75 ohm to 300 ohm baluns

[Lavane]

I'm installing an outdoor antenna and using one of those thin ribbon connectors to go in the window frame. I have 75 ohm cable connected from the antenna to the ribbon. My question is how much signal or signal quality am I loosing using a 75 ohm to 300 ohm balun connected to the tuner? Wouldn't it be better to just strip one end of the 75 ohm cable and connect it to the 75 ohm tap instead of using the balun connected to the 300 ohm tap?

 

[rmp]

The answer is probably yes. The Beezley site has info about balun losses. What does the ribbon have to do with it?

 

[avionic]

What does the ribbon have to do with it?

Probably referring to 300Ω flat lead as ribbon cable.

 

[Lavane]

Probably referring to 300Ω flat lead as ribbon cable.

No, it's a flat 75 ohm ribbon with a male coax connector on each end. They are used to put in the window sill so you can close the window. I didn't want to drill another hole in the wall.

 

[Lavane]

 

[damacman]

Wow - how cool is that? Never seen that before.

 

[avionic]

No, it's a flat 75 ohm ribbon with a male coax connector on each end. They are used to put in the window sill so you can close the window. I didn't want to drill another hole in the wall.

I've not seen that before. Would have been nice to have that about 1974 when I was doing a lot of TV aerial installations. No cable here back then..Strickly OTA Channels 5,8,11,13 and 21.

 

[Chip Chester]

If you can make the entire path 75 ohm F-connectors then do that. Apologies if I mis-read the options...

That window accessory is either 75 ohm all the way thru, or it has baluns at each end. Depends on the wire between the connectors. Spec sheet may or may not divulge that.

It may be possible to have a straighter shot if you put that device at the top of the bottom pane of the window, where the two panes meet. Won't be nicely tucked away, though...

 

[amptramp]

There used to be an antenna connection that went through a window. There were two square or round adhesive-backed aluminum foil sections that went on the inside and outside surfaces of the glass forming a capacitor with the window as the dielectric. There were connection tabs so you could solder 300 ohm twin lead to the outside and inside. Very simple connection that does not require modifying any part of the house such as drilling holes or slots. Double-glazing did not work with this, so it is quite rare now.

 

[Lavane]

I've not seen that before. Would have been nice to have that about 1974 when I was doing a lot of TV aerial installations. No cable here back then..Strickly OTA Channels 5,8,11,13 and 21.

Right? I found them on Amazon. This would have been very handy back then.

 

[Lavane]

If you can make the entire path 75 ohm F-connectors then do that. Apologies if I mis-read the options...

That window accessory is either 75 ohm all the way thru, or it has baluns at each end. Depends on the wire between the connectors. Spec sheet may or may not divulge that.

It may be possible to have a straighter shot if you put that device at the top of the bottom pane of the window, where the two panes meet. Won't be nicely tucked away, though...

I tried that. But the window slides sideways. I couldn't get the window to slide over it. If the window slid up, it would look better at the bottom for sure.

 

[Ylli]

If you can see the center conductor, then the metal in the window frame will modify the impedance of the line and cause losses. Look for a model that has ground plane on both sides of the center conductor. If you can find it, you want "Stripline" instead of "Microstrip".

 

[Lavane]

If you can see the center conductor, then the metal in the window frame will modify the impedance of the line and cause losses. Look for a model that has ground plane on both sides of the center conductor. If you can find it, you want "Stripline" instead of "Microstrip".
View attachment 1935787

That window is vinyl. But I understand what your saying. I swapped out the tuner that I first had connected to it. The sensitivity was 3.5mv. Where I live there aren't many stations. Most are 40 or more miles away. The tuner I tried next is rated for 1.7mv. I'm pulling in way more stations nice and clear. Not bad acually for a 1/2 wave omni on the roof.

 

[the skipper]

From what you describe I'm not too sure it's a balun in the sense that it has two transformers on both ends and is simply a "pass through" with no impedance alteration.

 

[Lavane]

From what you describe I'm not too sure it's a balun in the sense that it has two transformers on both ends and is simply a "pass through" with no impedance alteration.

You are probably right. It seems to be working alright. I've got a FM3 tuner I want to use once I track down the source of some hum, but for now I'm using a Marantz 112. I was able to solve one problem with it, but its still picking up a bit too much hiss. Nice tuner though. It picks up a lot of stations easily with this outdoor 1/2 wave antenna. Its been sitting on a shelf for years. I bought it and just never used it. I'll have to go over the service manual again to see if I can reduce the hiss. The model 105 I was using sounded good, but living where I do, its just not sensitive enough. I should just get a better antenna.

 

[EddyR]

Easy fix for window is to use a a short piece of zip or lamp cord as it is very close to 75 ohms. You can mount a coat connector on each end. If that is not thin enough Us a vice to flatten the center. I have soldered them direct to the coax
Ed