Scantenna

[pddispatcher]

Hello.

Wanting to raise the scantenna to about 55 feet and am wanting to attach a PL259 w/ LMR400 coax to this setup.

I remember seeing somewhere in the past there is a connector/adapter available for this project. I tried to search but didn't have any luck

Any suggestions/advice would be recommended.

BTW Should I go with LMR400 or RG-6

 

[k8mcn]

I would use the RG-6--you all ready have a 300ohm twin lead on the anntenna, and a converter that takes it down to 75 ohms. the converter terminates with an f connector---just run rg6 down to your scanner and use the provided f to BNC converter and your in business! I will get lots of people disagreeing with me, but i don't think the added cost of lmr400 (30.00 for fifty foot plus connectors) and changing to a different converter to get it down to 50 ohms will make a huge diferance in your monitoring.
Now if you were going to transmit UHF or Vhf, that would be a COMPLETELY different story.

Enjoy your scanntenna--they rock........

 

[pddispatcher]

So they make an adapter that connects the end of the coax that goes into a regular police scanner to a BNC - If so that would work freaking great.

 

[k8mcn]

So they make an adapter that connects the end of the coax that goes into a regular police scanner to a BNC - If so that would work freaking great.

My Scantenna came with fifty feet of rg6, and a f to bnc adapter-yours should have,if not they are available (in the old days at rat shack,Before cell phones )

 

[pddispatcher]

What I need is a motorola to BNC

http://www.radioshack.com/product/i...=bnc+adapter&kw=bnc+adapter&parentPage=search

Right there is the adapter I need.

 

[pddispatcher]

OK so here's my plan

I'm going to go to wal-mart when I get off work and pick up 75 Feet of RG-6 CATV with F connectors on both end. I will then go to Radio Shack and pick up a F -> to BNC... I have figured the following specifications up which I'm not sure if its accurate because its based on transmitting into the feedline and not receiving.

At 150 mhz @ 75 feet I'm looking at 2.64 dB Loss
At 450 mhz @ 75 feet I'm looking at 4.72 dB Loss

Is transmitting loss the same as receiving loss also?

So would this be safe to say that if I raised the antenna 25 feet the loss that I would be occuring with the extended coaxial cable would I effectly just be having the same thing as if it was say mounted where it is now at 25-30 feet w/ 50 feet of RG-6.

 

[pddispatcher]

Ok, Went ahead and got the Quad Shield RG-6 got 100 feet of it - I have about 10 feet excess and raised the scantenna to the top of the tower.... I'll get a picture of it within the next day or so.

Signals are so much clearer now and am hearing upwards of 70 miles away with just minimal static - I haven't programmed any farther agencies.

Antenna is now 820' ASL

 

[KT4HX]

Yes, receiving and transmission losses are the same. I presume you have also run the figures for LMR-400. Depending on what your listening targets are, the difference between the two cables could make or break your installation. As a comparison to your figures below, the same with LMR-400 are (and I have added 850 MHz):

At 150 mhz @ 75 feet I'm looking at 1.20 dB Loss (76.7% efficiency)
At 450 mhz @ 75 feet I'm looking at 2.00 dB Loss (62.6% efficiency)
At 850 mhz @ 75 feet I'm looking at 2.80 db Loss (52.0% efficiency)

For the RG-6 at 850 mhz @ 75 feet you get 6.40 db Loss (22.9% efficiency)

As you can see, loss with the RG-6 is over double the loss of the same length of LMR-400. If your targets are in your local area, then you will see little to no difference. However, with more distant listening targets, you will see the signal quality degrade at shorter distances with the RG-6 than with the LMR-400. I have always been a proponent of using the absolute best coax you can afford. No matter how good your antenna is, the cable can make or break your install (as can improperly installed connectors). So I recommend planning accordingly based on what you plan to monitor. Whichever route you go, happy listening.

OK so here's my plan

I'm going to go to wal-mart when I get off work and pick up 75 Feet of RG-6 CATV with F connectors on both end. I will then go to Radio Shack and pick up a F -> to BNC... I have figured the following specifications up which I'm not sure if its accurate because its based on transmitting into the feedline and not receiving.

At 150 mhz @ 75 feet I'm looking at 2.64 dB Loss
At 450 mhz @ 75 feet I'm looking at 4.72 dB Loss

Is transmitting loss the same as receiving loss also?

So would this be safe to say that if I raised the antenna 25 feet the loss that I would be occuring with the extended coaxial cable would I effectly just be having the same thing as if it was say mounted where it is now at 25-30 feet w/ 50 feet of RG-6.

 

[pddispatcher]

I have absolutely no 800 mhz transmissions around here - None at all.

Of course if I wanted to listen to 800 the closest would be Owensboro Police or Bowling Green Police Dept. which is both about 45 miles away.

All my local agencies are at 150 mhz with the exception of Louisville Metro and KSP which is on 450/460 mhz.

I have noticed a big difference from being 20-25 feet to 60 feet at the top of the tower now.

 

[KT4HX]

Not having any 800 systems as your primary target is great in this case. If you are indeed mostly interested in the local services and they are primarily VHF, then you should get by fine with the RG-6 that comes with the Scantenna. If you wish to expand your target area then you can certainly upgrade your coax at a later date. Happy listening.