Home Radio Road

Which tuner to get and getting the most from it. Thank God, for the radio!

No they're directional and need to be aimed as my post indicated.

The axis is at right angles to the two wires in the 300 ohm ribbon.

Their polar diagram is a figure 8. Like a figure-8 mike. The cross-section .. of the two wires is inside the two lobes of the polar diagram. IE <-OO->. Okay?

So that, when pinned flat to a narrow board aligned vertically, you can rotate it along that vertical axis it so that it points at the strongest signal in that room, for each station. A lazy Susan type rotating base is the most convenient.

Noting that most FM transmitters use mixed polarisation IE 50% vertical and 50% horisontal - a vertical dipole on a board with a rotating base is more practical than trying to orient a horisontal dipole to maximum signal.

I'd recommend that you at least twist the down-lead part of the ribbon to minimise its signal pick-up capacity. OR buy a 300/750hm balun and run coax to the tuner.

You could also add another dipole on the other side and run them in parallel. But you would need to wind a 150:75 ohm balun. But even that stuff is on the web! :-)

Hope this helps.

Once you can get reasonable signal strength on most stations you can begin mapping your preferred station's axes on to yr dwelling's plan.

Then you might have enough information to decide if you want a Rhombic or Rhombics. And, where to point them.

Retail ribbon dipoles are cheap. OTOH Plans of dipoles should be available on the web. 300 ohm ribbon has IIRC a propogation delay of about 5% so the 1/4 wave length for a given frequency in Mhz, should be divided by .95 which will make it a bit longer so that it does resonate at the right freq.

I suggest you either build one that's as long as you'ld need for 108Mhz OR just buy one and learn with it. Those are usually cut for ~98 Mhz.


Tim Bailey

Skeptical Measurer & Audio Scrounger

Edits: 07/11/17 07/11/17 07/11/17

This post is made possible by the generous support of people like you and our sponsors:
  Signature Sound   [ Signature Sound Lounge ]

Follow Ups Full Thread
Follow Ups
  • No they're directional and need to be aimed as my post indicated. - Timbo in Oz 14:48:25 07/11/17 (0)


Post a Message!

Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.