| Author |
Message |
    
707
| | Posted on Wednesday, June 13, 2001 - 1:13 am: | 
|
The takeoff angle and major radiation lobe are the key to any dx contacts, whether its "short skip" or intercontinental propagation. In fact, vertical antennas are poorly suited for short skip, from 150 to 700 miles, because of low takeoff angle and the null pattern above 45 degreees. OF course, if your path MUF is not very supportive of the band you are operating on, no amount of power will really ensure a contact, which in my book implies a two way conversation. As far as "power" is concerned, listen to the "superbowl"(ch 6) sometime after all other channels are quiet, and you will notice that these stations, running a KW or better plus ERP gain, will continue to be heard long after everybody else is gone. For those of use desiring to stay below that level of electrical consumption, the best bet is to have a good vertical(A99 or badass 5/8 wave)as high as possible and a horizontal beam at any height for really long DX. My present location does not allow conspicuous antennas, so I make do with a homebrew inverted L config. This gives virtually NO local coverage, but has almost a 180 degree radiation pattern, which means an equal amount of output is directed sharply upward for those short skip contacts and also out at between 15 and 40 degrees for the longer stuff. I routinely talk out to 200 miles at the same time as 1000 miles, running stock power. This link is a good wire antenna primer for those so inclined. The model is based on 80 meters, but the geometric fundamentals carry over to higher bands. http://www.cebik.com/ltv.html |
HAM CBer
| | Posted on Friday, June 15, 2001 - 1:23 pm: |
|
I have a 27.125 MHz. propagation beacon running only 20 milliwatts (that's 0.02 watts) on an A99 at 2,500 feet ASL that has been heard all over the country and Australia.
I have heard some guys on the east coast key up and make fun of the audio tones many, many times.
So, it is certainly not power that determines a band or even a path opening. However, higher power would improve the said S unit reading of the receiving station(s). |
Orion
| | Posted on Monday, May 26, 2003 - 7:59 am: |
|
Well, IMHO, I think power matters. Conditions are certainly most important. It just goes to reason I think that the RF that leaves an antenna does not stay consistent indefinitely. It does fade. A bit is lost traveling through toward the ionosphere, some is soaked up there. What get's bounced back on it's first skip will be less than what it had at the beginning of it's journey. When it lands, what will it be? Reflective water or land and what type of topography? A lot or a little can be lost there. How much juice will be left on each successive skip depends on what you started with. Sure, the Earth is only so big and sometimes 1 watt of CW can make it all the way around but if I was betting money on two rigs getting a signal to Australia from the US at any given time, I wouldn't bet barefoot.
At the start of this thread it was said: "I don't think a 1/2 watt will get you there, but you can do it...." which does say power matters. It sure doesn't matter as much as a lot of people think. Would never consider getting more than a 250 watter but that's a whole new issue. Anyway, that's what two bits on it. |
Kc0gxz
| | Posted on Tuesday, May 27, 2003 - 12:01 pm: |
|
Heterodyne Hill
Anyone can talk around the world with 1/2 watt and even less if atmospheric conditions are favorable. That's what QRP is all about.
And yes, a beam will make a difference. But if you want to stay with an omnidirectional antenna, try the I-Max 2000. It will handle 5-KW, (so they say), 24 ft in length, 5/8 wave and a band pass of 3 meg. What more could one ask for?
I have tried and tested many antennas during my 30+ years in the radio communication business and have never found one to be better. At the moment I am doing some experimenting to get one to work in 6 meters.
By the way, don't pay any attention to the high DB ratings on any of todays antennas. The manufactures are lieing through their teeth. They are compairing their antennas to a antenna that doesn't exist and never will.
Jeff, kc0gxz. |
|
