Re: Using the BC780XLT scanner to tune into 764 - 776 MHz and 794-806 MHz

Hi from Central Massachusetts,

First of all, thank you responding to my inquisitive post, and it is nice to see others still around to talk about this model. I purchased the bc780xlt after picking up a free bc950xlt and found my interest in radio rekindled. The bc950xlt was a fun scanner, I had converted all the light bulbs to L.E.D. along with tons of other updates, however, the 10.400MHZ crystal adhered to the top of the PLL chip had a wire shear at the crystal's base. The radio was fun and so I decided to actually put some money into a more recent radio, enter the bc780xlt, and I bought it knowing that it was the more modern bc780xlt. In terms of parts, I harvested everything from the bc950xlt, and then ditched the cleaned circuit boards and casing. I have since harvested several radios (non-repairable units only) which I picked up at no cost.

I source all my parts from other individual's discarded electronics and avoid purchasing new parts, this is a "green" method I have adopted, and as a result I can fix other individual's electronics faster and get them back into action. I know Uniden has declared end-of-life on the bc780xlt and that all work performed on the unit is a "make it" or "break it" undertaking. This is why I have not removed the fixed-soldered processor on the unit to dump the rom, re-band the rom, flash the new rom, and reinstall said processor...

I usually do customization and personalization of electronics when I have enough units for development. Unfortunately, the bc780xlt is not a unit that people say "I have [x number] of these that you can have for the development of needed solutions", and so I only have the single unit I purchased. Things I have done so far include cosmetic items such as changing the L.E.D. backlighting color over to a bright blue (this color is often more desirable than the stock Amber color.) Obviously the display contrast has been changed to restore display output and suit the new backlighting. I cut the PCB trace on the TAPE OUT connector and connected one side of a surface mount 10-dip switch (obtained from an old cordless phone ironically) which allows for the selection of which of the many discriminator taps is to be connected to the TAPE OUT port. This allow the unit to appear completely stock, no casing is drilled or modified, while allowing access to the digital signals (which as you mentioned the bc780xlt can not process.)
To toggle the dip switch one simply removes the four screws holding the top cover on the unit (the cover without the speaker, meaning this can be done while the radio is still connected) and flip the switches to the desired setting, one setting restores the factory TAPE OUT function, before reinstalling the cover and 4 screws. I have also added a connector to both the PCB and the front display PCB so that the front display can be detached from the unit, a cable connected to the unit, the cable run [x length] of distance, and connected to the front display. This allows for the physical control of the unit itself from a remote distance.

However, maybe my energy is wasted on such an old electronic, and I might be better off restoring the unit back to stock-bones. I could sell it and put more money into a more recent scanner so that when P25 phase 2 comes along I can smile knowing that I just dumped several hundred on a unit that is now just as feature-starved as the bc780xlt. Digital may be nice, but the government grants are only paying out on p25 phase-2, and I very likely will get burned buying any of the newest scanners at this very time and moment.

I could develop this unit, but I don't have enough units to do such, and I may just sell mine and forget this whole scanner interest. This hobby pays nothing and working on other items seems to earn money/barter. However, I will get the unit to tune the 700Mhz band as an image before I sell this bc780xlt, and I don't think anybody else wants to hear that digital garble other than myself.
--- In [email protected], "Tom Hirsch" <thirsch4@...> wrote:
>
> Hello from Central Florida,
> 
>    This great scanner was a breakthrough in its day, and still performs very well about 14 years after the first units were sold by Uniden.   However, it has its limitations.  One of those is that Uniden no longer supports this model with parts or service.   So if you have a part or circuit failure; or if you damage the unit, you have a piece of useless junk.   Your only parts source is to find someone willing to sell a working or non-working 780 that you use to replace your 780 (if you damage it), or cannibalize your newly-bought 780 for parts to fix the damaged unit.  And as far as I know, Uniden will not sell any kind of service manual or other technical information that one would need to do modification or repairs.
> 
>    From reading your post, it appears that you have the electronics knowledge and the circuit board skills to attempt a modification, but as explained above, that is a very risky endeavor.    After investing a lot of time and whatever money, your only result may be a broken scanner.   
> 
>    In addition, most if not all of the communications in the 700 MHz band are digital, which the 780 can't demodulate.   The 700 MHz trunking channels have a channel plan that is not in the firmware of the 780, and the radio would be unable to track any such trunk system.   And if these obstacles are not enough, the control channels for 700 MHz trunk systems are certain to have a 9600 baud rate, which is not compatible with the 780.   It will handle only the first-generation 3600 baud Motorola control channel.
> 
>   You would do better to purchase a new or used digital scanner that comes equipped from the factory to receive the 700 MHz channels.   These newer scanners also have greater sensitivity, and will receive systems that the 780 might not capture.
> 
>  So spare the surgery to the 780, and use it to scan all of the other radio services that it does so well.
> 
> 
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