Jump to content

Sign in to follow this  
Greg Pain

Converting external old vhf antenna to combo fm and dab

Recommended Posts

Posted (edited)

Does anyone have plans to convert an old analog vhf tv antenna to pick up fm and dab?

I have an old long range fm antenna with the main central beam about 3m long, and a large fringe vhf antenna which I'd like to convert. It doesn't need to be long range; a director, collector and reflector would be suitable, as it will be roof mounted. 

I'm not even sure if the combination fm/dab is possible. I haven't found anything on the net apart from modified coat hangers!

Edited by Greg Pain
Grammar error

Share this post


Link to post
Share on other sites

I thought a antenna is an antenna.

 

https://www.acma.gov.au/Citizen/TV-Radio/Television/TV-reception/do-i-have-the-right-antenna-system

Share this post


Link to post
Share on other sites

I thought a antenna is an antenna.

 

Thanks, but antennas are not just antennas. My old long range fm antenna won't pick up dab, even though it comes from the same transmitter on the top of Mt Lofty in Adelaide. I have enough antenna bits and pieces to reconstruct the dab/fm antenna which is really want I'm asking for.

Share this post


Link to post
Share on other sites
Posted (edited)

I thought that link might lead to something that may help, ah well.

Edited by Muon N'
Forgot a 't'

Share this post


Link to post
Share on other sites


Have you tried your antenna set up for Vertical Polarisation (turned on it's side)? It looks like DAB is vertical, and your FM antenna is most likely set as horizontal.

Share this post


Link to post
Share on other sites
Posted (edited)

The antenna on our units is the same one that was there before the advent of digital TV, works fine for Digital TV.

 

Marketing is quite powerful.

 

Like much of the world, Australia is shifting from traditional analog television to digital broadcasting. This means new set top boxes if your TV isn't already able to pick up digital signals.

But that doesn't mean you also need to change your antenna, says Dr Stuart Hay, principal research scientist in electromagnetics with the CSIRO's Information and Communication Technology Centre.

"Antennas made for analog TV signals work just as well for both digital and high definition signals. It's incorrect to claim that you need a special antenna," says Hay.

 

http://www.abc.net.au/science/articles/2011/05/19/3219974.htm

 

I just think of all the 'new' digital antennas sales, and the many perfectly fine antennas that are now in land fill.

 

Edit: so i guess, if the antenna you have is only VHF compatible then you need one that covers both VHF and UHF regardless if it is called analogue or digital.

 

Here’s the basics of how an antenna works:

A broadcaster, or transmitter, takes their content (which could be data, pictures, sound or some combination of all three) and converts it to electro-magnetic signals referred to as “radio waves”.

 

 

Edited by Muon N'

Share this post


Link to post
Share on other sites

I thought a antenna is an antenna.

 

Thanks, but antennas are not just antennas.

 

My old long range fm antenna won't pick up dab, even though it comes from the same transmitter on the top of Mt Lofty in Adelaide. It is over 3 metres long, has 7 directors focusing on ch3 and ch5 collectors with a reflector behind these. It is set for verticle polarization, so its pull is very strong. However, from what I've read, it is too 'frequency specific' to pick up dab.

 

Comparatively, my current tv antenna is a Hills 'bedstead' CA16 (obviously set horizontally). I need a strong antenna for tv like this one, as even though it is a high chimney mount, it has to pick up signal through dense trees and over obscuring hills (no line of sight) and is connected to 6 tv tuners. Signal strength on all these 6 tuners is close to 100%.

 

I have enough antenna bits and pieces to reconstruct the dab/fm antenna which is really want I'm asking for; small enough to connect to only two dab/fm tuners and obviously set vertically.

Share this post


Link to post
Share on other sites


Thanks Muon M' for the info, but I reckon I've been through these.

I have several damaged old tv antennas, with broken and missing elements. Rebuilding one to receive both fm and dab is my aim. Boom length with a director, collector and reflector dimensions and spacings is the info I can't find.

