FM aerials. Talk to me

[Mike Reed]

Maybe look for your nearest Transmitting station (I.O.W., someone said), work out approx. crow's miles and any intervening nasty topography (mountains in Hampshire????).. One can always achieve 'adequate' signal with bits of string, loft-mounted arrays etc. but there's only one sure way to achieve optimum deflection outside of big cities/transX close radius coverage. That is to align an external aerial mounted as high as you can. Boosters add noise.

It's a funny thing, but the difference, on a good tuner/system, between getting an adequate signal and a good one is clearly heard in s.q. terms. Omni-directional is certainly not the way to go for good FM reception. Just my two-pennyworth and I revel in what R3 (and others to a lesser extent) can put out in holographic images and realism.

 

[guydarryl]

Got what I hope is a minty grey FM4 incoming. Absolutely pointless, I suspect the old Denon I’ve got under the sofa here is probably better overall but I’ve always had a soft spot for them.

I used to own one, sold it and regretted it. Just like the feel and design.

Anyway it’ll need an antenna.

I’d probably prefer to not put a full roof one up, access this side isn’t great.

Any opinions as to how I’ll get on- I’m in a high spot at Winchester (SO22 6NX) and having a quick look there seems to be a big transmitter in Oxford with smaller ones in Basingstoke and Salisbury.

I’d be happy to do a dipole on the wall outside of I could do a loft mounted directional aerial?

Opinions welcomed.

Very similar situation to yourself - I recently bought an FM4 (love the look of it and curious), it has replaced a Denon 260L which I was very happy with.
despite some web comments about the poor selectivity of the FM4, I don’t think that is relevant in the UK/my situation. It has enough presets for what is available from my local transmitter and I am not fussed about DXing.

i am surprised how much better it sounds than my old Denon and am very pleased with the purchase.

My local transmitter is situated in Bradfield (Essex), but I live possibly six or seven miles away across the river Stour in a village in Suffolk - so the only obstructions that i can see are my wood burner chimney and a silver Birch in my garden.
i installed the aerials myself and I haven’t noticed and degradation in signal strength going from the Denon to the FM4.
Spoken word sounds more like a person with the FM4 and there is more “body”/“fullness” to R2 on music - strange that I am noticing more bass, as i play it through a pair of old Rega Kytes in my kitchen/dining room. R3 seems to be broadcast at greater signal strength than other stations (10 on incators !).



cant remember make/type of aerial, but pretty simple one, which i did use in my loft for several years.

 

[gez]

It can’t be that bad a signal area, Jim. A 12” piece of wire stuck in the back of the 75 Ω socket in the Denon gave stereo (just ) R3

I don’t think the FM4 will be as good as that?

What are their senstivity specs? Tuners usually specifiy the input senstitivity. Whichever has the lowest figure will be the one that'd be able to pick up the faintest stations with any given aerial.

Found the spec for the FM4: 25uV for Stereo

QUAD FM4 Tuner

 

[Eoin]

The denon TU-260 is stated as ‘0.9uV’
The quad has either ‘1.0uV at 30db quieting’ or ‘2.6uV at 50db quieting’

So, I’m not sure if that’s not comparing apples with bananas.

 

[Mr J]

FYI FM transmitter info at http://tx.mb21.co.uk/mapsys/fm/
Rowridge is the primary transmitter for this area and it's the one I use. Salisbury is a relay of this so you might want to try that as well (line of sight might be better from your location?)

I used this site to calculate the bearing and to position the aerial - https://www.mobilefish.com/services/distance_calculator/distance_calculator.php

Hope this helps.

 

[Eoin]

It does.

Looks like the antenna might be solved, thanks to Mr J.

Loft mouthing kit next and some cable.

 

[rhgbristol]

Also this is a rare undamaged by battery one, looks perfectly clean.

Anyone remember what the battery type needed is?

4.8v 100mAh Varta Mempac from memory.

If you are replacing the battery, you’d be wise to get the plastic container mod that Quad used to supply with replacement batteries.
It’s like a little plastic bathtub, that prevented future batteries from spilling their guts onto the PCB.

If you can’t get this, you could improvise with a small plastic project box to contain the battery, and wire it to the PCB using some small flyleads.

 

[davidsrsb]

The Quad tuners have normal sensitivities, not much worse than the best Japanese models.

 

[LostAtSea]

Don't buy a 'halo' antenna.

Oh. I did, but haven't used it yet. Are they... bad?

 

[Eoin]

4.8v 100mAh Varta Mempac from memory.

If you are replacing the battery, you’d be wise to get the plastic container mod that Quad used to supply with replacement batteries.
It’s like a little plastic bathtub, that prevented future batteries from spilling their guts onto the PCB.

If you can’t get this, you could improvise with a small plastic project box to contain the battery, and wire it to the PCB using some small flyleads.

Is this the fella?

