Antenna choices and/or design question

[Pro-95]

I listen to mostly 150Mhz and 800 Mhz as a general rule. Once in the bluest of blue moons I listen in on aircraft bands - 400 Mhz.

So the antenna of choice for me would be a generic all-around antenna???

What about two or three optimized antennas. Can they be combined into the same coax (without significant degredation) and sent into the scanner? Is there a "diplexer" to combine different freqs (antennas) into one coax?

I've been playing around with some antenna parts I've got laying around and I've been able to maximize the 800 Mhz but at a significant cost to the 150Mhz freqs.

Where is there some decent antenna design documentation so I can figure out what I am doing and what effect/affect is taking place.

TIA

 

[N_Jay]

I listen to mostly 150Mhz and 800 Mhz as a general rule. Once in the bluest of blue moons I listen in on aircraft bands - 400 Mhz.

So the antenna of choice for me would be a generic all-around antenna???

What about two or three optimized antennas. Can they be combined into the same coax (without significant degredation) and sent into the scanner? Is there a "diplexer" to combine different freqs (antennas) into one coax?

I've been playing around with some antenna parts I've got laying around and I've been able to maximize the 800 Mhz but at a significant cost to the 150Mhz freqs.

Where is there some decent antenna design documentation so I can figure out what I am doing and what effect/affect is taking place.

TIA

Go buy the ARRL books on Antenna design.

 

[Voyager]

I listen to mostly 150Mhz and 800 Mhz as a general rule. Once in the bluest of blue moons I listen in on aircraft bands - 400 Mhz.

So the antenna of choice for me would be a generic all-around antenna???

What about two or three optimized antennas. Can they be combined into the same coax (without significant degredation) and sent into the scanner? Is there a "diplexer" to combine different freqs (antennas) into one coax?

Yes, if you want to go with a single antenna, there are a few good ones that will work fairly well on all bands. I just put up a discone recently, and was disappointed to find that my old tri ground plane scanner antenna runs rings around it.

If you want something that will work better, you can get antennas designed for each band and combine them with a diplexer, or even a common duplexer connected in reverse. There are many companies that make such devices to connect multi-band radios to single antennas or vice versa. Diamond and Comet are two companies that make them. You should be able to find a relatively cheap one that will handle 144 MHz, 440 MHz, and 900 MHz in one unit. These will work fine for 150/460/800 MHz operations. Using one of these, you will see minimal loss and interaction among the different antennas. If you use one of these units outside, make sure it's either designed for it or seal it tightly against the elements. BTW, if you just connect the antennas with a 'T' connector, there will be interaction and degradation among the antennas.

The best antennas for each band will be directional Yagi (AKA Beam) antennas - the more elements, the better. But, you will have to point them in the right direction. While this will yeild the best performance, it is no the best choice if the signals you want to receive are in different directions in the same band.

You might want to do a Google search for "antenna design". It's always best to try the free sources before spending money.

Joe M.

 

[Pro-95]

Thanks!

There is definately some really good reading our there. I found a solid copper (plate) discone design with a brass center pole/sheild. Pretty darn small too for 800 mhz usage.

Question? Shouldn't a discone still be grounded? Or does the cone in discone handle that? Still providing for lightening protection to the pole though, right?

I also read about an apparently discontinued antenna called a monitortenna(sp) from Channel Master. Pretty wild design sort of like two discones with one inverted over the other. Seems like something like that would be fairly simple to build.

Then I ran across this puppy. :shock: Ferret Base Antenna :shock:
Holy smokes if it does all that it says and as well as it proclaims, why get any other antenna. It definately is something that would be (even over the rod discone) less suspetable to the winds we have around here.

 

[DXKW]

ANTENNAS

A DISCONE HAS NO REAL GAIN, BUT THEY ARE BROAD BAND. IF YOU DONT WANT TO BUILD AN ANTENNA THEN GO TO WWW.STRONG SIGNALS.NET AND READ THE TEST REPORTS.










THANKS
DXKW

 

[okla-lawman]

Comet makes a tri band commercial antenna. I am trying to get the
the exact specs but it is like 3/6/8 db 150/450/800 mhz. hm radio outlet can order one it is on there web site as a special order. I am getting ready to try one myself.

 

[DXKW]

scanner antenna

i use a gp9 lawman and put freqs in my yeasu 8100 for vhf/uhf and it works real well. i looked at the antenna on the website and it looked similiar to some of the dual band tri band antennas the make.






thanks
dxkw