A miracle is needed! (bad FM reception)

[sobolan]

I am mad out of ideas, and ready to go slap my grandfather for buying this pos house. He couldn't have possibly bought a worse plot in the whole town. There is highway level traffic two meters away from my windows, a steep hill behind the house that one day will burry half of it and NO fm reception.

I live 30km away form the big city and the big fm transmitters. There is also a relay station about 20km away. In town there is decent reception but at about 200 meters away from my house as the road makes a curve to the left entering some sort of a valley reception drops significantly and I get two stations with weak signal at most.

This summer I started renovations and decided to install an external fm antenna complete with in wall sockets. The fm antenna was mounted on a mast on the roof at the height of about 9 meters. I used EMP proof soviet era coax cable with dense copper shielding and shielded wall sockets. The antenna mast being insulated was grounded to a copper rod driven about a meter into the ground.

About the gear. At first I tried a vintage technics sa-5370 with questionable reception. With the muting function activated I got nothing. Deactivating it I got dissappointing reception for a couple of stations. Thinking that the receiver was old and deaf I hooked a Grundig s450dlx radio to the antenna and got almost the same bad results. In a week a Pioneer F757-mk2 will arrive and I am affraid that it will just gather dust.

Now the questions: Is an amplifier for the antenna useful? What else should I try? Raise the mast a few meters higher? A different antenna? (this is the one I have http://static.dipol.com.pl/images/pict/a0221.jpg ) Other ideas?

P.S. 1. Due to heavy interferences (although successfully suppressed by the cable shielding) all the wireless equimpent in the house was shut down during the tests.
P.S. 2. My quest is to be able to listen to a state owned station which airs radio theatre almost evey evening so as long as I can hear speech clearly I am fine.

Thanks for reading this big a** post.

 

[Mamrak1]

You aren't exactly using top quality receivers to pick up radio stations. I live in a valley and I use rabbit ears. I get fairly good reception in my location. Spend some money and get yourself a first class tuner. That or sell the house and move elsewhere.

 

[sobolan]

I know I am not using top class gear, but I also don't expect top class performance. I have some rabbit ears somewhere, will try those. Will also try a yagi antenna. If they all fail the only option will be to move the mast on the hill behind the house; the grundig seems to perform great there.

 

[HTHMAN]

As you probably know, FM is line of sight. If anything blocks that line, reception will suffer. Your best resolution will be to get the antenna as high as possible rather than get something that may have a better tuner.

 

[RxDx]

A yagi should give you noticeably better reception. Omnis don't offer much beyond local sensitivity.

Amplifiers just make the noise louder. Put as much metal in the air as high as you can afford- with a rotor.

 

[sobolan]

Does the length og the coax matter? Installing the antenna on the hill wil require at least 40 more meters of cable

 

[c.coyle]

Does the length og the coax matter? Installing the antenna on the hill wil require at least 40 more meters of cable

Only from the standpoint of signal loss. The longer the run of cable, the less signal at the antenna reaches your receiver. It sounds like you are using old coax, which becomes lossier as time goes by. 40 meters isn't that long, but I would invest in new, high quality, low loss coax. Or run open line (twin lead) from antenna to receiver and use a balun. As a general rule, open feedlines have lower losses than coax, but they are more hassle to install and maintain, and not always practical.

 

[sobolan]

I will buy the piece of cable since I ran out the soviet stuff, but even the more expensive coax looks cheaply built with thinner wires compared to the soviet cable. As soon as the heatwave goes away I will start working on the new mast on the hill. From there I should have better reception since there is some line of sight to the transmitters

 

[amptramp]

If the hill is on your property, install a reradiator array. That is a receiving antenna at the top of the hill linked by open feedline to another transmitting antenna pointed at your house. This is purely passive - no amplifiers or power necessary. Then you can use an antenna in the house (like rabbit ears) or an outside antenna to receive the signal from the transmitting antenna. You show an Omni receiving antenna but your transmitting antenna and the receiving antenna at the house should be directional. The Omni can be the receiving antenna at the top of the hill.

 

[c.coyle]

I will buy the piece of cable since I ran out the soviet stuff, but even the more expensive coax looks cheaply built with thinner wires compared to the soviet cable. As soon as the heatwave goes away I will start working on the new mast on the hill. From there I should have better reception since there is some line of sight to the transmitters

Thickness or thinness is largely irrelevant if all you are doing is receiving. Loss per given length, basically dependent on the dielectric material, is more important. That old Soviet stuff may be big and hefty because they were using it for transmitting as well as receiving.

I'm just curious. Can you post the what's printed on the jacket of the Ruskie coax, or better yet, a picture?

 

[sobolan]

@c.coyle There are no markings printed, on the cable. Here are the pictures. 1.5mm central conductor, transparent sleeve and thick copper mesh shielding. I have another piece used for the tv whick has even thicker shielding, it required 7.2 mm screw connectors. I don't know what the standards are, but from what I have seen pasing as coax cable nothing came close to this.

