Although the analogy of what I’ll use as an example is very much a ham radio thing, the essence applies to any conversion or modded repurposed or total conversion project.
In the CB world, there’s been a desire to turn your 20/40/80/120 channel rig into more, by quick win or major conversion.
There were simple examples, such as turning a UK FM MPT1320 spec set into an dual ‘band’ UK/CEPT coverage using a simple daughter board switch between mainboard PLL and the daughter board PLL.
On older American spec, there were similar mods, but the better sets already were designed to be multi-band just lacked the hardware found on the high-end models.
So those probably count as worth doing, given the inflated prices of modern 27mhz CB gear. For similar, in ham radio, 10m/28mhz conversions were for the ex-CB crowd and any ham wanting a practical cheap HF mobile a quick simple entry route just as old PMR/LMR kit was a solid starting point for a stable pre-tested basis for 2m/70cms (hi-band VHF and UHF donors respectively) and 50mhz/6m and 70mhz/4m from low-band VHF examples.
But realistically, unless you are literally wanting a very retro rig or wanting to reinvent a wheel for the experience, in many circumstances it’s a bit pointless if you’re ambition is to from channelised to full VFO operation using the classic mods nodded to include VFO control.
Given you can buy quad band or even 6 band VHF/UHF mobiles of the 25W territory fairly cheaply, the line between doing a fully mod of multiple LMR boxes to get your desired coverage or going with production multi-band definitely favours commercial on cost.
You see, modding the RF stage to one shifted band segment isn’t expensive or difficult mainly but really needs (as with a complex build) a bit more than a multimeter and demon tweaker CB knowledge. That said, with reliable tried and tested and well presented examples, for UHF/VHF, Chris Lorek’s articles and books were a brilliant investment in time saving and ease of modifications. In fact, if you had a few years of Ham Radio Today mags in your collection, you already had a handful of his conversions documented.
For earlier crystal controlled stuff, doing a blind display VFO conversion wasn’t that hard if you could find a stable VFO circuit or module. Adding frequency display was a premium costly addition back then.
But when it entered the availability of PLL synthesized LMR, just as with CB, it became a magnitude or two more complex. On the LMR side, you were up against a plethora of PLL logic than in pre internet days was hard to source data sheets etc for - either you borrowed from other’s experience or reverse engineered or wholesale bypassed with an off-board PLL solution and optionally a VFO functionality.
But when there was at least a few hundred cost difference for a 25W end result, then it definitely had attractive merits.
Of course, today you can buy display module equipped frequency counter pre-builds very cheaply to create the VFO display and with any of many pattern VFO (SIG gen intended) modules, it’s very cheap to actually turn a channelised set that will need a hardware fix into a tunable wider frequency set.
But if you’re wanting a very wide coverage non-segmented multi-band radio as an end result, you’re better of buying a commercial and employing the ingenuity into optimising and improving of what’s under the hood, leaving kits builds and hardware conversions as construction projects where the successful build is the win, but being practical isn’t necessarily necessary.
There’s a definite line where you do these things and why and have to at least realise where you need to decide where the line sits.
I like conversions, repurposed electronics and mechanics, so they’ll always be part of my hobbies, but when it comes to the shack, effective cheap off the shelf multi-band and mono band commercial units are my mainstay, with a few oldies I’ll rebuild out of sentiment, but I focus most of my design and construction into PL/MCU/SBC based designs in and outside of radio, buy knowing I’m equipped to take that into building logic controlled modules for when they are needed for radio application rather than out of fighting a locked down PLL synthesized hellbeast of a radio.
After all, it’s supposed to fun and a learning experience and getting a sense of achievement by building not much more than proof of principal at a silly cost isn’t much of an achievement in my book, more a testament to the insanity of the project.
Just do it in a way where the end justifies the means in a meaningful useful way, rather than a pride and ego fuelled way where you do for the sake of the doing.