Problems with Antenna Setup

[5Rya]

Here's my situation
I currently have a D130NJ antenna outside mounted onto the house around 25 feet above the ground. Due to my scanner being on the opposite side of the house I have 100ft of LMR-400 connecting the antenna to the scanner. I listen primarily to frequencies in the range of 120mhz to 500mhz. The reason why I am writing this is that I am wondering if maybe the antenna is not working right as it seems like not many channel are coming in with a good clear signal. I will say I do get many channels but most only come in with 1 bar on my BCT15X even though they are only 5-7 miles away. The only channels that come in clear are my local police and fire and even then on the fire department frequencies only the fire dispatch comes in clear, the tac channels often come in with lots of static. I do have a feeling that there are FM transmitters overloading the scanner so I did buy a FM Filter from Par Electrions today which should arrive sometime next week but from what I gathered it will only help with freq closer to the FM bands such as the airport.
I don't know if this has anything to do with it but I had to put a connector on each side of the LMR-400 and I also put in a lighting arrestor after the connector so it went like this:
Antenna -> Connector (http://www.amazon.com/Straight-SO-239-Female-Adapter-Connector/dp/B008X0ZHO8) -> Lighting Arrestor (http://www.amazon.com/LIGHTNING-ARRESTOR-Ham-Base-Antennas/dp/B004X80NO8) -> LMR-400 (100ft) -> Connector (http://www.amazon.com/uxcell-SO239-Female-Coaxial-Connector/dp/B0076UHL6S) -> Scanner (BCT15X)

After looking this over I see that the lighting arrestor says it is for CB and Ham radios, could the lighting arrestor be the problem after all? If so is there a lighting arrestor I could use instead of that?

Does anyone know of any solutions of how to fix this problem as I am pretty confident that the frequencies should be more clear and come in better then what it is doing now. Thanks - Ryan

 

[gewecke]

Re-inspect your installed connectors and make sure they're done correctly. :wink: 73, n9zas

 

[FKimble]

You can take the lightning protection device out of the mix and see if that helps your signals. Your first "connector" is an adapter. Your 2nd "connector" is an adapter. I am assuming your LMR400 came with UHF connectors already installed? Is the LMR400 real Times Warner L<R400 or a generic LMR400 "type" cable?

 

[TAC4]

Great antenna don't let the zero gain fool you. your signals should
be booming in. The trick is a very short coax run "max" 20 feet RG8U or X
then find the offending intermod station in your area in my case a pager
then make a simple coax stub filter to knock out that station. lots
of info on the net how to make one. Of course ground your antenna mast.
I buy pre made RG8U or X coax much easy to make the stub filter and
to get a 20 foot run. Also before install check all coax, adapters with
an ohm meter for breaks or shorts, just because they are new they
could be bad from the factory. The 65 feet of RG58 that comes with
the antenna goes right in the garbage bin.

Stub filter http://www.arcticpeak.com/antennapages/quaterwavestub.htm

 

[5Rya]

You can take the lightning protection device out of the mix and see if that helps your signals. Your first "connector" is an adapter. Your 2nd "connector" is an adapter. I am assuming your LMR400 came with UHF connectors already installed? Is the LMR400 real Times Warner L<R400 or a generic LMR400 "type" cable?

Ya, they are adapters not connectors and the link to the exact one I bought can be found here http://www.amazon.com/LMR-400-Times-Microwave-Connectors-Antenna/dp/B005K1AYCI.

 

[mmckenna]

That lightning arrestor looks to be a air gap type where when enough energy is on the line it arcs over to ground. Doesn't take a lot to damage or screw up in manufacturing. Also at less than $7.00, it's not a high quality unit.
I agree, take it out and try it again. If it's the cause, throw it away (far away) and get a PolyPhaser designed for the job.
Check all your connections. Even if it's cable with factory installed connectors they can still screw them up. This is where a multimeter can pay for itself really quickly.
Cheap adapters can fail, too.
If you have a short piece of coax, take that up and try connecting your radio directly to the antenna and see if signals improve. Work your way down the cable path checking each point and see if you can isolate the issue.
Key here is to do methodical trouble shooting, isolate each component one at a time until you find the culprit. Don't assume that there is just one failure, either, multiple things can be wrong.

