MT magazine UHF Satcom antenna project

[prcguy]

The junction of the four elements will get closer together, which is probably not a big deal and you will have to move the element hole pattern in 1mm from the edge of the elements to match the pattern on the pipe cap.

I would be more concerned with the resonant frequency of the dipoles being too low due to the wider and thicker elements. If you have access to an antenna analyzer you could build everything to spec then trim the element lengths to resonate around 257MHz.
prcguy

Originally Posted by buds

Hi, I am going to attempt to build this antenna. The main satcom sat here in Australia is the optus c1 which is a 45 degree look angle which should be great with this antenna.
I found some flat alum at work but its 40mm wide, which is just 2mm over one and a half inch. Would this screw everything up?? I could sand it down i suppose. Its also 1/8th an inch thick which should be all-right.

Cannot get the Tee adapter from anywhere here might have to get it from us.

[strandbiker1]

Mike:

I obtained temporary use of an AEA 140-525 antenna analyzer. I used it already to take care of the return loss/ VSWr on a double rhombic antenna I made which works great. I got the VSWR down to 1.07. Tomorrow, I will check the X wing to see how it works. Question, the AEA is only a 50 ohm instrument. I know we used your analyzer up to 261 MHz. This AEA can do auto produce VSWR graphs. Should I keep the 75 ohm RHCP cable attached when measuring the VSWR, as the connecting cable is obviously 50 ohm? This instrument makes things a lot easier to deal with.


Thanks,


Skip

[prcguy]

My X-wing is intended to feed 50ohm coax so check the complete antenna over the ground screen as it would feed your radio. If your antenna resonates too low in frequency due to fatter or wider material, trim all four elements keeping them the same length.

The phasing harness dimensions were tweaked with 75ohm loads at the antenna ends to simulate dipoles 1/2 wavelength above ground and a 50ohm Vector Network Analyzer at the common output of the T adapter.
prcguy

Originally Posted by strandbiker1

Mike:

I obtained temporary use of an AEA 140-525 antenna analyzer. I used it already to take care of the return loss/ VSWr on a double rhombic antenna I made which works great. I got the VSWR down to 1.07. Tomorrow, I will check the X wing to see how it works. Question, the AEA is only a 50 ohm instrument. I know we used your analyzer up to 261 MHz. This AEA can do auto produce VSWR graphs. Should I keep the 75 ohm RHCP cable attached when measuring the VSWR, as the connecting cable is obviously 50 ohm? This instrument makes things a lot easier to deal with.


Thanks,


Skip

[prcguy]

I'm overstocked on military satcom antennas and decided to sell one of my Trivec-Avant AV2040 portable fold out antennas featured in the MT magazine article.

The price on these has skyrocketed in the last few years and they usually fetch $400 and up and I'll offer to RR members first for $250. PM me for more info.
prcguy