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Old 7th Jul 2020, 12:59 am   #21
Skywave
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Arrow Re: FM signal boosting

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Originally Posted by Ted Kendall View Post
VHF propagation is line-of-sight for most purposes, so aerial height is the simplest way of getting more signal. That and accurate aiming, but I assume you've done that already.
In my experience at VHF, aerial height is the most dominant factor for long-distance reception with the amount of 'resonant metal' in the clear and accurate aiming being close seconds.

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Old 7th Jul 2020, 8:50 am   #22
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Default Re: FM signal boosting

Can I add a footnote to my previous statement. Following my posting last night I sat and listened to the recording in its entirety. Although initially the sound appears very good in places there are passages that did have an element of distortion, as if overloaded. It’s not the tape deck as I removed the booster out of the loop and went back to just the aerial and the Kudos. The result was much better, even though the signal level being received was lower. I think this is my compromise. The advice regarding quality over quantity appears to be correct. I will test out the alternative transmission sites as suggested and report back, if anyone is still interested.
Mike
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Old 7th Jul 2020, 9:12 am   #23
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Default Re: FM signal boosting

If you are in the service area of something closer, this should be worth a try - after all, the sound out of every transmitter is the same, given the PCM distribution network. Wrotham signal was rightly prized in the early days of stereo, because it had the best landlines from BH.
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Old 7th Jul 2020, 10:43 am   #24
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Default Re: FM signal boosting

You could also try inline attenuators if the problem (now) is too much signal. I've got a selection of vintage Belling Lee ones.

One more thing, I recently had a new FM aerial erected and the rigger said that the connection to old one was non existent. So, yes, I realise that it's hard to check but poorly made or non-existent connections are often a problem, especially once a few winters have had their wicked way.

Otherwise I agree with the general sentiment on here that you're doing well to get a decent signal at 75 miles. Excellent in fact.
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Old 7th Jul 2020, 10:53 am   #25
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Default Re: FM signal boosting

From looking at various service maps it does appear that the area south of Colchester has poor coverage. If the signal from Wrotham is clean then it may well be best to stick with that, even though it isn't very strong. I can't find anything that is obviously better. A low noise masthead amp on the mast may improve things a bit.
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Old 7th Jul 2020, 11:36 am   #26
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Default Re: FM signal boosting

Looking at the polar diagram of Wrotham it’s not true omni directional, luckily Tiptree appears to be nearly at the apex of one of the lobes, if you were further south the field strength would be less.
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Old 7th Jul 2020, 1:30 pm   #27
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Default Re: FM signal boosting

Maybe a bit off topic and naughty but FM rebroadcast units are very available some of these have a built in DAB receiver which I know the purest will frown upon heavy. But I am finding this as the only possible solution to the talks sport rubbish that appears to fill what’s left of the broadcast bands. I have been surprised at the quality of modulation produced on both am and Fm using my signal generator and IPAD as the source. If kept to minimum power levels and with careful frequency selection could be an option. Saying that my music appreciation is appalling anything over 3khz is a waste of bandwidth.
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Old 7th Jul 2020, 1:38 pm   #28
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Default Re: FM signal boosting

Even the very cheap FM microtransmitters intended for use in cars do produce a very clean signal, but it's a bit pointless to use an internet streamer or other digital source to drive a modulator rather than just hooking the streamer up to the hifi system directly. There will inevitably be some degradation.
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Old 7th Jul 2020, 3:17 pm   #29
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Default Re: FM signal boosting

Christian's dropped us all right in it.

It's time to question what the root purpose is.

With a stereo audio frequency signal pair being sent to a small transmitter and then received in a tuner and played through a hifi system, you have a system for showing the tuner working as it would have been used, back in the day and in a good signal area. This might be the interest in it. You could show a visitor each of several tuners, classics in their own era, working on real, current programme material. You'd be able to hear differences between the different tuners, but the quality reaching the ears with the best tuners would not be up to the standard the same tuner would have produced in its era, in a good signal area. Certainly not with DAB, and to a lesser extent with an internet or digital video broadcast source. DVB-T quality is better than DAB.

If, alternatively, the aim is to listen to the music in the best possible quality, then you can say that extra stages and processes cannot be making what existed earlier up the chain any better, so you connect the audio from your DAB/Internet or other source direct to the hifi amplifier and switch the tuner off.

