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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

    Lots of useful signal amid the noise in this thread, thanks. Though the 'noise' itself has some utility as well.

    Aside from the posts I acknowledged in earlier replies, these two later ones I also found particularly useful.
    KF4ZGZ: https://forums.qrz.com/index.php?th...cy-comms-situation.676444/page-2#post-5224679
    KK4NSF: https://forums.qrz.com/index.php?th...cy-comms-situation.676444/page-2#post-5225894

    I had arrived at notion of a ~60-80 foot inverted-vee (or perhaps horizontal) mounted at ~14 to 20 feet above ground independently after reading the earlier-posted NVIS articles; good to see my conclusions confirmed, thanks. For sake of convenience & ease of put-up and take-down I may even try to figure out a horizontal end-fed random wire for ~40 to 80M NVIS between 0 and 250 miles (avoiding the effort needed to feed a dipole out in the middle of a yard,) with caveats noted on antenna tuning challenges and possible "HF in the shack" hazards.

    Reviewing my initial post, I see I made the semantic error of using the word "mobile" when I meant "portable." I would probably buy a mobile rig & set it up as a home base-station for ordinary use, I just want to be able to take it with me & string up some kind of field-expedient NVIS antenna should the need arise. My mentioning "8 foot whip" shows how rusty my HAM knowledge had become; now that I've taken a weekend to review basic HF prop theory & antenna practice I'm under no illusions that I'll "get out" on NVIS prop with a short little whip. (Though I did see an interesting diagram of an 1960's vintage army vehicle with its ~15 foot bumper-mounted whip "tied back" in a long 90º bend to accomplish some level of field-expedient NIVS prop.)

    There is a huge variety & range-of-seriousness for "ecomms" scenarios. Anything from a little 5.0 to 6.0 temblor which might knock over a few buildings and injure 0.0001% of the local population to a full-on GIC / "Carrington Event"-type regional or national blackout possibly lasting for years. In the former situation there's probably not a dire need for HAM ecomms in urban areas with reasonably-hardened gov't-agency comms infrastructure. In the latter it is a virtual certainty that after a couple of days to weeks (at most,) most repeaters will be down & various forms of independent amateur radio powered from private gennys, solar panels, large batteries, etc. will be pretty much the only game in town. It's the larger/longer/scarier "grid out" situations that are my specific interest, though it would also be nice to be able to broadcast my situation ("Hi, _____ here, I'm alive, not dead, the house has not burned down, I will re-transmit daily on X.XXX Mhz @ XXX UTC) to those whom it does concern) even if public consumer-grade access to cellphone & internet service is unavailable. (Say, a 7.1-7.7 Bay Area quake that knocks out or traffic-jams internet / cell phone / TXT messages for ~3 to 7 days post-event.)

    Re: licensing, taking an on-line practice exam I scored ~75% (pass) on Technician class without any preparation. I'm sure a few hours of brush-up and review will easily put me in the Technician class, maybe a day or three and I'll also pass Amateur, when I have time to schedule those exams.

    About the State of CA and overall emergency prep -- I have a lot of respect for what the amateur-radio community generally, esp. in the US, has accomplished for emergency backup & assistance comms (sometimes becoming primary comms, situation depending,) and I can also perceive/understand how the tides may be gradually changing over a years-to-decades time frame as cellular / digital radio tech becomes ever more ubiquitous and specific attention is given to hardening it for disaster situations. After all, the entire HAM/amateur social phenomenon & culture is itself an off-shoot of technology; it is reasonable therefore to expect the culture to continue to change as technology develops. Maybe there's a bit of "saltiness" in some parts of serious HAM ecomms community as local governments start to say, reasonably or unreasonably, "we don't really need your services the way we once did."

