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CMD32 Repeater In Cuesta La Honda Is Up

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  • #11394

    The 440.100 repeater above Cuesta La Honda is operational. You will use CMD32 if you have programmed your radio with the Coastside communication plan. We expect excellent coverage with hand held radios within the Cuesta area. Since this is UHF, propagation will be pretty close to line of sight and those outside of the Cuesta area may not be able to work this repeater.

    It’s always worth a try.

    This repeater is not (presently) linked to other repeaters. Whatever happens on CMD32 stays on CMD32. 😉

    Details: 440.100 MHz, + offset, CTCSS: 114.8, TSQ, ID: W6SCF

    #11442

    Several people have asked questions on the topic of our repeaters. This might be a good forum to cover some of these and to review some of the topics we may not have talked about very much since we studied for our licensing exam.

    Q: Can I use the CMD32 repeater where I am? What area is covered by this repeater?

    A: CMD32 repeater covers primarily the Cuesta La Honda area. You may be able to “break” (get into) or receive transmissions from the repeater from spots outside the primary coverage area. You can find coverage maps on our web site under the “Information” > “Repeaters” tab. The maps work with Google Earth.

    Q: Can’t the covered area be larger if the repeater transmits with more power? If the antenna was higher?

    A: Repeater coverage is determined by the repeater’s transmit range and also by its ability to receive signals from you. Your ability to reach the repeater depends on the type of radio, its transmit power and the antenna that you use. A properly designed repeater should be neither an “elephant” nor an “alligator.”

    Q: Alligator? Elephant?

    A: An alligator is a repeater that’s all mouth and no ears. Its transmit range is much larger than the range of those trying to reach it. It’s a poor use of a limited resource (available frequencies) because it spills over into neighboring areas so they cannot use that frequency or adjacent frequencies. Likewise an elephant is all ears and a small mouth. It picks up signals from areas much farther away than it can reach. In engineering a repeater we take into account the type of user for the repeater: For CMD32 the primary user is presumed to have a handheld radio with limited transmit power and a relatively inefficient antenna. It is further assumed that the user will be in a relatively built up area, perhaps indoors or participating in an activity like sizing up damage on foot following a disaster.

    Q: Why does it matter if the area is built up or wide open?

    A: Broadly most of us use two bands of frequencies: VHF (or 2 meter wavelength) and UHF (or 70 centimeter wavelength.) Efficient antenna length is closely related to the wavelength of the transmission, so an efficient VHF antenna is roughly three times the length of a similarly efficient UHF antenna. Compact antennas are usually better on UHF than VHF. UHF frequencies are more likely to be attenuated by foliage (so not as good in heavily wooded areas) but the shorter wavelength is more likely to find its way deeper into structures by bouncing off walls. VHF frequencies are generally less likely to penetrate deeply into buildings (you may have to stand near a window to get a good signal) but are less affected by green leaves on trees. The longer wavelength VHF frequencies will also bend or wrap a little going over ridge tops so their range goes a bit beyond line of sight. Without getting into the math, let’s say that the bigger you are (as a radio wavelength) the flatter the hills and mountains appear.

    Q: So UHF is better for areas with lots of buildings?

    A: UHF frequencies can be less fussy in and around buildings. They also tend to be a better choice with hand held radios because they favor shorter antennas.

    Q: What about terrain?

    A: Terrain can work to our advantage. If we can limit the coverage area for a certain frequency we can greatly reduce interference from others using the same frequency. As an example: The PAVE PAWS over the horizon, early warning RADAR at Beale Air Force Base uses the same UHF frequencies as amateur radio. We cannot interfere with its operation. The coast mountain range effectively blocks our repeater from interfering with PAVE PAWS while repeaters on the other side of Skyline have had to greatly reduce their transmitter power or cease operation altogether to avoid interference.

    Q: Can we ramp up the repeater transmit power, then?

    A: There’s no reason to transmit with significantly more power than the hand held radios we’re trying to serve. Our aim is to match our receive and transmit footprints. When we add battery backup to the repeater design, adding more transmit power also means more draw on the repeater’s backup batteries.

