Reception problems

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W5TWX

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I have a 396 and i've been using a 1/4 wave unity gain antenna and getting pretty good results. It's tuned for a center freq of 861.5. The system i'm monitoring is a 800 MHz Apco 25 standard digital system.
Here's the link if you want to check it out. It's the Williamson County part of the Austin / Travis County / Williamson County / system. http://www.radioreference.com/apps/db/?sid=2

I bought a new 1/2 wave 2.5dB gain antenna that is tuned the same as the 1/4 wave. I'm getting full scale reception on the bar graphs, but i'm not getting all the transmissions. These antennas are both handheld antennas and are made by the same company. Antenex.

My question is this: Is it possible to overload the front end and not receive some of the transmissions? Is my reception too great?

I'm confused on this one! Any ideas?
 

DickH

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... Is it possible to overload the front end and not receive some of the transmissions? ...
Look around your neighborhood for a cell phone antenna site. If you're too close to one it can overload the front end. If that's the case, try the ATT (Attenuator). Try it anyway.
 
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Your problem is that this is a simulcast system. You will most likely be able to solve your problems with a yagi antenna.

Check this thread for how I solved this same problem on the Phoenix simulcast system.
 
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Sorry. Forgot to post it.

http://www.radioreference.com/forums/showthread.php?t=106057

If you are against hooking up that 396 to a permanent antenna then I guess this won't apply. I just thought you might want to hear things clearly for a change, which would require that you hook it up to a stationary yagi. There is no portable solution for simulcast issues.

A $500 scanner isn't going to match a much more advanced moto ht costing thousands when it comes to sorting out out of phase simulcast sites, so the above link is the only way I am aware of for hearing more of a simulcast system.

If there was a portable solution I would be the first in line to buy it (in line with hundreds of other Phoenix scanner enthusiasts).
 
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Yeah, it's a pretty frustrating problem for us scanner guys who have to deal with simulcast systems. I got so sick of the "cut-outs" I gave up scanning my own home PD for several years until I found the answer.

Even if six sites broadcast at EXACTLY the same moment, the signals hit YOU at a different time since you are at different distances. I have heard that the police portables have some mechanism for dealing with this and sorting it all out, and for what they cost I would expect them to.

With that said, even the cops and dispatchers here with their mega-bucks equipment STILL have problems copying tx's and often are heard saying "can you 10-9 that, you went digital..."
 

W5TWX

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Round Rock, Tx.
My self and several others in the area have been trying to figure this problem out about getting all the garbled transmissions. The simulcast thing is something none of us has given any thought to. I'll mention this to them and see what their thoughts are on this subject of not being able to understand some of the broadcast. I thought the answer might be, by getting a different antenna, that it might help. I've bought 3 new antennas trying to improve the reception and it hasn't changed the cutouts and garbled speach. I know they use encryption on the tac channels, but this insn't encryption.

Thanks for the assistance and you imput.
 

af5rn

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N. Tex / S. Fla
If simulcasting is indeed the problem, then a different antenna could possibly help, basically as a mechanical means of attenuation. Use of a lesser antenna may exclude more distant transmitters, allowing the closest one to come through with less interference. I can't say I have ever had to function in a system like that though, so that's just theoretical.

Sounds like a nightmare, Bro! Good luck!
 
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Trust me, I have lived this scenario out for years. A yagi pointed in such a way that one nearby site has some degree of gain, and the others are attenuated greatly, solves 90% of the problem. Yes some signal from the offending sites still gets through, but relatively speaking it is at a much lower strength when compared to the target site.

For me it makes the difference between garbled trash, and pretty decent listening.

If you are having the same problem as me (simulcast interference), no omni-directional antenna is going to help at all if you are in between several sites at somewhat similar distances.

I discovered the root of the problem by driving to spots where only one site could be "seen" by the scanners antenna, where all others were blocked out by mountains. Reception was near perfect. I also heard a few others in around here got perfect reception, and speculated that they must be located in spots where one tower is just so much closer than the others that a good signal ratio is achieved.

Credit to some unknown poster on RR too, I think from Maryland, who did the simulcast / yagi thing before I did, and inspired me. He also reported that reception went from horrible to about 90%.

The thread listed above goes into (probably too much) detail about the topic.
 
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