• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

Directional FM Antenna Questions

Steve Green NEPA

Steve Green NEPA

Mind now that this is from a non-techie who has to read directions to know which end of a soldering gun to hold.

Years ago, I recall reading about a home AM antenna system for DXers which involved more than one antenna to accomplish wild reception. A loop antenna and a longwire antenna were fed into a form of mixer. The destructive interference from one antenna and the constructive interference from the other antenna, when stirred and tilted and spun by the mixer, would make for improbable (and somewhat unpredictable) nulls and lobes. Supposedly, one could even null a closer station to hear another station farther away -- along the same bearing.

Is there a similar tool for FM DXing? Has anyone tried, say, mixing incoming reception from two separate outdoor rotor antennae to any noticeable or productive effect? If not, then I ask theoretically if such a project would do things like enhance weak tropo conditions, or have any other benefit?
 
Yes, you can use two FM Yagis separated by several wavelengths and phased to create an interferometer. The pattern of such an antenna has a very narrow main lobe and lots of side lobes.

Another possibility is using a large reflector dish to feed an FM antenna. Ideally, both the azimuth and elevation angle could be motor driven to receive two signals in the same direction, particularly high ceiling tropo and Sporadic E.

You can also play with separate polarization for some of these effects.
 
What I do now to make a local signal to null easier, is to feed my outdoor FM cable into a splitter/combiner (which you can get almost anywhere), also take a simple rabbit-ears, and put *that* also into the splitter/combiner on the same end as the outdoor antenna, then a cable out into the receiver. Aim the outdoor antenna at the desired station, then wiggle the rabbit ears (also lengthening or shortening them where needed) until the pest station is nulled the best. Works for me.

cd
 
I also used an old Rembrandt antenna switch on one of the antennas to induce phase and ratio diefferences, and could switch two cochannel stations that way. I have no idea what the different switch positions did, results were totally experimental and empirical.

Kids, look in your grandparents' attics for things like this, or on ebay.

http://www.godarusa.com/id72.html
 
The first thing I thought of is to get one of those VHF TV antennas that used to be so common.

Since FM and VHF cover the same range, you can't beat a simple old fashioned it for a good directional antenna, I would think.

I wasn't sure if they still could be found and I found this.....

http://www.google.com/products/cata...a=X&ei=GoeHTqSfO4-utwePpYw_&ved=0CLABEPMCMAk#


When I lived in South Jersey, I sometimes used the TV antenna on the roof aimed at New York to pull in the New York FM stations that couldn't be heard at all on a regular radio unless there was tropo.
 
An FM Yagi (the old FM4-G comes to mind) and a rotor will work wonders. The only issue is if there are two signals on the same frequency in ront and in back of the direction you are pointing (180 physical degrees). Rotate the antenna to point in the direction you want to receive.
 
I have two antennas & a "Phaser" made by Andy Bolin in Charleston,IL. Each antenna has a separate attenuator on it. It's a simple matter to make a 3400 watt FM station at 12 miles drop to the noise to reveal a weak translator on the same frequency at 37 miles--and that's under dead band conditions. More than once, I've killed WLHK 97.1 (a full class B at 23 air miles) to hear Columbus,OH (160 miles +/-) on the same frequency. Quite a few guys have these phasers...vital tool for the serious FM DXer. http://fmdx.usclargo.com/phase.htm
 
Does anyone have a contact for Bolin or have reverse-engineered his unit if he's no longer selling them? I'd love to own or build one if I can't get an off-the-shelf.
 
OKCRadioGuy said:
Does anyone have a contact for Bolin or have reverse-engineered his unit if he's no longer selling them? I'd love to own or build one if I can't get an off-the-shelf.
Click to expand...
His email is on that article... dxshack at gmail dot com. The thing is a miracle box...seems it was around $150.
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom