HomeMy WebLinkAboutItem 3.33.3
TOWN OF LOS ALTOS HILLS December 9, 2004
Staff Report to the Planning Commission
RE: SITE DEVELOPMENT PERMIT FOR A 79.8' FOOT EMERGENCY
COMMUNICATIONS ANTENNA: 60 -FOOT LATTICE TOWER WITH A 2 -
FOOT MAST, AND SIX (6) ANTENNAS; LANDS OF LOS ALTOS HILLS,
26379 FREMONT ROAD; FILE# 162-04-ZP-SD.
FROM: Debbie Pedro, Associate Planner-.,,,?
APPROVED BY: Carl Cahill, Planning Director
RECOMMENDATION: That the Planning Commission:
1. Approve the request for a Site Development Permit to install an emergency
communications antenna as proposed by the Emergency Communications Committee:
60' tall antenna tower with a 2' tall mast, one (1) 17.8' tall antenna and five (5) 5.5'
tall antennas (maximum overall height 79.8'); OR
2. Consider an alternative antenna design and direct the Emergency Communications
Committee to revise the antenna system proposal utilizing a retractable tower or a
lower height.
BACKGROUND
On July 15, 2004, the City Council unanimously approved a funding proposal from the
Emergency Communications Committee's to install an amateur (ham) radio antenna
system at the Los Altos Hills Emergency Operations Center (LAH-EOC).
The purpose of the antenna is to provide radio communications during emergencies and
disasters. Ham radio operators are a vital part of the emergency communication system.
In the event of an emergency where landlines and cellular telephone lines may not be
available, ham radio operators can provide emergency radio communications between the
Los Altos Hills Emergency Operation Center (LAH-EOC), Santa Clara County Office of
Emergency Services (OES), and other emergency personnel and service groups such as
the Red Cross.
CODE REQUIREMENTS
As required by Section 10-2.301.c.7 of the Zoning Ordinance, this application for an EOC
antenna system has been forwarded to the Planning Commission for review and approval.
The Zoning and Site Development sections of the Municipal Code are used to evaluate
the antenna including siting, development area limitations, grading, height, setbacks, and
visibility.
Staff Report to the Planning Commission
Lands of Los Alms Hills
26379 Fremont Road
December 9, 2004
Page 2 of 7
DISCUSSION
The subject property is located on the west side of Fremont Road. Existing buildings on
the property includes the new Town Hall which is currently under construction, the
13uissima Hills Water District office, and the Heritage House which will serve as the
Town's Emergency Operation Center. Surrounding uses include single-family residences
on adjacent properties to the west and north, and single-family homes across Espemnza
Drive to the south and across Fremont Road to the east.
The emergency communications antenna system will be located in the existing apricot
orchard approximately 30' north of the Heritage House. Although it will be located
within the vicinity of the future solar orchard planned for the Town Hall site, the antenna
system will not interfere with the installation and operation of the solar orchard.
(Attachment 3)
The principal question concerning the emergency radio antenna is what height provides
the radio operators sufficient ability to communicate. Many factors are relevant, such as
distance over which the operators are trying to communicate, radio frequency, output
power used, topography, and nearby structures or trees that may obstruct or interfere with
the effective transmission or reception of the antenna signals. The Emergency
Communications Committee has prepared a detailed report analyzing the requirements of
the EOC antenna and determined that the proposed system would provide reliable
emergency communication between LAH-EOC, Santa Clara County OES and other
emergency personnel in the event of a disaster or emergency. (Attachment 4)
EMERGENCY COMMUNICATIONS ANTENNA SYSTEM
The proposed antenna system has an overall maximum height of 79.8' and includes a
9'L x 9'W x 5'D foundation, a 60' self-supporting galvanized steel lattice tower
(AN Wireless Model HD -60), a 2' tall mast and six (6) antennas.
AN Wireless HD Series
Galvanized Steel
Antenna Tower
Model: HD -60
• Proposed height: 60'
using sections 1-6
• Six (6) antennas will be
mounted on top and along
the sides of the tower.
Staff Report to the Planning Commission
Lands of Los Altos Hills
26379 Fremont Road
December 9, 2004
Page 3 of 7
Antenna 1: A 17.8 feet tall Diamond X-51ONA monopole antenna (144/440 MHz)
currently located on a flagpole next to the Heritage House. The antenna is
used for medium to long distance communications and is proposed to be
mounted on top of the 60' lattice tower.
