GBPPR Tech Bulletin #6 - Transmitter Site Rules

Proper transmitter/receiver location is a concept amateur radio operators fail to recognize.  When you're dealing with high power signals literally next to each other, that Radio Shack education just doesn't cut it.

There are alot of people around that will tell you how to do something.  I'd ignore these people and listen to simple math and physics.

Just because you've been doing something wrong for 30 years doesn't mean it's right!

All GBPPR members are required to follow this bulletin.  Most of this infomation comes from the K7PP repeater system, Internet postings and college math & physics books.

Equipment NOT Permitted on Community Sites Without Express Permission of the Site Owner

  1. Any RF transmitting equipment without a FCC type acceptance.
  2. Add-on RF power amplifiers.
  3. Digital/analog hybriding in exiters, unless type accepted.
  4. Equipment which does not conform to FCC (or GBPPR) rules and regulations.
  5. Non-continuous duty rated transmitters used in continues duty.
  6. Transmitter circuits without harmonic filters.
  7. Change in operating frequency without site coordination with lessor.  (e.g. remote bases)
  8. Equipment not designed for high density site applications.
  9. Ferrite devices (circulators/isolators) looking directly into an antenna.  (e.g. notch-notch duplexors or no cavities at all)
  10. Nickel plated connectors.
  11. Cascaded receiver multicoupler/preamps without proper preselection bandpass filters and attenuators to prevent multicoupler/preamp and receivers front end overload.

Required Radio Frequency Interference Protective Devices

  1. Transmitters in the 25 to 54 MHz range shall have isolation of at least 20 dB followed by a lowpass filter or cavity providing a minimum of 30 dB attenuation removed 1.0 MHz from the operating frequency.
  2. Transmitters in the 130 to 225 MHz range shall have at least 50 dB of isolation followed by a lowpass filter and bandpass cavity with a minimum of 25 dB attenuation 1 MHz from the operating frequency.
  3. Transmitters in the 400 to 470 MHz range shall have at least 50 dB of isolation with a minimum of 15 dB of attenuation 1 MHz removed from the operating frequency.
  4. Transmitters in the 806 to 960 MHz range shall have at least 50 dB of isolation followed by a lowpass filter and band pass cavity with a minimum of 15 dB of attenuation 1MHz removed from the operating frequency.

Also it should be emphasized that the above specifications are minimum requirements.  Additional protective devices may be required based upon evaluation of the following information:

Antenna or Mounts

  1. Mounted only on approved side arms or other specified mount.  All inverted antennas must be designed by the manufacturer for inverted mounting.
  2. All mounting hardware hot-dip galvanized or stainless steel.
  3. Tagged with weatherproof labels showing manufacturer, model, frequency range and owner.
  4. Connections to be taped with vulcanizing rubber tape and covered with strech vinyl tape (Scotch 88) and Scotch-Kote electrical coating applied to tapered areas, including booted jumper cables.
  5. Must meet manufacturer's VSWR specifications.
  6. Antennas with corroded elements must be replaced within 30 days of notification.
  7. Must be DC grounded type or have proper lightning protection such as a PolyPhaser arrester or equiv.
  8. Unless otherwise authorized, all antennas must be encased in radomes.
  9. Mounting pipes must be cut such that they do not extend above the antenna mounting sleeve.
  10. Any corroded hardware must be replaced.


  1. Must be teflon dielectric N-type including chassis/bulkhead connectors.  PL-259 connectors are to be used only when no other type of connector is available on the equipment.  You must do 50 push-ups for each PL-259 connector used on a high-Q duplexer or cavity.
  2. Must be properly fabricated if field installed.
  3. Must be taped and Scotch-Koted at least four inches onto the jacket if exposed to weather
  4. Male pins must be proper length.
  5. Female contacts may not be sprung.
  6. Connectors must be plier tight as opposed to hand tight.
  7. Must be silver plated or brass.


  1. No RF preamps permitted in front end unless authorized by lessor.
  2. All shields must be installed.
  3. Must use helical front ends.
  4. Must meet manufacturer's specifications, particularly with regard to bandwidth, discriminator swing and symmetry, and spurious responses.
  5. Crystal filters/preselectors/cavities will be installed in receive systems as required.
  6. All repeater tone squelch circuitry must use tone and carrier detect (and squelch logic).


  1. Must meet original manufacturer's specifications.
  2. All shields must be installed.
  3. Must be tagged with licensee's name, equipment model number, serial and operating frequencies.
  4. Must have visual indication of transmitter operation.
  5. All low level, pre-driver and driver stages must be shielded.
  6. Output power may not exceed 300 watts unless authorized by licensor.

Combiners / Multicouplers

  1. Must meet manufacturer's specifications.
  2. Must be tuned using manufacturers approved procedures.
  3. Must provide a minimum of 55 dB transmitter to transmitter isolation.


  1. All cabinets must be bonded together and must be grounded to the building ground system.
  2. All doors must be on and closed.
  3. All non-original holes larger than one inch will be covered with copper screen or sold metal plates.

Return to Green Bay Professional Packet Radio for more info and contact information.