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FM/DAB
I have a Cambridge azur 650T tuner. I have a single coaxial cable that at
present feeds from a loft aerial (external is not possible) into the FM input via a coax connector. The DAB has an F type connector. I would like to be able to use both FM and DAB from the single cable. 1. If it is possible, what would be the most effective way of setting this up? 2. Is there an aerial that would support both FM and DAB? (I live in Wareham, Dorset - BH20 5BB) Thanks, Gordon |
FM/DAB
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FM/DAB
In message , tony sayer
writes In article , Gordon MacPherson gordon.macph scribeth thus I have a Cambridge azur 650T tuner. I have a single coaxial cable that at present feeds from a loft aerial (external is not possible) into the FM input via a coax connector. The DAB has an F type connector. I would like to be able to use both FM and DAB from the single cable. 1. If it is possible, what would be the most effective way of setting this up? 2. Is there an aerial that would support both FM and DAB? (I live in Wareham, Dorset - BH20 5BB) Thanks, Gordon Generally an FM vertical dipole, not that abortion known as a halo, works quite well on DAB in a lot of areas. You should get a very good signal from the Rowridge TX on the Isle of Wight. I believe that BBC DAB is from there and the commercial from Chillerton down in the same isle!.. Even if you used a 3 element Yagi I suspect there'd still be sufficient DAB signal as well as enhancing the FM ones.. I think that there are FM/DAB Splitters around, never used one as this is a DAB free zone!, do not use just a simple splitter as this will halve the available signal on each band... I think that the first questions a 1. What is the existing loft aerial (vertical, horizontal, dipole, groundplane, random piece of dangling wire etc)? 2. Have you tried connecting the existing FM feed (which presumably has a traditional Belling Lee connector) to the DAB F input (using an adapter)? If you already get good FM, and the DAB also seems good, then you may get away with a simple 2-way splitter (preferably a 'proper' 3.5dB splitter, and not a cheaper 6dB resistive job). If not, an even more-proper low-loss filtered splitter/diplexer would be better. [However, if you really do need a filtered job, signal levels must be rather marginal.] If you don't get good DAB using the existing FM, aerial, then you'll have to think about improving things - but only cross that bridge when you come to it. -- Ian |
FM/DAB
In message , RJH
writes On 30/07/2013 12:17, tony sayer wrote: In article , Gordon MacPherson gordon.macph scribeth thus I have a Cambridge azur 650T tuner. I have a single coaxial cable that at present feeds from a loft aerial (external is not possible) into the FM input via a coax connector. The DAB has an F type connector. I would like to be able to use both FM and DAB from the single cable. 1. If it is possible, what would be the most effective way of setting this up? 2. Is there an aerial that would support both FM and DAB? (I live in Wareham, Dorset - BH20 5BB) Thanks, Gordon Generally an FM vertical dipole, not that abortion known as a halo, works quite well on DAB in a lot of areas. You should get a very good signal from the Rowridge TX on the Isle of Wight. I believe that BBC DAB is from there and the commercial from Chillerton down in the same isle!.. Even if you used a 3 element Yagi I suspect there'd still be sufficient DAB signal as well as enhancing the FM ones.. I think that there are FM/DAB Splitters around, never used one as this is a DAB free zone!, do not use just a simple splitter as this will halve the available signal on each band... I was looking into this, and: http://www.aerialsandtv.com/fmanddab...fFM&DABAerials looks useful. Useful maybe, but I always worry a little when I see comments like this: "The round FM “Omni” type antennas do not perform as well as the half wave dipole and this reflects their design, which gives a theoretical minus 3 dBd gain figure. That's why we think they're crap and we don't stock them." There's nothing wrong with these omnidirectional 'halo' aerials provided the user knows what the performance is, and knows that he can tolerate the 3dB of signal loss compared with a straight halfwave dipole. But being horizontally polarised, they are probably pretty useless when it comes to the 'accidental' reception of vertically polarised DAB signals. -- Ian |
FM/DAB
One thing that everyone has missed is that DAB is vertically
