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Author Topic: Ireland  (Read 27675 times)

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Mark07

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Re: Ireland
« Reply #45 on: January 08, 2009, 07:32:36 PM »
External on the gable wall......Watson Radar extender with a pre-amp and Bias T

Sdoyle

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Re: Ireland
« Reply #46 on: January 08, 2009, 07:36:48 PM »
where can i get one of those?

S.

Mark07

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Re: Ireland
« Reply #47 on: January 08, 2009, 07:38:50 PM »
70 GBP from the UK for the antenna

besty

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Re: Ireland
« Reply #48 on: January 08, 2009, 07:50:07 PM »
£70 that's not including the pre amp and bias t?

robbieinderry

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Re: Ireland
« Reply #49 on: January 08, 2009, 08:13:58 PM »
hi denis i am in derry north west just got my airnav2009.
mybe pick your brains later,all the best.
from robbie
The name is robbie.
http://groups.yahoo.com/group/derryradiogroup/
Radio is hobby and one that can bring hours of enjoyment, build friendships and provide an escape from the trials of everyday life.

Mark07

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Re: Ireland
« Reply #50 on: January 08, 2009, 08:17:19 PM »
nope just the antenna.  I think the preamp and Bias -T, 12V adaptor etc all in is around 180 GBP

Mark07

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Re: Ireland
« Reply #51 on: January 08, 2009, 08:20:53 PM »
Hi Robbie,
Good to see another user in Ireland.  You should get good coverage across into Scotland from where you are.  I pick up the Ryanair flights into Derry on a regualr basis from my location both on Radar and Airband radio.

Cheers
Mark

Fenris

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Re: Ireland
« Reply #52 on: January 08, 2009, 08:24:52 PM »
£70 that's not including the pre amp and bias t?

Due to the low volume that the preamps and bias tees are made in (let's be generous in that view) and the weather sealing that the preamp needs, you are looking at about £155 extra for the ELAD units together. And add something for 12V power supply too, and about £25-30 for the coax and connectors, and it's not far short of £200 in total.

An ELAD pre-amp has a NF of about 0.9dB max, whereas the RB itself is probably about 2dB NF. A 10m run of Westflex 103 will increase that to about 3.5dB, whereas you are looking at about a total noise figure of 1.2dB for the case with the preamp. So, a 2.2dB worse NF translates directly to that much signal:noise reduction and thus a range reduction of 22.4%.

You can then decide if the benefit (and that's a theoretical calculation based on a clear take-off in all directions, a preamp does not get signals through a hill for instance) is worth the cost.

Yes, I should probably have put this in my RF Specifications thread, perhaps I will!

besty

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Re: Ireland
« Reply #53 on: January 08, 2009, 10:01:42 PM »
You lost me after the '£200 in total', but i got the idea a pre amp isn't going to work miracles.

Thanks for explaining for me.

Stuart

Fenris

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Re: Ireland
« Reply #54 on: January 08, 2009, 10:19:14 PM »
You lost me after the '£200 in total', but i got the idea a pre amp isn't going to work miracles.

Thanks for explaining for me.

Stuart

I was simply performing a cascaded noise figure calculation, based on my estimate (in the absence of confirmation) that the RB noise figure is 2-3dB. Essentially it means that the recoverable signal is reduced towards the thermal noise in the receiver, and hence is harder to recover the data.

A 3dB worsening is a halving in effective signal power, and range is proportional to the square root of power, so that 3dB is equal to root 2, or 1.414, then the reciprocal of that, 0.707, is the range ratio, so you lose 29.3% range.

Not trying to blind with science, but it's interesting to see whether theory and reality choose to agree with each other!

besty

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Re: Ireland
« Reply #55 on: January 08, 2009, 10:31:28 PM »
Cheers Brian

Mark07

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Re: Ireland
« Reply #56 on: January 09, 2009, 09:08:12 AM »
Lost me as well Brian but to simplify things for the non technical people like me here's what I did.

