resolved audio issues on 800mhz simulcast system

[Viking1]

We have a 4 site 800 simulcast system, it reaks havoc on digital scanners. I found a simple solution. Where I live 3 of the sites are to the north and east and one to the south. What I found was a 8 element 800mhz beam cell antenna. I hooked it up and pointed it at the south tower. Wa-la the other 3 sites are nulled oouut.

 

[Viking1]

This is the antenna I'm using, found it for $20

Product Details

 

[RoninJoliet]

WOW, they show that antenna as being at least 89-159 dollars....Where did you buy it at a ham fest??....I cut down a 4 element UHF beam for 800mgz, attached it to a piece of PVC, put it in the attic with 30' of LMR200 coax, faced it at the tower 25 miles away and "WALA" also.....

 

[DickH]

... and "WALA" also.....

Hey guys, it's a French word, VOILA! meaning, "There it is!" or "I found it" or something like that. It's pronounced VWA-LA. Good try, though.

 

[Viking1]

Hey guys, it's a French word, VOILA! meaning, "There it is!" or "I found it" or something like that. It's pronounced VWA-LA. Good try, though.

I'm not french and they bastardize our language with things like "Courriel" so I'll bastardize their language whenever I please thank you very much.....

 

[Viking1]

WOW, they show that antenna as being at least 89-159 dollars....Where did you buy it at a ham fest??....I cut down a 4 element UHF beam for 800mgz, attached it to a piece of PVC, put it in the attic with 30' of LMR200 coax, faced it at the tower 25 miles away and "WALA" also.....

Craigslist of all places. It's hooked up to 50ft of 1/2 inch andrews hardline.

 

[DickH]

... thank you very much.....

You are most welcome. If something is worth doing - it's worth doing right.

 

[Arizona_Scanner]

Solving Problems With Digital Simulcast Reception Cutting Out

Thanks for posting that's awesome to hear!

I figured this out about four years ago myself and it was a beautiful thing. I try to spread the word of this wonderful technique to all the scanner enthusiasts that I can and am happy you figured it out on your own and posted it here.

For those who are pulling their hair out trying to listen to their local digital simulcast radio system and are tired of the transmissions "cutting out", this can be the solution.

I used the Wilson 800mhz yagi antenna (made for cellular), and a N-connector to SO239 adapter and used LMR-400 cable down to my scanner with a another barrel connector SO239 and a short jumper lead to my scanner (PL259 to BNC).

The key to success with this technique, is that you must be able to point the antenna in such a way that ONE SITE comes in strong while the others are attenuated greatly. It worked great in the home I just moved out of, but doesn't always work. It worked in my hold house due to how my home sat in between the sites. In my new home where I am well outside of the entire system, it does not work because all of the sites are in relatively the same direction so I can't "screen out" all but one site. Any direction I point now, there are 2-3 towers within 10 degrees, so they all have gain due to the directional nature of the antenna. Fortunately I work right under a simulcast tower all day and get good reception at work at least!

So if you are wanting to find out if this will work in your case....

Look at where you lay out on a map compared to the sites in your simulcast system. Does it look like you can aim at one site while having all other sites at least 45 degrees off of the point of aim of the antenna? If so, go for it and you will probably be happy.

Important note: The best results are NOT necessarily achieved by aiming RIGHT AT a given tower. You will find that antenna gain is pretty good even 10 or more degrees off when aiming at a signal source. What is important is that you strike the best ratio between the gain you are giving your target site, and the ATTENUATION you are giving the other site(s). The best result can be and often will be aiming slightly OFF OF your target site so that the other site(s) are attenuated as much as possible. Experiment around....don't just assume the best result is aiming RIGHT AT your target site.

I went from 30% decode to 95% decode using this technique.

 

[W2PMX]

In my new home where I am well outside of the entire system, it does not work because all of the sites are in relatively the same direction so I can't "screen out" all but one site. Any direction I point now, there are 2-3 towers within 10 degrees, so they all have gain due to the directional nature of the antenna.

Important note: The best results are NOT necessarily achieved by aiming RIGHT AT a given tower. You will find that antenna gain is pretty good even 10 or more degrees off when aiming at a signal source. What is important is that you strike the best ratio between the gain you are giving your target site, and the ATTENUATION you are giving the other site(s).

Yagi antennas have notches - pretty deep ones - either side of the front lobe. What you really want to do is to drop the interfering signals into the notches. Look at the plots for various antennas and go for the ones with the deepest and broadest notches, not the ones with the most gain.

Another trick is to mount 2 antennas and combine them. (How you use lengths of transmission line to transform 2 50 ohm antennas - out of phase - to one 50 ohm feedline is another subject.) Aim one antenna to the station of interest. Then turn the other antenna to null out the interfering signal.