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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. WA7ARK

    WA7ARK Ham Member QRZ Page

    There is an optimum distance down the coax where I recommend you put a ferrite common mode choke. These QRZ postings explain why.

    https://forums.qrz.com/index.php?threads/more-efhw-questions.673816/page-3#post-5206725

    https://forums.qrz.com/index.php?threads/160meter-endfed-halfwave-antenna-on-a-65ft-tower.662105/
     
  2. KX4Z

    KX4Z Ham Member QRZ Page


    hi, thank you for those references. considering it as an extrmely off center fed dipole does make sense. I'm sorta concerned about common mode currents, so having to add a choke is perhaps a disadvantage rather than an advantage. Our particular interest is in NVIS antennas, so running the EFHW against ground, and making it either a sloping wire or an inverted vee (fundamental current peak at the high point, then) works quite well for us. Beause the impedance is so high at the feed point, it seems to me (i could be wrong) that a modest ground resistance causes very little loss. We checked our design on a spectrum naalyzer and found balun losses < 2 dB, and we were pretty happy with an antenna that did SO WELL.

    i ran one as a "vertical" for some tests related to RM-11831, at a less-than-heavily-used bus-stop and it worked out fabulously on the 2nd harmonic of the antenna, making a bunch of 20 meter connections.

    This is a very fun antenna, and I could kick myself for not discovering it many years ago....my loss! Your version looks FINE BUSINESS to me!

    Gordon
     
  3. W0IS

    W0IS Ham Member QRZ Page

    As noted above, the one thing hams are not allowed to do is broadcast.

    Now, it's frequently pointed out that after the zombie apocalypse, there will be no laws, and therefore it's not something that needs to be worried about. That is probably true, but how will you know it works? Amateur radio is not rocket science, but even in the best of conditions, it requires a certain amount of experimentation to make sure things are working OK. And that practice really needs to be done while the laws are still in effect.

    Amateur radio is designed for two-way communication. Especially if you have a short transmission, it's unlikely that the intended recipient would get you tuned in at just the right time. That's why when hams have "skeds," it's not uncommon to call for a few minutes until they reply.

    If I were going to send a one-way transmission reliably, then it would be a looped message that kept repeating for a long period of time. That way, if someone tuned in a few minutes late (because their cel phone clock wasn't working, etc.), if conditions were bad, or if they just missed it the first time, then they would be able to fill in the blanks. Unfortunately, that would also stand out like a sore thumb because it's not legal.
     
  4. KX4Z

    KX4Z Ham Member QRZ Page

    I had tried to point out that what is MOST useful is establishing relationships BEFORE a disaster.

    Any of you who haven't read what happend in Katrina.....when the police go 'home' it is a totally difffernt world!!! One you realy don't want to go out in, or broadcast in, or do anything to attract attention....not even smoke or light.

    Lets hope that never happens in YOUR neck of the woods.....pretty horrible when hospitals run out of painkillers and oxygen....and antibiotics.....

    SO: I urge that a better and much more useful goal is to shore up the volunteer spirit and work with your local officials to help fill in the gaps to prevent the "police from going home".

    In our locaal area, i helped the highest career sheriff deputy (the career head honcho) get his Tech, and General..and soon he'll have his Extra!

    Result? Our professionallism got noticed. Our antennas got fixed, our shelters got renovated systems for the first time; our gear was improved, our permissions to fix things were granted; our bacakground checks AND BADGES THIS VERY WEEK happened, and I just got approval to be able to wave my badge and the front door opens!

    Folks are being shown the door in some states.....we are being given the keys to the door in my county. And the same can happen anywhere....it took 3 years of real committment and an attitude of professionalism. But you can make an improvement in your community. Ifi it ALL falls apart due to some really horrendous thing....then yes, it may still degenerate into huge lawlessness.....but I know a great friend to know in times like that, and his family is likely to be in my 2nd floor bedrooms to wait it out. Can't ask for a better situation. He used to run the SWAT team....

    Cheers...
     

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