Logged in users > User Diaries
My fall project, ham radio tower work
SparWeb:
That looks awesome. Thanks for sharing the photos.
Are these all home-built antennas or do they have special components that you just have to buy no matter what?
It's probably a trick of the perspective and long zoom, but the booms look like they'd hit each other as you rotate them!
Mary B:
--- Quote from: SparWeb on October 27, 2022, 01:42:16 AM ---That looks awesome. Thanks for sharing the photos.
Are these all home-built antennas or do they have special components that you just have to buy no matter what?
It's probably a trick of the perspective and long zoom, but the booms look like they'd hit each other as you rotate them!
--- End quote ---
Commercial antennas, come as kits though! Lot of assembly required!
Zoom fake out, the towers are 40' apart...
SparWeb:
Please post about the Rx on the new antennas when you have them all hooked up. I for one am interested in Ham even if I haven't tried it. What kind of gain are you expecting? (oh well, pun intended I guess)
Mary B:
--- Quote from: SparWeb on October 29, 2022, 02:02:55 AM ---Please post about the Rx on the new antennas when you have them all hooked up. I for one am interested in Ham even if I haven't tried it. What kind of gain are you expecting? (oh well, pun intended I guess)
--- End quote ---
I will go from the top down
902mhz 21.12dbi - cable losses(about .75db)
222mhz 14.1dbi - cable loss(about .4db the higher you go in frequency the worse the cable loss gets)
1296mhz 26.54dbi - cable loss (about 1db)
50mhz 11.54dbi negligible cable loss... maybe .2db
Higher you go in frequency the easier it is to have a LOT of antenna gain in a small space. On 1294 the stack of 4 antennas(every time you double the number of antennas you gain 2.8db) takes up a 10' long x 30inch square space. You see 4 cables going to a power divider/combiner on the back of those 4 then it goes down the mast.
I use all Heliax coax except for some inside jumpers where it is not flexible enough. FSJ4-50(1/2 inch flexible Heliax) from antenna feed point to the main cable up the tower which is LDF5-50A Heliax(7/8 inch) on 902 and 222, on 1296 I use LDF7-50(1 5/8") Heliax, and 50 mhz is all FSJ4-50 to the house. FSJ4-50 is flexible so can go around the rotor and not kink. LDF5-50 is stiff enough I could cement 30 feet into the ground and leave it pointed straight up... takes 2 people to form a bend. The LDF7-50 is so stiff we had to use a conduit bender to make the curve by the house.
The larger the Heliax the lower the loss to a point. As you move into microwave frequencies at 10ghz and above it can act like waveguide... limiting it to LDF4-50(1/2 inch) Heliax and a LOT of loss unless you mount equipment up at the tower top. Higher the frequency the higher the cable losses! Loss is bad!
So far only 1296 is ran into the house, I need to drill a new hole in the wall from my entrance box so I have space for more cables. And fall is not the best time for band conditions on VHF and above. Air is to unstable. So far I have tested 1296 to 300miles and it works well.
902 and 222mhz bands do not have many users, they are USA only bands so equipment for them is all an add on with extra cables and more to go wrong LOL
I am building the four 432mhz antennas, there I will have 25.19db gain but fairly high cable loss on transmit a little over 1db taking my 750 watts out of the amplifier down to 600 watts at the antennas. I will have a mast mounted receive preamp so loss on receive is zero, I will have a net gain on receive of approx 25db.
Probably a bit more technical than you wanted LOL Sorry!
SparWeb:
Awesome. Give me something to chew on and go look up what you mean in places. I'm here to learn.
If you're "building" the 432's in the background, then what's left to go? I see them in the background and the four booms seem finished.
I did a search on "432 MHz" just to see what's on that frequency and found a bunch of weather stations and police radar - and some erratic google hits on "432 Hz" which the snake-oil sellers call the "healing frequency". Something for everyone, I guess!
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version