Weather-proof boxes

I’ve found Toolstation provide a range of weather-proof boxes, but they don’t file them very well in their online catalogue, so it is not that easy to find the information.

If you search on “waterproof”, you get a nice range of waterproof coats.

A search of “weatherproof” throws up this “Weatherproof Box IP54 12 x 19 x 30cm” which I used for the 3cm transverter & amplifiers.  I added a strap around the middle to help hold it tightly shut. It gets shaken well in the gales. I also drilled some drain holes in the bottom to release any accumulated condensation. The box has a set of rubber glands on the bottom for feeding cables through. The hinged lid means you are not having to fiddle about with screws in order to get at the contents. I added a bracket under the box so as not to distort the dish (not in the picture).

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A search for “moulded enclosure” offers these IP55 boxes. I have one on the main aerial pole housing the 13cm transverter (see banner picture above). There is a useful range of sizes and there are pre-cut holes handy for feeding cables through with grommets for encouraging the rain to stay out. Again, I’ve drilled drain holes in the bottom. The lid screws tend to rust, so I’ve greased mine, but stainless steel screws might be better.

I added one of the smallest IP55s to the lid of the 3cm box in order to cover a hole I made.

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I have heard of people pumping dry air into their outdoor boxes to keep the electronics dry, but I haven’t tried this.

Experiment with circular waveguide/feed for 3cm

I have loosely assembled a copy of Peter’s G3PHO’s plumbing fittings implementation of a W2IMU dual-mode horn. At the moment, it is stuck together with insulation tape. To this I have added my own experimental design of a waveguide crook. Behind the horn is a 135 deg bend, followed by a 180 deg sweep bend up to the main bit of waveguide. Then there is a wide 90 deg sweep into the box. So it is a bit like a shepherd’s crook, but bendier.

This has probably all been done before for an off-set dish, so it is probably not a “G3YJR Crook” at all, it which case, here it is again!

I’ve used 22mm copper pipe as circular waveguide. I’m not using any rectangular waveguide. Rectangular waveguide seems popular and there are probably very good reasons for using it, but as a newcomer to microwaves, I don’t know them.

There is a twist to the polarisation along the waveguide. I haven’t measured this yet, but it looks like about 45deg at the coax feed point. My SMA-coax transition accounts for this. The twist seems stable. I’ve mounted a weather-protective plastic box behind the dish. The SMA feed transition sits inside the box along with the electrickery.

The idea is to move the pre-amp/transverter from the end of the off-set arm into the box behind the dish in order to minimise the weight on the off-set arm, whilst keeping the losses low by using rigid waveguide. My coax transition has two SMA feeds at right-angles in order to allow for switching polarisation.

With the dish in the terrestrial position, looking at the horizon, the waveguide slopes gently down to the horn so that any condensation should dribble down & escape from the horn.

Feeding the crook/horn from the DB6NT shows the same monitor output as I got using my ex-LNB horn with my home-brew SMA-to-rectangular transition: 5 “units” on the moving-coil meter scale. This looks encouraging. I need a way to measure the insertion loss.

I added a bracket under the box so as to not distort the dish with the weight of the box (not in this picture). I bought the box from Toolstation.

I tested the horn straight into the SMA transition using GB3FNY as a source. And then with the crook in between.

The results seemed comparable with the old LNB horn, so that seems reasonable. One surprise was that when I removed the back-short (the 22mm plumbing cap) from the SMA transition and left the waveguide open, I couldn’t see any difference in the signal strength.

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Using the vertical polarisation SMA feed resulted in about a 20dB drop in signal (as predicted by Bryan G8DDK).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

13cm SG-Labs transverter

I’m experimenting with an SG-Labs transverter from Hristiyan LZ5HP, Bulgaria. The IF for this is 70cm & the local oscillator may be set to 1870, 1886, 1888 or 1968 MHz by  jumpers 1 and 2. I’ve selected 1888 MHz, so 1888 + 432 = 2320MHz.

It defaults to VOX mode, so when power is sensed, it automatically switches to transmit. It has a built-in antenna relay, but this may be switched out in order to add an external relay for a pre-amp and/or linear amp.

I’ve set the transverter’s power pot to accept 2.5W from the FT-817.

In order to be able to mount the transverter on the aerial pole, I’ve added some monitor wires to permit remote control/monitoring from the operating position:

  1. “I/P” red LED
    •  shows I/P power too high, off when power I/P is OK,
    •  blinking when external reference oscillator is unlocked
    •  on for 3s on switch-on
  2. “I/P” green LED – shows green when power I/P is correct
  3. “FWD” SWR      – to feed a high-impedance meter
  4. “REV” SWR        – similar, but for reverse power
  5. PTT                      – via the phono jack
  6. SEQ                      – to give an indication of when transmitting

The other cables up to the transverter supply 13.8V DC, 10 MHz reference and the 70cm IF. I’ve used double-screened RG223U coax for the IF. The cable umbilical is covered in insulating tape to protect it from UV light damage. 1.5 m of Westflex 103 (from WH Westlake) coax connects to the 34 element Wimo yagi. The yagi is usually mounted behind the reflector, but I’ve mounted it from underneath in order to better physically balance it.

The protective box is from Toolstation. This and the Wimo yagi are mounted to a “jockey” fibreglass pole which is strapped to the existing pole with Shelley clamps from Blake UK, Rutland Road, Sheffield. So the 13cm antenna sits right on the top; the transverter box sits a little way down the pole where I can get at it. I’m hoping the coax doesn’t upset the 23cm Wimo which it passes through.

So far, I haven’t heard any beacons from here on 13cm (except GB3ZME occasionally via aircraft scatter), so thanks go to Trevor M0TWS for his help in testing across town.

26-November-2019 – my first contact on the 2.30 GHz NoV band

13cm upgrade – SG-Labs Rx/Tx and “Split Mode”