Phoenix TRS - Yagi solves "cut-outs"

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After a few years of frustration TRYING to monitor the PRWN TRS, with its half dozen simulcast sites, I had resigned myself to simply scanning other things for the most part. It was that bad. When I picked up my latest PSR scanners, they did a better with the system at first, or so it seemed, but after a few days I realized it wasn't as much better as I had thought, and at times (especially during times of high activity - weekend nights), half of every transmission was cutting out and choppy, still. So back to scanning other things for the most part. At times on Friday night it seemed, I was only hearing a quarter of everything, with most all transmissions cutting out BADLY. I heard about 25% of what was said on "bad days". Ugly. And enough to turn my ears elsewhere.

After years of speculation of what effect a yagi would have on the situation I purchased a wilson 14db yagi with a center frequency of 855 off ebay for $60.

Ok first does it work? A resounding YES!! YES!!! Monitoring the phoenix system is now as pleasurable as any other p25 system in the valley!

Now like any other p25 system I know, there is the occasional garbled word or "digital" sounding voice, but those things are far and few between overall. So reception is not absolutely perfect, but I don't consider any p25 system around here to be totally perfect, they all digitize the voice occasionaly.

But up until now the Phoenix system was FAR FAR FAR worse than any other system around, and now it is the same.

So I am going to call this a RESOUNDING 100% SUCCESS!! I went from hearing 25%, to around 95% or better, which is as good as any other p25 system I listen to.

For about $100 total you too can actually monitor the PRWN for the first time. This of course unless you are one of those lucky few who live in a sweet spot already where reception is good.

But this is for all of you like myself who are SICK OF THE CUTTING OUT and want to listen normally again!

Now you need to understand a few things if you want to do this, so read on. It takes some thinking and planning as to HOW TO AIM YOUR YAGI. This is the key to making the most out of this method. Read on.

After first aiming it directly at the nearest transmitter with good but not perfect results, I determined something.

Unlike the typical use of a yagi, where you would point it directly at the antenna you are trying to receive from, this is a different situation.

I didn't need more gain from the transmitter on the mountain four miles away, I needed ATTENUATION of the other nearby towers, first and foremost.

Two others were fairly close, and the other ones were much farther, so I decided to focus on eliminating the signals from the closer two.

After looking at the radiation / reception pattern for the antenna, and seeing that the maximum attenuation occured at 90 degrees, I positioned it so that the 90 degree point was right in between the two nearby offending towers. A compromise if you will. Neither got the absolute maximum attenuation, but both got equally strong attenuation. By my calculation, with the 20db attenuation of my scanner, plus loss from the cable / connectors, this gave a total of about 61db attenuation to these two towers.

Now it may seem strange, but the antenna was not pointed directly at the tower I wanted, but 6 degrees off that mark, so that the other two WOULD GET MAXIMUM ATTENUATION. I am still getting 12db of boost for the site I want (didn't even need that really), but MORE IMPORTANTLY, I am ATTENUATING the offending towers TO THE MAXIMUM DEGREE, which is the REAL GOAL, not getting gain from the tower I am trying to listen to.

Trying to aim the yagi directly at the tower you want, very well MAY NOT give the best result, depending on your situation if you try this method. HOW you aim is important. Plot out all nearby towers and look at what their attenuation / gain with be with the antenna pointed various ways, with the end goal of attenuating the offenders as much as possible, while still pointed enough towards what you want TO NOT ATTENUATE IT.

I wanted to share this with everyone, and for the skeptics, I am planning a live feed of Phoenix PD in the near future. As far as I know it will be the first successful feed of this agency since the switch to p25 simulcast. My personal belief is that nobody has tried for the reasons listed above. It wasn't listenable, and worth the effort, until now.

The least I can do is share good listening with those who can't for whatever reason install a yagi and dedicate a scanner.
 
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Car roof yagi

Good idea! Ok, aside from a good mount, a computer controlled gps capable rotator would be needed so it is constantly rotated to the proper angle.

Wind noise could be an issue though...
 

AZScanner

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PHOENIX_SCANNER said:
Good idea! Ok, aside from a good mount, a computer controlled gps capable rotator would be needed so it is constantly rotated to the proper angle.

Wind noise could be an issue though...
Not to mention the Hamsexyness of it all... :D

Seriously, EXCELLENT work - I predict the local HRO is gonna have a run on Yagi's because of this. :) Thanks for your time and effort figuring this out for us. You rock!

