jimi
Well-known member
I know it sounds a daft question but would two reflectors be more effective than one? I ask because I've managed to inherit a second Firdnell & don't know whether to keep it or sell it!
Radar Refector(s)
- Thread starter jimi
- Start date
ParaHandy
Active member
Give it a (gentle) shake and if it rattles, bin it - the reflectors have collapsed.
Can't see much point in having two of them, better off having one good one.
Can't see much point in having two of them, better off having one good one.
rogerroger
New member
Twister_Ken
Well-known member
weight aloft
Don't put more weight up high than you have to, it decreases stability. If one r/r does the job, why hoist a second?
Don't put more weight up high than you have to, it decreases stability. If one r/r does the job, why hoist a second?
VMALLOWS
New member
I would think so. I hoist mine on the spreader, so what about one each side, each angled say 20 degrees from vertical. (outwards/inwards?). Someone will suggest an optimum angle I'm sure (22.5 deg, 45.0 deg??) ; however I think if we're talking of reflectors 'swinging in the wind' then more can only be better.
chrisc
New member
seem to remember an article about possibility of two cancelling
each other out . Or even one cancelling out the boats natural
reflection if the wavelengths happened to be same /but offset
by one wavelength . was this in YBW about 2 years ago ?
sorry ..... .just a jolly thought in this festive season.
each other out . Or even one cancelling out the boats natural
reflection if the wavelengths happened to be same /but offset
by one wavelength . was this in YBW about 2 years ago ?
sorry ..... .just a jolly thought in this festive season.
G
Guest
Guest
I remember the dutch magazine "waterkampioen" doing a similar test to the one mentioned in yw. Result was that more was most definitely less! Two or more radar reflectors resulted in a smaller echo because one reflector cancels out the other. I'd just stick to one radar reflector you know is good.
Boatman
New member
Two can cancel each other out, so sell it and enjoy an extra good Christmas
SimonD
Active member
How much are you asking?!
vyv_cox
Well-known member
It would be reassuring to know than any of them work, which recent PBO studies seem to deny. One of my calls at London Boat show will be to look at the new one (seen advertised in the RYA magazine) that seems to perform better than most.
Boatman
New member
Which one are you looking at? I would be interested to see and maybe do some tests.
ParaHandy
Active member
Did once ask a passing ferry (CalMac - much more obliging than P&O) if he could "see" me on his radar and was delighted that he could...so some do work.
Nevertheless, I fitted a radar set myself - just in case.
Nevertheless, I fitted a radar set myself - just in case.
vyv_cox
Well-known member
New Radar Reflector
It's called an Echomax 230. Designed by John Firth, DERA tested 1 Nov 2001. Apparently installed on various buoys around UK coast. Contact is echomaxsales@aol.com. If what the advert says is true it is pretty good. But they would say that wouldn't they?
I would welcome any test results you can provide. Do you have access to DERA results?
It's called an Echomax 230. Designed by John Firth, DERA tested 1 Nov 2001. Apparently installed on various buoys around UK coast. Contact is echomaxsales@aol.com. If what the advert says is true it is pretty good. But they would say that wouldn't they?
I would welcome any test results you can provide. Do you have access to DERA results?
Boatman
New member
Re: New Radar Reflector
No access to DERA results I wonder if the company would release them (if the unit is so good) I was planning to try testing it myself along with a few mates, have done this type of thing before and wasn't too impressed with some of the results. I have to admit the testing wasn't exactly sicentific but I felt it was better than nothing. One thing that was clear was that the more you spent the worse the return signal got. The bin liner full of tin foil got the best return.
No access to DERA results I wonder if the company would release them (if the unit is so good) I was planning to try testing it myself along with a few mates, have done this type of thing before and wasn't too impressed with some of the results. I have to admit the testing wasn't exactly sicentific but I felt it was better than nothing. One thing that was clear was that the more you spent the worse the return signal got. The bin liner full of tin foil got the best return.
rogerroger
New member
I'm not pretending I know the first thing about radar or the reflectors - but how could 2 possibly cancel each other out?
Surely they work on the premise that the angled metal will send a signal back from a wider range of angles - how could this be affected by the presence of another one ? Surely by that logic a huge container ship would send back a very small signal due to the many different heights / types of metalic surfaces ?
Roger Holden
www.first-magnitude.co.uk
Surely they work on the premise that the angled metal will send a signal back from a wider range of angles - how could this be affected by the presence of another one ? Surely by that logic a huge container ship would send back a very small signal due to the many different heights / types of metalic surfaces ?
