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I recently got an AntennaCraft FM-6 small yagi antenna with advertised 6dB gain (vs. halfwave dipole), hoping for much improved reception. Because of HOA rules, installed it in the attic (about 11 ft. up) on a rotator. To my disappointment, it is no better than the existing vertical folded halfwave dipole already up there (same area). The vertical dipole is omni-directional, needs no rotator, made from old TV twin-lead. In fact, the FM-6 is unable to deliver good signal for some stations which come in clearly with the vertical folded dipole. I took a TV rabbit ear, set the dipole length to 57 inches, mounted it on the rotator in place of the FM-6, and got very similar reception. I've examined the FM-6 carefully, can find no visible defects, all the elements are straight and properly deployed, using the same 300-75 balun to match the 75 ohm downlead (50 feet, quad shield) for all antennas. What the blank is going on? Does anyone have comparative results for the FM-6 vs. a folded dipole similarly located? I have a feeling the most significant different between them is that the folded dipole is usually mounted near the tuner in living space, whereas the FM-6 (and other outdoor "high gain" antennas are usually mounted high up outside or in an attic. I'm reluctant to buy another FM-6 (same as the famous Radio Shack small yagi) and repeat the experiments.
Follow Ups:
You may simply need a way of pointing it manually and mark the angles in for each station on the ceiling / roof frames.
WarmestTimbo in Oz
The Skyptical Mensurer and Audio Scrounger'Still not saluting.'
Read about and view system at:
http://www.theanalogdept.com/tim_bailey.htm
very strange results, see if you can get a swap, you should be able to.What is yr roof made of - and
What electrical wiring and other 'stuff' --- Water heaters (copper), copper pipes, AC-mains heating mesh just above ceiling --- is in the loft?
If there is such stuff / a small enough compass swing within all yr stations lie, then you might be able to use layers of vertical / horisontal chicken-wire mesh behind - grounded to outside mind with woven copper strap. In that arc < ---) or even tighter as in a concave vee < ---> .
I would recommend you borrow or buy a book about antennas or the ARRL handbook. 'Joe Cass's - Receiving Antennas' is VERY good and is reasonably uuntechnical - it covers a lot of stuff about antennas including yagis. And the AM MW/BCBand antenna stuff is excellent, as well.
WarmestTimbo in Oz
The Skyptical Mensurer and Audio Scrounger'Still not saluting.'
Read about and view system at:
http://www.theanalogdept.com/tim_bailey.htm
Yep, all horizontal tests done on rotator. Verticals, of course, don't need it, they're omni in the horizontal plane. It's always kind of puzzled me why people buy these ST-2 and other expensive vertical whips when a vertical twin lead half wave will do as well, at a small fraction of the cost. So far as the FM-6 is concerned, I have a message in to Antennacraft, haven't gotten a reply yet.
I have noticed that not only it, but also the simple dipole and the twin lead dipole when horizontal, all find one or two stations which although coming in with reasonable signal strength, have either a lot of distortion, or no audio at all, whereas the vertical twin lead dipole gets them all without those problems. The simple answer is that multipath reception is practically nil with the vertical antenna, and even the FM-6 is not able to find a good pointing for multipath rejection.
The FM6 does have a deep null at the sides, and a marked front-to-back ratio as expected, but just doesn't have the kind of forward gain I hoped for vs the twin-lead dipole, whether vertical or horizontal. Should average 6dB, but only gets up about 1-2 dB at most. I'll try to find and look over the reference you supplied, I don't have much antenna smarts, just know how to set one up and measure it's performance. Thanks for the comments.
And there's also the range of polarities - used by stations.I am betting that it will be good on ALL yr desired stations. As it is in a loft you can always use a wooden pole - if you are worried about a metal mast interacting with the metal elements once they are vertical.
FM can be - and once was - mostly transmitted in 'horizontal-only' polarity. But many / most? stations in Nth America now use mixed vertical and horizontal aka '45 degree slant' to assist reception in cars.
