Aerial for new Denon DM41DAB

[Andrew]

I still suspect that the Rowridge transmitter has something wrong with it. I can get R4 FM downstairs on the south side of the house, on my £5 Charity shop Sony portable with its telescopic aerial at an angle of about 30 degrees off vertical, while upstairs my 2006 Onkyo CR515DAb unit , conected to a

4 element horizontal FM aerial in the loft struggles to get a decent stereo reception.

I am planning to take the Onkyo the local BHF charity shop, so I manhandled the Wharfedale Linton 2's out of the loft where they have been since 2006 to include them in the gift. I bought from a neighbour in 1978, already 2nd hand.

They have been wrapped in plastic sheeting to protect from winter humidity. I removed the fronts and the rubber surround of the drivers is still perfect, while the tweeters have some sort of rubbery squishy covering, also ok, no sign of sticky gooey degradation.

My multimeter showed a reading of 6.6 ohms and 6.8 ohms, although I thought they were supposed to be 8 ohms.

Annoyingly, after connecting up to the Onkyo and tuning in to Scala, they sounded great, even at 112K bps. Maybe I'll keep the Lintons and just give the Onkyo to the BHF.

Without carting them up to Richer Sounds in Guildford and asking nicely if I could compare them with modern (compact?) speakers, it's difficult to know if there is any advantage in spending £++ on something that is just the same.

[Chris Hogg]

Resistance ain't necessarily impedance.

[The Natural Philosopher]

Tht is close enough!

Aerials are made to suit both!

[Chris Green]

Absolutely! The resistance measurements sound about right to me.

[Dave Plowman (News)]

I got a DAB car radio ages ago. Has separate FM/AM and DAB aerial inputs. The existing telescopic wing FM/AM aerial was useless on DAB - even with the correct adaptor (from Ebay) As was the DAB screen aerial supplied with the radio. Only when I paid rather a lot for an active DAB/FM/AM aerial (with separate downleads) did DAB work as it should.

[charles]

what is your roof coverd with?

8 ohm impedance - not resistance.

[Bill Wright]

Stop digging. Bill

[Bill Wright]

Channel 2 for instance, probably about 5ft or a bit less. One will be a bit longer than the other.

Bill

[Bill Wright]

Resistance is useless.

Bill

[jrwalliker]

Which is surprising, because the coax running through the middle of one of the elements actually creates a balun. Look up "sleeve dipole".

John

[stephenten]

*big grin*

Thank you, John... :-)

It also allowed me to attach the bottom of the 40 mm white waste pipe to the top of my aluminium aerial pole.

Thus, it was obstruction free and metal free space around the *entire* FM aerial... So effectively truly Omnidirectional.

There is a metal free gap of about 400 mm from the top of the aluminium pole and the bottom of the copper tube....

I chose white waste pipe instead of black as the latter has carbon black in it, which would affect aerial performance..

And I chose PVC white waste pipe rather than ABS for better weather resistance.

With it, I receive FM stations from the following transmitters here in Northampton:

Silverstone Sutton Coldfield Bow brickhill Northampton Oxford Peterborough Sandy Heath Irchester (Wellingborough) Farthinghoe (Banbury) Zouches Farm Wrotham Geddington Copt Oak

So that is 5 lots of BBC R1, R2, R3, R4, 4 lots of Classic FM, BBC OXford, BBC West Mids, 5 lots of Heart, BBC 3 Counties, BBC Northampton, BBC Leicester, Capital FM, GEM 106, Banbury, Inspa FM and Radio Silverstone

So still get BBC National Radio if several FM transmitters go down with engineering faults.... :-)

That is on top of all the radio on DAB, Freeview and Freesat.....

My DAB aerial is pointed towards Zouches Farm and gets the BBC, Digital 1, SDL, DRG, Switch, CE ensembles from there and the 3 local ensembles too (HBB, NOrthants & Oxford) which results in well over 100 DAB radio stations.

[Andrew]

Must have taken you days to select which ones needed a preset though ? :-).

Took me a couple of hours to find all the rowridge frequencies and ignore the wrotham ones (180 degrees away 'behind' my horizontal FM aerial in the loft). The DM41DAB doesn't seem to allow you to enter a known frequency on the remote, but simply use the TUNE+/- buttons to skip up and down the frequencies.

[Andrew]

especially at absolute zero :-)

[Andrew]

Marley 'Modern' concrete interlocking tiles. Originally a sort of salmon pink with a smooth surface, but now all the houses just look matt grey (and moss).

But Radio 1,2,3 and Classic FM are perfect. Only R4 FM is hissy

<snip>

[Andrew]

Pretty useless for AM too, I suspect. And being so close to the engine, DAB stood no chance either.

I always assumed that is why modern car aerials are at the back of the car, as far away from the engine as possible.

[Dave Plowman (News)]

The 8 ohm impedance given is nominal. It will vary with frequency. And I'd hope the DC figure you've given ain't tested in practice. ;-)

[Andrew]

Well I connected them up to the Onkyo and used the supplied DAB 'aerial' taped to a bedroom window facing North and the first program it picked up was Scala radio, which actually sounded quite good, even though the display showed '112 bps stereo'.

[Martin Brown]

If you were transmitting then load impedance matching is much more important but you can get away with murder if you are only receiving. I made a DAB dipole which works well enough apart from in very heavy rain when DAB radio invariably dissolves into boiling mud. I did balun it but the improvement in signal strength in band wasn't that impressive.

I have pretty much given up on DAB radio from a listening point of view. I would much rather have internet streaming at a sensible bit rate.

[Dave Plowman (News)]

Front wing mount was perhaps the most common position in AM only days. As close to the radio as possible.

A small roof aerial is likely cheaper and less subject to vandalism than a wing type?

[Dave Plowman (News)]

Odd. With a decent DAB aerial on the car - even with a radio which is now pretty old (no USB etc inputs) - the DAB reception round the SE is way superior to FM.

One journey I do quite frequently is SW London to Bognor - the pretty way. R4 FM on both cars is frequently unusable. DAB, rock solid. Same in central London round tall buildings.