FM antenna in the attic, cable?

CJVx

AK Subscriber
Subscriber
I’m thinking this will help take my FM listening to the next level. Looking to start with a standard rabbit ears antenna in the attic, which has the flat 300ohm leads. It would be a straight run of about 25 feet into my listening area.

My question is, should I use a matching transformer to convert the 75 ohms at the antenna, and then make a 25 foot run of coaxial cable, and then reconvert back to 300 ohms at my tuner...Or just get a roll of 300 ohm cable and make a continuous run of that. There could be multipath concerns with that as I would think not being shielded.

I’ll be using a Scott 310E, which supposedly has good multipath immunity, but I’d also like to rotate with other tuners which might not. Most of the tuners will only have 300 ohm antenna connections available.
 
I would stay with 300-ohm all the way and avoid the baluns. One of my antennas is a common twin lead folded dipole in the attic. I attached its leads to about 30 ft of twin lead cable, which comes down and connects to a Scott 310B. Very pleased.
 
You will get some loss in each balun so unless you have a poor-quality twin lead, stick with it. If you twist the 300 ohm twin lead at least one turn per foot, this gets rid of most of the signal impinging on the cable itself because anything induced on one side of the twist is cancelled by what is induced on the other side of the twist. You just have to keep the twist tight enough so the near-field sources and sources shaded by obstructions don't upset the cancellation.
 
Whatever the antenna is setup for.
In you case it is twin lead, so that be the one to use for the run.
Keep the run away from any metal duct work.
 
300Ω transmission line is getting harder to find these days. It used to be available everywhere, like light bulbs. Not so much any more. I had to order my last 100' roll since no local outlet stocked it.
 
You might want to try a rhombic antenna in your attic (for example http://sermes.ru/rhombic-antenna/). The web has lots of plans for these.

I built one in my listening room with standard 300 ohm flat antenna wire (you can get 100 ft rolls off Ebay very inexpensively). Mine is mounted on the ceiling of my room in a square pattern with each leg being 11 feet long- affixed to the ceiling with thumb tacks. I use the clear version so it's not very noticeable. It may be slightly suboptimal angle wise but I am pulling in tons more stations in higher quality than I did with a small dipole antella.
 
for 27 years now I have used the old standard "on top of the roof" TV antenna to feed my tuners. I ran a standard coaxial cable into the room(s) and then use a converter to take it to 300 ohms. works beautifully. I can pull in stations from all over hell and gone. Course, it's a full two story house, so the antenna is up there a ways.
 
300Ω transmission line is getting harder to find these days. It used to be available everywhere, like light bulbs. Not so much any more. I had to order my last 100' roll since no local outlet stocked it.

No luck finding a spool at Home Depot?
 
I second the FM rhombic. I put one around the ceiling/wall corner in my first apartment, was pulling in St. Louis, 120 miles away. Cost almost nothing. It is somewhat directional so you'd want to take note where you point it, but local stations should come in regardless of where the more sensitive end is pointed.
 
No luck finding a spool at Home Depot?

Not Home Depot, Lowes, Menards, Ace, True Value, nor even my local "master" hardware store. No electronics distributors exist around here any more (all three large ones closed about 10-15 years ago) and electrical supply houses never did carry any of it in inventory. There aren't even any Radio Shacks around here any more, and they used to have it by the spool.
 
I really think you would be just fine using the 300ohm adapter--which is available at menards, and coaxial cable to an old fashioned TV antenna in the attic. You would probably have to find a used now a days, but I just did this for an elderly friend whose house is somewhat "in a hole" comparatively speaking and his reception went waaay up.
 
Not sure how available it is, but it sounds like shielded 300 ohm twin lead is what you need. I have used it in the past, with great success, but haven't tried to find any lately.
Bill
 
I’m thinking this will help take my FM listening to the next level. Looking to start with a standard rabbit ears antenna in the attic, which has the flat 300ohm leads. It would be a straight run of about 25 feet into my listening area.

My question is, should I use a matching transformer to convert the 75 ohms at the antenna, and then make a 25 foot run of coaxial cable, and then reconvert back to 300 ohms at my tuner...Or just get a roll of 300 ohm cable and make a continuous run of that. There could be multipath concerns with that as I would think not being shielded.

I’ll be using a Scott 310E, which supposedly has good multipath immunity, but I’d also like to rotate with other tuners which might not. Most of the tuners will only have 300 ohm antenna connections available.

Although your rabbit ears antenna has 300 ohm leads, it is a 75 ohm antenna. The "folded dipole" which has two conductor wires on each leg of the antenna is the 300 ohm version. A simple 75 ohm dipole has only one one conductor per side, which describes the classic rabbit ears antenna.
I would go like this - rabbit ears to 75 ohm coax, 75 ohm coax direct to Scott tuner.
The Scott tube tuners work best with direct 75 ohm connections. I'm told it is NOT a 300 ohm input, but 110 ohms or something close, so 75 ohms is closer.

There are 2 screws for the Scott tuner antenna input, and one is grounded. So try it both ways, the center lead to ground will be poor reception, connected to the other one will be much better
 
Back
Top Bottom