927  MHz  repeaters


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Boston    K1RJZ     ( now on the air! )

Owner / Club affiliation Minuteman Repeater Association       License Trustee:  K1RJZ

Air date:  on the air

Linked:  Yes.  Full-time IRLP node 4977 to the Near-900 link-up to five other 900 MHz repeaters.  Rapidly growing.    Part-time Tuesday evenings only: MMRA net

Location:   47th floor penthouse, One Financial Center, Boston. This is a very high quality, well managed commercial rooftop with two towers

Coverage:  wide area in all directions but will also address a significant coverage area hole on the north shore and to the northwest.  As with many 900 MHz repeaters located in a populated area, the receive frequency is effected by unlicensed 900 MHz consumer and commercial appliances.  Although challenged by other RF sources, talk-in coverage is still quite good.

Repeater:  Motorola MSF5000  130W

Duplexer or dual antennas:  Dual.  RX antenna in a protected RX-only zone.  Tower-top-mounted, inverted. TX antenna on roof.

Antennas:  RX:  dedicated 9DB gain DB809 donated by K1WUK    TX:  dedicated 12 dB gain   PD-10017-6   Neither with downtilt.

Feedline:  RX: 200ft 1 5/8" Heliax donated by N1OTY,    TX:    60ft  7/8"  Heliax donated by Broadcast Towers. 

RX antenna tip:  685ft AMSL

Emergency power:  Yes.   House Diesel + 2200W APC UPS

Frequencies: 

  • User RX     927.775    DPL-244   non-inverted
  • User TX     902.775    DPL-244    non-inverted
  • Hear Clear = OFF

Status

  • Many people from a wide geographic area have been involved
  • K1RJZ:  purchase repeater and controller.  Start MSF-5000 recapping with initial tune-up (repeater works fine)
  • Repeater, TX antenna, duplexer and controller later donated to MMRA
  • N1OTY:  donate 200ft of 1 5/8" Heliax & connectors (RX) and delivered to Broadcast Towers in Bridgewater
  • Broadcast Towers: donate 60ft  7/8" Heliax with connectors  (TX)
  • Broadcast Towers: Heliax elevated to roof-level via window washer machine
  • K1WUK:  donate RX antenna, Heliax jumpers, Polyphasers
  • W1BRI:  tune-up duplexer, later to be turned onto TX and RX filters
  • N3HFK:  took over repeater prep and was lead on recapping, physical reconfigurations and final tweak.
  • N3HFK:  Anything to do with the local IRLP interface and setup
  • N3HFK:  Integrate S-COM 7K controller
  • K1IW:     Program S-COM 7K controller 
  • N3HFK, K1IW, W1BRI, K1RJZ, N1ZZN, KC1HO, N1JFU: Sunday  repeater "tune-up party" at N3HFK.
  • N3HFK, K1IW, W1BRI, K1RJZ:  Lug MSF-5000 to roof penthouse via three flights of fire escape  (350 lbs)
  • Now on the air with the permanent RX & TX antennas (TX on roof, RX on tower)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This is not your typical Spartan radio room.  Even by commercial standards, this is a very high-end facility which was designed to be more of a mission-critical datacenter.  The red box is the dry-pre-action fire suppression controller, FM200 fire suppression is in another section.   Diesel generator emergency power is also provided.


 

 

 


Polyphasers donated by K1WUK

 

 

 

A huge thank you for donated ham antenna tower rigging goes to Broadcast Towers of Bridgewater, MA. Work was provided while working on another customer project. 

 

 


 

 

 

Broadcast Towers is the exclusive tower rigger for One Financial Center. No rusted bolts, no unlabelled coax, no abandoned gear left on the roof. Their pride and quality of work is obvious. 

 

 

 

 


Helicopter shot provided by... someone.

 

 

Please consider these fine companies of you need tower rigging or you are looking to rent a very well-managed commercial tower site:

Tower Rigging: 
Broadcast Towers, Chris Loycano, Bridgewater
508-326-9485 

Communications Management:
Peter Kovaleski  860-684-1511

 



Good food and great company!

 

 

 


Also participating was Bob DiMattia, K1IW who was remotely programming the S-COM controller while he was in Dayton!

 

 

 

 

Particular attention was paid to audio quality and by the end of the day, everyone was quite pleased.  Audio frequency response and amplitude had to match between end user audio, voice ID's and IRLP linking.  The sharing of knowledge among these peer experts made the trip worth it for everyone.

 


This one is headed far outside of the Boston area.

 

 


Boston hardware relocation day.


These are some of the key players that made it all come together.  The large red bottles in the
rear are for FM-200 inert gas fire suppression.  This is a truly first-rate facility.

 

 

 

 

 

 

 

 


Permanent TX antenna  location      

 

 

 


 

Trying to optimize 900 MHz receiver performance


The roof-top site itself is very clean but the off-site and unlicensed urban 900 MHz environment
might be called "The Wild West".

 

 

 


Spectrum analyzer plot showing Part-15 unlicensed users on repeater input frequencies.
Without the RX filter included above, RFI extended well beyond 912 MHz.

 

 


Receive antenna performance improved but the Part-15 RFI also increased

 

 

 

Strategy #1   Relocate RX antenna


 

Now relocated. Possibly less exposure from urban Part-15 RFI while improving coverage to the west and north.  The shadowed area now orients to the south which already has very good linked 900 MHz repeater coverage from Hingham and Marshfield.  New location showed some improvements but not dramatic improvements to the west and north.

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