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Author Topic: Re: Radio Pushka tentative 6920 AM 0223 UTC 1 Dec 2021  (Read 1071 times)

skyman

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Re: Radio Pushka tentative 6920 AM 0223 UTC 1 Dec 2021
« on: December 02, 2021, 1843 UTC »
 ;D I agree with the flea invested Squirell, a vertical on HF only good if you have no hope of a dipole. You immediately lose 3 db of power and after that things get much worse as your ground eats RF like a wolf gulps goat meat. And if you have a linear amp, get ready on AM for the biggest heatwave and power supply stress. A Stretchy 10 watt even into a 100 watts amp will bust it. You would only get  100 x .33 watts or a huge in noise 30 watt carrier. Peak power is carrier x 4.. That is your amp needs to manage 500-600 watts with a hear sink. Even if you had a kw amp.. it will run red. Give you only 250 watts carrier, the 75 percent "other" DC input is waste heat. Now if you have a fancy class D amp.. now your talking. 90 percent dc efficiency. However, you roll those for yourself as none I know are available. Maybe old Stretch will get to that someday? So putting this to my goat engineers, a solid-state amp, rated at 100 watts PEP, can only give you a 25-watt carrier. Also, you'll need a fan, maybe two fans. That's why SSB is the chosen one.
« Last Edit: December 02, 2021, 1902 UTC by skyman »

skyman

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Re: Radio Pushka tentative 6920 AM 0223 UTC 1 Dec 2021
« Reply #1 on: December 02, 2021, 2112 UTC »
  Censorship.. black flag ? Post removed. I apologize, just moved to tech discussion ! Happy Hoilidays.
« Last Edit: December 02, 2021, 2114 UTC by skyman »

Offline Charlie_Dont_Surf

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Re: Radio Pushka tentative 6920 AM 0223 UTC 1 Dec 2021
« Reply #2 on: December 02, 2021, 2119 UTC »
I do not believe using a splitter to run both vertical and dipole will help much, if at all. The best way to go on 43 meters is a well constructed half wave cut for 6920 khz, and up as high as you can get it! The signals emanate perpendicular to the wire and are highly directional, so the orientation of the half wave determines how well you will be heard in a particular direction.

I'm going to give a more nuanced reply to Pushka. Skipmuck is absolutely correct on the technical details of the dipole. No argument there. However, I think that Pushka's approach of combining a dipole and a vertical could work. It all depends upon what they want to do.

A vertical with a good ground system (either elevated or radials on the ground) should have a reasonably low angle of radiation - the better the ground system and the better the soil conductivity, the lower the angle. This is good for long-distance coverage and not so good for close-in coverage. On the other hand, a dipole mounted at a low height, i.e., less than 0.5 wavelength above the soil, will have a very high angle of radiation - commonly called a "cloud burner" - to fill in areas that are 100-400 km away from the TX that the signal from the vertical might "skip over", if the TX frequency is below foF2.

If the vertical and the low dipole are combined by using an RF splitter/combiner, it might be an effective diversity antenna, giving the best of both worlds. Since Pushka is on the air 24/7, this might be a good way to take advantage of cycling conditions on 43 meters over the 24 hour cycle. Keep in mind that there would be only ~50% of the TX power going to each antenna at any one time, but if 100% of the TX is being wasted at any one time going nowhere, then perhaps he would be cutting his losses, so to speak. Again, it all depends upon his goals.

YMMV.
« Last Edit: December 02, 2021, 2206 UTC by Charlie_Dont_Surf »
I don't STRETCH the truth.

"Every minute I spend in this room, my signal gets weaker.
Every minute Charlie squats in the bush, his signal gets stronger."

 

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