 

[cobbers]

If you are in a high strength area and want to avoid faff then start by trying a simple dipole on your wall, up at 'picture rail' level. That did work work OK here. However I now use:

When I lived in the Birmingham area and was about 25miles from Sutton Coldfield in a 1st floor apartment a dipole worked perfectly - in fact the signal was too strong for my Harman TU9400 tuner and had to attenuate it.

 

[gintonic]

Ask here https://www.aerialsandtv.com/online-shop

we have dipole mounted in the loft, works brilliantly

 

[Jim Audiomisc]

The denon TU-260 is stated as ‘0.9uV’
The quad has either ‘1.0uV at 30db quieting’ or ‘2.6uV at 50db quieting’

So, I’m not sure if that’s not comparing apples with bananas.

Beware of bench measured 'sensitivities'. If they used a bench sig gen via a cable they will avoid real-world 'sky noise' which is present as soon as you point a real antenna at the great outdoors. That noise - particularly in or near a town/city can be *very* high. Thus in real use an antenna with high gain and a tuner with modest 'sensitivity' can be better than using a bit of wet string with a 'very sensitive' tuner!

 

[Jim Audiomisc]

Oh. I did, but haven't used it yet. Are they... bad?

See my comment about sky noise and note that their only 'advantage' is that you don't have to really know the direction to the TX. Low gain and accept garbage from all round you. Installers love them because a chimp can be eimployed to fit them as zero skill or time is needed. 8-]

Mathematicans can compare them to being as close as you can get to "You can't comb a hairy snooker ball smooth!" 8-}

 

[Jim Audiomisc]

Ask here https://www.aerialsandtv.com/online-shop

we have dipole mounted in the loft, works brilliantly

To me, its a sensible step to experiment first with a simple dipole in the room, and then if convenient in the loft. Can work fine and defeats a salesman telling you you *need* something big and costly on the roof.

 

[davidsrsb]

I used to use a Tandy 6 element in the UK.
There is little real evidence that the big Ron Smith designs really give much more gain. Nobody has ever shown any proper measurement or simulation. They do look impressive, though, but huge wind loading.

 

[Eoin]

Here’s a copy n paste of a Galaxie 14 antenna spec

Frequency	88	90	92	94	96	98	100	102	104	107	(MHz)
Gain	14.3	14.4	14.5	14.6	14.7	14.5	14.4	14.3	14.2	14.1	(dB)

Acceptance angle	55 Deg	Height	33"
Front to Back Ratio (98MHz)	31.2 dB	Width	68"(max.)
Windload @ 100mph	43 lbs	Length	44"

 

[davidsrsb]

That table doesn't say dBd or dBi, which are 2.15 dB different, so I suspect dBi.
My old 6 element can theoretically reach 8.5 dBd or 10.5 dBi. In practice 88 MHz to 108 MHz requires some detuning and a little loss of gain. Piling on extra elements, especially in a stacked way like the Ron Smiths is very unlikely to give the required bandwidth.

 

[Mike Reed]

Thus in real use an antenna with high gain and a tuner with modest 'sensitivity' can be better than using a bit of wet string with a 'very sensitive' tuner!

I'd substitute 'can' with 'would', Jim. I believe that in tuner design, higher sensitivity can be (is?????) at the cost of s.q. as these parameters are a trade-off. A good example, I s'pose, is the NAT 01 (and lesser siblings) which is quite insensitive but supposedly better quality as a consequence. I know from experience that wet string and Naim tuners are not bedfellows !

Here’s a copy n paste of a Galaxie 14 antenna spec

The G14 windload is 43 lbs but my G23 is quoted at 72 dBs. This from the R.S. handbook. Misprint or is there a correlation? Can't believe that my G23 survived for 9 years atop of a 3' rotator mast atop a 12' scaffolding pole on the highest of 5 chimneys above a roof 50' above the road looking out to the channel. Having said that, it was the 12 mast which was virtually worn through when I took it down; don't think it would've lasted another year !

 

[Jim Audiomisc]

I'd substitute 'can' with 'would', Jim. I believe that in tuner design, higher sensitivity can be (is?????) at the cost of s.q. as these parameters are a trade-off. A good example, I s'pose, is the NAT 01 (and lesser siblings) which is quite insensitive but supposedly better quality as a consequence. I know from experience that wet string and Naim tuners are not bedfellows !

The G14 windload is 43 lbs but my G23 is quoted at 72 dBs. This from the R.S. handbook. Misprint or is there a correlation? Can't believe that my G23 survived for 9 years atop of a 3' rotator mast atop a 12' scaffolding pole on the highest of 5 chimneys above a roof 50' above the road looking out to the channel. Having said that, it was the 12 mast which was virtually worn through when I took it down; don't think it would've lasted another year !

No idea what "72dBs" is supposed to mean, off-hand. No real dBi would come out like this for a passive antenna unless you meant Jodrell Bank! 8-]