From: kurt@cs.tamu.edu (Kurt Freiberger) Subject: THE REAL Standard 558 radio mod >From a sheet that I got from a vendor, here 'tis: MARS/CAP (Wide band transmit) 1. Remove battery and antenna. 2. Remove front case assembly block by unscrewing. 3. Remove tthe copper plate around the back side of the display section. 4. Remove the diode indicated by D2, and add a diode 1SS301 leaving other components intact as per the following drawing. 5. Reassemble radio and install battery. 6. Turn on power and execute master reset. --------------------------------------------------------------------- ------------+ +------------------------------------------ ! ! ! +------+ (PC board "donut") ! ! ! / +-----------+ +------+ / ! ! ! /---\ PC board trace/ ! D1 ! +--+ +++ ! +-----+ component layout ! ! +--+ +++ ! ! ! +-----------+ ! ! \+-+/ +-----+-+ ! ! ! +------+ ! ! ! ! ! ! +-+----+ +-+ +--+ +---+ ! ! ! ! ! <<< ---- CHANGE +-------------+ ! ! D2 ! +------+ +---+ ! ! ! +-----+-+ ! "Not to scale" ! ! +-----+ ** ** \**/ \/ +--------+ (about here) +------------+ ! ! ! ! +--+ ! +----+ ! ! PC board locator! +-----------------/------\--------+ ! +--+ ! ! ! ! ! ! ! ++ +-----+ ! ! ++ +-+ ! ! ! ! ! ! ! ! ! Opening for ! ! speaker about ! ! here (funny ! ! shaped opening) ! ............................................... I received the diode yesterday, and installed it. The mod DOES work!!!! I have not tested the ranges, but it DOES cover the entire 420-450 band now, which is what I was most interested in. ============================================================================== From: Harald Landvoigt ====================== ! STANDARD C 558 ! ====================== On march 3rd, 1993, I bought the Standrad C558S dual band HT. The price was 7,600 Austrian Schilling (approx. 580 US $ including all taxes). CTCSS is not included in the European version!! General information ======================= Body dimensions: 55*130*31 mm (with CBT151 battery tray) Weight: 355g (incl. batteries and antenna) RF output: 5W (high,12V) 2.5W (mid) 350mW (low) Freq. range of S version: VHF 144 - 148 MHz UHF 430 - 440 MHz Expanding the frequency range of the C558S =========================================== 1) software expansion(RX): I) reset the unit II) push and hold FUNC and press 3 - V/M ENT - 3 release FUNC and press PTT now the unit will RX 100-199 MHz (PLL lock range 100-173 MHz) AM + FM 300-500 MHz (PLL lock range 342-471 MHz) FM 800-999 MHz (PLL lock range 823-990 MHz) FM with this modification the HT can _NOT_ be tuned to all frequencies in the 900MHz and 350MHz band!!! TX remains 144-148, 430-440 MHz smallest freq.step: 144MHz.....5kHz 350MHz.....5kHz 440MHz.....5kHz 900MHz....10kHz 2)hardware expansion(RX): I) open the radio..... II) locate resistor R289. its the 0 Ohm resistor on the micro-processor- board, right of the connector for the sub-tone sql. unit. III) remove the resistor..... :-) IV) reset the unit RX/TX range remains the same as above, but now you can tune to ANY frequency in the 350 and 900 MHz band. 3) hardware modification (TX): I) open the unit..... II) remove the 'galactic' RF-shielding from the micro-processor board III) locate smd-diode Q221 (its the right one of the two smd-diodes)... IV) the type of this diode is DA115. exchanche it with a DAN202U or just solder a normal diode(1N4148) from the left pin to the lower right pin of Q221: type DAN202U smd diode: ------- | | | -|<-|== || | ==|- | || | | -|<-|== | | ------- type DA115 smd diode: ------- | | | -|<-|== || | ==|- | | | | | | |== | | | | | ------- | | | ---|<----- 1N4148 V) reset the unit.... the TX range will be: VHF:100-199MHz (PLL lock range 115-165 MHz :-( ) UHF:400-500MHz (PLL lock range 400-482 MHz !!) no TX in the 350 and 900MHz band Pro's and Con's of the C558 ============================= + one of the smallest 2m/70cm HT + extremly sensitive and low noise receiver(even on 900MHz) + very low power consumption + up to 200 memories with a lot of different scan modes + good keyboard layout (except the 1750 Hz burst tone!) +- the rubber-duck antenna works very good in the ham-bands and 900MHz but does not work at all outside the 2m ham-band :-( - the worst case I have ever seen -- so don't drop the C558!! ( Radio-Shack's CB walkie talkies can't be worse ) - some intermod. problems with high gain base-antennas ( but much better than the yaesu FT530!! ) - small LC-Display - no backlit keys - the mic/speaker cap ... you have to see THIS yourself :-( - press PTT and CALL/PL key to activete 1750Hz tone...