Magnum Dynalab ST-2 vertical omnidirectional FM antenna

[sood_spice]

@hemantwaghe

CD's are a digital format whereas FM is analog and there is no issue of "bandwidth". Fair enough that the software used at the radio station could be CD but they have ultra high end Digital to Analog Converters which are far superior than those available on commercial CD players.
It is fun to be able to listen to music without the constant hassle of switching CD's. It is always a suspense as to what song the RJ will play next. I could never put together the collection of music the radio station have.

It is a miracle device especially if you attach it to a high quality tuner!

 

[sood_spice]

@buswal

Please let me know how it works and for how long. I would rather spend 10k and have something that lasts a lifetime than spend 1k ten times in ten months!

 

[sood_spice]

@anuragn

The ST-2 is also for indoor use. Magnum Dynalab have a cheaper version for indoor use. I think the model is SR-100.

 

[sood_spice]

I suppose anything can be made at home. Main issue is the result. I tried many designs and ended up wasting my money and time!

Anyway, thanks guys for the replies.

 

[anuragn]

@buswal

Please let me know how it works and for how long. I would rather spend 10k and have something that lasts a lifetime than spend 1k ten times in ten months!

The home-brew design explained by buswal won't even cost a 100 bucks, and it's meant for indoor use. So you don't have to spend every month.
But I do agree that is may fall short in performance compared with an expensive readymade one.

@buswal: I will try your design with my AVR and give feedback. Actually I had tried the same with an All in one system but the result was not very encouraging.

 

[buswal]

Hi,

You can try with an old tv ribbon cable. If you are prepared to experiment, you can try copper rods fixed inside a tefflon pipe and fix it outdoor and it will last long.

Many of my friends are using similar antennas and normally it lasts for around 10 years.

If required you can add a booster/preamplifier also. If you are interested I can give some reference to get in touch with serious FM and Short wave radio DXers, some are doing it as a hobby/business.

The other alternative is go for a commercial make and be done with it.

cheers,

 

[sood_spice]

Guys,

In my experience and depending on your location an FM antenna is best installed outdoors. The signal is optimal at the top of the building. So if the receiver is located at a lower floor then the only option is to put the antenna on the terrace and wire it till the receiver. This unfortunately results in the cable draining the signal. The ST-2 has a 2.5 db gain and the loss over a 100 meter good quality RU 6 is only 1 db. Thus the satisfactory performance of this antenna!

PS - I am not advertising this antenna or anything. I just love it and think it's great!

 

[sood_spice]

@buswal

Does this design require a lot of space? One of the reasons I chose the ST-2 was that it takes up only two inches of space and is quite unobtrusive.
A booster amplifier was discouraging to me. If the booster is located atop the antenna it tends to boost all the station frequencies equally and this overloads the front end of the FM tuner It causes more problems than it solves. Moreover if there is any electric interference present in the signal that to gets boosted and is a nuisance to listen too.

 

[buswal]

hi,

It requires very less space. Commercial boosters with filters are availabe abroad. Booster is kept at the receiving end before it is connected to the antenna socket of the receiver.

You may try old tv ribbon cable in a "T" form. I mean take an old tv ribbon cable, split it at the top end for around 5 feet and make it in a "T" shape and then hang it away from the wall at a height as far as possible/ outside the window and see the results.

cheers

 

[buswal]

hi,

It requires very less space. Commercial boosters with filters are availabe abroad. Booster is kept at the receiving end before it is connected to the antenna socket of the receiver.

You may try old tv ribbon cable in a "T" form. I mean take an old tv ribbon cable, split it at the top end for around 5 feet and make it in a "T" shape and then hang it away from the wall at a height as far as possible/ outside the window and see the results.

cheers

 

[sood_spice]

Thanks for the design. Does copper not oxidize? Will a strong wind not destroy the TV ribbon antenna you have suggested?

 

[sukhjit_bhullar]

I am going for this fm antenna (homebrewed)- courtesy vu3nsh.
High Gain FM Antenna
(Single Quad Loop for FM Radio DXing)
by N.S.HARISANKAR - VU3NSH
Connect this 69 year old exotic Antenna and enjoy your FM band DXing.

FM Antenna

The quad antenna have a gain of 1.4 dB over a dipole and also operate over a relatively wide frequency. Quad antenna dipole to form 1/4 lambda each side makes a square. American Radio Amateur (HAM) Clarence C. Moore, W9LZX developed this system in 1939 for the Missionary Radio Station HCJB at Quito of Ecuadaor (South America). The altitude of the station was over 10,000 feet in Andes. The station was operated in 25 m band SW with TX power of 10 KW. The band width of a single dipole is quite narrow. The quad loop is having high gain and less corona discharges etc. The half lambda folded dipole impedance is 288 Ohms (300 Ohms) and this quad loop is having 125 Ohms feed impedance. Due to low impedance of the quad, there is no need of any matching, for a general FM receiver system.

