1. Seal Beach RACES ATV Design and Interference Issues in Seal Beach, California
By: Mike Maronta KC6YNQ

2. In Southern California only two 70 CM Frequencies are available for ATV, each designated by the Picture Carrier Center Frequency. They are:
MHz - ATV Simplex
MHz – ATV Repeater Inputs
Our original assignment was to install a receiving system at the Police Department to receive video from several adjacent City helicopters on MHz. The team was calling this “Whirlybird TV”.
Later we were asked to develop a portable ATV transmitter to send live video back to the EOC at the Police Department from anywhere in the City. Our only frequency choice for this was MHz as we already had a Receiving System in place.
Each ATV Channel is 6 MHz wide and contains the following components:

4. SCRRBA coordinates all frequencies in the 70 cm Band
SCRRBA coordinates all frequencies in the 70 cm Band. They have allowed other users to share this band within the 6 MHz ATV Channels. These other users are:
Point to Point 20 KHz Bandwidth Paired
Weak Signal
Satellite
The next Slide shows the Details of where these other users are located
within the two 70 cm ATV Channels.
Also it should be pointed we share the 420 to 450 MHz portion of the 70 cm band, on a secondary basis, with Military Radar.

7. So what does this this all mean
for
ATV in Seal Beach? It means we’re not going to get an interference free signal on MHz Simplex, most of the time! Some days are going to be better than others, depending on how much use the Point to Point links have. There is much less interference on the Repeater input Frequency of MHz, because the Satellite folks point their beam Antennas upward. We’re considering using this frequency during an Activation, aka Emergency,
if we can’t get through on MHz Simplex!
If we’re anywhere North of the PD, our Transmitting beam Antenna will be pointing South and shouldn’t interfere with Mount Wilson or Santiago Peak. If we’re South of the PD our Transmitting beam Antenna will be pointing North, and our signal will most likely get into Mount Wilson, but not Santiago Peak. The problem here is that since all the ATV Repeater Sites in Southern California are linked, what gets into one gets into all! We’re going to evaluate this on a case by case basis.

8. ATV is “Line of Sight”, except in very limited situations
ATV is “Line of Sight”, except in very limited situations. If you can’t see the receiving station antenna, in general, it won’t work. Our path from Leisure World back to the Police Department was blocked by Boeing Building 80. We were, however, able to bounce our signal off of the large Metal sided Assembly Building to get around this obstruction. That is “very” unusual.
We have tried to send an ATV signal “Over the Hill” from the Seal Beach Pier area to the Police Department, with limited success, actually a P2 signal most of the time with an occasional P3 signal. We tried this with our portable 11dbd gain yagi beam antenna from the porch of the Police Department Substation, about 10 feet above Ocean Avenue. Later we installed a permanent 11 dbd gain yagi antenna on top of the Lifeguard Headquarters, about 30 feet above Ocean Avenue, in hopes of getting a better path back to the Police Department. It didn’t work!
The next Slide shows the permanent ATV Antenna on top of the Lifeguard Headquarters.

9. On top of Lifeguard Tower at the Seal Beach Pier
11 dbd ATV Yagi
On top of Lifeguard Tower at the Seal Beach Pier

10. For those of you not familiar with the ATV reporting system, here it is:
P5 - Excellent: No discernible Noise
P4 - Good: Slightly Noisy
P3 - Fair: Somewhat Noisy, but not overly distracting
P2 - Poor: Definitely Noisy, making viewing tedious and obscuring finer detail
P1 - Barely Perceptible: Very Noisy and obscures all but the larger details
P0 – Is there really a signal there?

11. Excellent: No discernible Noise
ATV “P5” Picture
Excellent: No discernible Noise

12. ATV “P4” Picture
Good: Slightly Noisy

13. Fair: Somewhat Noisy but not overly distracting
ATV “P3” Picture
Fair: Somewhat Noisy but not overly distracting

14. ATV “P2” Picture
Poor: Definitely Noisy, making viewing tedious and obscuring finer detail

15. Barely Perceptible: Very Noisy and obscures all but the larger details
ATV “P1” Picture
Barely Perceptible: Very Noisy and obscures all but the larger details

16. Is there really a signal there?
ATV “P0” Picture
Is there really a signal there?

17. Pier to Police Department Path
Signal blocked by “The Hill”

19. After fooling around with this for over a year, we’ve decided there is no way we can get a Good P4 or Excellent P5 Signal from the Pier area to the Police Department without doing something “Unique”. Since the Pier Area is our main problem during a Disaster, except for Earthquakes, which includes flooding in the low areas do to heavy rain, surf, or Tsunami, we’ve decided the something “Unique” is required.
That something “Unique” is to move our ATV 70 cm Receiving System to the top of Boeing Building 80 and install a 2.4 GHz link from the Top of Building 80 to the Police Department. In addition to the Basic Hardware, 70 cm Omni Receiving Antenna, Coax, ATV Receiver, 2.4 GHz Antenna and Transmitter, we need a way to turn the receiver off and on remotely and turn on and off the 2.4 GHz Transmitter remotely. We’ll do that by utilizing DTMF tones thru our Repeater Controller which has four (4) spare transistor switched outputs which we’ll connect to four (4) DPDT relays.
In addition to the hardware, we’ll need concurrence from the Boeing Frequency Management group, which shouldn’t be a problem, just time consuming and paperwork intensive.
The Path and Profiles for this system are shown on the next four (4) slides:

20. Pier to Boeing Building 80 Path
Signal goes over “The Hill”

22. Boeing Building 80 to PD
2.4 GHz ATV Path

23. Boeing Building 80 to PD ATV Profile

24. Seal Beach ATV Equipment
Receiving System
The Receiving System consists of a Diamond X510NJ Omni Antenna with 9.5 db of gain, a Downeast Microwave L432LNA Preamplifier with home brew power inserter, about 60 feet of LMR-400 coax, a DCI VSB filter, a PC Electronics TVC- 4S Downconverter, a RFDM2 Demodulator with external S-Meter, a Video Distribution amplifier, a Radio Room 26" Flat Screen TV and EOC mounted 42" Flat Screen TV. We also have a home brew Ground Plane Antenna with coax switch for use when receiving Helicopter Video.

27. Seal Beach ATV Equipment
2. Transmitting Equipment
The Transmitting System consists of a VideoLynx 5 watt Transmitter and a PC Electronics FMA5-G Sound subcarrier board custom mounted
and wired in a Hammond Enclosure feeding a 25 Watt PEP Downeast Microwave model 7025 PA Amplifier connected to a tripod mounted Old Antenna Labs Beam Antenna with 11.0 dbd gain. Video is provided by a Sony DCR - SR47 Camcorder. Audio is provided by the internal Camcorder Microphone, or an external Audio 2000s Dynamic Microphone. Power is provided by a 35 Ah 12 volt battery, A Super PWRgate PG-40S battery charger, and a Samlex SEC-1235M      120 VAC/12V DC, 35 ampere regulated power supply.  Battery  life is approx. 3 h.
The next slide shows the details of this configuration:

29. Conclusions
1. We’ll consider using MHz during an Activation for Simplex ATV if we can’t get a reliable signal on MHz. 2. We’ll proceed ahead with moving the 70 CM ATV Receiving System to the top of Boeing Building 80 and install a 2.4 GHz link from Boeing to the Police Department.