Looking forward to the feed although I think *MINE* was the very first (or it might have been Dylan's feed - I forget now) :D. It was on teamspeak for a brief period but the quality sucked and my router kept randomly killing it. Same happened with the Windows Media Encoder and Icecast feeds I set up. Blah, what a headache.

I recommend using Gordon's server that's currently hosting the ScanArizona (www.scanarizona.us) feeds. I've heard good things about his servers and am thinking about hosting a Chandler PD feed there since we seem to be missing one of those and I've got an old BC895 sitting on the computer desk literally doing nothing at the moment. I've even got an old WinME box that can run it. Hmmm....

-AZ
 

ICP963

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PHOENIX_SCANNER said:
I wanted to share this with everyone, and for the skeptics, I am planning a live feed of Phoenix PD in the near future. As far as I know it will be the first successful feed of this agency since the switch to p25 simulcast. My personal belief is that nobody has tried for the reasons listed above. It wasn't listenable, and worth the effort, until now.

The least I can do is share good listening with those who can't for whatever reason install a yagi and dedicate a scanner.
A Phoenix PD Feed would be a VERY welcome addition to the www.ScanArizona.us site. If I can help you get that going please let me know. I am out of state right now at the Dayton HAMVENTION, but I will be back in Arizona on Wed the 21st. Feed setup is very easy with Gordon's setup on the server and we can help you get AlphaTags going on the feed if you are running a Uniden scanner, not sure on the GRE's yet.
 

hulka

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I have a problem also trying to hear it but the odd part is I can usually pick up the Fire on the TRS (dispatch) fine but not A4 (live in that section). I am still playing around some. I put a antenna in my attic, stupid HOA reasons, but still no luck.

Here is the question, how well do you pick up the other agencies now with the yagi installed?
 

ICP963

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hulka said:
I have a problem also trying to hear it but the odd part is I can usually pick up the Fire on the TRS (dispatch) fine but not A4 (live in that section). I am still playing around some. I put a antenna in my attic, stupid HOA reasons, but still no luck.

Here is the question, how well do you pick up the other agencies now with the yagi installed?
Phoenix Fire is not always on the TRS. About the only time you will hear one of the fireground talkgroups is if there is someone on the TRS that has a trunked radio tuned to that talkgroup.
 
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Update, thoughts

Well I had to pinch myself, and listen more to be sure I wasn't going insane from all the frustrating years of cut-outs, but it is really true. This setup works great. I will stand by my estimation that I now clearly hear at least 95% of all transmissions, which as I said, is as good as I get from Glendale, Maricopa County, etc. Even they "go a bit digital" every now and then, but it isn't enough to bother me in the least. I am a happy camper.

I have decided on a diamond cs-210a antenna switch, which will be here Friday. It offers 60db isolation at 800mhz and is rated through 1000mhz. Insertion loss is about .5db at 800mhz, which is nothing for out purposes here. This way I can leave it on the good old RS ground plane antenna (yeah sputnik as I have heard it called) most of the time with my favorite PPD tg's on my favorites list as I scan. If I hear something interesting, or if I just want to listen to simulcast a, then I switch to the yagi.

Now, the part that surprised me. I would expect with other transmitters such as Maricopa County and Glendale sitting at angles that yield -30db to -45db, they wouldn't come in well. I was a bit surprised to find that they come in well. I guess -30 or -40db isn't enough to stop the signal from getting into my psr-600 with plenty of punch to work well, especially with a roof mount antenna within direct visual site of most of these transmitters for the other systems. So yes, nearby 800mhz stuff will still work. So how is it solving my issue then?

My theory is that this is somehow related to the "capture effect" of fm radio. With the simulcast a situation. The tower I want is coming through to the scanners internals at about-10 db after losses and scanner attenuation (20db scanner attenuation, plus cable/connector losses subtracted from 11db gain at the angle I have chosen to mount at).

But more importantly the next closest towers are getting about 61db total attenuation. So I think it is all about the "ratio" between the power of the signal of the site I want, and the ones I don't. This improved ratio, where the one I want is much stronger than the others, along with "capture effect", seems to be enough to keep the weaker ones from breaking up the signal of the closer site. So it all works.

Yet with this said. other 800mhz systems can still be monitored (at least on the 600), even down 40-60 db (depending on their orientation to my yagi's focal point). So yeah, your other 800mhz stuff will work, though I haven't even tried to see what vhf high would do on this setup, probably not well, so plan on a switch for full spectrum monitoring.

