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In Reply to: RE: Are you really restricted to a small indoor antenna? posted by Jeff Starr on April 03, 2015 at 11:42:40
Rabbit ears are dipoles of a kind.It may perform better than the ST-2. It should be as good as a dipole and can be optimised for each desired station, a bit more easily. IF these is sufficient signal inside your house. Seems pretty marginal at present.
FM radio reception in the home is a systems problem, and the best results can only be obtained by a directional* antenna (* one with gain and some size). The gain helps to push noise down. The narrow pattern minimizes distortion and noise from multipath - indoor antennas are not as good at that, or not at all good at it.
I was gifted an 'FM?' whip antenna once, gave it away. They are basically boat antennas.
IME most tuners (even MD's?) have optimistic signal-meter needles. IF it has a numerical readout use that instead.
There are quite a few drawings of the rhombic in the FAQ article here at AA. Remember that if you are going to build a double rhombic with 300 ohm twin-lead ribbon - as the article mostly assumes - you mustn't twist the ribbon anywhere.
? Back before coaxial down-lead that's what we did to ribbon down-leads to stop them picking up any signal. ;-).
The rhombic can be made square [ ] or more <> but the long diagonal axis - through the loading resistors - needs to point at the station or stations.
That's why I asked did you know where these 'two?' stations are on the compass from you and how far?
You may be lucky and find that a diagonal axis of your largest room points at at least one of the stations. A square rhombic will probably have a quite wide beam width and may cover both. The spread out dual rhombic (it IS there) with two overlapping beam widths < might do do the job.
You'll need a map and to visit the USA's FMFool website. And a compass or two. I have a good GPS based compass app on my iPhone, and so you might/can use it inside the rooms as well. It won't be affected by magnetic materials. Depends on GPS reception in your home.
If you have a large rug in the room you might avoid pinning a rhombic to the ceiling.
Happy to be an advisor for a rhombic build, but the article is pretty complete on the practicalities IMO. Read it a few times and take notes.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 04/04/15Follow Ups:
Hi Tim, hey thank you for turning me on to the FM Fool website. That would be a good link to add to FAQ. I now know where the transmitters are. And that though they are both under 6 miles from me, the clean signal is more powerful, and at a better angle for the side of the house I have my system on.
Knowing how much room the Rhumbic could take, I want to try other options first. I need to go buy a good balun, the adapter I have is crap. Then I will try the plastic dipole, with a whole different layout.
I still find it strange the the old Yamaha had no problem with both stations, and my MD is being difficult.
When I get this sorted out, the Metz [ST-2] will be up for sale.
If I get your ok, I'll email you my address, the call letters and maybe you could look at FM Fool and help me understand the info a little better. And knowing where the two stations are, make some suggestions.
If I understand that antenna I linked to, it sounds like I'd be mounting it to the wall, with the antenna running parallel to the floor. Is that right?
Thanks for all your help, Happy Easter!
Jeff
you adjust the position and length of the two rods, and then you twiddle the knob. Usually I find that having the rod closest to the station's txer slightly shorter than the one behind it.I am in Australia, maate. So, you will need to get a topographical map of where you are which includes the transmitter (txer) sites.
You should also use google maps to get a compass picture of your home's orientation on the block.
Then you plot the bearings on the big map from your place to the two txer sites. Then plot them on to the block picture and from the room and tell me us about that.
And then use the phone app. to find where they might be in relation to your room with all its reflections. You may find there is one set-up that's best for both stations. You may need two very different arrangements for the rods and the knob. You may find that neither is exactly pointed where the maps you have done say they should be pointed.
This will be due to your room's own reflections.
I have been fortunate until ,now to have just one big tower on a tallish mountain to aim at for TV and FM. Now one of the two FM stations I listen to has moved some 15 degrees east of that mountain. And it is the one with the least signal. And, I am using a tube RF front end for my main tuner. IME tube front ends need much more signal to go fully quiet. So, I am thinking through all this myself.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 04/05/15
Hey Tim, thought The oz might have been related to "the Wizard Of Oz". Never considered you were in Australia.
Thanks to FM Fool, I got to thinking about the best location for my antenna. I took the two longest pieces of coax cable I had and put the antenna in the spare bedroom, which is closest to transmitters. I tried the plastic dipole first, still had noise. I put the Metz [ST-2] in there, just put up at about a 45 degree angle, and no more background noise. Both stations I listen to are about 6 miles away, and both are now clear and clean.
I just need to get a 30ft run of good coax, to neaten up the installation, and I'm done.
I appreciate all the advice. For anyone else, wanting to optimize their antenna placement, I've included the FM Fool link. You can see where your transmitters are, how powerful your station is, and much more.
It 'depends.'
You have got that, now.
:-).
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
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