 

[cbehr91]

100' of LMR400 seems like a lot. At 400 mhz that 2.5 db of signal loss. You're easily losing weaker signals with that amount of loss.

 

[5Rya]

100' of LMR400 seems like a lot. At 400 mhz that 2.5 db of signal loss. You're easily losing weaker signals with that amount of loss.

Would a preamp help with that?

 

[mmckenna]

Would a preamp help with that?

It would, but before spending more money, you need to check out what you have. 2.5dB of loss isn't going to act like a brick wall. Try tuning in on the NOAA weather channels as you make changes. It's usually a good solid signal that you can use for testing.

 

[mass-man]

While you use the NOAA weather broadcasts in the VHF range I would also check these frequencies for the local media and determine if one of them is used for re-broadcast of programming, ie always transmitting....then you are checking both ends of the range of frequencies you are most interested in....
Media Scanner Frequencies and Radio Frequency Reference

 

[5Rya]

It would, but before spending more money, you need to check out what you have. 2.5dB of loss isn't going to act like a brick wall. Try tuning in on the NOAA weather channels as you make changes. It's usually a good solid signal that you can use for testing.

Just checked it and found I get some static on it but nothing unbearable. Will compare that later this week when I go through each part of the system to determine what part is causing the issues. I believe it very well could be the lightning arrestor as it is very low quality and reading some of the reviews about people having problems with them is making me think it could be that.

 

[5Rya]

While you use the NOAA weather broadcasts in the VHF range I would also check these frequencies for the local media and determine if one of them is used for re-broadcast of programming, ie always transmitting....then you are checking both ends of the range of frequencies you are most interested in....
Media Scanner Frequencies and Radio Frequency Reference

Thanks for the advice, just checked them all and none are currently transmitting but I do remember that one of them rebroadcasts their live news so I will take a look at that and see what kind of static I get tomorrow.

 

[mmckenna]

Yeah, I'd be suspect of it. Nice thing is that it should be easy to bypass.

A bit pricy, but PolyPhaser brand is generally accepted in the industry and quality units. $40 - $50, but shouldn't give you any issues.

I hope it's an easy fix. These sorts of issues can be frustrating.

 

[5Rya]

Yeah, I'd be suspect of it. Nice thing is that it should be easy to bypass.

A bit pricy, but PolyPhaser brand is generally accepted in the industry and quality units. $40 - $50, but shouldn't give you any issues.

I hope it's an easy fix. These sorts of issues can be frustrating.

I really hope it is something simple like that, I would much rather pay $50 then have to be frustrated with setting up this whole outside antenna and running all the cable to only find I almost had better reception using my stock antenna.

 

[cbehr91]

Would a preamp help with that?

Maybe. Maybe not. It sounds like you're on the right track on troubleshooting your issue. Theoretically a preamp would overcome the losses in the coax. Practically, it could overload your receiver with outside interference and may actually make it less sensitive if you live in an urban area.

Good luck.

 

[5Rya]

Alright so I believe I have solved the problem. It ended up being the lighting arrestor, There also was a pretty big amount of corrosion occurring around the lighting arrestor which took me by surprise as it was sealed very well. After taking out the lighting arrestor and cleaning the adapter I get good signal. The only problem I have now which most likely has nothing to do with the antenna is that I just bought a used 536HP off of eBay and it arrived today. After fixing the antenna I hooked it up to my old scanner the BCT15X and I was getting full bars, I then disconnected it from the BCT15X and connected to cable to the 536HP and now I am seeing 1-2 bars with a lot of frequencies that were full bars on the BCT15X. I do have a FM Filter coming on Monday so we will see what that does but why would this occur?

 

[popnokick]

Bar-type signal meters are relative indicators of signal strength and are very seldom calibrated - particularly not across different models or manufacturers of radios. You could do your own calibration but you'd need test equipment producing a known signal level. And even if you did that, you might find that "three bars" on one radio equates to two bars.... or even four bars... on another. The readings are not absolute unless you calibrate each radio, and make a reference chart showing the range for each signal bar on each different radio.