- This topic has 4 replies, 2 voices, and was last updated 3 months, 3 weeks ago by M0PWX.
3 January 2022 at 14:08 #868WirelessParticipant
I have a single antenna mast available to mount my antennas to but wish to somehow mount several omnidirectional antennas to it. I appreciate there will be some shadowing but wish to somehow stand-off the antennas horizontally from each other to minimise the impact.
I’d like to place my Scan Stick, 1090MHz antenna (both verticals in slim fibreglass radomes) and (assuming I pass my Foundation booked for next weekend) a dual band vertical such as a Diamond X-50.
The mast itself is plenty sturdy (it’s designed to take an 80cm satellite dish and the associated wind loads) but I don’t know how I can best stand-off the antennas horizontally from each other. Again, I appreciate it’s not an ideal solution due to the close proximity and shadowing but I only have this mast without the option to mount another.
Any suggestions much appreciated.
3 January 2022 at 14:49 #869WirelessParticipant
As a follow-up, perhaps something like the J-pole and associated mast clamp as listed at the link below could be used…?
Again, thanks in advance,
30 January 2022 at 13:09 #970M0PWXParticipant
I would probably put the X50 at the top as the radiation patterns are horizontal and upward, the least radiation is down / below, this will mean the least interference on the RX antenna below
X50 on top also means you should get the best coverage for you 2m / 70cm
depending on the height of the mast and position relative to things that will block signals, i would keep about 1 metre between the bottom of the X50 and the top of the RX antenna as a minimum
30 January 2022 at 13:25 #971WirelessParticipant
Hi Peter, thanks very much for this info. Much appreciated. If I can get enough vertical separation I’ll certainly go down that route. Cheers, Rupert
30 January 2022 at 21:19 #983M0PWXParticipant
as a side point you will want to keep the coax as short as possible on the 1090 ADS antenna as attenuation per metre at that frequency is quite high
and that J-pole mount i would think not really man enough for the X50, as its like a friction fit from the wall plate to the pole
a better way if your budget allows is something like a T&K bracket https://moonrakeronline.com/tk-18-pair-of-heavy-duty-brackets this would allow (the 18″ brackets give about 14″ clearance to get out past your guttering), you can get different sizes depending how much clearance you need
this would allow a suitable pole like https://moonrakeronline.com/antennas/masts-poles-tripods?price=12.49-50.00, then you just need the U bolts and fixings for attaching the brackets to the house
you would then have enough room to mount your antennas
the J-pole bracket would be enough for the 1090 ADS and depending on the scanstick size may cope with that
for the X50 don’t skimp on the coax, losses on coax increase with frequency,
look at https://www.qsl.net/co8tw/Coax_Calculator.htm
if you put 10m of RG58 and 144mhz you lose 12% of the signal, (435mhz you lose 20%)
RG213 10m at 144mhz you only lose 6% (435mhz you lose 11%) (1090mhz you lose 18%)
that loss is in both directions (TX and RX)
so coax choice is important, as well as position and height of the antenna, RG213 is easy to work with as its stranded core and not a solid dielectric or RG-8 which is a bit better than RG213 but seems hard to find
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