Antenna 2: An existing 37 MHz EOC antenna specifically designated for
communications between LAH-EOC and Santa Clara County OES.
Currently located on the roof of the Heritage House, the antenna is
proposed to be mounted on the side of the new tower.
Antennas 3-6: Four (4) new 5'6" tall 144/440 MHz antennas to provide simultaneous
operation of multiple radios during an emergency. These antennas must be
vertically aligned with each other and separated by a distance of about 12
feet between mounting points in order to be functional. The antennas will
be affixed to the side of the tower at heights of 24', 36', 48' and 60'
respectively. This arrangement will allow transmission and reception on
multiple frequencies.
Antenna 1 Antenna 2
17.8' Diamond X51 OA 6' EOC-OF
Antennas 3.6
5'6" Diamond X -50A
Staff Report to the Planning Commission
Lands of Los Altos Hills
26379 Fremont Road
December 9, 2004
Page 4 of 7
Photo Simulation of Proposed Antenna System
PUBLIC SAFETY
A key issue concerning the antenna system is public safety. The tower may become an
attractive nuisance because it is easily accessible from nearby streets and pathways and
the climbable tower is inviting for children to climb or play on. To prevent potential
$teff Report to the Planning Commission
Lands of Los Altos Hills
26379 Fremont Road
December 9, 2004
Page 5 of 7
injuries to the public and to protect the equipment from vandalism, staff recommends the
installation of a 6' tall black vinyl coated chain link fence and access gate around the base
of the tower. The area around the fence shall be landscaped with vines or shrubs to
mitigate the visual impacts of the structure from neighbor's view. (Condition #4)
VISIB=y AND LANDSCAPE SCREENING
There are a number of existing trees and shrubs around the perimeter of the property and
a double row of mature eucalyptus and fir trees along Fremont Road which will screen
the lower portions of the structure from neighbor's view. However, due to the height of
the tower which is approximately 3.5 times the height of the new Town Hall building, the
antennas will be visible from neighboring properties and streets, particularly along
Fremont Road. -
ALTERNATIVE DESIGN
Given the size and height of the proposed antenna and the aesthetic and visual impacts to
the surrounding neighborhood, a retractable antenna tower may be the preferred
alternative.
According to the technical analysis in the ECC report, a "minimum antenna height of 40
to 50 feet" would provide reliable 144/440 MHz propagation to all defined points of
communications during an emergency (i.e. Santa Clara County OES, repeater sites, etc.).
There are a number of retractable (crankup) antenna towers available on the market that
will meet the 40'-50' height requirement. An example would be Texas Towers Model
TX -455 galvanized steel tower which has a nested height of 21.5' and an extended height
of 55'. (Attachment 5) Including the 2' mast and the 17.8' antenna, the height of the
tower will be 41.3' retracted and 74.8' fully extended. The antenna structure will stand at
41.3' when not in use. However, it should be noted that the retractable tower design
would preclude the use of Antennas # 3-6 because of their vertical mounting
requirements.
CONCLUSION
The Commission can decide to approve the antenna system as proposed by the
Emergency Communications Committee. However, if the Commission determines that a
retractable tower is a feasible alternative, the antenna design will need to be revised and a
condition should be added requiring the antenna tower to be in a fully retracted position at
all times except during a Town declared emergency or during the once/month emergency
communication training and exercise.
Staff Report to the Planning Conunission
Lands of Los Altos Hills
26379 Fremont Road
December 9, 2004
Page 6 of 7
CEOASTATUS
The project is categorically exempt under Class 2 (Replacement or Reconstruction) of the
State CEQA Guidelines
ATTACHMENTS:
1. Recommended Conditions of Approval for the Site Development Permit
2. Minutes from the July 15, 2004 City Council Meeting
3. Email from Greg McPheeters, Ecoengergies regarding the location of antenna
tower and solar orchard dated November 4, 2004
4. Emergency Operations Center Antenna System Proposal and Report prepared by
the Emergency Communications Committee dated July 6, 2004
5. Specifications for Texas Tower TX -455 Retractable Antenna
6. Aerial Map and Site Plan
Staff Report to the Planning Commission
Lands of Los Altos Hills
26379 Fremont Road
December 9, 2004
Page 7 of 7
ATTACHMENT I
RECOMMENDED CONDITIONS FOR SITE DEVELOPMENT PERMFF
FOR AN EMERGENCY COMMUNICATIONS ANTENNA SYSTEM
26379 FREMONT ROAD (LANDS OF LOS ALTOS HILLS)
File #162-04-ZP-SD
1. No other modifications to the approved plans are allowed except as otherwise
first reviewed and approved by the Planning Director or the Planning
Commission, depending on the scope of the changes.