Have just turned on RB and have 22 flights 4 of which are not showing any 'tracking' data.  This is with Bias-T switched on and powering the pre-amp.

Have disconnected it and flights fell off to 17 flights 9 with no tracking data.

Re-connected and my flights instantly pulled in 28 flights 4 of which have no tracking data.  Also the furthest flight I was receiving with pre-amp swithced on was 207nm with it switched off 165nm.

Each time I do this there is a significant change in the number of flights which tells me that the pre-amp is certainly working well and having a significant impact on what I am seeing and tracking.

Also what I find interesting is that you talk about loss in the cable.  I am running 20 meters of coax from my antenna to where my desktop is located!

Am I missing something here!

AirNav Support

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Re: Ireland
« Reply #57 on: January 09, 2009, 09:20:24 AM »
Preamps do make a difference of improvnig your range for RadarBox.

Fenris we are software guys here so we don't fully understand what you have written either but your calculations do not set with reality.

Everybody who has bought the preamp kit from our site has had an improvement in range. Depending on location, some customers have picked up 30-60% more aircraft.
Contact Customer/Technical support via:
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rocket

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Re: Ireland
« Reply #58 on: January 09, 2009, 09:26:33 AM »
Hi All,

I'm watching this thread because it came up in our website referrer stats.

I often get asked about the mast-head pre amps, and whether I stock them - I don't! (Although I can supply if someone really really wants one, although they usually don't want it once I mention the extra cost of the bias-T)

I am not a great fan of pre-amps, I've never known one to be as selective as you would want, and also they can overload the front end of the receiver. Some people like them, some don't. "Horses for Courses" on this one.

So, putting the cat amongst the pigeons - what do I advise to increase reception on the RadarBox?

Firstly, the antenna mentioned already in this thread or if you want something slightly smaller then I recommend the Radrama antenna. Antenna should be up in in the clear and have as good a view of the sky as possible.

Next, the co-ax!
Short runs can be twin shielded RG8X mini-8 (below 10m) above that you want good quality RG213, Westflex or similar.

But, there are always losses with co-ax so my tip is to get your radarbox as close as possible (sheltered, not outside) to the antenna using a longer USB A-B lead for connecting to the PC (much cheaper than a pre-amp to recoup lost signals!)
Best wishes
Mark
Rocket Radio

Fenris

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Re: Ireland
« Reply #59 on: January 09, 2009, 09:48:18 AM »
Preamps do make a difference of improvnig your range for RadarBox.

Fenris we are software guys here so we don't fully understand what you have written either but your calculations do not set with reality.

Everybody who has bought the preamp kit from our site has had an improvement in range. Depending on location, some customers have picked up 30-60% more aircraft.

For reference, I'm an RF engineer with more than 25 years of experience, so the calculations are correct in terms of the theory.

However, there are other effects going on too, so what I have calculated is not the whole story, it is also necessary to know what the RB ADC/FPGA combination (the receiver back end) does in the presence of multi-path signals and in the presence of time-overlapping signals at different strengths. And its selectivity, the ability to reject other local signals on various other frequencies.

Perhaps I'll write something a little more detailed when I have time, as always no one is required to read it, it will be for information only.

What I will say is that improving the system noise figure by a couple of dB could, under some circumstances, create the increase in aircraft received you mention simply because the radiated pattern from an aircraft can sometimes lead to signal loss at less than the theoretical maximum range because of nulls aligned with the direction to the RB in question. A few dB in that case can make the difference between a low enough error rate to receive a complete message and missing that message. It's all about statistics, there are very few certainties involved. The same situation twice may result in successful reception on one occasion and not on the other.

That's why I was pointing out that it's up to the individual to decide if that £200 is worth spending, and that will depend on how much coax they need to run, and how cluttered their horizon is. There is naturally their perception involved too.

Did I say this wasn't easy? I'll say it again then - this isn't easy!