What am I doing wrong! IC-718 and MFJ 949E

Discussion in 'General Technical Questions and Answers' started by kd7nmn, Jul 28, 2007.

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  1. KC0W

    KC0W Premium Subscriber QRZ Page

    The number is closer to 200 feet.

    To find the length of the longer of the two vertical sections of a J Pole antenna, the formula is: 705 ÷ MHz.


    Tom kcØw
     
  2. AG3Y

    AG3Y Guest

    It would be interesting to try, though, wouldn't it ? [​IMG] Maybe made of wire, and strung out horizontally. Would it become a "NVIS" antenna in that mode ? HMMMMMM ! ! !
     
  3. N3BIF

    N3BIF Guest





    "I have not failed. I've just found 10,000 ways that won't work."    

    Thomas Alva Edison
     
  4. Guest

    Guest Guest

    After reviewing your post. Follow the advice about seeking help from a near by radio club. You need personal help from an experienced amateur radio operator, your not going to solve your problem in this QRZ forum.

    Good luck,

    Frank
     
  5. KJ3N

    KJ3N Ham Member QRZ Page

    IF this guy is trying to load a 2m J-pole on 80m, I now remember why I don't go into Q & A very often.

    OMFG! [​IMG]
     
  6. AG3Y

    AG3Y Guest

    He probably read the advertisement, " you can load a wet shoestring with this tuner ! ! ! "

    It's posts like this that draw me TO Q&A.  SOMEONE has to offer a helping word !    If it's not you, who is it gonna be ? [​IMG]
     
  7. KJ3N

    KJ3N Ham Member QRZ Page

    It's posts like this that make me run as far away from Q & A as possible. I need to keep my blood pressure at a reasonable level.

    Ok, here's my helping word to this person:

    This is a technical hobby. Anybody who doesn't tell you that, is doing you a disservice.

    If you can't figure out why a 2m J-pole doesn't load on 80m (even with a tuner), then you'd better get an education real quick.

    May I suggest an outrageous idea, like reading books? The Handbook and the Antenna Book leap to mind.

    Well, it's not going to be me, Jim. I can't relate to someone who seems to know absolutely nothing. I expect at least the vaguest hint of a clue. I've not seen evidence of such.

    He's all yours.
     
  8. N3BIF

    N3BIF Guest

    The guy is only a general, give him a break  [​IMG]
     
  9. VK6ZGO

    VK6ZGO Ham Member QRZ Page

    After reading this thread, my flabber is terminally gasted!

    I thought that those people who were always moaning "It's all going to the dogs!," etc,were just rhe old  QRZ-ers going over the top as always.
    This ,however has got me thinking that you do have a big problem with your licencing system.

    It has also caused me to re-examine my attitude to the "Foundation" licence in this country.

    The Foundation licence is mainly associated with how to use radios, operating ettiquette, & some basic concepts.
    It does not pretend to be a test of Electronic theory.
    That said, I have heard, & worked a number of "F" calls, & have not heard from any of them,the  gap in in the knowledge exhibited in the original posting.
    Perhaps you do need a Foundation licence!

    Now to kd7nmn:

    The very term "80metres" is a bit of a giveaway that you might need a big antenna at these frequencies.

    Thinking on this, perhaps it's not so obvious in a non-metric country.

    To give a bit of an idea, the TV towers you see sitting on hilltops are around 145m high ,which equates to about 475ft. a little bit more than half that height is 80m.

    Big isn't it?

    If we stick with metric measurement, we find that if we divide the speed of light in metres/sec by  the frequency in Hz,we get the wavelength in metres.
    0r: wavelength in metres= 300,000,000/freq  inHz

    This is a  basic concept in radio!!

    Luckily, most of the time we  refer
    to frequencies in MHz,so we don't have to work with the

    000,000 bit ,this cancels out to give the formula :

    wavelength in metres=300/freq in MHz

    It also works the other way round:

    freq in MHz =300/wavelength in metres

    From this, we can see that say: 3.5MHz has a

    wavelength of 300/3.5=about 85.7 metres.

    The US allocation goes up to about 4Mhz=75m which is why it is often referred to as the 75m band instead.

    Looking at the 2 metre band we find that it goes from 144MHz to 148 MHz, that is from a
    wavelength of 300/144=2.08m approx, to a wavelength of 300/148=2.027m approx.

    A 2m antenna at 80 m is so short that it doesn't look much different to an open circuit coax, so even if you use an antenna tuning unit, it will be trying to match to effectively a open circuit, & it won't work.

    I would suggest using the metric measurement whenever you are visualising what an antenna should look like,as it gives a direct conversion to frequency by the above formula.

    Now go & find an ARRL Antenna book & read the theory section!!

    73 VK6ZGO
     
  10. VK6ZGO

    VK6ZGO Ham Member QRZ Page

    Sorry about the typos
    VK6ZGO
     
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