polarised. Thankfully all FM transmissions in the UK are now of mixed polarisation (i.e. they have both horizontal and vertical components) so turning your FM aerial vertical (if necessary) will not be a problem (electronically - might be physically!) As others have said a simple single half-wave vertical VHF dipole is the best as (a) it is just about a full wave at DAB frequencies so will work albeit with a mismatch and (b) it is near enough omni-directional so will not limit you to your source Tx station. -- Woody harrogate three at ntlworld dot com |
FM/DAB
In article , Woody
wrote: One thing that everyone has missed is that DAB is vertically polarised. Thankfully all FM transmissions in the UK are now of mixed polarisation (i.e. they have both horizontal and vertical components) so turning your FM aerial vertical (if necessary) will not be a problem (electronically - might be physically!) You beat me to commenting on the polarisations. I suspect that having a VHF antenna 'work' for DAB may simply be using its coax as the DAB antenna because the actual antenna is a hopeless match at DAB frequencies. :-) That said, I just made a DAB antenna using two bits of wire taped to a wooden stick. (Flower support from the garden center.) 8-] Slainte, Jim -- Please use the address on the audiomisc page if you wish to email me. Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html Audio Misc http://www.audiomisc.co.uk/index.html |
FM/DAB
Gordon MacPherson wrote... The DAB has an F type connector. I would like to be able to use both FM and DAB from the single cable. 1. If it is possible, what would be the most effective way of setting this up? It depends on your existing signal level, if it is good then you could use a simple passive splitter but you may need to use a signal booster to compensate for the loss incurred in the splitter. I'm in a similar situation, in that our communal aerial system provides a single combined (very good) FM/DAB feed. I tried various ways of getting this to to my FM & DAB tuners including a couple of passive splitters and they were fine for DAB but degraded the FM signal too much compared to a direct connection. In the end I got one of these 1 in 2 out amplifiers http://www.philex.com/catalogue/prod...d=116&cat=1069 which works well for both DAB and FM. It has a variable gain control which allows you to fine tune things. Here are the results of using that on the end of a much derided FM halo. http://goo.gl/maps/sF9Yh -- UnsteadyKen |
FM/DAB
In message , Woody
writes One thing that everyone has missed is that DAB is vertically polarised. No we haven't. That's why I asked what the existing FM aerial was (but you've snipped it all). Thankfully all FM transmissions in the UK are now of mixed polarisation (i.e. they have both horizontal and vertical components) so turning your FM aerial vertical (if necessary) will not be a problem (electronically - might be physically!) As others have said a simple single half-wave vertical VHF dipole is the best as (a) it is just about a full wave at DAB frequencies so will work albeit with a mismatch and (b) it is near enough omni-directional so will not limit you to your source Tx station. If the existing FM aerial is horizontal, to get DAB it would be better if it could be turned vertical. It should still work well for FM. As you say, its length will be a complete impedance mismatch for DAB, but it might work well enough. If not, that's the time that the OP needs to think about doing things a bit 'more properly'. -- Ian |
FM/DAB
In message , Jim Lesurf
writes In article , Woody wrote: One thing that everyone has missed is that DAB is vertically polarised. Thankfully all FM transmissions in the UK are now of mixed polarisation (i.e. they have both horizontal and vertical components) so turning your FM aerial vertical (if necessary) will not be a problem (electronically - might be physically!) You beat me to commenting on the polarisations. I suspect that having a VHF antenna 'work' for DAB may simply be using its coax as the DAB antenna because the actual antenna is a hopeless match at DAB frequencies. :-) Aerial impedance mismatch doesn't cause pickup on the coax. However, if the receiver is getting a reasonable signal, it's possible that a lot of it isn't coming from the aerial, but is being picked up on the coax. That said, I just made a DAB antenna using two bits of wire taped to a wooden stick. (Flower support from the garden center.) 8-] Indeed, most true enthusiasts will have done something similar. Bamboo canes also play an important part in such experimentation. Wire coathangers (straightened, of course, and cut to size!) can also be used as aerial elements. Unfortunately, the OP hasn't come back yet to say what his present FM aerial consists of. -- Ian |
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