Pre-Amp Installation...any use installing it downstream by the box itself?

[CYYZGUY]

I know this has been discussed before, and unfortunately I am not able to install a pre-amp on mast head at my location due to no electrical.......

But is there any benefit at all, in installing a pre amp right before the radarbox itself?  I tend to get alot of hits on the fringe of my polar diagram and I was wondering if this would help.  I do have the Band Pass Filter installed as well cutting out most other RF and interference.  The fact that I am getting hits on the fringe of my polar diagram means a weak signal is coming through.....I was just hoping it would help somewhat.

thoughts?

Jason

[neroon79]

No, because you only can amplify signals, that are strong enough to be amplified. If the signal is already about to vanish into the noise, you won't have any benefits, as all amps will amplify the noise too.

[CoastGuardJon]

Hi Jason, exactly as Ingo says above , plus the extra connectors and circuitry will cause 1 - 3 dB LOSS!   So, no, no ue whatsoever!   Elsewhere on this site, you give the impression that you're looking at installing a new or another antenna - what's the problem with installing a pre-amp at the antenna;s base - power gets fed to it through a Bias-T arrangement, where it can do what it's intended to do - amplify signals received to overcome  the losses, a long co-ax run, can incur.   Concentrate your efforts (and investment!) in just getting an antenna up as high and clear a line of sight to the horizon as possible.

[CYYZGUY]

Hi Jon, thanks for the reply.  As you may or may not know, I already have my antenna installed higher then probably anyone else on this site at 35 Meters above the ground.  Unfortunately I have about 90 Feet of LMR 400 coax running down into my apartment.  I am just experimenting around with different ideas to tweak my reception a little bit more.

All advice and ideas are always welcome!

[SteveJ]

Generally preamps are installed at the antenna to help overcome cable loss. Unfortunately, by installing it at the box, those weak signals that you're trying to amplify have already been lost in the cable.

[neroon79]

Don't you have any electrical power source at your radarbox? Because usually these pre-amps getting their power over the coax cable using a power input T at the receivers end ( in this case the radarbox) of the cable.

[hofs]

Hello
i use 85 mtr of ecoflex 15 cable  and a pre amp just behind the aerial. There is no need for electricity because the pre amp on the top gets its power through the coax cable.
The pre amp power supply is installed just before the radarbox behind the computer where electricity  normally is no problem.
In the case of lightning or thunderstorm i can easily disconnect the aerial and shut of the power to the pre amp.
Fred

[CoastGuardJon]

There seems to be a little bit of confusion creeping in here, so let's try to clarify.   To get any worthwhile benefit from a pre-amp, it needs to be installed as close as possible to the antenna, ie on the mast head preferably.   A pre-amp requires a power supply.   It's power can be supplied directly, but usually more conveniently by being "squirted" up the co-ax from close to the receiver, either a radio or in this case a RadarBox.   To ensure that the power doesn't get "squirted" into the RB as well, involves a clever little device called a Bias-T, which sends the voltage up the co-ax, but not down into the receiver as this could burn out the front end.   A pre-amp can only boost a signal received by an antenna, to overcome losses in long lengths of co-ax.   A pre-amp will not make up for a crap antenna location or lack of transmitted signals.    If there's no signal, it cannot magic one up.  A pre-amp, being an electrical circuit with connectors and components, will cause "insertion" losses by being there, and also will create a small amount of electrical "noise" which is unwanted.  Height of antenna mounting site with clear line of sight is right!  Hope there's nothing I've omitted.  There endeth the last lesson!

[Col]

Hi

This is a very helpful thread as I know nothing about aerials but I have just been given the green light by the wife to get an external aerial fitted - I currently use the standard antenna on my windowsill. I haven't got exact measurements but I am guessing that I will need to use about 15-20m of co-ax to get to the RB. Assuming that I get decent grade coax my question is whether I would need a pre-amp? Is it the case that it will always improve matters or is there a chance that I will just pick up more noise? Or will I only know once I have the set up in place?

