Okay, 'splain this to me.

[Thumpy]

I took electronics in high school. I really liked it, but instead I chose to go into data processing (dumbass, I should been a plumber, dogcatcher - anything but a goddamned computer geek)! But I digress...

What I would like to know is this: If I hook up a tuner to a dipole or to my BIC Beambox, I get a reading on the signal strength meter (assume the tuner has such a meter). Let's say it reads '2' on an 0-to-5 scale. BUT, if I only hook ONE of the antenna leads up, I get a higher reading on the meter. Why?

[bolly]

the owners manual for my KT-7550 says that you should only use the 75ohm, or, the 300ohm antenna hook-up and not both simultaneously. I get better reception if I hook wires to both of them, at the same time... :scratch2:

[johndoe3]

Interesting....
I have a Pioneer SX-1050 that, as you know, is supposed to have a great tuner. Mine just doesn't pull stations in like it should. Tuner just seems a little weak on this one.
So, I did exactly what you mentioned, I hooked up only one wire from my dipole to the 300 ohm leads on the back. Guess what?
The reception is what I would expect this receiver's tuner to have!

[hpsenicka]

Curious... does it make a difference which of the two 300 Ohm leads it is connected to??

[Thumpy]

Curious... does it make a difference which of the two 300 Ohm leads it is connected to??
It doesn't seem to make any difference. Either one connected appears to provide the same degree of signal strength improvement over having both leads connected.

[Celt]

It'll work better if you wear a tin-foil hat and stand on one leg with both arms outstretched! :D (just messin' wif ya guys ;) )

[bolly]

hey celt, shiney side inside or out? :lmao:

[VinylHanger]

The antenna is designed to pick up the signals from the air. However, depending on where you are set up, it will be picking up the signals after they have reflected off of several different things. So depending on how your antenna is set up or not set up, it will cancel certain reflections. So just go with whatever works. <------ this is just my laymans observations during the last 2 years living in the crappiest recepting spot in town.
We are on the bottom of a large hill that has most of the areas transmitters on it. All the signals go right over our heads, then bounce back from the other side of town. Depending on how I park in the driveway, or where someone is standing in the house makes a difference in both TV or radio reception, as well as cellphone reception. We can now tell what type of rig is driving by, by the way it interrupts the tv reception.

[RichPA]

hey celt, shiney side inside or out? :lmao:

Shiny side out, bolly - everybody knows that! :D

[hoahao]

I have noticed that too, using only one connect for the 300 ohm seems to do better.

I have gone the "professional route" regarding my choice of head gear. You Just Cannot be Too Careful out there. I urge all and sundry to take proper measures!! You guys Do know that evil emanations come through your tuner and are implanted into your brain without you knowing it.
http://zapatopi.net/afdb/ <;-)

[Thumpy]

You guys Do know that evil emanations come through your tuner and are implanted into your brain without you knowing it...
Yup, it's called "Clear Channel Communications". Very dangerous.

[Holst]

Just curious, Bolly and ReEdger, do your tuners have a switch for 300 and 75 Ohm 'tennas? And yes, it's shiny side out!

[bolly]

no switch on my KT-7550, or CT-1010 holst. :no:

[Holst]

I assume that means both are always on, and a matching transformer one one or both. I also assume the tuner looks at this (assume = I've worked in radio for 29 years and stiff feel RF is as predictable as cat's) as greater acreage on your antenna. I bought a Luxman in 1977 that has a short piece of wire running between it's 75 and 300 ohm connections, and no switch. I left it there.

[Celt]

Two of mine have 75 ohm F connectors only. Most tuners/receivers simply have a balun between the 300 ohm in to the 75 ohm posts.

[EddyR]

I use to design and build antennas for several military and tv companies in the 60's.It's hard to explain in a few words but I will try. If you were using a outside antenna and it was aimed at the station it would work best with both leads hooked up. But using a 300 ohm dipole inside many times it will not see a direct signal and is picking up many reflections and will work better as a random wire antenna by using only one wire. If you want to try some thing simple that works very well and has a little gain try this. Take a piece of any wire 80 inches long and cut it in the center and feed it with any close spaced wire{75 ohm} speaker wire will work even lamp cord will work. Place it near the ceiling or even try it vertical.It has about 2db gain and works well in many locations.Try it on the 75 ohm input. Most people use 75 ohm leadin on outside antennas but I like 300 ohm much better as it does not need a perfect match to the antenna as 75 ohm does.The is almost mo signal loss in 100 ft of 300 ohm wire but 100 ft of 75 ohm will kill 20-30% of your signal at FM frequency's Did this help or did I loose you?
Ed

[Thumpy]

I use to design and build antennas for several military and tv companies in the 60's.It's hard to explain in a few words but I will try. If you were using a outside antenna and it was aimed at the station it would work best with both leads hooked up. But using a 300 ohm dipole inside many times it will not see a direct signal and is picking up many reflections and will work better as a random wire antenna by using only one wire.

Okay, I guess it makes sense.

If you want to try some thing simple that works very well and has a little gain try this. Take a piece of any wire 80 inches long and cut it in the center and feed it with any close spaced wire{75 ohm} speaker wire will work even lamp cord will work. Place it near the ceiling or even try it vertical. It has about 2db gain and works well in many locations. Try it on the 75 ohm input.

Sounds a lot like a dipole to me, except that the "arm span" of a typical dipole is more like 72 inches. Can 8 inches make that much difference (for an antenna - I know what you guys are thinking!) ? Do I attach both leads of the close spaced wire to the 75 ohm connector?

[hpsenicka]

b Most people use 75 ohm leadin on outside antennas but I like 300 ohm much better as it does not need a perfect match to the antenna as 75 ohm does.The is almost mo signal loss in 100 ft of 300 ohm wire but 100 ft of 75 ohm will kill 20-30% of your signal at FM frequency's

Ed,

One of the benfits of using coax for the lead-in cable is to reduce the likelihood of picking up interference, multipath signal, etc.... how much of an issue is this with standard 300 ohm antenna cable? Is there anything you would recommend to minimize this problem?

I have heard that twisting the 300 ohm cable will help... any comments or suggestions?

[EddyR]

A half wave dipole at 100 mhz is about 52 inches . The antenna made 80 inches is a 3/4 wavelength but it still matches the lead in. Connect one lead to the center of the 75 ohm input and the other to ground.This simple antenna will pick up about twice what a standard dipole will.It receives the signal at 45 degrees to the wire and has four strong lobes of pickup instead of two like a 52 inch dipole.If you make it longer you get a mismatch at the lead in wire and you will loose signal.
Try it and let me know how it works. I have one in my workshed and the ends are one foot lower than the center and it still picks up stations 85 miles away. The reason your one wire works better than two is the lead in wire is not matched to the antenna.You can use coax as a lead wire if you want but it looks ugly on the wall.
Ed