 

[sobolan]

Ok, so yesterday the Pioneer F757-mk2 arrived and today I got the chance to hook it up for a very short time (still working on the house) and what a difference! I messed with the antenna a little, lengthening the mast with about 1.5 meters(we currently have 43 degrees celsius at noon so no chance of working outside) which made almost no difference, until I hooked up this beast.

It only locks on three stations clear with stereo, but due to its high sensitivity I receive ALL of them in mono. All the stations are listenable. Even the car radio looses its reception about 300 meters away from my house, but this tuner pulls signal in like a black hole. I have to say I am amazed by its performance. WOOO HOO!!!

 

[WobblySam]

Only from the standpoint of signal loss. The longer the run of cable, the less signal at the antenna reaches your receiver. It sounds like you are using old coax, which becomes lossier as time goes by. 40 meters isn't that long, but I would invest in new, high quality, low loss coax. Or run open line (twin lead) from antenna to receiver and use a balun. As a general rule, open feedlines have lower losses than coax, but they are more hassle to install and maintain, and not always practical.

Old coax (unless you have nitrogen-filled heliax) should be used only as ballast in your trash can. As coyle noted, flatline offers lower loss over long distances, but you've got to keep it clear of everything. Bad coax can rob you of every bit of advantage that a good antenna might afford you. Look for some Belden RG-6 - if it's available where you live.
Good luck

 

[ConradH]

+1 on coax. What you care about is loss per length, the lower the better, at the frequency of interest. As an example, I ran some small RG-174 down to my lab so I could have the antenna above ground. The losses in the cable are so high in the FM band (-8.8 dB/100'), I lost much of the advantage of raising the antenna. Worse, it got the antenna closer to the main computer system here, so more noise. Get some decent RG-6 (-2.0 dB/100') and don't run extra lines to distribute to different rooms. Antenna to receiver. That might get you into the stereo world.

 

[c.coyle]

All of the above, plus keep away from off-brand coax, such as the RG6 they sell at Home Depot. Copper clad steel center conductor and skimpy aluminum shield. I wouldn't trust their attenuation (loss) figures - if they publish any. Although I have no experience, I would also be leery of Ebay coax.

I myself would stick with Belden from a reputable source. AK favorite Blue Jean Cables sells Belden 1505A (RG-59 type) and 1694A (RG-6 type) by the foot. Expect to pay almost a dollar a foot for high quality RG6, less for RG59, but worth it in weak signal situations.

 

[sobolan]

You guys make me work in the scorching sun. So I took the new coax that I have bought (best I could find) and made a second line to the antenna to see how it compares to the old nos stuff that I used. After playing with all the tuners available I couldn't make a difference between the cables, the signal had the same levels and didn't improve (the technics needs an alignment). So I guess the old stuff is still ok?

What made a noticeable difference was replacing the cable between the wall socket and the tuner. I had a piece with moulded jacks and replaced it with a diy one. Noise filtering improved with the new one.

I also tried to run an open line connection but it is not viable. It gets overloaded with rf noise from all the crappy wireless stuff in the area(cirps, squeals, motorboats, hum and all kinds of other crap) although the reception is a bit better. Maybe I am doing something wrong?

 

[ConradH]

Theory has open transmission lines beating coax every time on losses, but in the real world it often isn't practical. That antenna probably doesn't offer much gain and you should consider the above suggestions for something directional, with better gain, and a rotor. Or just point it towards the station you care about.

 

[KentTeffeteller]

Case in point, at this house in Oak Ridge, Tennessee, I'm in a valley on the low elevation. I get around 12 or 14 FM stations from 18-40 miles away, all but one or two are reasonably strong Stereo reception on my McIntosh MX 114 FM tuner/Preamplifier. On a wire dipole. If I had a high gain yagi on a rotator, I'd double this or even triple this feat. The HH Scott 312D in the living room gets a dozen FM signals reliably. It's more sensitive than the McIntosh tuner preamplifier.

 

[dewdude]

You may be getting multipath..which at the right phase can kill your signal entirely.

Try a yagi. They are extremely directional and if the problem is multipath...it may null out with the multipath.

FM is line of sight, but there is diffraction of signal that helps in situations.

If your noise increases with open balanced line...something isn't right. The theory woth that stuff is you have a balanced signal...so any noise that is common on the line will cancel out. Higher noise would indicate a major imbalance in the antenna, transmission line, or a problem with the balun..since most FM tuners use an unbalanced signal in to the tank.

When installed PROPERLY, balanced line will have MUCH less loss than coax. The trick is keeping it away from all metallic objects...as that causes an impedance transform.

If you think RX with that stuff sounds tricky...I transmit with it. But the loss is well under what it would be for coax.