Roger Holden
www.first-magnitude.co.uk
Bergman
New member
I really don't follow the logic of this.
US Government spend mega mega bucks on stealth technology. All they needed to do was hang 2 reflectors on aeroplane and it disappears from radar.
Can't be right.
Cancellation can occur between 2 or more aerials (which is what a reflector is) but only in specific direction. Thats how most directional aerials work. Relative phase between 2 signals - additive in one direction subtractive in other.
This does involve maintaining very very precise distance between 2 aerials.
Look at the aerial on a lifeboat - 4 vertical antenna arranged in a square. This gives a directional "fix" on a received signal using this principle.
Have 1 fixed and other swinging about should provide stronger reflection. Theoretically a 3db increase in received signal.
US Government spend mega mega bucks on stealth technology. All they needed to do was hang 2 reflectors on aeroplane and it disappears from radar.
Can't be right.
Cancellation can occur between 2 or more aerials (which is what a reflector is) but only in specific direction. Thats how most directional aerials work. Relative phase between 2 signals - additive in one direction subtractive in other.
This does involve maintaining very very precise distance between 2 aerials.
Look at the aerial on a lifeboat - 4 vertical antenna arranged in a square. This gives a directional "fix" on a received signal using this principle.
Have 1 fixed and other swinging about should provide stronger reflection. Theoretically a 3db increase in received signal.
VMALLOWS
New member
That's precisely why my post said 'swinging reflectors'. In order to cancel each other out both reflectors would have to be very precisely aligned in anti-phase. In reality I'm certain the effect would be to minimise 'blind spots' in the reflection, and sometimes enhance the signal.
ean_p
Well-known member
Surely the reason that rdf ariels work is that the induced(into the ariel)voltage when recieveing the same signal equals the same and hence has no bias either way....thats a totaly different concept to a plastic box of tin foil 'bouncing' a radio wave back to its source.....a reflector is not in any sense an ariel.....a more similar equivilent would be to say that an echo sounder receiving a signsal from a collection of rocks on the sew bed would show non of them because the signals would cancel each other out!!!!!....really.......well we do have a problem don't we.........
G
Guest
Guest
Make that "one reflector CAN cancel out the other". This does not lead to you disappearing of the screen completely, it just makes the blip smaller. Possibly so small that you will be filtered out with the clutter! Why would you want two reflectors anyway, isn't one decent one enough?
Bergman
New member
No
Sorry
Fraid you're wrong
A reflector IS an aerial.
Remember "window"
cut to half wavelength of radar signal.
Signal from radar induces voltage in reflector which then acts as an aerial and effectively re-transmits signal.
A conventional aerial takes power from transmitter through a piece of wire (feeder) a reflector takes power from transmitter "over the air" much more loss than feeder otherwise no different.
A UHF TV aerial has lots of elements, but only one connected to TV. All others receive signal and by virtue of phase and spacing make the connected element receive more of received signal from a particular direction by same process.
If worked like bottom of sea to echo sounder you wouldn't need reflector - all of boat would work to "bounce" signal back.
RDF aerials work by comparing the phase of incoming signal received in 4 aerials arranged in a quarter wave square. Measurement of phase difference between aerials and lots of hard sums gives direction from which signal is coming.
Your ears work on similar principle - detect phase difference between left and right ears gives direction from which sound comes. Thats why phasing is important in stereo reception.
Sorry
Fraid you're wrong
A reflector IS an aerial.
Remember "window"
cut to half wavelength of radar signal.
Signal from radar induces voltage in reflector which then acts as an aerial and effectively re-transmits signal.
A conventional aerial takes power from transmitter through a piece of wire (feeder) a reflector takes power from transmitter "over the air" much more loss than feeder otherwise no different.
A UHF TV aerial has lots of elements, but only one connected to TV. All others receive signal and by virtue of phase and spacing make the connected element receive more of received signal from a particular direction by same process.
If worked like bottom of sea to echo sounder you wouldn't need reflector - all of boat would work to "bounce" signal back.
RDF aerials work by comparing the phase of incoming signal received in 4 aerials arranged in a quarter wave square. Measurement of phase difference between aerials and lots of hard sums gives direction from which signal is coming.
Your ears work on similar principle - detect phase difference between left and right ears gives direction from which sound comes. Thats why phasing is important in stereo reception.
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