High Pass Filter Needed?

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tweiss3

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I have a SDS200 installed in the car, with a HP RF Limiter between the permanent mounted (hole drilled) NMO150/450/758 antenna (swept here by mmckenna). I remember it did pick up some CB, though that traffic is almost nothing.

I'm diving into adding HF+6 to the car at 10W, and the conclusion I've come to is I have no real good options except to add a screwdriver antenna, which would end up being 3' from the scanner antenna.

Question 1, with the RF limiter inline, do I need to add a HPF?
Question 2, I've been looking, and I need VHF high to be picked up still, so I looked at mini-circuits and there are two that might work for my situation:
Are there any better options?
 

Ubbe

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With a highpass filter you could probably use the scanner while you where transmitting. It's a good $40 investment.
I would go with the 150MHz version instead of 100MHz to exclude FM broadcast. Are available in both SMA and BNC versions.

/Ubbe
 

tweiss3

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No to what? No need for a filter? No to either of the options or no to the whole idea?

With a highpass filter you could probably use the scanner while you where transmitting. It's a good $40 investment.
I would go with the 150MHz version instead of 100MHz to exclude FM broadcast. Are available in both SMA and BNC versions.
/Ubbe
SMA is perfect, as the RF limiter is SMA. Place before or after the RF limiter?
 

Ubbe

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SMA is perfect, as the RF limiter is SMA. Place before or after the RF limiter?
RF limiters have active semiconductors that might introduce mixing products at certain signal levels and also to not stress the semiconductors you should have the highpass filter before the limiter to reduce the risk of any problems. Remember that SMA has a tendency to come loose and probably needs to be retighten after some use, especially in a vibrating vehicle, but not too tight if using tools. So use some sort of light threadlock fluid.

/Ubbe
 

prcguy

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Before adding a filter or even the limiter I would transmit on HF through 6m and measure the level picked up by the tri-band scanner antenna. The OP mentioned 10 watts and that is nothing to worry about. Even at 100 watts the little tri-band scanner antenna is not going to pick up much but you will never know until its measured.

Adding anything to the scanner to protect it at this point is like putting on a band aid before you have an injury. You don't know if you will get an injury or where it will be or how big it is, so why bother until all the facts are in?
 

Ubbe

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It's like wearing a cup because you could get a kick in the groin. There's nothing wrong in being prepared. Something could change after a measurement, the wind could pick up and antennas blow into each other or at least very near and drastically change the signal level received.

/Ubbe
 

prcguy

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I won't leave my house these days without a cup.

It's like wearing a cup because you could get a kick in the groin. There's nothing wrong in being prepared. Something could change after a measurement, the wind could pick up and antennas blow into each other or at least very near and drastically change the signal level received.

/Ubbe
 
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