Advice on bands & antennas needed for my emergency-comms situation

Discussion in 'General Technical Questions and Answers' started by MCNALLY04, Oct 11, 2019.

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  1. MCNALLY04

    MCNALLY04 QRZ Member

    40-something-er here, lots of IT and electronics experience, have always read about HAM radio but never pursued it. I'm planning to study for & pass a Level 2 / General license exam sometime in the next year.

    My core interest in HAMmming is for emergency/disaster prep. I live in the Bay Area, California, USA and would like comments & suggestions for the most robust bands and antenna setups to meet my specific needs.

    I want to be able to communicate directly and reliably (simplex / no repeaters, no digital intermediaries) with other HAM operators in the Bay Area (~20 mile radius), and with some HAMs up in northern CA, about 100-250 miles north of San Francisco.

    My budget allows for good-quality equipment (i.e. Yaesu FT-857D for example,) whatever I buy would be capable of 100W radio output. I want to go with mobile-type equipment so I can power it & move it more easily should the need arise.

    My base station location would be 2-story single family home in an urban setting, lowlands (0 to 75 feet elevation above MSL), with a max vertical whip antenna size of 3 to 8 feet (the shorter the better) and antenna mounting location 26' above the local street level. (Though I could also run up to 20' horizontal dipole wire antenna inside a wood-framed attic if that was to advantage.) There are no tall buildings or structures blocking LOS anywhere within 1 mile.

    Assuming good-quality consumer-type shortwave receiver on the other end, at a range of 10-25 miles (such as a Sangean ATS909X,) will my transmissions be easy to tune in & hear? What about at 125-250 miles out? (Assuming reasonably good reception conditions on the far end, i.e. suburban or rural density, etc.)
     
  2. KM4DYX

    KM4DYX XML Subscriber QRZ Page

    Your 125-250 mile circuit should be QED for sky wave prop, 60 meters during the day and 80 meters night. You'll want dipoles or horizontal loops at around .2 wave lengths above ground level for maximum gain to zenith. I'll include some reading material that should be helpful. Ground wave prop on 80 should do the trick out to 20 miles, terrain permitting, but you'll need vertical antennas for that.

    untitled - 2015-Witvliet-NVISElevationAnglesandAntennaHeight-IEEEAntPropMag.pdf

    http://on5au.be/content/a10/wire/n4.pdf
     
    KK4NSF likes this.
  3. MCNALLY04

    MCNALLY04 QRZ Member

    Thanks for the detailed-but-succinct reply, it's exactly what I was looking for & I have enough grasp of radio concepts already to be able to understand the reference materials.
     
  4. AG6QR

    AG6QR Subscriber QRZ Page

    The most useful bands will depend on time of day and time of year. If you want reliability, you'll need band agility to adapt to conditions. It would be good to have the capability to use everything from 160m to 20m, though 40m, 60m, and 80m are most likely to be useful. Power can help.

    I'm in Marin, and our local RACES group goes through this exercise every week, with varying results. You never know for sure which band, if any, will work until you try.

    Propagation is a funny thing. Local contact can be harder than distant, because the ionosphere reflects better at shallow angles. I remember hearing a local friend of mine on 40m one evening talking to a station in Ohio. After they concluded, I called my friend. He couldn't hear me, but the Ohio station could, and we had a nice chat. My friend was about 7 miles away, but with a substantial ridge between the two of us.

    Our RACES group will often resort to having a distant station relay in order to pass messages around the county. Usually the relay station is west of the Rockies.
     
  5. MCNALLY04

    MCNALLY04 QRZ Member

    Thanks for your remarks.

    For you and/or any others who read & care to reply to this thread, I'd appreciate pointers to a few of the best comprehensive guidebooks / texts on antenna theory & practice (as applicable to amateur radio.) Prefer stuff written at the level of of BS / 4-year-level college engineer's-prep physics and basic calculus. Anything below that will be over-simplified, anything beyond it (i.e. post-graduate level electrical engineering) is out of my reach.
     
  6. KM4DYX

    KM4DYX XML Subscriber QRZ Page

  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Actually, the 20-mile radius is pretty easily covered on the 2 meter ham band (FM) provided the other station ("listeners" or operators) have a 2m outdoor antenna.

    From here at my home (average elevation for the area, it's 850' asl but actually in a big valley with 2500 to 5000' hills around in most directions, several miles away) I can easily "work" other hams using only 2m hand-held transceivers with small whip antennas about 10 miles away; but if those same stations connect decent outdoor antennas above their roofs, that extends to 20 miles pretty easily. This involves no repeaters, it's just point-to-point simplex.

    80m (or 75m "phone") also works well for short distances and people should be able to receive you with decent shortwave receivers if they want to.

    The 125 to 250-mile stuff is better served on 40 meters or 75 meters, with 40m working better during daylight hours and 75m working better after that, provided the "receiving" stations actually have antennas (like wires up in trees or something); if they rely on an extendable whip from a portable shortwave receiver, maybe not.

    For decent "transmitting" with 100W on those bands takes an antenna longer than 20' to be anywhere near "efficient." An STL (small transmitting loop, which is also used for receiving) for those bands is not such an easy project and unless built of very robust components will not handle 100 watts of transmitting power. An experienced loop builder who knows what he's doing and can find tunable high voltage capacitors and do everything just right can probably make one for a couple hundred dollars, but there isn't a lot on the market. It's an experimenter's paradise.
     
    AG6QR likes this.
  8. AI3V

    AI3V Ham Member QRZ Page

    Its a fantasy to think you will have reliable communications on a 250 mile link with the antenna size and power you post.

    And then wanting to be able to go mobile and maintain the same link is double down fantasy.

    Rege
     
    K7MH likes this.
  9. KM4DYX

    KM4DYX XML Subscriber QRZ Page

    40 hasn't been much good for short skip lately. I couldn't hear the SOTA guys in east TN/west NC (300 miles ish) on 40 today but the guys on 60 were Loud and Clear.

    [​IMG]
     
  10. AI3V

    AI3V Ham Member QRZ Page

    Bs is right.

    You obviously have never even attempted to listen for stations at the range you want.

    Anybody that $ell$ you equipment and tells you it will do what you want is taking advantage of your ignorance.

    Here is a hint: what am and fm broadcast stations can you receive on a"good-quality consumer-type shortwave receiver on the other end, ...(such as a Sangean ATS909X,)"
    At your proposed 250 mile range , and what type of transmitter power,frequency, antenna height, size and location are they running. And what time, day or night?

    It won't be 100 watts, and a attic antenna from a subdivision.

    Rege
     
    Last edited: Oct 12, 2019

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