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Randy Roberts, the founder of Spread Spectrum Scene Online, was an avid ham radio operator. Listed below is his proposal for a spread spectrum radio for ham use. The information is a bit dated, but can still be of interest for someone who wants to do some tinkering....
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Related Pages on SSS Online

KC6YJY's (Randy Roberts') Proposal for
the SST-1 "Universal" SS Radio-Modem for Ham Radio Applications

Download Orcad .DSN Schematic & PADS .PCB Files and 16C64 Microprocessor Code! (~200K ZIP file)

We want to encourage experimentation with SS techniques! When SSS was a paper publication, we published a number of "how to" articles, one or two variants on the theme of a DS STA radio (for Buass' STA), two gener- ations of "Ham Hopper" transceiver designs and a number of other tidbits for the avid or budding experimenter. Here's our first update:

Here's my proposal:

I (and RF/SS) will grant a THREE YEAR NON-EXCLUSIVE LICENSE to TAPR [or any other Bona Fide Amateur Radio Organization], at NO COST WHATSOEVER, which includes a relatively complete design and documentation package for a "Universal," DSSS / FHSS / Hybrid FH-DS radio-modem with the following initial design characteristics and specifications preliminarily outlined below.

This licensed design package will allow the user to rapidly assemble the pieces needed to offer either kits or completed products to the Amateur Radio Community. These kits can be modular in capability and can be designed with expansion in mind. The performance of this licensed design is State of the Art in every way. It uses the latest in ASIC technology and provides better than commercial WLAN SS communications that rival what the US military are using today!


  1. The radio-modem is used ONLY for Amateur / non-commercial or to-be-negotiated educational uses.

  2. TAPR (or any other Bona Fide Amateur Radio Organization) and other assorted / interested volunteers supply labor and materials, as needed, to fully develop and test this new design.

  3. TAPR (or any other Bona Fide Amateur Radio Organization) sets up a Project / Team organization to provide direction, guidance and start on a "Ham Radio SS" Standard, ASAP!

  4. The draft standard mentioned in (3) above is ready for circulation and comment by 1 May, 1997 AND that the Final Interium Standard for Ham SS operations is released by 1 August, 1997.


  • Half duplex on the air communications
  • TX - RX & RX - TX Switching Times: 500 microseconds, design goal
  • Frequency Range: 24 to 34 MHz (TO BE USED with an OUTBOARD LINEAR TRANSVERTER for operating frequency band.)
  • TX output Power: > +13 dBm (20mw) average
  • RX NF:< 3 dB
  • SS Mode Capability: DSSS, FHSS, Hybrid FH-SS
  • Process Gain: 10 to 18 dB with DSSS / up to 30 dB with FHSS / > 40 dB with Hybrid FH-SS
  • DSSS Chipset: STEL-2000A (same as Zilog Z87200)
  • FHSS Chip set: Analog Devices AD9955 (Fast option) / AD7008 (Slow option)
  • "SMART" Radio Setup & Control: PIC 16C64A
  • HOST I/O: slow speed = RS-232 / high speed = Synchronous Serial (SIO) port (HDLC-like) -- both I/O speeds use Tx / RX handshaking
  • Data Rates: 1 bps to >250 kbps
  • Master Clock: 80 MHz TCXO, freq. stability , +/- 10 ppm
  • Frequency Hopping Speed: 1 microsecond maximum, design goal
  • PN Codes: Fully Programmable in length and selection
  • FH Codes: Fully Programmable in length and selection
  • Multiple Access Capability: Fully Programmable / User selectable
  • Baseband Data Protocols: TBD / TBS
  • HOST / TNC Characteristics: To Be Developed
  • OSI Communication Modes / Level Definition: To Be Developed
  • Applications / Application Software: To Be Developed
  • Physical: Two PCBs - each about 3" x 5" (TWO sided), design goal (See Baseband PCB Breadboard at top of page)
  • POWER Required: + 11 to 14 VDC at less than 1 amp
  • Other Characteristics: TBD / TBS


*** HOT from the LAB -- ACTUAL Spectrum Plots from our HP8561A *** Spectrum Analyzer on the RF/SS Breadboard SST-1 Radio-Modem

1.28 MCPS PN - Data Rate = 20.3 kbps w/o PA 1.28 MCPS PN - Data Rate = 20.3 kbps w/PA

The plot on the left is without any power amplifier on the radio- modem's output. The righthand plot is with a linear 100 mW power amplifier. Both plots use a master XTAL Osc. of 5.12 MHz for a PN Chip rate of 1.28 MHz (see first spectral nulls at +/- 1.28 MHz from the suppressed carrier). Data rate for both plots is 20.3 kbps -- for a processing gain of 63 chips per bit or 18 dB. NO DATA is being transmitted in either plot!

*** Here's another View: ***

1.28 MCPS PN - DR = 20.3 kbps - 1.8 MHz BW(-20dB) 1.28 MCPS PN - DR = 20.3 kbps - Delta lines=DR

The lefthand plot shows the radio-modem's actual occupied RF Bandwidth -- BW(-20 dB) -- or 99% BW = 1.8 MHz (this is only 1.41 x Chip Rate!) The markers are a "little" hard to see -- aren't they? The righthand plot shows the details of the spectral lines within the DSSS signal. The lines are 20.3 kHz apart (= the Data Rate). Note also that the (suppressed ) carrier is 20.67 dB down from any line! Both plots uses an X.O. of 5.12 MHz for a PN Chip rate of 1.28 MHz and ALL plots here use BPSK-DSSS modulation. NO DATA is being trans- mitted in either plot!

*** Want to go FASTER?: ***
*** How about larger plots?: ***

7.25 MCPS PN - DR = 120 kbps - ISDN you say!

This plot uses an X.O. equal to the carrier frequency = 29.000 MHz for a PN Chip rate of 7.25 MHz and a Data Rate of 120 kbps. NO DATA is being transmitted in this plot!

*** How about SLOWER?: ***

1890 CPS PN - DR = 30 bps - EME anyone?

This plot uses an "audio" clock = 7560 Hz for a Chip rate of 1890 Hz and a Data Rate of 30 bps (that is 30 Baud!) This might work for EME -- anyone want to try it? NO DATA is being transmitted in this plot either!

*** How About another Band?: ***
*** How about Frequency Hop?: ***

We will be posting this kind of info plus more test results, schematics and lots of other stuff on this proposed design, if there is any interest -- email us if you want more info!

Click here to see complete schematics & download, Orcad .DSN & PADS .PCB Files as well as Microprocessor Code


Ham Radio SS Resources:

SSS Online's Ham Topics Menu Page
Download NTIA's US Frequency Allocation Chart -- 101k Adobe Acrobat file.
TAPR Spread Spectrum Page
TAPR Spread Spectrum Page

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