FM Antenna over Ethernet

Problem: I ran cat6 and coax throughout my house. But for some reason the notion of installing an extra coax or simple antenna wire never occurred to me. Now I have no way of using my nice FM tuner unless I hang an ugly dipole from the wall.

Solution: I have an extra Ethernet connection available near my audio equipment. I simply used the cat 6 run as an extension - allowing me to hang a dipole antenna in my data closet out of site.

Step 1 Tuner Side

(pictures could be provided if there is adequate interest)

I made the connection at the tuner by putting an rj45 connection on one end of the cable. Then at the other end I simply unjacketed about 1.5 inches of wire. then stripped off one inch of insulation from all 8 wires. Then I twisted 2 pairs into one bundle and the other 2 pairs in the other. Then connecting one of each of the wire bundles to the two FM antenna connectors on the tuner. The pairs you use doesn't matter just as long as you stay consistent. I used the Blue pair and green pair together and the orange and brown pair together.

Comments

[Weegee097]

Awesome idea! On the tuner you should have both those cable bunches screwed into the 300ohm input, as with one connected to both the 75ohm and 300ohm, you are losing more than half power. However this is a great idea, and I will recommend it to some of my friends. Thanks!

[techwiz]

DId you make those circut boards?

[cowen]

That is a store bought wire enclosure and packs

[jaydenthorup]

Another thing that may help is that the length of the antenna is a direct ratio to the frequencies received. For instance your 49 cm half of the dipole will recieve 120 mhz best.... just outside the frequency. http://www.crompton.com/wa3dsp/hamradio/antcalc.html can help you calculate the length... also half  and double the length act the same way. Approx measurements needed is either 74.30 cm or half at 37.15 cm converted from inches.

[Drofnats]

Fantastic, I was trying to fathom out how to add an FM antenna without a dipole on the wall, your suggestion reminded me I had installed a phono system thru my house. Hey presto, plugged it in with a dipole on the other end. Tremendous. Thanks.

[static]

 At one time it was a common trick to run a wire from the radio to the metal finger stop on a telephone to improve reception. I don't think the finger stop was connected to the phone wiring, but just bring the radio into closer proximity to the wiring was enough to help. Then miles and miles of phone line was up in the air, not buried.

[static]

 Respectfully this is an antenna that resembles a dipole. I have no doubts it works, but under the theory that when it comes to reception the more wire the better. The standard dipole has a feed point impedance of 75 ohms. The impedance  at the feed point of a folded dipole is 300 ohms. The reason I call this an antenna that resembles a dipole is because there is no distinct feed point, the "feed line" is also acting as part of the antenna. Not a problem when it comes to reception unless it passes by something that creates inference, but it means  there are no "balancing issues to be concerned with.

[lukethedog]

How about using an ohm meter to test out the impedance. Start out by using one pair and test by putting the probe on each end. Then add a pair at a time and see if you can get to the impedance that you need.

I also once knew but have long forgotten the length that a dipole needs to be to receive 88mhz to 108mhz (US FM broadcasting).

I found loads of information at this site in my search

http://www.educypedia.be/electronics/antennadipole.htm

[static]

 An ohm meter is used for measuring DC resistance, not useful for measuring impedance. The "standard" formula for designing a dipole is 468/ frequency = the length of the dipole in feet. I'll mention more about the antenna in a comment to the article.

[Yerboogieman]

There is so much you can do with ethernet cables, they are amazing.

[biospot]

Nice Idea, and it's good that you do the experimentation on this. I wasn't sure how I would get my FM (and AM) signals out to my various sites. You prove it works.

However.. I would point out one simple change that may make an improvement on your system.. or may not. The test would be very interesting to me.
The idea is that each twisted pair rejects the pickup of radio interference if each wire of a twisted pair is connected to opposite sides. The way you have wired it, each twisted pair is actually a single long antenna wire, and picks up radio waves. So, the wire traveling from your radio to the computer closet itself is a very long antenna.
IF you changed the wireing by untwisting the pairs at the ends, and wired them as 4 wires "solid" and 4 wired "striped", then each twisted pair would reject noise from Flourescents, computers and other EMI generators.
The big question in my mind is does your method gather more radio waves, or more interference from other devices....
In any event, I will try it both ways myself one day.
I would also wonder if 1 pair of the 4 pairs could be dedicated to AM connections. I hate to have something unusable. In that case, I am certain it would be best for 1 twisted pair to be used on both sides of the connection. AM will pickup huge amounts of EMI, unless you use a twisted pair. I even have a wired loop antenna I got with an AM radio that uses twisted pair as the antenna lead in wires, so I am certain it will work.  If you try it, I would be interested to see the results in your "improved" PDF
Thanks for an intersting Instructable

[bleachworthy]

good idea, don't mind noah, he's just old and crabby. (I really don't know him)

[noahw]

Old and crabby? I am young and vital! The robot makes me say those things! Please believe me!

[bleachworthy]

*ERROR* :#(6c:6f:6c) Does not compute, shutting down. lol, I'm just messin' with you.

[Derin]

*puts ubuntu flash drive in**lets hd eraser software

[ReCreate]

Screws Ubuntu *puts windows XP+Windows 7 Unattended install Flash drive in(that means it does everything for me without asking)*

[klingoncowboy4]

"*** in case you dont know better - DONT attach your antenna to your router/hub - you want only dead wire - no network traffic anywhere near your antenna."

LMAO could be interesting... but I don't want to try it with any of my current networking or radio receiver equipment

[n7tcf]

From the pictures, the wire could have been any type. The author is probably within the strong signal area of the fm station. Receiving antennas are very forgiving if the signal is strong. I would avoid locating the antenna near live network wires, especially parallel to them. Finally, what is ugly about an antenna? I have decorated my house with 8 outdoor antennas. Santa uses the front yard here.

[klingoncowboy4]

indeed this is just a simple dipole still cool use of CAT5

[jasen]

I have "some" rf knowledge. one pair should be enough. cat5e works to 350Mhz so it will work ok in the fm broadcast band but it has the wrong characteristic impedance (100 ohms each pair instead of 300 ohms or 75 ohms) probably the best compromise is wiring one pair to the 75 ohm terminals (as you did) and using a balun at the antenna end. for am it appears that your receiver uses a lonewire mine expects a loop antenna, not a longwire, network traffic may contain signals that intefere with am

[Lurch]

Just 1 comment. I'd have split the pairs between the 2 terminals on the tuner, i.e. whites to ground and solids to centre. Other than that, good idea. I've got cat5e cables all over the house doing allsorts of random things!

[nhojdyoll]

gigethernet or 1000mb uses all 4 pairs

[VIRON]

There are 4 unused wires in most ethernet cables. That includes the 2 middle wires. Use those! And if you don't hear any data noise on some stations with that, I've totally underestimated the skill of Modem and NIC engineers! For example, I think they were fools to downgrade from coax to telephone wire, and claim higher bandwidth! I haven't seen it work. The bold claim for CAT-6 is 600MHz, which is similar to Cable TV. That's 6 times higher than the FM band carrier frequencies require.

[Daleeburg]

Just to add on. The used wires in a normal ethernet cable are 1,2,3, and 6, so if you use 4,5,7 and 8 you should be fine (in a 10/100 network, I dont know about 1000). If you are in the B wiring standard (w-orange, orange, w-green, blue, w-blue, green, w-brown, brown) then the blues and browns are unused.

[gamer]

that last pic is of ur home network system? holly crap, too much to see for now

[noahw]

I think that there would absolutely be interest in seeing how you made your FM antenna over Ethernet cable. Can you add in some pictures and then republish this project?