Coax for Digital Scanner

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railroadertwo

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As I am considering buying a Pro-197 that is currently on sale, I am wondering if RG8 coax , would be suitable for a Radioshack Pro-197 Digital Scanner, I am a Amateur Radio Operator (Ham), and have some lying around, I generally use LRM-400 Flex for my ham radios but don't have any on hand at the current time. Thanks KC0WNY
 
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kg4ojj

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The same rules apply for listening to public safety as they do for amateur radio operation.

If you want to listen to 800MHz or higher, you'll need the cable that has the least amount of loss per foot. As you know, the higher the frequency, the greater the loss (in dB) per linear foot. RG-8 is usually good, as long as the lengths are reasonable. Whatever antenna you match with it will add/subtract from your overall reception ability (but you knew that).

I've used RG-8 and RG-58 and have had great results. Most of my cable runs have been short (at or less than 25 feet) and paired with a decent antenna. All depends on your situation.

Worst case: try it. If it fails to make you happy, save your pennies and buy some higher quality (low-loss) cable later. RG-8 is rated at 50 ohms, which is perfect for that scanner.

Here's a reference for RG-8 cable. At 900MHz, it's not bad: 50 Ohm Braided Coax Cable, RG8 Cable | TESSCO 800 472 7373


73,
 

n5ims

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As I am considering buying a Pro-197 that is currently on sale, I am wondering if RG8 coax , would be suitable for a Radioshack Pro-197 Digital Scanner, I am a Amateur Radio Operator (Ham), and have some lying around, I generally use LRM-400 Flex for my ham radios but don't have any on hand at the current time. Thanks
RG-8 should work OK since you have some on hand. LMR-400 would be better, but since it isn't on hand, no need to spend the money. A good grade of RG-6 would also work fine if you have that on hand as well (but I'd use the RG-8 if I had both).
 

W2PMX

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RG-8 has about twice the loss of LMR-400, so if you're not concerned with 800 MHz (RG-8 has over 6db/100 feet loss [more than 75% of the signal] at 800), it shouldn't be too bad. RG-6 is even worse - over 8db at 800.
 

mike_s104

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If you are going to mount an antenna, use a really short piece of what you have at the antenna and see if you can in fact receive what you want. If you can and the signal is strong and you're happy, run that in the house. If not, go with a better cable.

This is what I did with RG6 with compression F connectors and I'm very happy with it.

Sent from my ADR6400L using Tapatalk
 

bobriff

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If you are going to mount an antenna, use a really short piece of what you have at the antenna and see if you can in fact receive what you want. If you can and the signal is strong and you're happy, run that in the house. If not, go with a better cable.

This is what I did with RG6 with compression F connectors and I'm very happy with it.

Sent from my ADR6400L using Tapatalk
Correct me if I'm wrong, but RG6 is 75 ohm cable. I believe the cable impedance should match the antenna impedance (typically 50 ohms) for best performance,

You're not transmitting, so you won't damage anything, but you will not get ideal performance with an impedance mismatch.
 

mike_s104

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Correct me if I'm wrong, but RG6 is 75 ohm cable. I believe the cable impedance should match the antenna impedance (typically 50 ohms) for best performance,

You're not transmitting, so you won't damage anything, but you will not get ideal performance with an impedance mismatch.
Yes, you are correct. It does work. Like I said, try it and if your happy with it, then use it. If not, look at some better cable.

Antenna Specialists Scantenna comes with 50' of RG-6.

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railroadertwo

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Well, I ordered the Pro-197, and I have a Diamond Scanner Base antenna, 25-1300 MHz, will be running about 50ft of cable to the scanner. I live in SE Kansas in a town that is so small, the city limit signs are on the same post , so some of the traffic won't be receivable, I am hoping to be able to monitor the Highway Patrol and state radio and other digital traffic. I have a Pro-2051 for local stuff. Thanks for the input. KC0WNY
 

n5ims

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Correct me if I'm wrong, but RG6 is 75 ohm cable.
You are correct, RG-6 is 75 ohm cable.

I believe the cable impedance should match the antenna impedance (typically 50 ohms) for best performance, You're not transmitting, so you won't damage anything, but you will not get ideal performance with an impedance mismatch.
The impedence of both a radio and an antenna have an impedence at a stated frequency (or frequencies for multi-band ones). For something that's wide band like a scanner or discone, the stated impedence is only at some of the frequencies in that range. It may be the stated 50 ohm impedence at one frequency, say 150 MHz, but be 25 ohms at another, say 40 MHz, and 90 ohms at another, say 300 MHz. That's why it's OK to use 75 ohm cable on a scanner. A tranceiver, however, would cover a much narrower band of frequencies, where the 50 ohm stated impedence would be critical. Even those would have different impedences outside of the designed transmission range.
 

Ed_Seedhouse

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In any event this is only a 50% mismatch and basically unnoticeable except for the most extreme situations. Assuming the true impedance of the antenna is exactly 50 ohms, which it hardly ever is, the SWR would only be 1.5 and for all practical purposes perfectly suitable even for transmission of fair amounts of power. With a receiver 75 ohms is fine and indeed the cable TV industry uses 75 ohms because it is best for receiving over long runs. Lots of hams use 75 ohm cables on VHF because it is cheaper.
 
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