[MRCA] Pondering the conversion of the BC-620 radio for eithet Ham or CB use.

[mkdorney at aol.com]

Some countries outside the US actually do have CB bands that use FM, but that doesn't help things here in the US, so........
 
There are three ways to go with this.  The easiest is to just get a BC-659 or SCR-608 and work 10 meters between 28.300 and 29.700 MHz FM.  But that doesn't satisfy the purists in the vehicle hobby, who say their tank, etc didn't use the BC-659 or SCR-608 because they were Artillery radios ( the SCR-608 verses the SCR-508 presents the same dilemma for these purists).  I've seen more than a few who have BC-620's or SCR-508s and use them illegally, and they don't care about legalities and will not change until they are caught doing so, mostly because they don't think there are other options that don't upset their sense of absolute authenticity, and they figure they haven't been caught so far, so they'll continue to press their luck ( yeah, that's really stupid on their part, I know ).
 
   The other two options for the BC-620 and SCR-508 are more complicated.  The first would involve modifying these radios to add the needed operating frequency range to get these radios to operate in the phone section of 10 meters. Now I know this kind of thing has been done with the BC-1000 to boost it's operating frequencies into the phone section of the 6 meter band.  I'm wondering if anybody has tried to do with the BC-620 or the SCR-508 to get them to operate on frequencies in the phone section of 10 meters.  What would it involve?  Would it be a simple matter of having custom crystals cut and installed in the radios, or are other modifications needed to be done to the radio to make it work?
 
    The second option would be to somehow convert these radios to CB band operation ( AM ).  In addition to custom crystals, the radios would have to have their modulation changed from FM to AM, if that's even possible without messing with the outward appearance of these radios. The costs would probably scare off most owners.  Figure a vehicle guy would have a repair/modification budget of $1000 for their radio ( including repair of the power supply).  I don't think any conversion could be done along with what would surely be other needed repairs to make that an attractive option.  Also, lets face it, especially with the BC-620 being only a two trick pony frequency wise, one of the CB channels that would have to be installed in these radios would have to be channel 19, and it may not be economically or electrically possible to even do that.
 
Mark D.
WW2RDO
 
In a message dated 5/30/2018 9:24:18 AM Eastern Standard Time, crp.wd8axb at comcast.net writes:

 
Mark,

The BC-620 is very wideband FM, something like upwards of + - 15 kHz! Citizens Band is 6 kHz AM!

Nothing compatible!

And in the U.S., using FM in the CB band is illegal.

Perhaps a more reasoned approach is the BC-620, paired with the right crystals, or a set of these new adjustable crystal-replacement mini-circuits, and TEST to see if the 620 will work in the 10 meter FM band.

Find out what multiplication is used for the crystal fundamental frequencies for the 620 and 659. (?) 
See if there might be compatibility there. (?)

73, Charlie WD8AXB
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