Will an amplifier Help?

[durgin]

Right now i have a bearcat bc 248clt and a radio shack 20-176 mounted in the attic and im running rg 6u too it. I want to be able to pick up rochester minnesota and the twin cities. Right now i can hear rochester police which is about 35 miles from me but its not coming in very clear. I live in lake City minnesota if anyone wants to now. I want to no if an amplifier will help pull in the signal better or not, and if the rs antenna can handle it.

 

[SCPD]

The amplifier or signal booster should help, but a by product for using it could be interference. The antenna will not care if you use a signal booster, you only need to worry about that for transmitters not receivers.
Can you sneak a 19 inch bare wire in a tree or something? Anything outside is better then inside for antennas.

 

[wa8vzq]

My best guess is that an amplifier will not help much because of your geography but you might give one a try. You don't need a lot of gain. A typical preamp of a Motorola two-way radio is on the order of 6 dB. I haven't been to Lake City but have been to Red Wing. I am guessing that if your terrain is similar to Red Wing then you will not have good enough line of sight hear either MSP or RST easily. Your best shot would probably be to use a yagi an point it up the river. You may be able to hear multipathed signals coming down the river valley. It looks like the direct, overland path to MSP is unlikely on a regular basis. That being said, you may have good chances of hearing both due to ducting or otheranomalous propagation this time of year until about 9-11 AM. After that the air temps pretty much equalize and you will lose the paths. This is pretty constant effect in this part of the country this time of year on 2 meters. Should work similar on the other freqs as well. Keep in mind that MSP has switched to digital for most police and fire comm. Those signals need better line of sight so your success may not be as good with those as with analog systems.

Dan
Apple Valley, MN

 

[durgin]

Thanks for the responses. Yeah in lake City there are alot of hills around so it makes it hard to hear anything south of me like rochester. But I can hear all the way to Eau Claire county Wisconsin police dispatch, which comes in pretty clear. And i can also pick up red wing, and hastings police with no problems.

Hey Ac7xc you were talking about running a wire outside and hanging it in a tree. What kind of wire would you use for that?

 

[RevGary]

Just stopped in to check on something else - I'll give that one a go...

RG58U is acceptable for this application. Take off 19 inches of the black outer insullation and remove all but one half inch of the white core insullation over the center conductor. Then peel back the braided copper down over the next 19 inches of outer insullation and tape it tightly in place at the bottom. This makes a coaxial ground plane and has slightly better receiving characteristics than not pulling the braid down over the outer covering. Just use a non conductive support to hold the tip of the antenna to the tree. An old PLASTIC tooth brush works well as an insullator to secure the antenna to a horizontal branch with good quality electrical tape. Learned this one from the military (to be used as an emergency antenna and it works nearly as well as any quarter wave). JUST REMEMBER that whenever there is a rainstorm, the tree is a target for lightning and so is that cable. Use appropriate measures for dealing with that possibility.

 

[durgin]

how far can i run the wire?

 

[RevGary]

I probably would try to keep it under 75 feet from the tree mounting to the radio receiver. Anything more than that will start to loose signal within the electrical resistance of the cable. There are other 52 ohm cables that can be used, but RG58U is cheap, available, structurally compatable with this project and works very well. Let us know how it works out for you if you do construct this type. Good luck with it and BE CAREFULL in that tree!

 

[durgin]

Alright i'll give it a try? And i'll let you know how it works.

 

[durgin]

What would work better running that cable that has the shielding cut off it, or running my radio shack 20-176 on the 10 foot pole. And the run will be about 50 feet

 

[durgin]

The cable would be mounted on the same 10 foot pole outside. Which would work better. I cant really get to a tall enough tree with only 75 feet

 

[RevGary]

I would suggest the Radio Shack antenna outdoors FIRST. Depending upon weather in your area right now, doing anything outdoors could be difficult in the cold. Even though that antenna is multi band, it's design will most likely do a better job than the coax constructed antenna because of the lower radials on the 20-176 acting as a ground plane, more so than the coaxial antenna. One of the reasons that the 20-176 may not work inside your attic as well as you want it to is that some construction companies have used a metallic underliner under some roof installations and that underliner, if used in your residence, could effectively block some of the RF energy getting to the antenna indoors. Moving it outside will most likely do a better job for you. If I remember correctly, your antenna has a vertical element and two additional elements at a slight upward angle. Position that antenna so that series of vertical radials in perpendicular to the transmitter location that you are most eager to receive. It is an omni-directional antenna, but placing it's profile 90 degrees to the station MAY increase the signal to noise ratio for that distant station and allow a better chance of reception.

 

[Al42]

RG58U is acceptable for this application.

That'll lose almost half the signal at 150 MHz for a 75' run. There's no reason he can't use the RG6 he already has to decrease the loss a little.

 

[durgin]

What kind of cable should i use for a 50 foot run and how high should i mount my antenna. I'll probley use my radio shack 20-176 antenna,

 

[durgin]

Also i live in a single level house.

 

[Al42]

What frequency? Loss increases with frequency, so cable that's good at 40 MHz is totally useless at 800 MHz.

Go to http://www.ocarc.ca/coax.htm, plug in different cables and different frequencies and see what you get. Ideally you should shoot for 2db or less loss - the " Matched Loss" box. You can live with 3db - that's half the signal lost - for matched antenna, receiver and cable. Since you're not going to have a good match at most frequencies, the 2db loss you get for a particular cable/frequency/length will probably translate into 3db or 4db loss in the real world - and that's about all you can tolerate unless you have a great antenna and a great antenna location.

 

[durgin]

Mostly In the 150-160 range.

 

[airgreek]

I use a Motorola Signal Booster and it rocks.

 

[Al42]

RG6 - 1.7db loss.
RG58 - 2.4db loss - quite a difference.

Much more expensive, but LMR-400 - 0.76db loss.

Airgeek, whether any particular amp will help depends on what signals are floating around (strong signals can cause an amp to intermod), how much gain is needed, what receiver the amp is feeding (GRE receivers overload very easily) and a lot of other factors. Just because that particular amp is good in your situation doesn't mean it'll be good for everyone.

 

[Randall]

Right now i have a bearcat bc 248clt and a radio shack 20-176 mounted in the attic and im running rg 6u too it. I want to be able to pick up rochester minnesota and the twin cities. Right now i can hear rochester police which is about 35 miles from me but its not coming in very clear. I live in lake City minnesota if anyone wants to now. I want to no if an amplifier will help pull in the signal better or not, and if the rs antenna can handle it.

better than an amp is a good directional antenna like a tv antenna turned to vertical polarization (with the elements up and down instead of horizontal when used for tv signals) and aimed at the target , also as the antenna goes higher up the signal will get stronger so try more elevation if you can get it outside of the attic.the log periodic antennas used in tv applications are non resonant antennas with very wide bandwidth which are perfect for scanner applications if turned vertical to the polarization used by mobiles.