 20= 27.525
2= 27.455 7= 27.515 12= 27.585 23= 27.575
3= 27.465 8= 27.535 13= 27.595
4= 27.485 9= 27.545 14= 27.605
5= 27.495 10= 27.555 16= 27.475
SW1 DOWN / SW2 UP (NB/ANL-LOW-BRT): (Ch. 1-40) 27.605 to 28.045

06-01-2019, 03:16 PM
you should put or have it put back to original the if you still want extra frequencies/ channels use a EPROM conversion now crystals needed easy to install and very stable and reliable and all channel will be compatible with the like of galaxy and other similar type of multi band radio's then you will have great radio. hope this helps.

10-06-2019, 12:01 PM
Very good radio only with audio .but frequency expansion very limited especial going down.and no display counter .add of crystal to take it further down .

10-08-2019, 11:58 AM
EPROM conversions work with almost all radio pll types even the noted MB8719 which used 2 different frequency crystals a 11.1125 MHZ or 11.3528 MHZ also look for the 148 gtldx that has most channels and has a diode matrix that makes it simple to add or change the bands and most radios can have a frequency counter or reader added

30 years radio engineer commercial CB radio ham and marine experience

10-08-2019, 12:10 PM
here is a couple of examples of the EPROM boards i designed and built back in the 1980s2379 2378

10-08-2019, 05:41 PM
I understand what you are say i am also in that field i dont do cb radio. but this one of the radio i dont like.never only thing about them is the audio last sound great

10-09-2019, 09:09 AM
they have great audio because of the if stages and the xtal filter although they are only 4 watts they are great radios if left alone too many are butchered hence the bad name but if properly aligned they are very nice radios i had 1 back in the 80s and i had used 1 of the EPROM boards to make it a 5 band radio with some mods to the VCO and PLL its all just my thoughts and experience with them.