80cm dish for 3cm band suffered damage

This dish has been up for some years and gets a real battering in the gales. I had noticed it was aiming a bit upwards, out of alignment.

On closer inspection I found the mounting bracket had suffered some metal fatigue:

Also the dish itself (pressed aluminium) had started to crack around the heads of the mounting screws:

I took the dish down, so I am off the 3cm band for the time being. 

It was only earlier this year that I fixed the electronics so that I was back on the band! But now the mechanics have failed. Perhaps having a box of electronics mounted on the back may have added to the stresses of wind? I accept that the dish has survived for some years and through bouts of terrible weather. It has been in a very exposed position, sticking out above the ridge off the roof. These bog-standard satellite dishes probably last quite well, mounted lower down in sheltered locations.

Hear is the 80cm dish in prime condition, just before I put it up on its pole. So the dish must have been up 5 years or so. That is a lot of wuthering. Wuthering Heights!

I may have a more robust dish which might take its place. 

Redudced signal from Es’Hail2 satellite

The carrier-to-noise ratio from the video beacon was lower than usual:

A dish for Es’Hail-2, QO100

Last year I experimented with using a 13cm band yagi for the up-link and an LNB strapped alongside my horn on the dish I use for terrestrial work for the down-link.

I’ve now put a dish up for the Qataris’ Es’Hail-2 satellite. It is a 1.1m off-set PrimeSat dish.

Prior to putting it up,  I had bodged a bit of aluminium  box tube to take the dual-band feed. I checked the dish’s focus with a few stick-on mirrors and the sun as an light source. There did seem to be a bit of distortion in the dish, though it looked in excellent condition, with no visible damage. I may be able to squeeze out this distortion using the braces for the LNB arm.

Bearing in mind how windy it gets here I’ve used belt and braces in mounting the dish. I decided not to get the larger 1.3m dish. I felt the 1.1m dish would be easier to manoeuvre  up to the roof and also it would be less affected by wind. I’ve used two steel chimney lashings to hold two brackets. I decided the usual aluminium pole might not be up to the job, so I set a section of steel scaffold pole in the brackets. The dish’s two clamps are fixed to the bottom of the pole. In case of the dish clamps somehow working free, there is a third clamp at the bottom of the pole to stop the dish dropping off.

I’ve fitted braces to the LNB arm to hold the arm steady in the wind.

Being low down on the chimney and on the easterly side of the house, the dish is in the lee of the strong westerlies and south-westerlies.

The 13cm patch antenna in the bigger plastic box is not really working as circularly polarised. It is more like linear, effectively from a dipole, but the return loss is quite good. The patch is fed with a shortish length of Ecoflex 10.

The LNB has a bit of “satellite” coax taking the signal back into the station. I found the connectors on my thin “WiFi” coax were very poorly fitted. I use this to carry the 27 MHz reference oscillator signal to the LNB. I soldered a proper SMA connector on the LNB end of the cable. An LNB lens takes the signal from the dish which is then piped along a short length of copper waveguide (22mm domestic copper pipe) into the LNB. The waveguide is held by pipe clips mounted on short lengths of stainless steel studding. The LNB has a bit of a twist on it in an attempt to optimise the match to the polarisation from the satellite.

I sealed all the connections with self-amalgamating tape.

See Dual Band Feed construction.

Note: I had originally mounted the N-type socket for the patch feed with the socket mounting flange inside the plastic box, but this meant the N-plug did not mate reliably, so I re-mounted the socket on the outside of the box.

3cm SHF UKAC 22-August-2017

I managed to lash up the 80cm dish minutes before the contest in a patch of decent weather. There was quite a bit of insulation tape & bungie cord holding the bits together. A Blue Peter job really!

Last month I managed to work Denis G3UVR over the Pennines. I was using just the LNB horn (10dB gain maybe?). He was quite easy copy, but he struggled to hear me on my 0.25W approx. We aimed at the direct path.

Tonight we were Q5 to each other on CW. I was still using about 250mW and probably with greater losses in the coax couplings.

The dish looks more robust on it’s new roof pole – Peter G3PHO has given me a section of thick-walled aluminium scaffold pole. The upper part of the pole is steadied by some chimney-bracket extensions, custom-made by Blakes of Rutland Road, Sheffield. The azimuth rotator has some play in it, so the dish can waggle a bit.

At the end, I even managed to hear Peter G3PHO off a reflection. I could read him sending my callsign. He struggled to hear me however. He is tucked away behind a couple of hills roughly south of me, so a very difficult path. Mandy M0MDY is also a tricky path from here and she was obviously struggling to hear me, but we completed OK.

South is difficult! I am a bit down from the Crosspool hill-top. The top of the Crosspool tower looks a nice reflection target however, maybe with a bit of elevation.