Reference no: EM132798318

Transmission Line and Antenna Installation Assignment

Your company is submitting a bid on installing a continuous weather UHF broadcast site for the Coast Guard. Your boss asks you to prepare the materials you will need to install the radio equipment and antenna. You must now plan and calculate how all of this equipment will work together under a heavy duty cycle of 100% continuous broadcast.

The location is on the inside passage of Georgia Straight. The small island is mostly bare rock (Basalt) with not a lot of soil.

The transmitter frequency is 400.000 MHz. The cable run will be 26 meters up the side of a small steep hill. The cable type will be JAN-C-17A / RG-214/U military grade. The transmitter, supplied by the Coast Guard, will be putting out 100 watts. The antenna is a 50 Ohm omnidirectional SCALA K751637 (assume an internal balun) which will create an internal VSWR of approximately 1.2 to 1.4.

The radio enclosure is already in place and has been properly grounded by another contractor. Inside the enclosure a bulkhead grounding bus bar has already been connected to the site grounding network. The cable tray also requires grounding.

The tower is supplied and is 6 meters tall. The anchor pins and guy wires were also provided and grounded. Another contractor has taken care of tower installation and grounding; it is already "in place". You must purchase and install all other materials

The tower top must also have a Lightning Rod installed. Look up correct grounding procedures for tower top lightning arrestors.

One neatly drawn illustration has been provided for this assignment. You must add-in, to the PDF, all connector losses. The drawing is the layout ground plan, as seen standing on the ground (side view), Question #12 (show all cable installation features). The Polyphasor lighting surge protector is located inside the transmitter shack and is connected, by a Jumper Cable, to the transmitter's RF port, on the equipment rack. The other Polyphaser port is connected to the outside cable, passing through the wall, to be directly connected to the antenna's input connector. Inspect the antenna spec sheet for RF connector type compliance.

You are also asked to create costing quote to show the installation price your company will charge. Take a tip from the Supplemental Materials handouts, on all the items you will require to assemble a complete materials list. Labour costs will be omitted. Use fake prices for the materials required. The bid must use separate columns for unit price, quantity, and total item price on each line. At the bottom of your list show the total cost, then add 12% tax and indicate the final price of your materials list for the proposal bid.

The following questions need to address. Neatly show all your work for each question including formulas. Indicate where you obtained your data for your calculations.

Include all spec and data sheets in your assignment, and use as reference material.

You must provide a completely labeled "side view" drawing (provided) of the installation including all component names and grounding points.

Question 1. Transmission line loss for cable only.

Question 2. Calculate the wavelength inside the transmission line.

Question 3. The lightning protection device (polyphasor) is directly connected to the transmitter output jack (for simplicity sake). It must also have its own site grounding cable. It has a 50? input/output impedance.

a) Explain why the Lighting Rod must have its own tower grounding cable (bare copper #6 AWG gauge).

b) Explain how a polyphasor device works.

Question 4. Describe how you would check grounding for the pre-installed equipment rack, which is holding your transmitter. Look up the proper way this should be done.

Question 5. When installing an outdoor cable "Grounding Kit, describe the method of connecting it to your grounding setup. Look up the proper way this should be done.

Question 6. Check the specifications for the chosen antenna. What is the maximum VSWR it will produce? Due to the collapsing "Near Field" there is always a small amount of reflected power occurring from antennas. VSWR =

What type of connector is at the input to the antenna?

Question 7. Calculate the total loss between the transmitter port and the antenna's input connector. Include all devices in your answer. Assume there is a loss of 0.1 dB per connector (spec of 0.15dB is only for 10 GHz). Assume a 0.5dB loss for the Jumper Cable between the surge protector and the equipment rack. Use spec sheet for Polyphaser loss. Show all work. (insert your own drawing here)

Total Loss dB Expected power at the end of the cable.

Calculate the ERP (Effective Radiated Power uses a dipole reference), in Watts, you would expect to see coming off the antenna. (Ignoring I² R losses) The antenna is in perfect condition so assume optimal efficiency. Hint: Refer to your system sketch. Show all formulas and calculations.

Total Loss of Tx line = Gain of antenna in dBd =

Input power level to antenna base = W ERP = W

Question 8. What is the maximum input power specification for the antenna?

Does the input power to the antenna exceed the manufacturer's specs?

Why do you think your boss chose this particular cable? Back up your rational with data.

You may want to do a little on-line research. Study the cable spec sheet carefully.

Question 9. Upon completion of the installation project a 50? Dummy load is put in place of the antenna. You perform a VSWR check using a Bird Thru Wattmeter at the transmitter O/P jack, and obtain a reading of 17 : 1. Assume Transmitter O/P Z = 50?

What would be the forward power reading on the Bird Thru Wattmeter? W

What would be the reflected power reading on the Bird Thru Wattmeter? W

Is this an acceptable situation? If it is not, explain why. Provide two points in your answer.

What would be the most logical cause(s) of this problem?

Next move the Thru Wattmeter, up the tower, between cable and antenna feed point.

What forward power reading would you expect to see on your Bird Thru Wattmeter, if it is located between the cable and the antenna? W (expected power into ant.)

(Recall Step #8)

What reflected power reading you would expect to see on your Bird Thru Wattmeter, if it is located between the cable and the antenna? W
Assume maximum antenna VSWR value is in effect. Show all work.

How would you locate the problem? Assume you do not have access to a TDR.

What corrective action must you take to fix the problem? 2 marks

Question 10. A nearby Telus cell site is creating radio interference on your broadcast.

What installation error(s) have you made?

How would you correct this situation?

The following "As Built" drawing has been provided by the government tender. Site and tower grounding has already been completed by another contractor. On basalt outcrops diamond drillers create deep holes in which metal rods were inserted. Bare metal cables are clamped together to link the grounding points. You must make, or check for, the following ground connections:

a) Building Ground Bus (Done)
b) Transmitter rack (Done)
c) Polyphasor & building cable exit (You must add)
d) Outside cable tray (Done)
e) Tower to grounding rods inside bedrock (Done)
f) Lightning Rod bare copper (#6 AWG gauge) cable to Tower Ground (You do)
g) Tower ground clamps to cable Grounding Kit locations, (You do)

The following building grounding plan (provide top-view PDF) must be included in your assignment, along with the provided Tower Grounding illustration (side-view provided PDF).

Question 11. Use the provided "side view" perspective PDF. Start with the radio enclosure (with transmitter inside) end with the antenna (on top of the tower). Refer to your Handouts for assistance. Make sure that all cables, grounding points, devices, and connectors have an arrow indication; with a label for each item and gain/loss in dB, where applicable.

You will also be graded on neatness.

Question 12. Create a fictitious Billing Receipt page which shows: a) Name of item b) Quantity of item c) Total cost of items. Be thorough and include ALL items required for the bid. At the bottom of the sheet add up all costs and add 12% taxes. This sheet(s) must be type written. Omit labour costs.

Note: Include the Cable Grounding Kit in your parts list along with a sufficient amount of # 5 grade bare copper grounding cable. Actual prices are not required, they must be "made up". In the interest of saving time. Prices for each item will be factious, but quantities will be evaluated.

Attachment:- Antenna Installation Assignment.rar