    Q: How about adding more batteries to the repeater?

    A: Batteries need to be replaced on a regular basis if we want reliable operation. We have been replacing them on a four year cycle at the end of which they should retain 60-90% of their original rated storage capacity. As I write this approximately $10 of each club members’ annual dues go towards battery replacement costs. When we design each backup system we take into account how long the equipment must operate before we can get redundant power running and how much safety factor we can afford. These choices play an important part of how club membership dues are determined.

    Q: So, if CMD32 covers Cuesta and CMD33 covers Pescadero and Butano, what is the VHF (CMD31) repeater’s purpose?

    A: CMD31 is designed to cover the larger South Coast and South Skyline areas combined. The lower, VHF frequency gets into canyons and valleys better than UHF frequencies do and is not as strongly attenuated by vegetation. A longer antenna is more effective and so mobile radios in cars and fixed base stations with outside antennas will fare quite a bit better than a hand held radio with a “rubber duck” antenna.

    Q: When should I use CMD31?

    A: It’s fine to use it at any time as an area-wide repeater and as the resource that connects us all together. If there were a really large scale disaster where radio traffic from many strike teams would overwhelm CMD31 then communities would be encouraged to use their community repeaters and then to coordinate using the area-wide repeater: CMD31. Further requests for resources could be passed to the county level operating on CTL95. Eventually, as resources allow, we hope to link the various community repeaters so that your nearest repeater can be used for day-to-day wide area communication with the option to un-link them in the event that traffic becomes overwhelming.

    Q: Is there any restriction when I should not use CMD31 (or CMD32 or CMD33)?

    A: Avoid interfering with others using the repeater is the ground rule. Almost everything else follows from that. If you are participating in a directed net then follow the net control operator’s instructions. If you are not participating then wait until the net is completed to use the repeater. If the power is out and the repeater is operating on standby batteries then keep your messages brief and stick to essential traffic so the batteries will last longer. Outside the basic rules our repeaters are open to all licensed amateurs.

    Q: Got it! So it’s ok to use CMD32 while hiking with friends, as an intercom calling my spouse or kids (licensed!) in for dinner, checking if we need something from the market or post office, or…?

    A: Exactly! CMD32 (and CMD33) is high quality, local communication within your neighborhood. It will generally be better quality in more places than using the simplex (VTAC and UTAC) frequencies since the repeater sits high above you. It is a good resource to organize and to check in with your neighbors.

    #11443
    Casey, KA5WAX
    Participant

    Thanks Peter, that’s very easy to understand. It’s a keeper. I’m now motivated to start checking out
    how CMD33 would work as I am wandering around down here.

    May I share this overview with our Butano group, as much as for licensing inspiration as anything? With attribution of course, but perhaps no email addr so you are not awash with more questions.

    As you know we’re managing to nibble at the CERT training over time.

    In parallel we’ve been programming more and more BFs and man I would
    like to get some more licensed operators out of the current interest.

    #11445

    Thanks for your kind words, Casey! Please feel free to share with your group. My contact email if there are questions is [my callsign]@arrl.net

    I’m here to assist in whatever way I can.

    #11448
    Eva, KN6CZD
    Participant

    Great write-up, Peter. Love it!
    I wish there was a way to make this kind of information more findable on the website.

    #11449
    David, KM6DOV
    Participant

    Eva,
    The website committee is taking exactly this sort of request into consideration. If you’d like to be a part of improving the site, please consider joining.

    #11450
    Eva, KN6CZD
    Participant

    Sure, sign me up 🙂

    #11451

    If you have a question about something, I am very sure someone else shares that same question. The easiest way to find an answer is to ask.

    If you do that then you’ve helped someone else out as well.

    #11454
    Mary, AF6IE
    Participant

    Yes, thank you Peter. As you know I’m a fairly long-time ham but your explanation made a lot of things clearer for me.

    #11456
    David, KM6DOV
    Participant

    FYI, CMD33 works great in Loma Mar.
    CMD32 does not.

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