I have very nice range to the north when placing the antennna to the north, and good range to the south when putting it on the south sude of my apratment, only 10 meters between the 2 locations.
I was wondering if it was possible to use dual antennas with any extra "combiner" for the same radarbox in order to get better rage from both the north and the south.
Thanks
This has been discussed in the past
http://www.airnavsystems.com/forum/index.php?topic=1232.msg9167#msg9167 (http://www.airnavsystems.com/forum/index.php?topic=1232.msg9167#msg9167)
Nortonbeak
Will admit missed that topic myself, thanks for providing the link, its something I have been thinking about myself
Thanks for the link.
I didn't find it on my search.
Probably wrong keywords/
Thanks!
I recently bought a "phasing harness" from Haydon Comms for UHF - ex military surplus - cost about £7 (very expensive when made I would think) although I've not trialled it yet - very high quality and heavyweight co-ax - it's got 2 chances - it'll work or it won't!
But how do you make your own custom phasing harness to connect 2 antennae the width of an apartment? easy
50 ohm feeder to the centre of a T connector (n-types!)
Connect the antennae to each arm of the T connector with ODD 1/4 wave multiples of 75 ohm coax - equal lengths either side. 300/Frequency * velocity factor of coax to determine wavelength.
LMR400-75 or LDF4-75 Heliax is good (if you can get hold of it) for the phasing lines.
Feed the radarbox with a short patch lead (n-type to SMA). Short length should allow you to use more workable feeder.
hth
Wal2t
Just gets better, you don't have a quick drawing by any chance do you
Malc, the drawing is very quick hence the scribble. It's not ideal that we are using lots of connectors at 1GHz and it's not ideal in the OP's situation in that the dividing leads would need to be so long but it should work ok for extending coverage in this case. It assumes the antennae are external types fed with N's (anyone who feeds a UHF antenna with a PL259 should be severely beaten with it ;) )
Wal 2t
Anything is better than trying to imagine it from words
Thanks for this and i'm sure others will benefit also
Despite any impending discussion whether or not there is any interference from each other
another approach to using two antennas feeding one receiver is to make use of one single length of
1/4wave(or odd multiple of) series transformer right after the T-Connector to the receiver.
Thus you can use your favorite Coax as avbl or used before.
Using two equal lengths of 50 Ohm Coax from each antenna to the T-Position,
then followed by said 75 Ohm length. Since 1/4th is difficult to determine with connectors so close use a practicable length of odd multiples and then connect to your rundown length of 50 Ohm again.
1 using 50 Ohm in the first place is to keep mismatch between antenna and cable small,
Cable nominal 50 Ohm - Antenna nominal 50 Ohm (who really knows ?) are matching.
2 since both feeders are T-connected thus in parallel the resulting output will have 25 Ohm
Impedance and this has to be raised with a.m. length of 75 Ohm cable.
Its output will have an odd result of 43.3 Ohm, which is close enough to the nominal 50 Ohm Line.
Whatever 75 Ohm coax you get your hand on, carefully check its Velocityfactor and apply
to your calculated choosen transformer length.Slight Mismatch here 50 : 43.3 less than 1.2,
which may be neglected for receiving purposes.
One word of warning though, those who are inclined to use this method for their Discones or LPDAs
the description 1/4wave series transformation points out this method is frequency dependent
and ideal for a defined single freq only.
Klaus
Quote from: Yachtie45 on May 24, 2009, 08:12:08 PM
Despite any impending discussion whether or not there is any interference from each other
Hi Klaus, I'm not trying to be pedantic, but I would point out that it's because of the distance between the 2 antennas the same signal is received slight out of phase by each twig, rather than "interference" which infers rfi or emi being emitted or generated.
Quote from: Yachtie45 on May 24, 2009, 08:12:08 PMthe description 1/4wave series transformation points out this method is frequency dependent and ideal for a defined single freq only.
From the RB and SBS point of view we are looking only at 1090 MHZ or 27cm wavelength - scanners are a whole different ball game!
CG Jon
thanks for pointing that out to others, I knew but have not found the appropriate expression.
2nd that is exactly what I meant in this sentence
brgds