2. Prior to beginning any grading operation, all significant trees are to be fenced
at the drip line. The fencing shall be of a material and structure (chain link) to
clearly delineate the drip line. Town staff must inspect the fencing and the
trees to be fenced prior to commencement of grading. No storage of
equipment, vehicles or debris shall be allowed within the drip lines of these
trees. Existing perimeter plantings shall be fenced and retained throughout the
entire construction period.
3. No outdoor lighting shall be installed on or around the new antenna structure.
4. A 6' tall black vinyl coated chain link fence and access gate shall be
constructed around the base of the antenna tower. Vines and shrubs shall be
planted around the fence to screen the structure from public view.
5. No signs shall be posted on or around the antenna structure except for public
safety warnings.
6. A building permit shall be obtained prior to the installation of an antenna
structure, pursuant to the requirements of the Building Code.
7. Any, and all, areas on the project site that have the native material disturbed
shall be protected for erosion control during the rainy season and shall be
replanted prior to final inspection.
ATTACHMENT.r
Warshawsky explained that he is very sympathetic to the Horton's situation. Their map
was approved two years ago and this should be a very simple request. Unfortunately,
their land is very beautiful and adds so much to the Town and since the original approval,
new information has come to light. Warshawsky added that he would like to take
advantage of the sixty day window to review all options and see if the issues can be
resolved and a compromise that is amenable to everyone can be reached. He noted that
the building pads are appropriately located and it is just the conservation easements that
need to be addressed.
Councilmember Fenwick suggested that the only reason for the Council to deny the
extension is to acquire the conservation easements on the property adding that pathway
easements can be required at the time of development. He would support approval of the
extension request because the areas in question are not suitable for development.
Mayor Pro Tem Kerr expressed his hope that the applicant could review the requests for
conservation easements in the areas of concern. This property warrants conservation
easements. He noted that he could not support approving the extension at this time but
he is interested in seeing the issues resolved and suggested that the decision be postponed
to a future meeting.
Mayor O'Malley explained that he had voted in favor of the conservation easements
when this project had been before Council for the original approval. He believed that the
property warrants conservation easements and he would be in favor of having the
applicant and staff work to resolve the issue and identify the conservation easements and
return to the City Council in August for consideration of the extension request.
MOTION SECONDED AND CARRIED: Moved by Kerr, seconded by Warshawsky
and passed by the following roll call vote to continue the item for thirty days and to
revisit the request for an extension at the August 19, 2004 meeting.
AYES: Mayor O'Malley, Mayor Pro Tem Kerr, Councilmember Cheng and
Councilmember Warshawsky
NOES: Councilmember Fenwick
ABSENT: None
ABSTAIN: None
6.2 Consideration of Proposal for the LAH-EOC Antenna Installation
City Manager Cassingham reported that before the Council was a proposal presented by
the Town's Emergency Communications Committee for the installation of an antenna at
the Town's Emergency Operations Center. She introduced Jim Abraham, Emergency
Communications Committee Chairman for the presentation of the proposal.
Jim Abraham explained that the report before Council was very detailed. and self
explanatory and he was available to answer any questions.
11 City Council Meeting Minutes
July 15, 2004
Councilmember Fenwick reported that the Emergency Communications Committee bad
voted unanimously to support this project. It had been thoroughly reviewed and
considered by the Committee.
MOTION SECONDED AND CARRIED: Moved by Fenwick, seconded by Cheng and
passed unanimously to approve the proposal for the Town's Emergency Operations
Center antenna installation.
6.3 Selection of Voting Delegate — League of California Cities Annual
Conference -September, 2004
City Manager Cassingham reported that in the past, when a representative from the City
Council has been unable to attend the League of California Cities Annual Conference,
Council has appointed her as their voting delegate. She added that if any Councilmember
is considering attending the Conference, Council might want to consider designating
them as the voting delegate.