I have two good quality tuners. One Sony 'ES' model with a few tricks in it, and a carefully restored Revox that used to belong to the BBC as either one of their monitoring receivers, or as part of a re-broadcast backup. Not a bad credential for a tuner!

What they serve to do for me is to allow me to hear just how awful is the processing applied to all stations except Radio 3.

They're only turned on when there is some content I particularly want to hear, or Radio 3 when I want to hear something different.

They are nice objects to have and things of engineering interest in their own right, but I may be in the position of someone with a couple of racing cars in his garage, but no access to a racing circuit.

Whether or not this makes sense is a matter of opinion, but it's my choice and my freedom.

David
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Old 7th Jul 2020, 3:46 pm   #30
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Default Re: FM signal boosting

I still prefer decent FM stereo to any other broadcast source - for one thing, it doesn't drop out the way online does and for another it hasn't the compromises imposed by the data rate of DAB as she is spoke.
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Old 7th Jul 2020, 3:56 pm   #31
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Default Re: FM signal boosting

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Originally Posted by Linnovice View Post
Seriously, I recorded the R3 concert this evening using my Kudos tuner with nothing else connected to the booster. The quality is extremely good so perhaps that is the answer. I can’t say hand on heart that I have ever been overly impressed with the Troughline. I’ve always likened it to what my mum would say about the radiogram in the fifties. “It’s a smashing bit of furniture and has a lovely tone”.
I suspect you have answered your own query here. The Troughline is of an earlier time and place. Pension time, comes to us all eventually.
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Old 7th Jul 2020, 7:27 pm   #32
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Default Re: FM signal boosting

I'm wondering what antenna you're using, and whether it is polarised correctly to receive your preferred transmitter.

In times-past (1970s) I used a FUBA UKA8 with a rotator - it was horizontally-polarised. These days most FM transmitters are either slant-polarised (the main BBC/commercial stations) or vertically-polarised [the rather-more-listenworthy licence-free stations with transmitters on top of tower-blocks].

Choose your polarisation according to your taste - but always remember that directional antennas provide 'free' gain - which comes without amplifier-noise, and can help exclude 'multipath' background-twitternoises off the back of the beam.
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Old 7th Jul 2020, 7:53 pm   #33
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Default Re: FM signal boosting

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Originally Posted by G6Tanuki View Post
I'm wondering what antenna you're using, and whether it is polarised correctly to receive your preferred transmitter.
From the BBC doc in post #8.for the upgraded Wrotham transmitting aerial which I understand is still in use.
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Old 8th Jul 2020, 9:18 pm   #34
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Default Re: FM signal boosting

Line of sight the distance from Wrotham to Tiptree is 40 miles, not 75 miles. A three or five element horizontally polarised Yagi antenna should give you a very strong and multipath free signal, the output of Wrotham for R3 on 91.3mc/s is 240kW!
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Old 8th Jul 2020, 9:27 pm   #35
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Default Re: FM signal boosting

40 miles is much more viable with an outdoor aerial, but the signal still won't be 'very strong'.
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Old 8th Jul 2020, 9:32 pm   #36
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Default Re: FM signal boosting

It's a similar distance (37 miles) from Wrotham to where I live in Eastbourne, I am at sea level and get a signal of over 1mV (60dBuV) on my calibrated Sony ST-SB920 tuner using a 3 element yagi in the loft.
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Old 8th Jul 2020, 10:05 pm   #37
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Default Re: FM signal boosting

I have a five element yagi horizontally orientated. Very comfortable for the pigeons apparently.

As previously advised, I think I’ve found my answer to the question. Although according to the handbook for the Kudos the signal strength should be in excess of 70% to enable ‘cd quality’ reception. I’ll resign myself to the 64% as indicated. The quality is extremely good in comparison to my other tuners and perfectly acceptable. I’ll put the Troughline at the end of the queue on Thursdays at the Post Office 😎
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Old 8th Jul 2020, 10:36 pm   #38
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Default Re: FM signal boosting

Quote:
Originally Posted by Radio Wrangler View Post
Christian's dropped us all right in it.

It's time to question what the root purpose is.

