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Re-Radiating Antenna's

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Hi folks


I have just taken delivery of a Re-Radiating antenna.. and on first use.. Recievin antenna outside (not at the best angle, it should be horizontal)and the Transmmiting antenna on my desk things are looking good.


Just to give you some idea, here are a couple of piccies.


Ant off http://www.staff.ncl.ac.uk/ian.paterson/ante%20off


Ant on


I'm working on a set up I can use in car and field.. Should be interesting icon_smile.gif


Moss de Boss... Sorta

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Could you post a piccy of the antenna? I'd like to see how big it is.


Also, does the GPSr show the position of the antenna or the GPSr? If it's the antenna, it'd be good for in cars and houses but not so good for locating caches in trees unless it's a) better at picking up the signal than the poxy Vista patch antenna and :D portable enough to carry around.


If it shows the antenna position just think of the applications. You could place a few near your caches and have hours of fun while geocachers get confused about where they are.




The second ten million caches were the worst too.


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Originally posted by jeremyp:

If it shows the antenna position just think of the applications. You could place a few near your caches and have hours of fun while geocachers get confused about where they are.

Or stand 35ft away and see how long it takes before The Hornet turns up. icon_wink.gif



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Sorry bout the quality but me batteries are low in my digi cam an flash didn't go off.


Antenna pic



The Tx Antenna is about 60mm high..


Does it show it's own location or that of the GPS.. I dunno as yet.. will do a little experiment later and find out.


The system amplifies the RX signal by about 35db I belive.. and this Tx antenna has a range of 2-3 meters. The Patch antenna has a magnet in the base.. ideal for sticking on the care roof and the Tx antenna has a couple of suckers for mounting inside the car or where ever.


Leads are about 5 mtrs long.


Moss de Boss... Sorta

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The signal from the Satalites is very weak.. hence when your gps picks them up they are effected by buildings, TREES (everyones favourite) etc. Therefore when you look at the bars on the satalites page they indicate the strength of the recieved signal from the sats. The lower the bar the weaker the signal.


On the Re-radiating antenna there arw two aerials, one recives the signal (Rx) and one Re-transmits the signal (Tx)


The signals from the sats are picked up by the Rx aerial (antenna) and fed via the cable to a small amplifier in the base of the Tx aerial. The amplifier boosts the weak signal into a stronger one and then sends to a small transmitter which sends it to the TX aerial and so to the outside world.


The GPS picks up this much enhanced signal.


The advantage is that in trees or cities you get a signal which the GPS can work on. It won't improve things in dence woodland, but if you have a location of say 70-80 ft error in a wood, with this you should get back to your 20 odd ft mark..


It won't better that as the algorithums in the GPS software have theire limitations also..


Moss de Boss... Sorta

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I guess this is to get round 'GPS proof' Car Windscreens. My eMap works fine in the car. I would buy anything that would help me find Caches under trees but I don't fancy lugging a car battery about and/or wiring myself up so I look like a Borg.






LASSITUDE- (noun) Tiredness and apathy: a state of weariness accompanied by listlessness or apathy[15th century. Via French from Latin lassitudo , from lassus 'weary'.]

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Originally posted by Lassitude:

I guess this is to get round 'GPS proof' Car Windscreens.


Wouldn't one of the small, flat, antennas that have a magnetic 'foot' be less expensive?


I have one which I adapted from a GPS PCB that I bought some time ago. I took the plug which came with the antenna off, and soldered a BNC socket (which is what my GPSIII+, and some other units use) on instead.


Signals are much improved using this antenna on the roof of the car.


I suppose people who use units with no facility for attaching an antenna connected with a length of cable have to use the re-transmitting system though.


I have thought about mounting a small metal plate on a pole, and taking this with me to mount the external antena on when walking. A bit awkward, but might make a bit of a difference when under the trees. I think I've seen pictures of people with antennas on poles, in the USA, as well. Anyone know where these come from?


--... ...--


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Re-radiating antennas only work when you are very close to the Tx (transmitting) antenna due to the huge path loss from it, which will overwhelm the gain from the Rx (receiving) antenna/amplifier gives.


It will probably be OK for use in a car but Hornet has absolutely no chance of it being any use at all!!



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I hope to get the other version of this type of antenna and rig it to my day pack. The Tx range is only 0.45cm as against 2-3 meters so should be no problem with Tx swamping Rx.


As they draw only about 30mA a seald 12v 1.3Ahr lead acid battery should keep it powerd for a good days caching at an all up wight of 0.6 kilos.


By my reconing this is no worse than running round with yer GPS in one hand and your PDA in the other icon_smile.gif and 0.6k is nowt to the weight of junk I carry when I'm out an about icon_biggrin.gif


Moss de Boss... Sorta

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I saw a Magellan re-rad antenna for about £70 in Maplin about a year ago. I thought this was a bit steep so I set about building my own.


Luckily enough, I had a spare Motorola active antenna which was the basis of the project. Using some other spares and about 20p's worth of extra material, I built the antenna and it has performed well to this day.


Total cost - 20p!


OK, the antenna would have set me back about thirty quid, but £30.20 is still better than £70!


Team Tate


Remember - if it's moving, it's not dead...

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