Mayor O'Malley will review his schedule to see if it is compatible with attendance at the
League conference. The City Manager will be the voting delegate in the absence of any
Councihnember's attendance.
6.4 Consideration of Amicus Curiae Letters to the California Supreme Court -
Town of Tiburon (Urgency Item)
Assistant City Attorney David Warner reviewed the request before Council from the
Town of Tiburon's attorney. He explained that it involves the question of the authority of
a JPA over the traditional power of cities and towns to control land use within their
borders. They are seeking a letter from the City Council asking the Superior Courts to
grant a review of the case.
Council discussion of the issue ensued and they concurred that they would support the
request from Tiburon.
MOTION SECONDED AND CARRIED: Moved by Fenwick, seconded by
Warshawsky and passed unanimously to send the amicus curiae letter as requested by the
Town of Tiburon.
7. REPORTS FROM COMMITTEES SUB -COMMITTEES AND
COUNCILMEMBERS ON OUTSIDE AGENCIES
Councilmember Fenwick reported that he had attended the Emergency Communications
Committee meeting.
Mayor Pro Tem Kerr reported that he and Councilmember Cheng had attended a meeting
at Foothill College to discuss local government and public agency issues. At the
meeting, a future foram to discuss public sector benefit costs sponsored by the College
and the Town of Los Altos Hills was proposed and he would like to agendize discussion
of this proposal for the next Council meeting.
12 City Council Meeting Minutes
July 15, 2004
Page 1 of 2
ATTACHMENT 3
Debbie Pedro
From: Greg McPheeters [
Sent: Thursday, November 04, 2004 11:53 AM
To: Debbie Pedro; Tony Vierra
Subject: RE: Ham Radio Antenna at Town Hall
Great — I see no problem or impact whatsoever to the PV Solar array.
Greg
Greg McPheeters
Applications Engineer
www.ecoanergies.com
From: Debbie Pedro [mailto:dpedro@losaltoshills.ca.gov]
Sent: Thursday, November 04, 2004 10:49 AM
To: Greg McPheeters; Tony Vierra
Subject: RE: Ham Radio Antenna at Town Hall
Hi Greg,
The 60' antenna tower is self supporting and of lattice construction. I am told by the Emergency Communications
Committee chairman that there will be no guy wires. The foundation will be 9'x9'x5' (deep). They will need a trench and
conduit from the tower to the heritage house (approx. 30').
Debbie Pedro
Associate Planner
Town of Los Altos Hills
Phone: (650) 941-7222 xt. 237
Fax: (650) 941-3160
-----Original Message -----
From: Greg McPheeters [mailto:
Sent: Thursday, November 04, 2004 8:03 AM
To: Tony Vierra
Cc: dpedro@losaltoshills.ca.gov
Subject: RE: Ham Radio Antenna at Town Hall
Tony —
The antenna location should be fine. Will there be guy cables? Can they show where the guy cables will land?
the tower is as tall as I recall it being, that could be worth checking.
Greg
Greg McPheeters
Applications Engineer
www.ecoenercies.com
From: Tony Vierra [mailto:
Sent: Wednesday, November 03, 2004 3:05 PM
To: Greg McPheeters
Cc: 'dpedro@losaltoshills.ca.goV; Tony Vierra
Subject: FW: Ham Radio Antenna at Town Hall
1?110 04
Page 2 of 2
Greg,
Attached is a photo showing the proposed location of the new antenna needs to install for their ham
radio/emergency operations center. It doesn't look like it will interfere with the proposed location of the solar
panels but I wanted to get Eco -Energies to confirm.
Let me know what you think
Thanks.
TBI Construction &
Construction Management
Tony Vierra
Project Manager
(
-----Original Message -----
From: Debbie Pedro [mailto:dpedro@losaltoshilis.ca.gov]
Sent: November 03, 2004 2:19 PM
To:
Cc: Carl Cahill
Subject: Ham Radio Antenna at Town Hall
Tony,
I am working on the Ham Radio Antenna project at the new Town Hall and wants to make sure that the location of
this proposed antenna (north of the heritage house) will not intefere with the solar orchard. Attached is an aerial
photo showing the antenna location. Please let me know if there are any problems. Thanks.