Planning / Execution:

Print out the yagi's field pattern drawing, and study it. Get a map and plot out your locations, as well as any transmit site within 10 miles or so. You want to angle the antenna so you get the closet site with some gain (doesn't need to be maximum gain or be pointed right at the site), while making sure you get MAXIMUM ATTENUATION of the next one or two closets sites, to eliminate interference.

There are other scenarios I can imagine, where you may have to get even more creative to get your signal. If the closest site for example, has another site behind it at the same antenna angle, my exact approach may not work. You might actually have to focus on a lone, yet more distant site to eliminate the other CLOSER sites, so that only ONE site is heard. If you have several nearby as I do, it makes the most sense to angle the antenna so both (all) offending sites are attenuated equaly, even if none of them get maximum attenuation.

Remember the goal is to make sure that no site other than the one you are focusing on, comes anywhere near the signal level of the target site.

So your antenna probably won't be aimed right at your target site. Mine is aimed about 18 degrees off the target site, but keeps both nearby offending sites at least -56db down. So doesn't being aimed 18 degrees off target hurt me? No. It means instead of 13db gain (aimed perfectly dead on), I "only" get 9db of gain. Not much of a difference. But the ATTENUATION of the other sites goes from -25db on one site to more than twice that, simply by my antenna being pointed 18 degrees off of the target site, instead of right at it. And this attenuation is what matters, not a slightly reduced gain for the target site. The RATIO of signal is what is important, and that 18 degrees gives me the highest ratio of gain for my target site, and attenuation for the offending sites.

For some this solution will be easier than others.

PLAN CAREFULLY FIRST.

I used autocad to plot everything out and measure angles accurately, but it can all be done by hand if you take the time and care.

Everyone's unique location will require it's own unique version of this solution, depending on how things lay out.



DO NOT GROUND ANTENNA MOUNT. Use wood to mount on, or wrap your existing metal mast with electrical tape. The whole antenna assembly, driven and non-driven elements, boom, clamps, etc. ALL ACTS AS THE ANTENNA, and is all connected to the center conductor. Metal antenna mounted to grounded metal mast = shorted antenna. Remember this part. Use a static discharge unit inline, and make sure it is grounded properly.

My appologies for the long-winded post, but I wanted to be sure I was crystal clear on the details, especially HOW you aim the yagi.

Parts used:
Diamond CX-210a - $45
http://www.universal-radio.com/CATALOG/switch/1636.html
Wilson 800mhz yagi #301111 - $55 on ebay - more left
http://www.wilsonelectronics.com/ViewProductB.php?ID=13
N-Male to SO-239 adapter at antenna - $5
9913 cable and silver PL-239 connectors $25 (I think)
MFJ lightning discharge unit from HRO $30
Total: $160 plus your time.

P.S. - I have broadband (cable) and a computer to dedicate, so if you could, please tell me who to contact for more information on the best way to make this happen. I no longer have a 996 so I have to do this somehow with the 600. Thanks.
 

AZScanner

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PHOENIX_SCANNER said:
P.S. - I have broadband (cable) and a computer to dedicate, so if you could, please tell me who to contact for more information on the best way to make this happen. I no longer have a 996 so I have to do this somehow with the 600. Thanks.
Hmm, I kept quiet to give the owner of ScanArizona a chance to pipe up but I guess he isn't watching the forum. :D

Head on over to ScanArizona.us and PM the admin (Gordon). He can get you all the particulars on hosting your feed there.

Looking forward to the feed! I miss monitoring PPD (Simulcast D rarely carries their traffic).

-AZ
 

ICP963

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AZScanner said:
Hmm, I kept quiet to give the owner of ScanArizona a chance to pipe up but I guess he isn't watching the forum. :D
I do watch the forums, but I have been out of state for the last week. :)
 

GordonE

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PHOENIX_SCANNER said:
P.S. - I have broadband (cable) and a computer to dedicate, so if you could, please tell me who to contact for more information on the best way to make this happen. I no longer have a 996 so I have to do this somehow with the 600. Thanks.
E-mail me at gordon@scanarizona.us and I'll send you the setup instructions and software and add the feed to the site.

Thanks!
Gordon
 

AZScanner

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bump - Any luck on that feed, Phoenix_Scanner? I had Tempe/Chandler up and running within a matter of minutes thanks to Gordon's preconfigured version of Oddcast. The feed did go down this morning for a bit but no fault of Gordon's - Windoze installed an update and rebooted itself while I was asleep. :D

-AZ
 
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Feed

I fully plan on it very soon, just been tied up with things around the house, remodeling at the moment.

This weekend I plan to spend some time playing with this.
 
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