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A guide to receive far away FM stations
- Thread starter mundle2002
- Start date
- Replies 53
- Views 88,775
@essbebe , bought RG58U/C RF cable 50 ohm impedance,cost here is rs 20 / m. replaced the coax .without using the booster , the signals are getting down from ant without much attenuation definitely much better than coax.But since i'm using a booster i notice only a minimal improvement in the reception just by replacing the cable. but still i'm forced to use 300 ohm cable for a short length from ant to booster input because that gave better result.all other sites including to the receiver -rg58u is used.that was my observation and best combination noted by trying different permutation and combination.As u suggested it, I thought better to post the result i got in detail. connecting rg58u directly from ant (without booster )to car stereos arial gave a very good result.thank u for ur suggestion ,now I also believe that if an external arial is used for radio we should connect it with 50 ohm cable rather than 75 ohm coaxial cable . with regards mcx
@mcx
Thanks. glad to help. usually i don't open other forums . mostly bsnl/mtnl/and Airtel forums. Please do send a PM , if you feel, I can be of help, just mentioning the thread. Just the info, that I am an experimenter in Electronics/wireless/ etc. will do.
For reference :Antennas - Indoor
Thanks. glad to help. usually i don't open other forums . mostly bsnl/mtnl/and Airtel forums. Please do send a PM , if you feel, I can be of help, just mentioning the thread. Just the info, that I am an experimenter in Electronics/wireless/ etc. will do.
For reference :Antennas - Indoor
Hi Essbebe , Can u please tell me about vertical and horizontal polarisation of fm The Yagi is designed for horizontally polarised signal right ?or is it the other way ?Is there antenna designs for vertical .I've seen some antennas similar to yagi but erected in such a way that the plane of the elements are perpendicular to the ground surface.
Valid point.
Simple . Mount the same antenna parallel or vertical to ground plane .
For TV /FM normally parallel. For Amateur radio ( Bandwidth usually 25 Khz. Vertical to GP.
TEST : extend the Telescopic antenna in FM receiver and try Vertical and Horizontal mode and change direction. for best reception. and confirm signal polarisation.
Reference : Google search FM broadcast polarisation.
FMBroadcastAntenna.com | FM Broadcast Antenna's
Simple . Mount the same antenna parallel or vertical to ground plane .
For TV /FM normally parallel. For Amateur radio ( Bandwidth usually 25 Khz. Vertical to GP.
TEST : extend the Telescopic antenna in FM receiver and try Vertical and Horizontal mode and change direction. for best reception. and confirm signal polarisation.
Reference : Google search FM broadcast polarisation.
FMBroadcastAntenna.com | FM Broadcast Antenna's
thanks essbebe , will 90 degree turning work with quad antenna to receive vertical polarisation ?, i think our transmitters are definitely vertical and may be both vert and horizontal, is it not ? anyway i will try tomorrow morning. now the reception is generally bad since so much of heavyrain and lightening towards the evening in kerala: makes the distant Fms noisy.May be due to effects of global warming we are getting record summer rainfall. and HAPPY VISHU to all of u in this forum bye
@/members/mcx/
see the circuit given there. Whether copied from Popular Electronics, or an American web site or EFY makes no difference. Theory is same. But nowadays very difficult to get electronic parts for home construction.
https://broadband.forum/fm-radio-stations/24979-fm-radio-reception/
Your FM radio tuned circuit is for 88 to 108 MHz.
The bandwidth allowed in the IF usually 10.7 Mhz with a narrow B/W
for B/C audio.
So no possibility of local TV station breaking through. even if you use a untuned RF amplifier.
assume your TV audio FM signal say 67.75 round it to 67.7
When you tune 88 MHz the L.O will be 88+10.7= 98.7 MHz
When you tune 108 MHz the L.O will be 108+10.7 = 118.7 MHz.
So TV FM audio cannot generate the 10.7 MHz IF.
98.7 minus 67.7( approx) IF 31 MHz
118.7 minus 67.7( approx ) IF 51MHz.
You can check this. A local FM say 108MHz will be heard around 88MHz also.
108+10.7=LO 118.7 Normal 88+10.7=98.7 LO (image)
signal 108 mixes with 98.7 to give reception when dial shows 88 MHz
see the circuit given there. Whether copied from Popular Electronics, or an American web site or EFY makes no difference. Theory is same. But nowadays very difficult to get electronic parts for home construction.
https://broadband.forum/fm-radio-stations/24979-fm-radio-reception/
Your FM radio tuned circuit is for 88 to 108 MHz.
The bandwidth allowed in the IF usually 10.7 Mhz with a narrow B/W
for B/C audio.
So no possibility of local TV station breaking through. even if you use a untuned RF amplifier.
assume your TV audio FM signal say 67.75 round it to 67.7
When you tune 88 MHz the L.O will be 88+10.7= 98.7 MHz
When you tune 108 MHz the L.O will be 108+10.7 = 118.7 MHz.
So TV FM audio cannot generate the 10.7 MHz IF.
98.7 minus 67.7( approx) IF 31 MHz
118.7 minus 67.7( approx ) IF 51MHz.
You can check this. A local FM say 108MHz will be heard around 88MHz also.
108+10.7=LO 118.7 Normal 88+10.7=98.7 LO (image)
signal 108 mixes with 98.7 to give reception when dial shows 88 MHz
@/members/mcx/
see the circuit given there. Whether copied from Popular Electronics, or an American web site or EFY makes no difference. Theory is same. But nowadays very difficult to get electronic parts for home construction.
https://broadband.forum/fm-radio-stations/24979-fm-radio-reception/
Your FM radio tuned circuit is for 88 to 108 MHz.
The bandwidth allowed in the IF usually 10.7 Mhz with a narrow B/W
for B/C audio.