 

Share this post


Link to post
Share on other sites
56 minutes ago, Muon N' said:

I just think of all the 'new' digital antennas sales, and the many perfectly fine antennas that are now in land fill.

 

Edit: so i guess, if the antenna you have is only VHF compatible then you need one that covers both VHF and UHF regardless if it is called analogue or digital

OP wants to pick up radio, not TV.

 

11 minutes ago, Greg Pain said:

Rebuilding one to receive both fm and dab is my aim

Bob has the good oil.   DAB is on VHF 9A vertical .... it might also get FM ok.

Share this post


Link to post
Share on other sites

Depends how far you are, line of sight ?.... just a wire will do as all some dab+ radios come with. If little ways out a telescopic whip antenna will do. For us with line of sight either the wire not even uncurled... or whip antenna not even extended does fine. Full reception. If you have a screw f type antenna connector you can pick up a telescopic whip antenna from likes of sangean for $10 posted !

 

if mobile, pure for instance and pioneer also now provide a small stick on antenna both work surprisingly well in dab+ receiving range (check the abc reception charts)

 

as a digital radio early adopter (mobile, portable and in home) even prior to going live and with previous gen trials as well I can attest to capability of all these :)

Share this post


Link to post
Share on other sites
Posted (edited)

Obsolete the multi element , try a SOTS "state of the science" omni-directional

https://www.scribd.com/document/396824710/FM-AM-Antenna-Setup-Standard-50-cm-1-8th-wave-Unit

Reasonably much, all frequencies and modulation system widths can be coarsely said to be possible from one antenna as too the data information scheme as DAB has being 128 bit rate CD digital audio mastering computer generated.

The problem is resonance (SWR Standing Wave Ratio) in small receiver elements is massively critical to good operation for the intended purpose of frequency

OR put economically, "how to operate well by tuning with the least construction resource material and thus expenditure" !

The most critical feature of an antenna is impedance (attenuation) and inductance (gain) that are usually conventionally set up by winding the aerial as a coil,

HOWEVER, there are "various other ways" to cause inductance and directional discrimination of signal.

 

 

Edited by theoldnic

Share this post


Link to post
Share on other sites


Posted (edited)
On 16/03/2019 at 8:38 AM, Greg Pain said:

Does anyone have plans to convert an old analog vhf tv antenna to pick up fm and dab?

I have an old long range fm antenna with the main central beam about 3m long, and a large fringe vhf antenna which I'd like to convert. It doesn't need to be long range; a director, collector and reflector would be suitable, as it will be roof mounted. 

I'm not even sure if the combination fm/dab is possible. I haven't found anything on the net apart from modified coat hangers!

The only true problem TV antennas have is they are directional and to a lesser extent are also designed to propagate reception with a higher gain dB than an omni-directional ordinary antenna

Of DAB+ or FM , EMR (Electro Magnetic Radiation) in the EMS (Electro Magnetic Spectrum) are all radio waves r.g. "visible light", simply different frequencies.

An antenna is simply a material device that is reactant with EMR with a sub set of design constructed properties that give it good propagative characteristics to cause "induction" of the EMR to produce electric current.

Why some antennas are stipulated for particular frequencies is one of the properties of the antenna called SWR Standing Wave Ration that has good harmonic properties for the induced voltage at the stipulated frequency.

The following is a "city use antenna" that is omni-directional but may need "attenuation" to use on a tv receiver in a city, it is not constructed the normal way an omni-directional antenna is made, and is more unusual of its physics principals than a parasitic element tv antenna.

https://www.scribd.com/document/400632904/FM-AM-long-range-30-cm-housing-1-16th-wave-Antenna-unit-setup

This shows how different it all gets,

tv antennas as most are simply made for both production and resource cost to selling performance.

 

In short, any electric conductive piece of metal is an antenna of any frequency, but there are ways of raising the efficiency for particular frequencies (you seem like you are on the right track...).

 

Edited by theoldnic

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...