23 iulie 2020

Hamradio is for gentlemen

I was working on a HM radio late at night and I was listening to 20m band as it was a pretty good propagation.
At 14.194 kHz, ER4DX was calling for South America DX.
At one time, an Italian station had answer to his call but Mr. Vasile expedite the Italian very quick with "no Europe, only South America, DX only" and continues to call.
After a minute, a station from Maroc answers and Mr. Vasile, ER4DX started a pretty nice QSO. Then some SA stations and after a while, a Romanian one.

Well, in my opinion, the way he refused the call from Italian station was RUDE. Hamradio is about friendship, it's about human to human connection in a weird World of selfish people...
Maybe that Italian ham needed a new country in his log!
Maybe it was someone in distress. Maybe who knows, he just wanted to test his station!

A real ham will not refuse to answer to a call from a station... Any station! This is real HAMRADIO!
If you are hunting a continent it's OK to call that way and to specify it but, if a station from other part of a World calling you worth answering! it will not take more than a few seconds to answer and TO EXPLAIN that, you are calling for specific part of the world while there is a path in the propagation!
The QSO with Maroc and Romania (and right now, just while I am writing, a Polish station) will not take an eternity but for that Ham may be important!

So, fellow hams, please, dont be rude and reject answers from other countries while you are hunting for specific calls!

You will be remembered as REAL HAMS, last gentlemen in this World!

20 iulie 2020


YB0EMJ - The G5RV Multiband HF Antenna
The G5RV
Multiband HF Antenna
Over the last 40 years G5RV dipoles have become the most widely used general purpose multi-band antennas in the world.  Good performance, modest size, low cost, simplicity, and versatility are the reasons for this popularity. Invented in 1946 by Louis Varney, whose call sign is G5RV ("Silent key" on June 28, 2000. He was 89).  The basic antenna measures only 102 feet across the top, and is fed at the center through a low loss 34 feet feed-stub. The interaction between the radiating section and the feed-stub makes the G5RV easy to match on all-bands from 80 through 10 meters with an ordinary low-cost antenna tuner. In spite of small size, it provides dipole equivalent coverage on 80 and 40 meters.   From 20 on it favors DX with four to six low angle lobes reaching out in all directions.
The design center frequency of the full-size version (configured as a 3/2-wave dipole on 20m) is 14.150 MHz, and the dimension of 102 ft is derived from the formula for long-wire antennas which is :
LENGTH ( in feet )= ( 492 ( n - 0.05 )) / f (MHz)
= ( 492 ( 3 - 0.05 )) / 14.15
= 102.57 ft ( 31.26 m )
(n = number of half wavelengths of the wire)
In practice, since the whole system will be brought to resonance by the use of an antenna tuner, the antenna is cut to 102ft (31.1m).
In some cases, this is still too large to fit in one's yard, and not everyone can convince their neighbors to allow one to stretch the wire across property lines. In this case, a half-size version, covering 7 to 28 MHz is useable.
Conversely, some amateurs would like to have 1.8 MHz capability, and have the 204 ft ( 62.2 m ) length necessary for this array. The antenna does not need to be put up as a flat-top array, but can be installed as an inverted-V.
If the antenna is raised as an inverted-V, the included angle at the apex should not be less than 120 degrees.
The center of the antenna should be as high as possible, of course, and the matching section should descend at a right angle to the array. THE MATCHING SECTION :
The matching section may use with several ways :
Open Wire :
It is recommended that the matching section be constructed of open-wire feeder for minimum loss, as it always carries a standing wave on it. Due to the standing wave on it, the actual impedance is unimportant. Ladder Line (Window-type line) :
The next most-desirable matching section would be made from window-type open wire line, either 300-ohm, or 450-ohm. This is basically a ribbon line, like heavy duty TV-type twin lead, with #16 to #20 wire, and "windows" cut in the insulation every 4 to 6 inches. The advantage of the "window" line is that the conductors won't short together if the line twists in a high wind. "TV" Twin Lead :
The main disadvantage of the TV-type twin lead is durability. The advantage of it is that it is readily available at electronics outlets. Do not use the "shielded" twin lead. The shield will degrade the matching section, especially on 3.5 or 7 MHz.
The length of the matching section is an ELECTRICAL half-wave on 14 MHz. The actual physical length is determined by the following formula :
LENGTH ( in feet ) = ( 492 x VF ) / f (MHz) ( VF = the velocity factor of the matching section ) The velocity factor is determined by the type of line, and the dielectric properties of its insulation. For the three types of line discussed so far, the VF is :
  • Open wire = 0.97
  • Ladder line (Window line) = 0.90
  • "TV" twin lead = 0.82 By substituting the VF in the formula, and calculating for a center frequency of 14.15 MHz, you come up with the following matching section lengths :
  • Open wire = 33.7 ft ( 10.28 m )
  • Ladder line (Window line) = 31.3 ft ( 9.54 m )
  • "TV" twin lead = 28.5 ft ( 8.69 m )
  • This matching section is connected to the center of the array, and allowed to descend vertically at least 20 ft or more, if possible.   It can then be bent and tied off to a suitable post or line, and connected to the coaxial line, and run to the Antenna Tuner. TABLE OF FULL-SIZE, DOUBLE-SIZE and HALF-SIZE :
    Band Coverage3.5 - 28 MHz1.8 - 28 MHz7 - 28 MHz
    Length of Antenna102 ft ( 31.1 m )204 ft ( 62.2 m )51 ft ( 15.55 m )
    Matching section :
    - Open wire33.7 ft ( 10.28 m )67.5 ft ( 20.56 m )16.9 ft ( 5.14 m )
    - Ladder line 31.3 ft ( 9.54 m )62.6 ft ( 19.08 m ) 15.6 ft ( 4.77 m )
    - "TV" twin lead 28.5 ft ( 8.69 m )57 ft ( 17.38 m ) 14.3 ft ( 4.35 m )

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