The Radio Information Board

E.F. Johnson

Model: 242-8640

FCC ID: ATH2428640

it is a Black square box. It has a volume knob but no squelch knob so i assume it must be LTR trunked radio. it has a "N" Connector i am assuming it's 800mhz.I also assume by the size of the heatsink it has 15w RF out. The Vol. knob act as a ch/group select on a momentary push style switch. the display is blacked out but i opened the radio up and it had 2 leds and a numeric led. it has a RJ45 mic jack.

Robert P. Chrysafis (Batman)(kc8gpd)

More info......

it is 896-902mhz Hmmmm!! wonder if it will do 902-928 Ham band. Could not find out if it was Conventional or LTR it has 20w RF out. it has 2 programmed ch/fleet. still not sure if it is LTR or Conv. and also do not know ch/fleet capacity.

Any help appreciated.

Thanks

Robert P. Chrysafis (batman)(kc8gpd)

It's actually 896-902 and 935-941, those are the tx and rx sections of the 900 mHz commercial band. It should be capable of conv and LTR, probably capable of at least 8 channel or systems. Likely won't do the ham band easily. I've talked to a few folks about this, and I believe it would require some surgery on the VCO stripline (no big deal in itself) and editing of the frequency table in the prom. Those radios (all johnson LTR, actually) used FCC chanel numbers for the 800 and 900 mhz frequencies. The programming interface is a simple rs-232 to TTL conferter. Software is on the russian radio software sites. Let me know if you're interested in converting this, and I can point you towards someone who's playing with them. Good luck, Will

Thanks for the info will.

i am interested in moding this radio. also need to make a mic for it need info on mic wiring and interface cables.

Also i would be interested in a schematic for the rs232 converter and the web adress for the russian rss site and the user/password for it.

Robert P. Chrysafis (batman)(kc8gpd)

Will I'm interested in that mod as well... my email is n3ita@hotmail.com

The 8640 is a 10ch 900mhz radio that can only talk to a rptr. meaning
it can not to simplex.. It can be converted to the 900mhz ham band with
a 25mhz split.. It requires a new micro processor with the mods in
the firmware and a SMD cap change in the VCO..

-Pete