-----------------------------------------
Debbie Pedro
Associate Planner
Town of Los Altos Hills
Phone: (650) 941-7222 xt. 237
Fax: (650) 941-3160
t2i7/2nn4
LOSAMSHILLS AITACHMEN
Mal os Altos Hills Emergency Communications Committee
Iwo
CALIFORNI mergency Operations Center Antenna System Proposal
July 6, 2004
The town of Los Altos Hills will likely be dependent on amateur radio
communications in time of emergency. A situation could develop where landline
telephone was unavailable and cellular telephone has been demonstrated time and
time again to be unreliable if useable at all in emergencies. Emergency operations in
the field require radio communications. The town has no functioning municipal
radio system thus leaving the amateur radio operators as the only source of
communications for the town. Training drills have demonstrated a clear need for
simultaneous communications utilizing four radios at the EOC as a minimum. The,
use of multiple radios operating in the same frequency band requires that the
antennas be arranged so that the radios do not interfere with each other. The only
practical way to provide the isolation between antennas is through vertical spacing.
The required antenna configuration requires a tower structure 60 feet in height.
The proposed antenna system will be located approximately 30 feet northwest of the
Heritage House (the EOC). The tower is self-supporting and of lattice construction.
It meets all current town structural requirements, provides OSHA approved
climbing safety equipment, and offers the option of increasing the height if future
requirements dictate. The proposed antenna system will comply with all town
zoning and building standards. The cost of the antenna system will be
approximately $14,500. The funding for the project is available and has been
appropriated for this fiscal year from CLEEP funds.
The attached pages contain details of the antenna system requirements in a layout
type of presentation along with diagrams of the tower and location at the Town Hall
site.
The Emergency Communication Committee requests the City Council's approval
for the purchase and installation of the proposed antenna system.
Jim Abraham,
Chairman for the Los Altos Hills Emergency Communications Committee
26379 Fremont Road
Los Altos Hills
California 94022
630/941-7222
Fax 650/941-3160
Proposal for the LAH-EOC Antenna Installation
Jim Abraham, Chairman
Ray Egan
David Pratt
June,2004
Emergency Communications Committee
Los Altos Hills
1. Objective:
Provide reliable emergency communication capability between LAHEOC Amateur Radio
Operators, Los Altos Hills and Santa Clara County emergency personnel.
2. Required capabilities:
2.1 Ability to have at least four simultaneous communications on Amateur Radio
Frequencies. Experience from simulated emergency drills has shown that fewer
communication channels limit the information flow required in an emergency.
2.2 Capability for City, County and Sheriff radio communications (one operator
capacity for each). See attached Requirements Specifications document for more
detail and specifics.
2.3 No reduction in communication capability in the event that power, telephone,
cellular and Internet resources are compromised.
2.4 Maximum realistic probability of communication under any atmospheric
conditions at any time between required cities and county locations
2.5 Ability to replace antennas within an hour or so in order to assure full capability
during emergency conditions.
3. Recommendations:
3.1 In order to maintain simultaneous operation of all communications links described
in 2.1 and 2.2, above, the antenna structure will require 7 antennas with those on
similar frequencies stacked vertically. This will minimize interference across the
various links and greatly increase the likelihood of simultaneous operation.
Calculations have shown that 12 foot separation will be adequate. City, County
and Sheriff frequencies are different and these antennas may be installed
between the Amateur Radio antennas.
3.2 Line -of -sight communications from our Los Altos Hills Town Hall location will
provide maximum likelihood of communication under adverse circumstances and
in some cases for any likely communication. By arranging antennas for their
intended use, a 60 foot tower with an 18 -foot monopole antenna on top of it is
required. Other antennas would be installed lower on the tower.
3.3 In order to quickly change out antennas not operational, minimum disruption
would be involved if the tower may be climbed and is equipped with safety cable
attachments. Lattice tower design best provides this capability. An AN Wireless
tower is recommended due to its' design and versatility. It is supplied in 10 -foot
knocked -down sections which are bolted together on the ground. The completed
tower may be raised by a crane onto a prepared concrete base imbedded
section. We are recommending use of six sections, numbers one through six
(rather than the smaller five through 10) which will enable future expansion to 100
feet in the event that changing needs require the additional height.
