question for short 75 ohm cable run

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skatertj

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I currently have a larsen 50 ohm RG58/U Dual Shield cable that is running directly into my scanner on my car. I am having overload issues with my pro-2055 and i plan to try the RS FM trap. I have some spare RG-6 tv cable laying around and am thinking of cutting it about 6 inchs from the F connector then crimping on a bnc connector to the other end and trying out the trap. Would this short of a run from the 75 ohm fm trap be ok? Heres my plan to clarify.

Antenna cable w/BNC male connector -- to BNC female/F male adapter -- to trap -- Out trap with male F connector/cable(tv coax 75ohm)to bnc male connector--into scanner.

Hope that is easy to understand...
 

Thayne

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Surely no harm can come from trying it--75 ohm cable works for receiving only.
 

prcguy

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Is the overload from FM broadcast or paging transmitters or something else? If your not sure you should identify the actual problem before making any changes, otherwise it's like having a cut somewhere and randomly sticking bandages around hoping to stop the bleeding.
prcguy
 

skatertj

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Well, I have no bleed over from any other signals but anytime I try to get frequencies around 153-155, they come in fuzzy with attenuator on or off. With it off, its way worse! Attention helps abit. I have read other posts with people who have the same scanner and put on the fm trap and it solves the problem so I thought I would try it. Idk what the real problem is...
 

skatertj

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Well, I stand corrected. As I decided to see if I was getting bleed over, sure enough, if i turn squelch all the way down, you can hear slight radio stations. One started to come in very clear and it was on the frequency of 97.5
 
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VE3RADIO

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In my experience the fuzzing can be a couple of things.. could be electric energy caught in the line from a storm or it could be water.

As for 75 ohm cable it would work for receiving only but would have a very high loss and should in an ideal situation have a balun to bring it back to 50 ohm.

How long is your run of RG-58? Generally RG-58 should not be used for anything other than car/mobile installations as there is just too much loss. I would rip the cable out and run some RG-8X or some RG-213.
 

K9WG

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... snip ...
As for 75 ohm cable it would work for receiving only but would have a very high loss and should in an ideal situation have a balun to bring it back to 50 ohm.

... snip ...
I beg to differ. A 75ohm cable will not introduce that much loss for either RX or TX.
 

W6KRU

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In my experience the fuzzing can be a couple of things.. could be electric energy caught in the line from a storm or it could be water.

As for 75 ohm cable it would work for receiving only but would have a very high loss and should in an ideal situation have a balun to bring it back to 50 ohm.

How long is your run of RG-58? Generally RG-58 should not be used for anything other than car/mobile installations as there is just too much loss. I would rip the cable out and run some RG-8X or some RG-213.
The OP was asking about using 6" of RG-6. How much loss would that cause? Actually RG6 has less loss than RG-8X, especially at UHF frequencies.
 

nanZor

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Well, I stand corrected. As I decided to see if I was getting bleed over, sure enough, if i turn squelch all the way down, you can hear slight radio stations. One started to come in very clear and it was on the frequency of 97.5
Sure sounds like the fm broadcast trap will be the ticket - especially since you can hear them and the 2055 doesn't even have fm broadcast coverage. :)

Try the RS trap - although the rs traps have the notch above 100 mhz, you may not have a sufficient notch depth to really nail it - which usually means upgrading to a PAR or other higher-quality fm band notch. The RS trap is definitely worth a shot however!
 

skatertj

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I was actually just talking about a short run of RG6. Its about 2-3 feet long. Its there to hook up my FM trap. The FM trap did help some but im sure a PAR will do better. I also did have a TV station come in once or twice. I dont know what station it is though. Im beginning to hate this scanner because of all its intermod issues. I know I have to upgrade to a narrow-band one by this year. I think I will be getting a uniden next.
 

zz0468

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If you were to transmit (i know the OP is not) it would eventually burn out your radio.
This is incorrect. The mismatch is relatively minor, and the losses involved in impedance matching often exceed the losses in the coax caused by the mismatch itself.

Can we just kill this tired old rumor that it will burn out a transmitter once and for all? Thank you.
 
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