Terrible intermod with noaa weather repeater

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kjvonly1611

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I have a BCD396T and certain frequencies (usually in the 155Mhz range) break squelch with terrible intermod from our local weather repeater. This repeater is over 5 miles from my house so I don't understand why it's so strong but it only happens when there is an actual transmission on these frequencies and it only happens when I plug the scanner into my outdoor antenna with the power injector. Anybody have any ideas on how to alleviate this?

When the squelch is broken I get data noise, squealing, wobbling and of course the weather.

I have the attenuation on for the weather stations.

If I unplug the power injector I can't pull in the distant freqs, but I'd like to listen to the freqs i'm getting the intermod on.

I have done the firmware update to 3.xxx

When all is said and done this is the first digital scanner I've owned and I am NOT impressed with all it's bugs.
 

gewecke

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Intermod and overload are things we all deal with when using scanners. I'm not real familiar with the 396 but maybe try using the attenuator or experiment with antennas, that may help with your intermod. ;)

73,
n9zas
 

zz0468

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A likely scenario is that the preamp inside that active antenna is overloaded by something, and that would create all sorts of intermod. That something may or may not be the NOAA weather transmitters. If the mixing is occurring inside the antenna, then there's nothing you can do about it at the scanner.

If your scanner has an attenuator, you can try switching it in and out. If the intermod goes away with the attenuator on, then it's occurring in the scanner. If the attenuator has no effect, then it's in the antenna.

Consumer grade TV type active antennas are notorious for having really poor quality preamps that are easily overloaded.
 

kjvonly1611

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The built in, channel by channel attenuation does help cut down on it... but not totally eliminate it, plus I have to be quick on the ATT button, especially if i'm across the room when it happens :)

Do you think getting a higher quality injector or a preamp would help?
 

W8RMH

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Bugs? You are using an antenna and amplifier which was not designed for a scanner, to receive stations beyond the intended range of a scanner, which is resulting in interference in the normal operation of a scanner, and you want to blame the scanner???

That's like putting jet fuel in your car to make it go faster and wondering why it won't run right and blaming the car.
 
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kjvonly1611

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Bugs? You are using an antenna and amplifier which was not designed for a scanner, to receive stations beyond the intended range of a scanner, which is resulting in interference in the normal operation of a scanner, and you want to blame the scanner???

That's like putting jet fuel in your car to make it go faster and wondering why it won't run right and blaming the car.
This isn't the only "bug" i've found, the 155.25Mhz birdie is as annoying as they come but I found a workaround for that.

If you can convince my park association to let my put a ST3 15' up a mast on my roof more power to you but I'm limited to this or the stock antenna and variations of stock obviously, but only inside.
 

jim202

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Think about this. What happens if you take a balloon and just keep pushing more air into it? The same thing is going on inside you fancy antenna system. Too much signal is overloading the scanner.

Don't blame the scanner and the weather transmitter. Blame your antenna system.
 

kjvonly1611

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Think about this. What happens if you take a balloon and just keep pushing more air into it? The same thing is going on inside you fancy antenna system. Too much signal is overloading the scanner.

Don't blame the scanner and the weather transmitter. Blame your antenna system.
More criticism with no real solutions. And I wonder why my other friends avoid these forums like the plague.
 

kjvonly1611

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Instead of criticism why don't we speak solutions....?

It's obvious to everybody INCLUDING MYSELF that my antenna aint exactly optimal but remember what rules I have to follow... Like NO VISIBLE ANTENNA SYSTEMS ALLOWED.

Solutions please...

Would a dipole mounted right on the ridge line work? etc... etc... etc...
 

w2xq

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Sounds like you could use a single-frequency notch filter such as described in the thread http://forums.radioreference.com/ra...003-sale-prices-effect-now-2.html#post1693447. I haven't tried the PAR filters but you can do some research, e.g. https://www.scannermaster.com/WAF_125_Tunable_Notch_Filter_p/28-531165.htm, for yourself. If I were in your situation, I would probably go try something like https://www.scannermaster.com/AH_W100RX_Multi_adjustable_Telescoping_Antenna_BNC_p/40-541717.htm set onto the windowsill, using appropriate lengths of coax to put the filter in the antenna feedline. Just to be clear, I have no vested interest in Scannermaster or these products, nor can I vouch for their performance. I just found these items by looking on the 'net. HTH.
 

zz0468

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Instead of criticism why don't we speak solutions....?

It's obvious to everybody INCLUDING MYSELF that my antenna aint exactly optimal but remember what rules I have to follow... Like NO VISIBLE ANTENNA SYSTEMS ALLOWED.

Solutions please...

Would a dipole mounted right on the ridge line work? etc... etc... etc...
Quit getting defensive. You've been given a solution. Your active antenna is the likely culprit. You need to try something else.

A dipole on the "ridge line"? I though you said no visible antennas. How about you define the rules a bit better, and maybe someone can make a specific recommendation.
 

zz0468

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Since it looks like most of what you want to hear is on VHF highband I would try a Ventenna and a narrowband pre-amp if I found that I needed a pre-amp
I would strongly urge the OP to avoid the preamp, since it's an intermod problem he's trying to cure. With conditions such as strong overloading signals, no visible antennas, etc, he's going to have to accept whatever minimal reception he can get. He's already been set up with conditions where an optimal installation is impossible. Therefore, anything left will be a compromise. A compromise will not have the best of reception, and thats just the way it goes.

Those pesky laws of physics just suck, don't they.
 

jdm911

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another vote for PAR Filter! I would try this before you make any other change...order directly from them.
I use two of Dale's filters and they did wonders. In fact, it took me some time to figure out where my interference was coming from and after ordering the wrong filter he let me exchange it.
 
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zz0468

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another vote for PAR Filter! I would try this before you make any other change...order directly from them.
That would only be effective under two conditions:

1. It's placed IN FRONT OF any active devices i.e preamps.

2. The interfering signals are outside the pass-band of the filter. If it's a notch filter, the notch has to be tuned to the frequency that's causing the overload condition and narrow enough to not filter out the desired signals.
 
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