3.4 Amateur Radio Antennas recommended are Diamond X -50's and Diamond X500.
These model antennas are currently used at the LAH-EOC and have proven to be
reliable with virtually no maintenance.
4. Budgetary Cost Estimates
4.1
Tower -60 foot
$5180
Shipping—Knocked down $660
— Assembled sections $1498
4.2
Base
$ 5000
Excavation & forms
Cement mix —12 cu. Yd.
4.2
Antennas (4 for Amateur Radio)
$ 550
1 ea Diamond X-500
3 as Diamond X-50
4.3
Feed lines
$ 320
500 ft. LMR -400
(Connectors, lightening arrest, etc, not incl.)
4.4
Crane and installation
$ 660
$165/hr x 4 hr minimum (2 hr on-site)
4.5
Contingency and miscellaneous 15%
$ 1166
4.6
Assembly and Erection
$ 500
4.7
Total
$14436
5. Attachments:
Communication Antenna System — Requirements
AN Tower Information
Tower quotation
Elevation drawing
Foundation drawings
Photos of typical 60 -foot installation
Site Location
Respectfully Submitted,
Los Altos Hills Emergency Communications Committee, Jim Abraham -Chairman
Communications Antenna System
Technical Analysis
Town of Los Altos Hills, California
June 2004
Emergency Communications Committee charter provision:
The Charges to and Duties of this Committee are to: provide emergency
radio communication services between the Los Altos Hills Emergency
Operation Center (EOC) facility using federally sanctioned amateur (ham)
radio operating frequencies in accordance with federally mandated amateur
(ham) radio operating requirements and procedures and:
1. The Santa Clara County Office of Emergency Services
(DES).
2. Amateur (ham) radio operators throughout the Town of
Los Altos Hills and surrounding areas.
3. Surrounding area municipal emergency communication
facilities, hospitals and emergency service groups such as
the Red Cross.
General
The purpose of the Communications Antenna System is to provide the radiating portion of the Town of Los
Altos Hills radio communications facility. This facility will provide for the following radio communication
services:
L Disaster Emergency Communications including:
a.
Santa Clam County EOC Net
b.
RACES resource net
u
RACES command net
d.
RACES packet net
e.
LAH-ECC repeater link
E
City -to -County microwave data link(future)
Definitions: EOC --- Emergency Operations Center
RACES --- Radio Amateur Civil Emergency Service
Packet --- Digital data communication
Points/Areas of Communication
Although general area coverage of Los Altos Hills, Santa Clara County and adjacent areas is essential, there
are several defined points of communication with the Los Altos Hills EOC. These points are repeater sites,
the Santa Clara County EOC and possibly adjacent city EOCs. Initial points and frequency bands to reach
from the LAH-EOC:
I. Santa Clara County EOC
SCC Bldg, San Jose
37 MHz
2. Santa Clara County EOC
SCC Bldg, San Jose
144220/440 MHz
3. Repeater
La Cresta water tank, LAH
144 MHz
4. Repeater
EI Camino Hosp, Mt. View
144/440 MHz
5. Repeater
Loma Priem Mm
144 MHz
6. Repeater
Black Mm
144 MHz
7. City EOCs (PA, LA, MV)
City Centers
(future?)
Path Profiles
SCC Bldg, San Jose. This path is 13.1 miles long with the LAH end at an elevation of 225 feet and the
terminating end at and elevation of 68 feet — both ground levels. There is an obstacle 26 feet higher than
LAH at a distance of 0.6 miles. Line of sight to an antenna on the County Building, assumed 80 feet high,
would require a minimum antenna height of 40 feet at LAH to clear the obstacle.
La Cresta water tank. This path is 0.4 miles long and is line of sight although through vegetation. The water
tank is at 490 feet ground level.
EI Camino Hospital. This path is 3.3 miles long with the LAH end at an elevation of 225 feet and the
Hospital end at 164 feet — both at ground level. There is an obstacle 41 feet higher than LAH a a distance
of 0.6 miles. Line of sight to an antenna on the hospital roof, assumed 50 feet high, would require a
minimum antenna height of 50 feet at LAH to clear the obstacle.
Loma Priem Mountain. This path is 24.8 miles long. Loma Priem is at an elevation of 3760 feet; however,
the peak is directly behind Mt Umunhum at a distance of 21 miles and with an elevation of 3440 feet. It is
not possible to achieve line -of -sight from the LAH Town Hall location.
