Wednesday, 29 April 2015

I=============Antennas Antennas Antennas==============I

“When Marconi suggested the possibility of wireless transmission of sound (the radio),he was committed to a mental institution. But people like Lincoln, Edison, and Marconi were strongly motivated. So they didn't give up. They somehow knew that the only real failure is the one from which we learn nothing. They seemed to go on the assumption that there is no failure greater than the failure of not trying, and so they continued to try in the face of repeated failures.”― John PowellWill the Real Me Please Stand Up?: 25 Guidelines for Good Communication

There is nothing like a good antenna for getting your signal out to the waiting world of radio and Guglielmo Marconi had some whoppers look at the one he used in Poldhu thanks to the GB2GM website for the pic

Antenna's are VITAL if you are going to be transmitting and you have to match the impedance of your antenna with your radio.
You can do it in various ways and most hams  choose  a radio with a built in antenna tuner , though there are very good external automatic and manual ones out there . I am not  going to review any here , there are too many , just Google the one's  you are interested in.I am not going to say which ones I have or which one I like but if you visit my QRZ webpage you will see what I use . (that's a link by the way) 

Suffice it to say that for an antenna that is unbalanced you WILL need to tune it for the  frequencies you want to work on .t I have found there is nothing like a dipole for the frequency you are working on, (like say 20 mtrs this being one of my favourite bands )  tuned to be resonant (note RESONANT) on that band with a good SWR from the lower end to the upper  end of that frequency  , you will find you do not need an antenna tuner so that most of the power that you use will be effectively radiated, there will be losses due to coax and fixing etc but most are to small to be relevant. 

I have built a Rybakov antenna , and this required me to make a 4:1 un-un . This works fine for vertical use with the wire up a fibreglass fishing pole , but again I needed an antenna tuner to use it and the effective radiated power from the antenna would have been a lot less than what I was using. the point being that all the power was being taken up by the un-un and making the rf effectively heat up the box it was in ,sending the rest to the wire  for transmission  so 50 watts in and perhaps about 30 watts of radiated RF . I am probably wrong on this but it can make a difference.

So what am I trying to say ? Well its always better if you can get an antenna for the band you are working , and most hams who have towers or a nice large garden can use the likes of yagi antenna. One particular antenna I liked using on my rotator was the  cushcraft MA-5B mini beam .

I think that's enough for now,  just get out there and make or  buy a GOOD antenna and no  matter what the radio  you have ;if your antenna isn't up to the job you won't get out and you won't be heard. The  amount of power (wattage) doesn't matter. My good friend 2E0STZ has used 2 watts into his M0CVO antenna on JT65 and PSK31 and has been heard halfway around the world  and he doesn't need a tuner for that particular antenna on some bands which is why he can be heard , most of the power was EFFECTIVELY radiated  . 

Well that's all for now I hope you enjoy reading my blogs .

Phil de M1PAC (c) 2015 m1pac productions 

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