With a stereo audio frequency signal pair being sent to a small transmitter and then received in a tuner and played through a hifi system, you have a system for showing the tuner working as it would have been used, back in the day and in a good signal area. This might be the interest in it. You could show a visitor each of several tuners, classics in their own era, working on real, current programme material. You'd be able to hear differences between the different tuners, but the quality reaching the ears with the best tuners would not be up to the standard the same tuner would have produced in its era, in a good signal area. Certainly not with DAB, and to a lesser extent with an internet or digital video broadcast source. DVB-T quality is better than DAB.
If, alternatively, the aim is to listen to the music in the best possible quality, then you can say that extra stages and processes cannot be making what existed earlier up the chain any better, so you connect the audio from your DAB/Internet or other source direct to the hifi amplifier and switch the tuner off.

I have two good quality tuners. One Sony 'ES' model with a few tricks in it, and a carefully restored Revox that used to belong to the BBC as either one of their monitoring receivers, or as part of a re-broadcast backup. Not a bad credential for a tuner!

What they serve to do for me is to allow me to hear just how awful is the processing applied to all stations except Radio 3.

They're only turned on when there is some content I particularly want to hear, or Radio 3 when I want to hear something different.

They are nice objects to have and things of engineering interest in their own right, but I may be in the position of someone with a couple of racing cars in his garage, but no access to a racing circuit.

Whether or not this makes sense is a matter of opinion, but it's my choice and my freedom.

David
Good points David.
I'm in the unfortunate situation of living in a shadow area from the local BBC transmitter at Caldbeck. Our house in the Eden valley is situated nearer to the valley bottom and on the "Wrong side" so that no Aerial can give me a clean and strong signal. I'm using a 17 element!!!!!!! Ron Smith Galaxie aerial, professionally installed and its still not able to get a clean signal. Various reasons including multipath.
Had we been able to get the bungalow we were after originally at the top of the village, we'd get a really good clean line of sight, at the crest of the hill I can see the lights on the mast. That's the way the biscuit crumbles.
Anyway given my interest in radio for its own sake, I quite like the idea of being able to rebroadcast good quality source material to my collection of FM tuners including a couple of troughlines, which I think have an excellent sound quality but they do need a very good clean signal.
I did wonder about repurposing one of those Pure DAB car adaptors, I can lay hands on one I used to use in the car. line input as well as DAB, ironically we have a good DAB signal from the transmitter in Penrith, the BBC didn't see fit to put an FM repeater there and no surprises really.

As to sound quality, I can get the Hi Res BBC feed from the internet and feed it into the DAC on the Hi Fi, we have amazing fibre broadband out in the sticks! Very little if any dropouts and as good an audio feed as the BBC gets on R3.
But it doesn't have the romance of FM and I cant describe it but I feel the actual sound quality on FM, given that its from a fairly basic digital feed has something that doesn't set my ears on edge. Its probably my imagination.

Ho Hum I did wonder if its worth trying to rotate "Jodrell bank" as the wife calls it towards Pontop Pike as I can just about get a signal from there with the aerial pointed away from it and hope the pennines haven't blocked too much. or too much multipath reflections.

A.
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Old 8th Jul 2020, 11:46 pm   #39
Ted Kendall
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Default Re: FM signal boosting

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Originally Posted by bikerhifinut View Post
I cant describe it but I feel the actual sound quality on FM, given that its from a fairly basic digital feed has something that doesn't set my ears on edge. Its probably my imagination.
Give me straight PCM, albeit companded, any day rather than the data rate chomping that goes on elsewhere. There's nothing imaginary about DAB artefacts.
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Old 9th Jul 2020, 5:45 am   #40
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Default Re: FM signal boosting

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Originally Posted by paulsherwin View Post
75 miles is a very big distance for FM, even with a good external aerial and a big transmitter.
I've just done a quick calculation, that's 120km.

The Life FM Mid Dome site is 110km from here, 33 dBW (around 2 kW) EIRP and I'm getting a pretty good signal here from a 3 element yagi, cut down from our old band I/III TV aerial. It's ok around town in a car as well, but a bit of fade sometimes behind tall buildings.

Reception on portable radios can be a little hit and miss but it still works.

I suspect the difference is that Mid Dome is 1478m ASL and a clear line of sight.
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