Black Mountain. Although this site is not presently used by the County emergency communications, it may
provide an alternative to the Loma Prieta site for use in the North County. This path is 4.6 miles long. Black
Mountain is at an elevation of 2806 feet and there is no terrain clearance obstacle.
City Centers. Possible links to Los Altos, Mountain View and/or Palo Alto at 1240 MHz or 10 GHz will
require line -of -sight including most vegetation. The path to Los Altos (1.4 miles) and Mountain View (3.2
miles) centers both require a minimum of 60 foot anterum height at LAH assuming a 50 foot height at the
centers for terrain clearance. Since this suggests a height of at least 80 feet to insure vegetation clearance for
these paths from LAH, it is recommended that a repeater at the La Cresta Tank be provided for this service
if implemented in the future.
Antenna Separation
In order to provide simultaneous, or concurrent, transmission and reception on multiple nets (frequencies),
it is essential to provide isolation between antennas. This is necessary to prevent a transmitter signal on one
channel from overloading the receiver on another radio due to the strong signal. The isolation required is
generally accepted to be about 30dB. (At the present time, the antenna arrangement at the Heritage House
prevents use of more than one radio at a time.)
In order to provide 360 -degree coverage, vertical antennas are used. At our primary frequency band of 144
MHz, vertical separation of at least 12 feet is necessary to obtain the 30 dB isolation. (In contrast,
horizontal separation would have to be at least 105 feet.)
Note that the surrounding cities all use a tower with vertical antennas for V HF/UHF
communications at their communication centers.
From the above path profile descriptions, it is apparent that a minimum antenna height of 40 to 50 feet
would provide reliable 144/440 propagation to all points except Loma Prieta. (Reliable communication at
144 MHz to Loma Prieto may be possible through the use of a high -gain directional antenna.)
Prior analysis and discussion has shown that the 144/440 antennas must be vertically separated by a
nominal distance of 12 feet between mounting points in order to attain a desired isolation of 30 dB. Since a
minimum of four 144 MHz radios are to be capable of concurrent operation, this indicates a need for a
tower 60 to 70 feet in height assuming the lowest antenna at a height of approximately 25 feet and the
highest mounted on the top of the tower. Thus antennas would be mounted at 24, 36, 48 and 60 feet above
the base of the tower.
It is assumed that the 37 MHz DOC antenna can be mounted on the tower in a compatible location with the
144/440 MHz antennas without interference with amateur operations since the frequencies are significantly
different If needed, further isolation between this radio and the amateur radios can be provided through use
of filters.
NOTE: The prior discussion is based on a "useable -case" scenario for communication within the Santa
Clara County area. That is, an attempt has been made to provide line -of -sight clearance to all major points
of communication except as noted. At VHF frequencies, and to a lesser extent at UHF frequencies, signals
will be diffracted, or "bend", around limited obstacles. Thus, a maximum tower height on the order of 60
feet coWd be used with only modest degradation to communication capabilities.
Antennas
Separate antennas are required for each of the services described above which may be in concurrent
operation. Flexibility requires that the antennas may be used for any service compatible with the antenna
characteristics and the attached radios.
144220/440 MHz Antennas. Prior experience in the LAH-EOC has shown that Diamond omni -directional
vertical base -station antennas are suitable for both area coverage and the point-to-point paths discussed
above. Presently in use at the LAH-EOC is the Diamond X-510NA 144/440 MHz antenna (8.3/11.7 dB
gain, 17.2 feet long, 90 mph wind). This would be the primary antenna mounted at the top of the tower.
Other antennas used include the Diamond X -50A and Comet CX333, 144/220/440 MHz, antennas.
Although Diamond antennas are used as an example, a number of alternate manufacturers exist with similar
antennas for base station application.
37 MHz Antenna. This antenna is assumed to be non -interfering with the above VHF antennas. In the event
of desensitizing of receivers, traps or other filtering methods may have to be applied to reduce the effects
between this antenna and the VHF antennas above.
High Frequency Antenna Although not planned at this time, interest has been expressed in the future
addition of HF communications for use during a major disaster emergency. Therefore the tower should be
capable of accommodating a rotator and multi -element beam and/or rapidly deployed sloping -wire antenna
at the top of the tower. If a rotateabe beam were installed, the top -most vertical antenna would be
remounted on the rotator shaft above the beam.
