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Jumper Cable Recommendations

NFR85

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#1
Newbie with a question:

I have Davis RF 9914F 75' both ends are BNC. And the connector is PL-259. I need jumper cables. These go into multicoupler.

The 1st scanner monitors strickly 800 MHz. The scanner is right next to the multicoupler and it measures 18 inches.


The 2nd scanner monitors UHF and VFH. What jumper cable would you recommend at approximately 20'?
 

mmckenna

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#2
RG-58, LMR-195, etc.
For a short run, you want something flexible and light that won't put strain on connectors. For a short run, the loss is negligible.
 

Ubbe

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#3
When you mention PL259 I guess it is the antenna connector. Try to use a BNC-PL259 adapter and secure the coax so it cant move with metal clamps, like a hose clamp. If you use plastic cable ties they usually go brittle and fall off when exposed to sunlight.

I try to use cheap RG6 cables as much as possible as those are so easy to make yourself with F twist on connectors and then I use adapters for BNC or whatever but only to fixed equipment like base scanners and multicouplers and also CATV splitters and attenuators that already have F connectors. To portable radios and SDR sticks I buy flexible pigtails RG174 with either the correct connectors or a bunch of standard SMA cables and use the appropriate adapters to multicouplers,splitters, filters and attenuators.

If you use RG58 then check that you get one that has a fully covering braid and not a cheap one that doesn't stop external interfering signals and makes your coax work as an antenna. As mentioned attenuation are not an issue with short runs but shielding are. The impedance difference from 50 ohm to 75 ohm cables/equipment are no problem as your scanner and antenna have a much higher difference from a nominal 50 ohm over their frequency range.

/Ubbe
 
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#4
Not knowing what your entire antenna/multicoupler system is I would simply suggest that you connectorize your main feedline based on the components you have, adapters have no place in a permanent installation.

Regarding the jumpers, LMR-195 type cable would be my suggestion. The price is comparable to RG-58 at this point so in my opinion there is no longer a reason to but solid center conductor RG-58. Especially when you are talking about 20ft. 'jumpers' the loss is no longer negligible at 800MHz.

Will you notice a difference? Depends what kind of system you are listening to. A system designed for to portable coverage for your area, you could probably receive it with a paper clip. But for a system with a coverage area several miles away you will need all the signal you can get.
 

NFR85

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#5
Thanks for the suggestions. My next question is what is a reputable company to buy from? Did anyone hear of Show Me Cables in MO?
 
Last edited:

mmckenna

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#6
Thanks for the suggestions. My next question is what is a reputable company to buy from? Did anyone hear of Show Me Cables in MO?
https://www.theantennafarm.com/catalog/coaxial-cable-342/custom-made-cable-assemblies-344/

As for the RG-58 vs LMR-195, you are looking at about a 1dB difference with the 195 being the better one. 20 feet at 850MHz….
Hard to hear 1dB in a hobby application.
LMR-200 might be a good option too. 100% foil shield.

If you are buying new prefabricated cables, then absolutely go with the LMR-195, but if you are going to fabricate your own and all you have is RG-58, then it would be just fine.

As for the prefab'd cables, spend the extra $ to get the heat shrink put on. That helps with strain relief where the coax enters the connector.
 

NFR85

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#7
https://www.theantennafarm.com/catalog/coaxial-cable-342/custom-made-cable-assemblies-344/

As for the RG-58 vs LMR-195, you are looking at about a 1dB difference with the 195 being the better one. 20 feet at 850MHz….
Hard to hear 1dB in a hobby application.
LMR-200 might be a good option too. 100% foil shield.

If you are buying new prefabricated cables, then absolutely go with the LMR-195, but if you are going to fabricate your own and all you have is RG-58, then it would be just fine.

As for the prefab'd cables, spend the extra $ to get the heat shrink put on. That helps with strain relief where the coax enters the connector.
I think I'll go with Times Microwave LMR-195 add heat shrink. and BNC on both ends. I should be good with that.
 

osiris

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#8
I have a question on connectors. Can I use a T connector between 2 scanners or do I need a splitter, like in a TV installation?
Thanks in advance.
Bob
 

737mech

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#9
I have a question on connectors. Can I use a T connector between 2 scanners or do I need a splitter, like in a TV installation?
Thanks in advance.
Bob
Bob, You can but there will be signal loss, basically you will split the antenna signal by half if you add a tee or a splitter. How we get around that is by using multicouplers. They are powered splitters with amps built in to make up for the signal loss of splitting. Some of us use cable drop amp/splitters. I have found the electroline drop amps are good but be careful. I use the 8 port amps for eight scanners but only because the amp is low power output only 3.5db. That's a good number to make up for the splitting. Now if you look at the specs of other drop amps you might find +7.5db or more. Most modern scanners can't handle that strong signal and you pretty much won't hear anything. It all depends on your location and antenna setup. There are expensive multicouplers available from Stridsberg. I hear they work great. I'm the guy that goes cheap until it doesn't work. EDA drop amps are cheap and they work. I'm currently scanning on 11 scanners with one antenna doing just fine but in my city I have rf noise so I use FM traps before the drop amps. That helps on AM aircraft bands.
 

osiris

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#10
737mech
Thanks for the info. I don't have any RF interference where I am & I love cheap! Do you have a link for the ones you use ? I googled edp drop amps and didn't get anything.
Thanks, Bob
 
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#11

Ubbe

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#13
T-connectors can work if you don't get interferencies between scanners. There's often a weak carrier from a scanners antenna port that are related to the scanning frequencies so that you hear a pulsating carrier on the other scanner.

When one scanner are on a 700-900MHz frequency and the other on 25-500MHz they'll use different front end filters and will not rob the antenna signal from each other as the filter for the "wrong" frequency have a much higher impedance. If the scanners are on the same frequency band they will have to share the signal equally between each other the same way a splitter will do and will cut the signal level in half, but the splitter also have isolation between ports so that an eventual interfering carrier are attenuated enough to not be heard.

Proper splitters will cut the signal to half but you have no interference problem between scanners and T connectors gives you higher signal levels depending how the scanners are used but gives a higher risk of listening to pumping noise on channels that are analog and doesn't have CTCSS/DCS tones programmed, like marine and air bands. Try a T-connector first and see how it goes.

/Ubbe
 

osiris

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#14
I have a "T" connector in the line and it seems to be working fine. However I am trying to pull in some farther away weak signals. The link to the Electroline dist. amp above says it has + 7db gain, is that a problem for close stronger signal stations?
Thanks Bob
 
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