Category Archives: Mount

3cm, 6cm, 9cm, Antenna, Dish, Feed, Mount

Upside-down Dishes and Rotary Clamps

May 2, 2024 smithn Leave a comment

Inverted 1.2 metre dish with 10 GHz waveguide feed connected. The 5.7 GHz horn is fitted so a 3 degree elevation change brings that band into play. Having the feed at the top with the dish inverted keeps the rain out of the horn and removes any risk of hitting your head on the arm when standing on the roof rack. Bracing bars are 10 mm carbon fibre tube with quick-detach fittings epoxied into the ends. Elevation strut is a cheap 12 volt mechanical actuator.

The rotator fits on a mast section that tilts over so the dish can be worked on for band changes. It rests on a trestle or “mast scissors” when luffed over. This is the 3.4 GHz setup with a commercial C band scalar choke on a 9cm feedhorn I made for Tony

Rear view of the dish with two ODUs for 5.7 and 10 GHz

Another implementation of the rotary mast clamp. This one has a side entry for use on narrow lane verges. It also has a ground-mounted tilt plate and rotator. The fishing-rod stand allows you to lower the mast but it remains supported above ground for adjustments and band changes.

The second version of the clamp. The brass nuts fit on to captive clamps with 3/4 inch spigots to allow rapid removal of the clamp from the roof rack.

Close-up of the mast clamp with the gate open, showing the rollers and the knurled locking nut

The first prototype clamp

The 2.4 metre mesh dish on Tony’s van-mounted 60ft pneumatic mast

Elevation mechanism I made for the 2.4 metre mesh dish. The arm at the right is for the counterbalance weights

Porthole feedthrough in the mesh surface to allow shorter feeders to be used. Brass insert in the Delrin bush is for the quick-detach carbon fibre feedpoint support rods. Designed to be dismantled while standing on the van roof on a stormy winter night in pitch darkness with horizontal sleet on a Yorkshire Dales hilltop at 54 degrees North.

Mount, UHF

432 MHz Moonbounce array elevation mechanism

March 27, 2021 smithn Leave a comment

I’m working on an elevation pivot plate for a large 70cm moonbounce array for a friend. The design uses a 40 x 30cm plate with clamps and alignment blocks to carry GRP and aluminium tubes to support the array and LNA/phasing harness. This is the first stage, making the knuckle and pivot pin and bearing bushes/carriers. The bodies are aluminium, the shaft is 316 stainless steel and the bushes are phosphor bronze. It will have dust caps and grease nipples. The bushes are in two parts with a 1mm grease groove between them

So far, it is looking OK. More to follow.

One of the bearing bushes and mounting blocks being checked for fit

The original concept for the knuckle is here: https://www.g4dbn.uk/?p=1618 and this is the story so far of the machining,

The 100 x 100 x 150 mm aluminium block

Facing the block, bit of unnecessary slow-mo trickery

Shiny!

Turning on a mandrel to form the second boss

Knuckle finished and bored to take the pivot shaft

Pivot shaft machined to size, with flats for the grub screws and locked in place

Machining and tapping the bearing carriers. M10 spiral flute tap clearing the chips very nicely

I made a mandrel with a threaded hole to turn the bearings from a piece of an ancient slab of bronze that I remember my dad using in the 1960s as a soft anvil

Block fitted to the mandrel ready for OD machining and facing

Removing the semi-finished bush from the mandrel

One half of the first bush pressed into one of the the bearing carriers

Boring the completed carrier and pair of bushes to fit the shaft with a 5 micrometre clearance

13cm, 23cm, 9cm, Antenna, Dish, Mount, SHF

Dish Feedpoint Mounts

September 18, 2020 smithn Leave a comment

Tony G8DMU has a 2.4m mesh dish on his van. He uses a variety of feeds, and they are all different diameters. I made up a quick-detach support ring to fit an RF Hamdesign multi-band ring feed, but Tony’s 23cm feed is larger, so I made up some extension blocks and a set of cheeks and spiders to support the different feeds.

The original ring feed, with the adjustable ends on carbon fibre struts, QD sockets and attachment brackets

First step was to extend the ring to fit the large feed

Blocks inserted into the ring to increase the diameter and provide attachments for the spiders and cheeks

I made up a stainless steel internally threaded clamp nut to fit on a stainless threaded bar fixed into the block with Loctite, so I didn’t have to worry about threads in the aluminium getting damaged.

The big 23cm band feed in the clamp ring

Next step was to make support cheeks/crescents to hold the multiband ring feed

Adjustable crescent with a knurled brass head on a pointed stainless steel thread, with a brass insert to spread the force and prevent wear on the Delrin

Fixed crescent, milled from Delrin and threaded M5

The 3.4 GHz feed is the smallest, so I milled a support ring and fitted support rods with threaded ends to fix to the holes in the outer ring. The threads were M5 so they fitted easily through the M6 threaded hole in the clamping block.