Feedlines
The cable runs for this tower from the radios will be at least 90 to 130 feet. Therefore, low -loss cable is
essential if the antennas are to be used effectively at 440 MHz. Either LMR400 or 9913 cable is suggested
as a minimum. The final design may select lower loss cable as appropriate. A 1240 MHz antenna feed may
require LM600, or equivalent, to provide suitable loss characteristics. Provisioning of a 10 GHz antenna
will be discussed when additional data is available for the D -Star repeater system.
Tower
Since this is a typical communications tower requirement, a standard manufactured tower should be
acceptable. The number of antennas to be accommodated, the tower height, site restrictions and the need for
easy maintenance, strongly suggest use of a self-supporting lattice tower.
Suppliers of lattice construction towers include Rohn, Trylon, AN Towers and Valcom/Microilect. A
number of other manufacturers/constructors design and provide custom design towers. Once the antenna
requirements are finalized, the weight and wind loadings can be calculated and used to select an appropriate
tower design. It is expected that the design will be required to meet 70 mph wind in this area.
Conclusion
In order to meet the requirements for emergency communication within the Town of Los Altos Hills and to
the Santa Clara County Emergency Communication sites a tower height of at least 60 feet is needed. This
will support simultaneous operation of multiple radios which will be required in an emergency situation.
The tower should be climbable, with appropriate safety devices, to facilitate mature relocation or
modification in emergency conditions if required. A lattice tower provides these features.
R. Eger
D. Praa
June Ia, 2004
June 14, 2004
Ray,
we did have a 9% price increase approx. 8 weeks ago - I anticipate no
other price increase this year.
Your revised price quote is below:
1)
AHW HD -60 Tower
$2,390.00
2)
Step Bolt Kit - 6 Sections
$240.00
3)
60' Safety Lifeline System
$180.00
4)
Seven 5' Sidearms
$1,575.00
5)
DBI-SALA Safety Sleeve
$240.00
6)
Full Body Harness
$280.00
7)
CA State PE/SE Stamped Drawings
$275.00
8)
Shipping - Knocked -Down to 94022
$880.00
9)
Shipping - Fully Assembled Sections
$1,610.00
**Shipping assumes delivery to a commercial consignee
Please call or email with any questions.
Kind regards,
Dan R. Simmonds
President
AN Wireless Tower Co.
CAGE Code 3BY85
PA DGS VID# 181126
TX CBL/QISV VID# 1760713573200
www.anwireless.com
Section; Face Dimension$,&Weight
.
12.00'
519/32'
22 13/16"
26 13/32"
3010U,
33'19M"
3)3/$"
40 13J16"
9413/32" Seetieq 10
In ib,
SeItM 9
1221h5'.
S.i n 6
173 Pon
S.W.d 1
176 lbs
Section#
182s'
Section.$'
189165
43.00' S.Wm 4228
Ise.
See J. 1
234 @s
5¢06¢1 2
94 b5
S.m.n 1
279 lbs
Dimensions for a 100 -foot tower. The bottom six section will be used, sections
seven through ten could be added if required in the future.
Texas Towers, US Tower TX Series Tower Page Page 1 of 1
ATTACHMENTS
tenstewer com 18081272-M7
! saks®texastowers.am
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US Tower TX Series Crankup Towers
The US Tower TX series crank -ups are self supporting steel rowers, large enough to
wmmmodam most amateur rotators. The tower is constructed using 21 foot sectors, with a
four foot overlap designed to improve strength and prevent section binding while rasing and
lowering the tower. Cross bratlng Is Used at high stress areas to further mores. the strength
of the tower. All are hot dipped galvanized to resist rust and mmoslon, assuring Years of
enjoyment and trouble free service. All TX series towers are supplied with a hinged T -base,
base bolts, installation template, rotor plate, and top plate. All non -motorized models are
Supplied with a lead actuated hand winch. The TX -072110P Is supplied with an MDP -750
motor drive, and the TX489MDPL is Supplied with MDPL-1000 motor dr'we.
US Tower Home Pane TX Options r,, gack Home
httn://www.texastowers.com/txseries.htm 12/2/2004
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Emergency Communications Antenna
for the Los Altos Hills Emergency Operation Center (EOC)