Vastly Improved Simulcast Receive

RadShackFan · May 23, 2018

I've been having the typical simulcast receive problems everyone else has. A commercial radio engineer friend of mine suggested shielding the antenna from all but the closest or the desire tower. I came up with this. Don't laugh too hard, it's working. I simply took a piece of cardboard, covered it with foil and placed it to null the towers I didn't want the scanner to hear. Been in use for 3 days now & I have no complaints.

jonwienke · May 23, 2018

A directional antenna is the best way to overcome simulcast interference issues, and that is what you've created. As long as it works, it doesn't really matter if it's ugly.

RadShackFan · May 23, 2018

This setup is in our "weather room" we use during tornado warnings & such. My regular radio room scanners are connected to a yagi antenna in the attic and function as expected.

I just thought those having to use smaller indoor antennas due to restrictions or other reasons would find the idea useful.

I_am_Alpha1 · May 23, 2018

Laugh? Why, it's perfect. Exactly what you have to do with simulcast. Would you be willing to perform a test? If you want, remove the cookie sheet and report here if there is a difference in reception. Many believe a ground plane is required for reception, I claim not--a third party tester, like yourself, can set the record straight. Thanx...and enjoy your invention.

wa8pyr · May 23, 2018

qslmark said:
I've been having the typical simulcast receive problems everyone else has. A commercial radio engineer friend of mine suggested shielding the antenna from all but the closest or the desire tower. I came up with this. Don't laugh too hard, it's working. I simply took a piece of cardboard, covered it with foil and placed it to null the towers I didn't want the scanner to hear. Been in use for 3 days now & I have no complaints.

Don't laugh, as long as it works!

That's basically a classic corner reflector, by the way.

RadShackFan · May 23, 2018

I_am_Alpha1 said:
Laugh? Why, it's perfect. Exactly what you have to do with simulcast. Would you be willing to perform a test? If you want, remove the cookie sheet and report here if there is a difference in reception. Many believe a ground plane is required for reception, I claim not--a third party tester, like yourself, can set the record straight. Thanx...and enjoy your invention.

Removed the cookie sheet. The GRE 800 went from 5 bars signal strength to 4 bars. To my ears it appeared the volume had been slightly reduced. Otherwise it still worked.

Guess I'll cover that funky cookie sheet in foil while I have it out.

RadShackFan · May 23, 2018

wa8pyr said:
Don't laugh, as long as it works!

That's basically a classic corner reflector, by the way.

I didn't even think of that until your posting. If I recall correctly Arrow Antennas used to sell amateur radio corner "beams" quite a few years ago.

iMONITOR · May 23, 2018

Back in 2009 I started playing around with corner reflector antennas. I ended up buying a Maxrad MCR806.

25494d1254798733-corner-reflector-antenna-ncdbsa_194_a.jpg

I discovered that it's better to try to null out the additional offending towers in a simulcast system than it is to use a Yagi to boost the signal level of one.

The O.P.'s solution was much less expensive! It's certainly easiest enough to try. Good going qlsmark!

wa8pyr · May 23, 2018

qslmark said:
Removed the cookie sheet. The GRE 800 went from 5 bars signal strength to 4 bars. To my ears it appeared the volume had been slightly reduced. Otherwise it still worked.

Guess I'll cover that funky cookie sheet in foil while I have it out.

If you can, figure out a way to connect the cookie sheet to the reflector to see how that affects things. It may make things better.

N8IAA · May 23, 2018

wa8pyr said:
If you can, figure out a way to connect the cookie sheet to the reflector to see how that affects things. It may make things better.

It seems that it is touching the cookie sheet in the picture.

Larry

slicerwizard · May 24, 2018

I_am_Alpha1 said:
Many believe a ground plane is required for reception, I claim not--a third party tester, like yourself, can set the record straight. Thanx...and enjoy your invention.

And your theory didn't hold up.

Take away half of the antenna and reception degrades - go figure.

bob550 · May 24, 2018

Dinnertime conversation with significant other:

Spouse: "Dear, I can't seem to find my good baking pan? I was going to make Aunt Grace her favorite lemon
cookies. Have you seen it?"
You: "Um, er, eh, no. I haven't seen your pan lately. What pan was that again?"

bharvey2 · May 24, 2018

I was having a lot of issues monitoring the simulcast P25 public service network in my area, especially when using SDRs. I built a corner reflector and it really cleaned up the signal.A high gain yagi works well too.

RadShackFan · May 24, 2018

wa8pyr said:
If you can, figure out a way to connect the cookie sheet to the reflector to see how that affects things. It may make things better.

Very interesting results. I covered the cookie sheet with foil, then used an alligator clip jumper to connect the reflector to the cookie sheet. No change. I then connected the cookie sheet to the outside of the BNC connector on the antenna. Signal strength remained @ 5 bars, but the volume on the received signals increased. The traffic seem clearer as well.

Guess this proves the theory that a permanent mount (like an NMO) is better than a magnetic mount since it provides a ground to the negative side of the antenna. I always trusted that, but this is the first time I actually heard the difference.

bharvey2 · May 24, 2018

You might also try adjusting the distance between the antenna and the corner of the reflector until you get an optimum signal strength.

wa8pyr · May 24, 2018

N8IAA said:
It seems that it is touching the cookie sheet in the picture.

"Touching" and "Electrically Connected" are two different things, as I learned to my sorrow when I was a young ham once. Once. . . .

wa8pyr · May 24, 2018

qslmark said:
Very interesting results. I covered the cookie sheet with foil, then used an alligator clip jumper to connect the reflector to the cookie sheet. No change. I then connected the cookie sheet to the outside of the BNC connector on the antenna. Signal strength remained @ 5 bars, but the volume on the received signals increased. The traffic seem clearer as well.

Guess this proves the theory that a permanent mount (like an NMO) is better than a magnetic mount since it provides a ground to the negative side of the antenna. I always trusted that, but this is the first time I actually heard the difference.

I've always liked cookie tins with NMO mounts for this sort of thing. The sit nicely on a shelf and the ground side of the coax is connected to the cookie tin, giving a much better ground plane.

Might be troublesome to get the foil-covered reflector to sit properly behind a cookie tin, though.

markjrenna · May 24, 2018

I like using my Unication G4. I can move around and not be tied to a stationary antenna. I had terrible LSM issues. Now that's a thing of the past!

I_am_Alpha1 · May 24, 2018

slicerwizard said:
And your theory didn't hold up.

Take away half of the antenna and reception degrades - go figure.

Theory...no, fact. It still works with very little change--which could be accounted for by say the cookie sheet reflecting signal or any number of factors. By your logic, no handheld or scanner on the planet should work because they don't have ground planes on the antenna.

I just took a small motorola 800mhz antenna and put it on my XTL5000 mobile on the desk and receive full strength--no ground plane.

N8IAA · May 24, 2018

wa8pyr said:
"Touching" and "Electrically Connected" are two different things, as I learned to my sorrow when I was a young ham once. Once. . . .

Found that to be true when I was building a SWR meter and keyed up:lol:
Larry

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