Connecting a folded dipole (gain : 2.14 dB, 1.45 m long and 300 Ohms) to a FM receiver of 75 Ohms input, without any matching, its efficiency becomes to 65% (VSWR-4) and a 125 Ohms quad at 75 Ohms receiver without matching it will get 95% efficiency (VSWR-1.66) with an extra gain of 1.4 dB over a folded dipole. Due to this 3.54 dB gain from a quad loop there will be a terrific FM Radio reception. Using a split dipole, having 75 Ohms feed impedance, there will be correct match of 75 Ohms FM receiver system. But one of the element will be isolated and it makes static and lightning problems. if we ground the cable braid (shield), the entire quad or foled dipole antenna system get grounded and it avoid the threat from static or lightning effects.

FM Radio allocation in India is from 88 MHz to 108 MHz. So the mid frequency is 98 MHz. The equation for getting the wave length of the conductor is (300 x 0.95) / 98 MHz. i.e. 2.908163 meters. If we divide this value by 4 we can get the Quarter Lambda length. i.e. 72.70 cm, we can take it as 73 cm or 74 cm. Due to skin effect of VHF frequency the element should be a tube having more than 4 mm dia or use 3/8th tube for getting good efficiency.
Connection To Radio

Really gr8 design, i just followed the design and built it under Rs.200 and its working very well i have been able to listen 11 FM(atmost, regular 8) stations in my city. Really appreciate the design. just one thing i would like to ask regarding earthing. what should be depth for burying the copper beneath the surface for making it effective against any lightining.

 

[ilak2k]

Hi sood_spice,
I am interested in getting this Magnum Dynalab ST-2. I can see how this antenna looks like. But how is the actual connection made between the receiver and this antenna? does it come with a wire? what wire or plugs have you used?

 

[buswal]

dear sukjit bhullar,

Great to hear the good news that you successfully homebrewed the fm antenna. have a great time dude.

cheers,

 

[anm]

I am going to get this antenna setup over the weekend.

 

[gobble]

I am going for this fm antenna (homebrewed)- courtesy vu3nsh.


High Gain FM Antenna
(Single Quad Loop for FM Radio DXing)
by N.S.HARISANKAR - VU3NSH
Connect this 69 year old exotic Antenna and enjoy your FM band DXing.

* Type : Self Resonant Loop, 1 Lambda
* Gain : More than a Dipole (1.4 dB+)
* B/W : 88 MHz. to 108 MHz.
* Noise : Very Low
* Impedance : 125 Ohms
* Polarization : Vertical

FM Antenna

The quad antenna have a gain of 1.4 dB over a dipole and also operate over a relatively wide frequency. Quad antenna dipole to form 1/4 lambda each side makes a square. American Radio Amateur (HAM) Clarence C. Moore, W9LZX developed this system in 1939 for the Missionary Radio Station HCJB at Quito of Ecuadaor (South America). The altitude of the station was over 10,000 feet in Andes. The station was operated in 25 m band SW with TX power of 10 KW. The band width of a single dipole is quite narrow. The quad loop is having high gain and less corona discharges etc. The half lambda folded dipole impedance is 288 Ohms (300 Ohms) and this quad loop is having 125 Ohms feed impedance. Due to low impedance of the quad, there is no need of any matching, for a general FM receiver system.

Connecting a folded dipole (gain : 2.14 dB, 1.45 m long and 300 Ohms) to a FM receiver of 75 Ohms input, without any matching, its efficiency becomes to 65% (VSWR-4) and a 125 Ohms quad at 75 Ohms receiver without matching it will get 95% efficiency (VSWR-1.66) with an extra gain of 1.4 dB over a folded dipole. Due to this 3.54 dB gain from a quad loop there will be a terrific FM Radio reception. Using a split dipole, having 75 Ohms feed impedance, there will be correct match of 75 Ohms FM receiver system. But one of the element will be isolated and it makes static and lightning problems. if we ground the cable braid (shield), the entire quad or foled dipole antenna system get grounded and it avoid the threat from static or lightning effects.

FM Radio allocation in India is from 88 MHz to 108 MHz. So the mid frequency is 98 MHz. The equation for getting the wave length of the conductor is (300 x 0.95) / 98 MHz. i.e. 2.908163 meters. If we divide this value by 4 we can get the Quarter Lambda length. i.e. 72.70 cm, we can take it as 73 cm or 74 cm. Due to skin effect of VHF frequency the element should be a tube having more than 4 mm dia or use 3/8th tube for getting good efficiency.
Connection To Radio

Buswal
Is this for indoor use or outdoor? I want to try building an indoor antenna. The image is too tiny, do you have the reference article?

--G0bble