Using Cat5 Cable

[SCPD]

This might be a simple yes or no. I was wondering if it is possible to us Cat5 cable in place of coax? The pole I am thinking of mounting my vhf antenna is close to around 200ft away from where my radio is. Is it possible to convert the coax into Cat5 then back into coax to connect to the antenna? The cable will have to go threw a pipe that is alreaedy buried underground and not sure if normal coax will fit.

Sorry if this sounds like a stupid question. But I am somewhat new to this still.
Any info will help. thanks you!

 

[gewecke]

No. Cat 5 cable is not designed for radio comms at all but is designed for data, as there's no shield present to keep you from losing your signals before they get to your receiver. Splicing cable at all, will cause so much attenuation at your receiver that you would be lucky to hear anything.
A great cable to use, which is cheaper would be rg6 quad chield. You can get this almost anywhere that sells hdtv supplies.

73,
n9zas

 

[IredellMon]

Even with good coax, or hardline for that matter, a 200 foot run is an issue. Think of it this way, with the stock antenna that goes on the back of the scanner you might get a signal of S3 (scale is 0-9). The tower mounted specialty antenna might get you a signal of S8.. but by the time it travels 200 feet, depending on the quality of the feedline, it might be down to S1-S5. So you might get a better signal for your ~$300, or you might not.
Can you make a short run to the attic? Even a antenna hung from the ceiling near the scanner might be better than a 200 foot run.
Also consider that for most scanning, you don't need or want a killer signal.. cause that is just what it will do if there is a strong transmitter in your area like a FM station.. it will overload the scanner. In the case of simulcast systems you might get problems also (dont sweat that for now however)

If you want further advice you should provide the following:
1. Where will the monitoring (scanner) be located. Is there extensive metal around? (Metal building?)
2. What is the terrain and distance(s) to the transmitter(s) you want to hear? Are they in different directions?
3. How well does a "rubber duck" type ant work on the scanner (for your intended listening).
4. What bands of frequencies are you interested in

 

[prcguy]

CAT 5 cable consists of four pairs of balanced transmission line of around 100 ohms impedance and each pair has a different twist rate to provide isolation between pairs.

Regular CAT 5 is rated up to about 100!Hz and CAT 6 up to about 1GHz as an RF transmission line. You can use it to some extent for radio use if you can deal with the 100 ohm impedance or you can buy or make matching transformers to use with 50 or 75 ohm equipment.

I suppose you can also parallel two of the four pairs and that should make a 50 ohm transmission line. it would be interesting to make up a 100ft run with PL-259s and sweep for loss and VSWR. If I can find some time I might give it a try.

Also, quad shield doesn't really have any advantade over single shield for scanner use, the loss is the same and the extra shielding only benefits in tightly bundled runs with higher frequency satellite signals that can run over 2GHz where signal leakage is more of a problem.
prcguy

No. Cat 5 cable is not designed for radio comms at all but is designed for data, as there's no shield present to keep you from losing your signals before they get to your receiver. Splicing cable at all, will cause so much attenuation at your receiver that you would be lucky to hear anything.
A great cable to use, which is cheaper would be rg6 quad chield. You can get this almost anywhere that sells hdtv supplies.

73,
n9zas

 

[SCPD]

well i had a Discone antenna on a 10ft mast on top of my roof and it worked great before but just installed a new taller mast on the garage roof(detached from the house). The scanner and kenwood tk-730 are in a bed room, so just wood and normal building materials. My area is somewhat flat with a few hills right in the center of the county but our county fire just switched to simulcast system. Around my county is all VHF with a UHF system around 30miles to my west that i will be using a separate yagi to reach that.
I will just mount a new antenna where it was before. Im thinking of getting a Tram 1480.
Thanks for the help guys

 

[IredellMon]

Sounds like you have a good handle on your situation and options. One thing that stood out to me was the mention of the simulcast system. If the signal from two (or more) of the simulcast transmitters is about equal that could be a problem so you might want to use the yagi to focus in on one or the other if that problem develops. If there is a simulcast tower in the same direction as the 30 mile distant UHF station, then a yagi in that direction would be golden and probably still pick up enough off the sides and back to keep you happy.

Some trial and error will no doubt be needed but for receiving sometimes less is more. I wonder how the scanner would pick up if you carried it to the garage roof. If you get a very strong signal there (for your targeted transmission) then it might be worth running good quality feedline to a mast mounted antenna. On the other hand if the signal on the roof is still weak or marginal then even a good antenna on the garage mast would usually not work too well by the time the signal went through 200 feet of coax (unless it VERY good coax, ~$2.50 a foot type,. hardly worth it IMHO) A preamp is a possibility but then again we are adding to the cost when it might not be needed. I use a home made groundplane in the attic with the TV cable installed in the house walls 20 years ago as the feedline. (lossy cable) but it works well for me!

BTW, All my comments were geared toward receiving in fact, if you’re going to be transmitting with the Kenwood (or anything else) then there are additional considerations.

 

[mpddigital]

Coaxial Cable for a long run to a VHF antenna

Actually for good coax a VHF antenna line of 200 feet is doable. This is not to say that the shorter the run the better, that is usually the case, but we have set up runs as long as 250-300 feet with LMR-400 or LMR-600 at VHF freqs and seen reasonable loss. By using coax designed for microwave use you can run a fairly long line at lower freqs without too much trouble.

Remember, loss for any type of coax is frequency dependent. The higher the frequency the higher the loss. Also, each time you double the size of the coax it cuts your loss roughly in half. Consider your antenna and cable as a system, you start with X amount of gain from the antenna and subtract Y amount of loss from your coax. X-Y= total effective gain

Location of the antenna is a separate factor. The idea for a higher remote antenna is to achieve better LOS or unobstructed access to signals. Location is a trade off, more cable loss or loss due to blocked signals, which is worse for your set-up.

There are other considerations but for the most part the basics are enough. Hope it helps!