Sunday, February 26, 2023

Moving the A50-3S Closer to Home

A3S/A743 on tower, A50-3S nearby.
Nearly five years ago, I mounted a Cushcraft A50-3S out in the yard. I figured this would work for a few months until I found a more permanent solution. This lasted way longer than I expected.

It was a good move. I worked 48 states, plus 39 countries using that antenna, despite feeding it with 120 feet of RG-8X which likely adds 3 dB loss.

In July 2021, I asked the SEDXC email reflector for advice on how to work Europeans on 6m. I heard others working them, and even heard a few myself. For the most part, however, I could not hear them, or I couldn't get them to hear me.

The first piece of advice was to get a better feed line. RG-8X is not a good choice for VHF, especially with over 100 feet. The second bit was to mount the A50-3S a little higher. It's taken me a year and a half to get there. I've finally taken the first step.

The first question: where to put the antenna? The mount in the yard used a mast concreted into the ground that originally supported a Cushcraft R7000. I considered moving it to my 50 foot tower below the Cushcraft A3S/A743. The option allowed for easy rotation, and would have been convenient. However, with antennas in close proximity at five feet away, I believed there would be too much destructive interaction. I needed a mount point further away.

View of installation.
Without room for additional towers, I opted to mount a mast against the house, about 30 feet away from the tower. This location is close to where coaxial cables exit the house, which meant a shorter feed line. An older but serviceable piece of 9913 had sufficient length, so the feed line problem was solved.

How to mount a mast to the house took a bit of figuring. I used a small 6" wall mount on the eave of the house, just below the gutter. This gives the mast enough distance to clear the gutter. The bottom of the mast sits in a pole mount on the railing of the deck blow. The mast is the same 19 feet using two 10 foot pieces of rigid EMT I used to mount the antenna in the yard. 

Erecting the antenna was a little bit of a challenge. I used a rope and pulley hooked on the wall mount to raise the mast into position, then lifted the mast up on the railing. The weight of the rigid EMT made this harder. 

Reflector askew
In the process, the reflector of the antenna brushed up against the roof, which knocked it out of alignment. It doesn't affect the operation of the antenna terribly much, but I will fix it eventually.

The mast bracket is not cinched on the mast, to allow for rotation. Jam nuts are used to keep the bracket U-bolt from loosening.

The result has the antenna around 27 feet (8m) high, next to the house, fed with about 50 feet of 9913. This should be a substantially better than out in the yard.

I plan to replace the mast with some aluminum tubing, as well as adding a rotator, which should put the antenna a couple of feet higher. That will also give me an opportunity to straighten out the reflector alignment. 

In the meantime, I'm ready for this year's Es season in plenty of time.

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