So no possibility of local TV station breaking through. even if you use a untuned RF amplifier.
assume your TV audio FM signal say 67.75 round it to 67.7
When you tune 88 MHz the L.O will be 88+10.7= 98.7 MHz
When you tune 108 MHz the L.O will be 108+10.7 = 118.7 MHz.
So TV FM audio cannot generate the 10.7 MHz IF.
98.7 minus 67.7( approx) IF 31 MHz
118.7 minus 67.7( approx ) IF 51MHz.
You can check this. A local FM say 108MHz will be heard around 88MHz also.
108+10.7=LO 118.7 Normal 88+10.7=98.7 LO (image)
signal 108 mixes with 98.7 to give reception when dial shows 88 MHz
i think u r not much familiar with cable tv technology.
More the different signals at the booster input, more the mixing of different frequencies. Check the filters of adjacent channel tv modulators & their mixers. If the filter is not attenuating -60db of adjust channel audio & video, it is getting over. This is not the place to go more in detail.
I hv done the market survey also. I got the info that at many places they get tv sound in the fm channel. They are using vhf boosters. Hence we hv decided to go our own way. Developing proper fm booster.
see the circuit given there. Whether copied from Popular Electronics, or an American web site or EFY makes no difference. Theory is same. But nowadays very difficult to get electronic parts for home construction.
https://broadband.forum/fm-radio-stations/24979-fm-radio-reception/
Your FM radio tuned circuit is for 88 to 108 MHz.
The bandwidth allowed in the IF usually 10.7 Mhz with a narrow B/W
for B/C audio.
So no possibility of local TV station breaking through. even if you use a untuned RF amplifier.
assume your TV audio FM signal say 67.75 round it to 67.7
When you tune 88 MHz the L.O will be 88+10.7= 98.7 MHz
When you tune 108 MHz the L.O will be 108+10.7 = 118.7 MHz.
So TV FM audio cannot generate the 10.7 MHz IF.
98.7 minus 67.7( approx) IF 31 MHz
118.7 minus 67.7( approx ) IF 51MHz.
You can check this. A local FM say 108MHz will be heard around 88MHz also.
108+10.7=LO 118.7 Normal 88+10.7=98.7 LO (image)
signal 108 mixes with 98.7 to give reception when dial shows 88 MHz
i think u r not much familiar with cable tv technology.
More the different signals at the booster input, more the mixing of different frequencies. Check the filters of adjacent channel tv modulators & their mixers. If the filter is not attenuating -60db of adjust channel audio & video, it is getting over. This is not the place to go more in detail.
I hv done the market survey also. I got the info that at many places they get tv sound in the fm channel. They are using vhf boosters. Hence we hv decided to go our own way. Developing proper fm booster.
a bit about me. Hail from Ernakulam but working in Abu Dhabi. An electrical engineer from REC Nagpur dealing with EHV substations but having interest in electronics from childhood. Revived the interest about 3-4 years ago when my Bose system did not receive FM stations here. Memeber of AV Forums and Yahoo Groups on Sangean ATS 909, Sony 7600GR. Came across this forum while searching for FM Stations in India when I went on vacation in August 2008. On reading through this thread I think there is some misconception regarding antennas and the connections. Open ended Dipoles have a charateristic impedance of 75 ohms. So a 75 Ohm cable is the best match. normally all receivers are designed with 75 ohms input imepdance for FM (or some with an inbuilt balun for 300Ohm lead in cable). Hence, RG6 or RG59 cable should be used for FM reception. Nevertheless, you must use a 1:1 balun to match the unbalanced coaxial cable to balanced antenna. A simple balun is just 5 turns of the coax about 1 inch diameter at about 2 inches from the connection point to the antenna . Atleast for 1/4 wavelength the cable should be at 90degrees to the antenna to avoid stray pickups. Dipoles are directional if mounted horizontal and omni when vertical. Yagi are made of dipole with reflectors and directors to make it narrow band. 50 Ohms is normal for transmitters / tranceivers. Ground plane atennae are 50 Ohms.There you use RG8 or RG58 cables. A J pole is another Omni solution. It worked for me but the municipality do not allow ugly antenna sticking out of the apartments. So removed it. Folded dipole have 300 Ohms impedance and there you use a 300 ohm ribbon cable or use a coax with proper balun. I am using vertical omni dipole with RG6U cable and 1:1 balun to catch FM stations 160kms from Abu Dhabi in Stereo mode. This is the most 'invisible' solution I can think of for my setup. Of course weather plays an important part in reception. For omni directional antenna you could have two dipoles at right angles and connected with a 1/4wave delay line. But you may have to live with multi path interference. Present FM stations have both horizontal polarisation and vertical. H polarised were used in the olden days when people used to listen to radio sitting at home with old bulky radios. When radios became small and were available in cars you couldn't have H polarised for proper reception. You need V polarised fo proper car / mobile reception. So all stations have both H and V. In FM you have to also fight with multi path distortions especially in urban areas and for that you need an antenna with very narrow band.. A Yagi. You need a rotator for serious DXing to narrow on the desired station Similarily if you have tuner with a wide band filter you may hear muddled sound due to interference from adjascent stations. A good tuner with a narrow band filter and Yagi with rotator would make a lot of difference There is no common solution for proper FM listening unlike SW. Correct me if wrong. SubbuBose 321 HTS, SONY BRAVIA KLV-40D300A,Yamaha AX496 Amp, Yamaha CDC 685 CD Changer, Yamaha KXW421 tape deck,Jamo E855 spkrs, SANGEAN WR3, SANGEAN ATS 909, SONY 7600GR PC SELF MADE - E6750/2.66GHz,2GB RAM,580GB HDD
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