Antenna wiring scheme advice needed

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kkemper13

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I need a bit of help and guidence and hope you guys can help.

I have a GRE PSR-500 and it's mainly used inside my house but I do take on-the-go at times...which is why I bought this instead of a basestation. However, the reception in my area is horrible for anything other than my immediate area, and at times that's iffy. I just moved into a house with a nice hip roof that affords me the ability to mount an antenna in the attic and still have plenty of room to adjust if need be....outside is not an option due to the HOA. I'm currently looking at the D130NJ Diamond Super Discone and I'd like the ability to distribute to multiple rooms so that I can move the scanner to whatever room I'm in.

Ideally, I'd like to run from the antenna in the attic to my network rack in the basement (60' run roughly), from there it would enter a splitter and from the splitter disburse to whatever room I want a feed, with the longest run being roughly an additional 60'. I've looked at using LMR-400 from Time Micro, but I just don't know if that's overkill or not. Also, putting the splitter at the antenna and then distributing to the multiple rooms would probably be more ideal in limiting the total run of cable, but running multiple cables down from the attic poses some issues as I intend to use existing holes drilled for the OTA antenna wiring.

Is any of this flawed? Is there a better way...either in practice or equipment?

Any guidence is greatly appreciated.
 

copperhd

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I run the same antenna & have it split to four different rooms using RG6 & it works pretty good. I'm also in a valley between two hills about ten miles from the nearest city, but hear cities 25-45 miles away clearly. If I was going to do it over I would run the LM400 for my first & longest run to the splitter & then run RG6 for the subsequent feeds to the other rooms. RG6 is low loss cable, widely available, flexible, easy to run/hide & cheap. Don't let the 75 ohm resistance fool you because it does not matter for receive only. You do however want to make sure your splitter will cover the freqs you want to listen to or it will be all for naught.
 

prcguy

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I would run LMR400 from the attic antenna to a quality amplified multicoupler like Stridsberg, then some smaller coax like LMR240 from the multicoupler to the individual receive areas. I might also use an FM trap/VHF high pass filter like the HPN-30118 filter sold through Scanner Master and put that in front of the Stridsberg to reduce potential interference and Intermod problems.

This will probably get you a lower system noise figure than just the antenna and coax feeding the scanner alone since the NF will be set by the antenna, feedline to the multucoupler and the noise figure of the active multicoupler. The Stridsberg should have a better noise figure than the scanner, plus it has a little gain per port which will offset the loss from runs of coax to the various receive areas.

I personally would not use an amplified CATV splitter or TV coax and any 50 to 75 ohm mismatch problems will have the same impact on receive as it does on transmit. I would also take a look at your rack of network junk to see if there is anything that would introduce RF interference to your receive system.

If you do it right the first time, you'll not have to worry or wonder how much better it could have been.
prcguy
 

kkemper13

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Thank you both for the information and guidance.

prcguy...Would the HPN-30118 filter be best suited to put directly at the antenna, then have the 60' run to the Stridsberg or would it be better to have the 60' run from the antenna and then put the filter directly in front of the Stridsberg? Also, do I need 50-ohm terminators on any unused outputs of the Stridsberg?

I definitely want to do it right the first time. I currently am remodeling my family room and have the drywall torn off, so now's the time to run it and do it right. If I tear into the drywall later, after paint, I might end up divorced.
 

prcguy

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Placing the filter at the antenna or right at the multicoupler input should have no difference in reception but you would have to water proof it at the antenna end. The filter will have the same slight loss at the band pass frequency ranges you are listening to and at or near the cutoff frequencies there may be a slight difference measurable on test equipment due to radical phase shifts in the filter skirts and VSWR between the cable and filter at those points, but that's to be expected.

I'm not up on the port to port isolation of the Stridsberg divider but its good practice to terminate all unused ports which will reduce VSWR problems which cause amplitude and phase ripple at the output. That's probably not a problem for scanner use but for other applications like passing 30+ MHz wide digital satellite signals can cause an increase in bit error rates.

I like LMR240 for short/medium runs and there was someone on Ebay selling packaged 50-60ft chunks with odd connectors for about $14 and new BNC connectors and crimpers are cheap.
prcguy

Thank you both for the information and guidance.

prcguy...Would the HPN-30118 filter be best suited to put directly at the antenna, then have the 60' run to the Stridsberg or would it be better to have the 60' run from the antenna and then put the filter directly in front of the Stridsberg? Also, do I need 50-ohm terminators on any unused outputs of the Stridsberg?

I definitely want to do it right the first time. I currently am remodeling my family room and have the drywall torn off, so now's the time to run it and do it right. If I tear into the drywall later, after paint, I might end up divorced.
 

copperhd

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Yeah, that all sounds good, but on receive only there is no such thing as a "mismatch". Even the ST2 antenna comes with RG6 CATV cable when purchased new & they work just fine with it. Now all of that elaborate, costly material will work just fine, but the major detectable difference (possibly the only difference) you will detect is in the size of your wallet.
 

jonwienke

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Not true. Impedance mismatch causes a percentage of RF to reflect back to the source, regardless of the power level of the signal source, or whether the signal source is a transmitter or antenna. The dBs of signal loss caused by mixing 50- and 75-ohm coax is exactly the same regardless of whether you're transmitting or receiving.
 

kkemper13

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I'm definitely not opposed in doing it cheaper, but I only want to do it once. I have miles of RG6 quad laying around that I can wire up as a test to see how well it works. If I'm not convinced, then I'll spend the additional money for the LMR-240 for the runs to the rooms, multicoupler, etc....still keeping the LMR-400 from the antenna.

Thanks again to all of you for info and guidance. While there's always differences in opinions, I have enough to think about and test to see what works the best in my situation.

Thanks again.
 

prcguy

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The ST2 and similar antennas are made by TV antenna companies so its not a coincidence it uses a TV transformer and TV coax. It's designed that way (a compromise design) and it doesn't mean any antenna is fine with 75 ohm coax.

I've seen the effects of 50 to 75 ohm coax mixes and have had to track down many problems in my professional career where someone mingled the two and didn't know any better. The mismatch problem may go unnoticed in some cases and others its an obvious problem.

I prefer to do things with good engineering practice, do it once and not skimp. My stuff works really well, looks great and will last a lifetime, how bout yours?
prcguy

Yeah, that all sounds good, but on receive only there is no such thing as a "mismatch". Even the ST2 antenna comes with RG6 CATV cable when purchased new & they work just fine with it. Now all of that elaborate, costly material will work just fine, but the major detectable difference (possibly the only difference) you will detect is in the size of your wallet.
 
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