And there's also left or right hand circular polarisation - as with a helical antenna!
In our city (Canberra) it used to be vertical only, because VHF TV already was vertical. It is mixed now.
Very hilly city, not so much that houses are on the hills* but they still reflect.
Canberra is mostly open space, with several large nature reserves* as well as the urban spaces which are large as well. There are 5 'town centres', in addition to 'the parliamentary triangle' with all the 'official buildings'! Three artificial lakes.
WarmestTimbo in Oz
The Skyptical Mensurer and Audio Scrounger'Still not saluting.'
Read about and view system at:
http://www.theanalogdept.com/tim_bailey.htm
Can't do that - the roof supports are at various angles and locations, such that even horizontal, I have to mount the FM6 only 2 feet off the attic floor, barely miss the supports in one area. If vertical (elements vertical, boom horizontal) rotation will be severely restricted. It would be possible to rotate from NW to N only, though. Or S to SE, take your pick. Great idea, though.
BTW, forgot to say, the roof and attic walls are non-metallic, vinyl siding. A lot of wires snaking all over the attic floor, though. There is no electrically clear area to mount the antenna because of that. Really sloppy wiring, they just lay on the rafters, running directly from one place to the other, no design at all.
Aswe say down under, give it a go. Search - on 'antennas' AND 'FCC' - here
WarmestTimbo in Oz
The Skyptical Mensurer and Audio Scrounger'Still not saluting.'
Read about and view system at:
http://www.theanalogdept.com/tim_bailey.htm
I'd rather not irritate my neighbors and fight with my HMO. There are other ways to get what I want. The signal atrength and quality is OK, the noise I'm getting on my favorite FM station (WGMS, Wash DC.) seems to be from "HD radio self noise". WGMS is one of those who broadcasts HD digital FM out on the sidebands, and the tuner in my HK 3480 receiver doesn't have the narrow-band IF filters to fully "scrape off" the HD outliers. Even so, it does a reasonably good job, have to turn up the volume pretty high to hear the background "shhhh", especially with the FM-6 antenna. Although the FM-6 doesn't deliver higher signal strength than the vertical folded dipole, its signal results in better quieting. Brian Beezley suggests I install a post-detection filter in the tuner section to get rid of this residual HD radio self noise.
Dale.
This suggests to me that the SS meter on the HK is one of those 'light UP on a wet string' meters I have come to know well.Once they're at about 80-90% on the dial they take a LOT more signal before they - barely - move.
I hate IBOC, Sirius and daat reduced audio in all its forms except MPEG2' audio layer at 512 kbps and adjusted for performance on transients / attacks that begin all notes. On OUR national public FM-Classical(Jazz too!) service that's what the - necessary - satellites transcieve, and it IS okay.
Not as good as it was - I reckon ;-)!- but acceptable, and their live stuff is amazing - still!
CD is acceptable, but analogue tapes or broadcasts of acoustic concerts - on a good 'unprocessed' FM station - can still piss all over it.
As can music IN the studio with the announcer. Strikingly good. Let alone interviews!
WarmestTimbo in Oz
The Skyptical Mensurer and Audio Scrounger'Still not saluting.'
Read about and view system at:
http://www.theanalogdept.com/tim_bailey.htm
http://www.audioasylum.com/forums/tuner/messages/5529.htmlWhile the post-detector filter goes in - a suggestion I would second, also get the tuner checked/aligned, and tweaked. NB Power supply behaviour and decoupling - can be a BIGger audible issue - around certain chips even in front-ends, than can putting sexy parts in the audio output stages. Good but sensible $$$$$ parts are vailable anyway, right up to excellent like stock but selected styroseeal caps.
WarmestTimbo in Oz
The Skyptical Mensurer and Audio Scrounger'Still not saluting.'
Read about and view system at:
http://www.theanalogdept.com/tim_bailey.htm
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