Fuzzy reception: new radio, single-lead antenna

[Joel_BC]

We've got a converted barn with a metal roof, and my wife uses it as her art studio. Recently she bought a CD-player/FM-radio unit that will also play music from her iPod. The radio plays pretty well, but can be slightly fuzzy on her favourite station - which is at 91.7 mHz. It's not fuzzy all the time, but will be for five minutes or so, then clear again for about the same amount of time.

Practically speaking, I believe it's an antenna problem. The unit came with a single-wire "antenna" - the wire being around three feet long that just comes out of a hole in the plastic housing of the radio. You can string the wire out and tack it up, and that's the only option provided. But there are no terminals to attach any sort of antenna input by screwing wires in place.

I tend to think that even with this "single-lead" type of antenna, there must be some way to improve it... like connect the wire to some sort of external antenna arrangement (either bought or homemade).

First question, can something be improved - even with a single-wire input?

Second, is there an antenna type that would be recommendable for this situation?

Third, will the metal roof on the building limit the benefit of any antenna placed within the building itself? (We get a couple feet of snow, so I suppose any external antenna would have to be attached to the roof peak, right?)

Thanks.

[mrvanwinkles]

You can try and hook up an outdoor antenna and connect it to that simple wire antenna coming out of that radio - but no guarantees with that.

It may be difficult to "couple" / get a good signal into that type of simple antenna connection.

Your radio may be picking up noise of some type from inside the building or nearby - that may be your problem with the intermittent noise.

And also - as you mention - the metal of the building roof is probably interfering with good signal reception.

Important:
But with an outdoor antenna you will also need some surge protection / lightning protection to ground ... on the antenna lead-in wire before it comes into the building. That's required by Electrical Code, and is just good safety practice.

I would suggest a different FM radio that *DOES* have a proper antenna input connection.

And I would also suggest a COAX type input wire (usually the standard RG6 Coax). The COAX is a sheilded type of input wire and will help keep any noise from adding to the signal anywhere along the length of the input wire.

As you suggest, a mast and antenna *ABOVE* the PEAK of the roof is likely the best spot for it. (Because the roof is metal - to get good signal reception you may need to place the antenna to clear the peak of the roof by several feet - maybe even 6 feet or so - hence the need for a MAST. No way to know for sure - you must experiment and try ... )

One typical type of antenna for FM is crossed horizontal folded dipoles.

It is essentially two horizontal folded dipoles of correct length for FM, connected together, and mounted "crossed" ie. at 90 degrees from each other.

This results in an omnidirectional pattern ie. it receives equally well from all directions.

This should get you all your local FM stations - pretty good - in theory.

If properly placed in a good spot - trial and error / or some testing may be required ... it might perform well enough to get you some stations from a little furthur off as well.

Consult with a local antenna shop ... you can probably buy or order outdoor FM antennas like that at a pretty reasonable price.

I recommend buy quality and do a good installation.

Good reception, good signal and good sound quality in the wife's art studio will definitely enhance creativity ... and she will definitely love you for it !

[Joel_BC]

A little update. I don't know how long my luck may hold... I tried connecting that single antenna wire (provided with the radio unit) to the electrical ground in the building's line-current electrical system. And it seemed to solve the problem.

In other words, I made "a green-wire connection" to ground. And the lisping every time an announcer or singer used the consonant s disappeared. I say it seems to have solved the problem because I've only listened for 20 minutes.

Can anyone explain to me why it's worked?

[BCScott]

I'd say what you've done is lengthened the stock antenna. I've found that adding a length of single wire to one of these clock radio type antennas often improves the reception. It may be atmospheric, also. I've found that when you're at the margins of reception, differing atmospheric conditions give differing levels of reception. Some days it's clear, some days it's fuzzy.

[stampeder]

Please tell us where exactly you are - we can get a better idea of the circumstances that way. Also see the following thread covering the same issue:

http://www.digitalhome.ca/forum/showthread.php?t=153564

[classicsat]

Many book shelf and component stereo receivers are coming with a Belling Lee "PAL" connector, commonly used on TVs where the PAL TV format is used. The stereos usually come with a wire the plugs onto the centre terminal of the PAL connector.

If the stereo is one of those, one can get a PAL to F adapter, and use regular mast mount antennas.

[Joel_BC]

Stampeder asked:

Please tell us where exactly you are - we can get a better idea of the circumstances that way. Also see the following thread covering the same issue:

http://www.digitalhome.ca/forum/showthread.php?t=153564

We're in the mountain region of southeastern British Columbia. Columbia region - not too far above the US border, but in a narrow valley with fairly steep mountain ridges to east and west. Our place is located a ways from the "repeater" tower serving analog FM and TV transmission. We're slightly on the edge of a strong signal for 91.7 mHz (that station my wife likes).

BCScott said:

I'd say what you've done is lengthened the stock antenna. I've found that adding a length of single wire to one of these clock radio type antennas often improves the reception. It may be atmospheric, also. I've found that when you're at the margins of reception, differing atmospheric conditions give differing levels of reception. Some days it's clear, some days it's fuzzy.