    About the changing relationship between amateur radio & government, I sense a distinct shift (or perhaps ongoing evolution) underway in how 'the government' treats 'the citizens,' and I can see, particularly under the current federal administration, a constriction and formalizing of govt. <--> citizen / volunteer rapport. Put another way, due to the polarizing and intensifying of political opinions (on any and all sides, whether right/left/center) and the increasing tendency of people on many sides to "get nasty" in response to actual or merely perceived offense -- many sectors of gov't are "pulling up the ladders" and keeping more distance between themselves (their workers, their public image, their liability) and the general public by giving citizen & volunteer orgs short shrift, the cold shoulder, rescinding "the benefit of the doubt," etc.
     
    Last edited: Oct 14, 2019
  2. KX4Z

    KX4Z Ham Member QRZ Page

    first -- unless you are a PRiOR involved volunteer in a larger group, you ar probaby unlikely to want to be doing a bunch of radio communications after anything MAJOR, other than "fitting into the flow" of what you realize is being done. I think that is how things worked out in Katrina (I wasn't there, I just read about it). And that is how things worked out early in the goings of Puerto Rico, with 6,000 messages moved by ont-the-spot volunteers I would encourage sustained involved with a group that obviously knows their stuff.

    On antennas -- there are a zillion solutions. The ones you suggest are fine. You might look into RESONANT haf-wave endfed using a 49:1 balun Our local group "discovered" these just recently and buillt 15 or so of them ans they are just fabulous. I wished i had known about them earlier. A ton eaiser to do than a lot of things I've done over the years. Here is an article that helped us: https://qsl.net/nf4rc/2019/InstructionsEFHW.pdf

    Lastlly --- avoid being a loner!
     
  3. AI3V

    AI3V Ham Member QRZ Page

    The acronym "nvis" keeps getting posted as if throwing any wire up, a few feet off the ground, and by magic you have a 250 mile radio link.

    I foresee much wa$ted money, and lack of desired communications in your future.

    Rege, who once got to see (and fix!) just what it took to communicate to and from a aircraft carrier with hf radio.
     
  4. KM3F

    KM3F Ham Member QRZ Page

    A ya non believers, look up a YouTube video call GUN GUY.
    He brings in another video about CA state shedding the importance of Ham radio as Ecom back up.
    And ya though I was spreading miss information.
    Check it out for yourself and debate those sources in your own state.
    .
    BTW i'm not putting down the importance of amateur radio in a disaster when everything is out, but the gov won't let you in an area for first hand info to help them unless you have the ID THEY require and will take it at the Ecom center from another operator.
    Otherwise your running solo ham to ham.
     
  5. K6BRN

    K6BRN XML Subscriber QRZ Page

    All righty, then! THATS what's wrong with the world! And I almost missed it.

    NOTE TO SELF: Send in willing/gullible hams equipped with APRS to find the center of major forest fires. When the signal stops, read the last coordinates and you've found it. Brilliant!
     
  6. N8TGQ

    N8TGQ Ham Member QRZ Page

     
  7. N8TGQ

    N8TGQ Ham Member QRZ Page

    I've been using these end fed half waves for years. They will also work on multiples of half wave- 40meter will work on 20, 15, and 10 with some adjustment when building it.
    I wonder about using only half the toroid. Mine have always been evenly spaced around the whole toroid. Does using only half add something I dont know about?
     
  8. KX4Z

    KX4Z Ham Member QRZ Page

    I don't know either. in our 49:1 we used tightly spaced turns, but a really smart guy in the group told us that actually cuts down on the high frequency end, because of inter-turn capacitance, so we might have been wrong to do that.....

    Gordon
     
  9. WA7ARK

    WA7ARK Ham Member QRZ Page

    I take issue with the idea that an EFHW antenna as depicted in that .pdf is a Marconi-style ground-referenced antenna. An EFHW is really a Hertzian dipole, which works best if the transformer/driven end and the wire is horizontal and as far from the dirt as possible!

    This naive and wrong-headed idea that the transformer should be low to the ground is circulating on the web and lots of YouTubes, but it is wrong!
     
  10. KX4Z

    KX4Z Ham Member QRZ Page

    so do you allow radiation from the coax shield? Where do the electrons return from? I seem to remember some law that you have to have two conductors or such..
     

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