The reason I ask is that I will get someone in to install the aerial (as I don't intend getting on the roof!) so either I install it straight away or not at all so I am looking for some guidance.

Thanks

Colin

[Lou]

I`m in the opposite situation to CYYZGUY my aerial is only 43 feet above sealevel ( 14 metres ) I installed the Kinetics pre-amp kit last summer and have found it to have really improved my range and hit count. The pre-amp is installed 18" below the aerial this is then fed into the house by westflex, power is fed up the feeder by the supplied adapter ( no need for power at the aerial ), the interesting thing for me was that although the range improved the counts in my flights increased by about a third at the height of the holiday season. I live in London close to the Thames at Blackwall Reach right under the EGLC and EGLL flightpath and have Luton Stansted Gatwick and Southend within a 35 mile radius it is quite normal for me to have in excess of 300 hits in my flights on any summer weekend, hope this helps in your situation

[CoastGuardJon]

Hi Colin,short answer yes! If you can install the thicker and heavier Westflex type co-ax, you'd be able to get away without, but this cable is stiff and doesn't like tight bends.  If using RG58, I think you would benefit from a pre-amp.   Don't buy cheaper co-ax, copper is expensive and you get what you pay for.   Cheap co-ax = lower quality and quantity of copper, especially in the screening - the braided outer layer, which keeps out/reduces interference.   If you're in the UK, Nevada stock some good quality co-ax and connectors.   You can always add a pre-amp later if antenna is fairly easily accessible, and more than a couple of db loss with the length of cable used (this can be checked if you can connect lap-top and RB at antenna base whilst installing, compared with including any more than a few metres of co-ax.   HTH. CGJon

[Col]

Hi

I have just had my external aerial installed. I got the following kit from Waters and Stanton which included a pre-amp.

http://www.wsplc.com/acatalog/RADAR-COM-20_RADAR-EXTENDER_Antenna__A12-1090__BT-12__all_necessary_coax_leads_20m.html

It was mounted on a 10ft mast on my roof so I was hoping for an increase in returns compared to the standard aerial on my window sill and I wasn't disappointed. I have tall trees blocking reception to the South and West so I was not expecting much improvement from those directions but to the North and East I have a clear view.

Normally I would pick up approx 30-40 returns with a max of 50 at any time. Maximum range was about 110 miles if I was lucky. When I connected the RB to this new set up I immediately picked up 150 aircraft with a maximum range of 210 miles so quite an improvement. Still not much to the South or west but I will wait to see how the polar map builds over the next day or so to see whether there has been much change in these directions.

[CoastGuardJon]

Hi Col,
Thanks for keeping us posted, sounds as though the oulay has been well worth it!  Please keep us up to date and if poss. in a couple of weeks when polar diagram has fully stabilised (if you're on 24hrs) please post before and after installation polars.
Regards CGJon

[Col]

Hi Jon

As promised here are a before and after polar map from my setup. As you will see the basic profile of my polar map has not changed as I still have poor visibility to the South and West but very good to the East. The range has definitely been extended as I can now pick up aircraft over AMS. Also to the South where I could only manage about 20 mile range I can now pick up aircraft down on the South Coast. 

However, range is not the only improvement - previously I would average about 30-40 aircraft at a time with a max of about 70. I now average about 120-140 and I have had 200 being picked up. My daily log has risen from about 2,200 - 2,600 entries to over 5,000! I now am able to follow aircraft all the way to touchdown at Heathrow as well as about 500ft for Luton and 2,000ft for Stansted.

Obviously moving from using the standard aerial on my window sill to a roof mounted external set up has made a big difference and adding the pre-amp has added to that! Suffice to say that I am pleased with the outcome!

Cheers

Colin

[Runway 31]

Quite a difference Col, thanks for showing

Alan