Yeah, I believe there could be some atmospheric factor in the reception.

[mrvanwinkles]

Joel_BC - you mentioned:

We're slightly on the edge of a strong signal for 91.7 mHz (that station my wife likes).

... in a narrow valley with fairly steep mountain ridges to east and west.


Well ... if your wife is mainly interested in just that one station [ 91.7 ], and you are down inside a steep valley, and "near the edge" of that station's reception, with atmospheric conditions creating noise at some times.

Then ...

Rather than an omni-directional FM antenna that receives from ALL directions...

Consider testing instead a *DIRECTIONAL* FM antenna with *GAIN* dedicated for that 91.7 FM station. Mount it and point it permanently at that "repeater" tower.

Or maybe more simply - just a *SINGLE* horizontal FM Folded Dipole [ Bi-directional ], rather than the double crossed horizontal omni-direction dipoles.

[ ? Presumeably the signal is coming from the South or from the North, down the length of the valley ? Because unless the repeater transmitter is up on one of the ridges of that valley ... it is difficult for signals to get into the valley from over the valley ridges, from the East and West ]

What direction, and from how far is that signal coming from ?
( ie. where is the repeater transmitter located relative to you and the valley ? )

From down the length of the valley ?

... you've got serious terrain conditions. being in a valley like that.

I suggest some tests be done with an antenna by hand first, and see if you can improve reception of that one station you're interested in.

"Atmospheric Conditions" - Ya I can imagine Mist, rain, fog, precipitation ...whatever developing and hanging around in the valley.

[mrvanwinkles]

A post of mine:

http://www.digitalhome.ca/forum/show...1&postcount=98


Skyscan website ( How to build and FM antenna. 3 element & 6 element yagi )

http://www.skyscan.ca/Antennas.htm


The 3 Element FM YAGI

http://www.skyscan.ca/3ElementYagi.htm

For a 92.1 Mhz FM antenna suggests:

Lengths:
reflector (back of antenna) 162.cm
driven element (centre) 160.3cm
director (front of antenna) 146.cm

Spacings:
The spacing between the reflector and driven element is 89.2cm; driven element and director 48.7cm.


Comment:
I built this 3 element one, more or less, with some scrap steel rod I had, in Kingston, and tested it out.

Yes, it demonstrated some gain and directivity, pulling in stations that were a little further away better, and rejecting some interfering stations and noise from the back.


The Dimensions Table for the 6 Element FM YAGI

http://www.skyscan.ca/dimension_table.htm

For 91.7 Mhz, table suggests:

Lengths cm :
Dir 1 138.4
Dir 2 140.7
Dir 3 142.3
Dir 4 143.9
D.E. 154.7
Refl 161.9

Spacings cm (along boom) :
D4 - D3 81.8
D3 - D2 81.8
D2 - D1 81.8
D1 - DE 40.9
DE - REFL 40.9


Simplified as a 3 [or 4] Element YAGI for 91.7 Mhz:

So if you used some of the 6-element numbers for 91.7 Mhz, simplify... and build a 3-Element Yagi [or 4 element Yagi] with those numbers ...

i.e. build the 6 element FM Yagi specifically for 91.7 Mhz, but just OMIT the first 3 directors (or even the first 2 directors) ... to make it simpler and shorter ...

i.e.

Simplified 3 or 4 Element Yagi, 91.7 Mhz:

Lengths cm :
[Dir 3 142.3 ] ?
Dir 4 143.9
D.E. 154.7
Refl 161.9

Spacings cm:
[D2 - D1 81.8 ] ?
D1 - DE 40.9
DE - REFL 40.9


Materials ?
They are recommending copper wire and a wood frame to support it. O.K. for some basic testing.

BUT ... if testing is positive, and you want to build a final good antenna, to stay up and outside:
Many others have built larger antennas like this with metal TUBE.

ALUMINUM: Thin wall aluminum tube is the ultimate - light, strong, and conductive.

Alternate:
1/2" Copper tube for the D.E. - Driven Element - dipole.
(Copper is good, very conductive for the active "receive" element)


Galvanized Steel tube ( 1/2" Electrical Conduit Tube ? EMT Tube for the Reflector and Directors )
( less expensive for the REFL AND DIR's, still does the job, and saves some cost )

[ Could *ALL* be made of steel galvanized tube ... D.E. too ... and will probably work fine as well ]

[mrvanwinkles]

Here's a post, a thread, and some pictures.

In the OTA Forum, Antenna Research and Development section

Thread: DIY VHF-HI Yagi Using K7MEM Tool - Success!

Forum Member Poutanen. built a large YAGI for TV ch 7 from tube.

This gives some idea how the thing is built / what it looks like.

http://www.digitalhome.ca/forum/show...4&postcount=22

http://www.digitalhome.ca/forum/show...6&postcount=24