Just Sharing This CCTV Pan & Tilt as Az-El Mount

[s-band]

I wanted a full az-el mount for the Prodelin 1.2m and bought a CCTV pan and tilt. The Prodelin is too heavy for the mount I got so I tried it with a CM 1.2 (99p on Ebay). It works reasonably well but would benefit from a pole to pan & tilt adapter that allows a counterbalance to be fitted. I just used what ever bits that were laying around to try it out.

Good points:
It has potentiometers to provide absolute position information so it is easy to return it to previous positions precisely.
It could do full az-el 360/90 if I sorted out the mount.
Easy to fit CM 1.2
Cheap units appear on Ebay from time to time.

Bad points:
It doesn't have worm drives so can windmill although it stays where it's put most of the time. A counter-balance would help. It probably should be parked with the dish on its back when not in use.
It has AC motors so can't be speed controlled. The elevation is ok but he azimuth is too fast and shakes the whole lot starting & stopping. The speed is ok for Ku and below on the 1.2 but would not be easy to use on Ka.
It needs skew control for linear polarisation

It proves the idea but I need to try to find a much bigger one with DC motors & worm drives for the Prodelin 1.2m.



The CM1.2 is quite convenient to attach an X band feed. Here's a scan of 12W WGS-3

 

[blademedia]

Well thought out G, it looks a nice neat setup.

 

[Captain Jack]

Nice cheap Egis

 

[s-band]

I'm not sure it compares well to an Egis but it is ok for a light dish up to 1.2m
Here are a couple of pics of the insides and one of the X Band feed and LNAs

 

[s-band]

The pot position feedback is nice as it is absolute but I wanted to try it on a normal positioner and maybe an RC2000 so I've added pulse outputs. I drilled nylon spacer to interference fit on the back of the motors and fitted chopper wheels and optical sensors. (no, they are not held on by Blue Tack, it's epoxy putty). The most awkward part was keeping all the wires out of the way of the chopper wheels when I put it back together.



I managed to slow the motors down by using an audio amp and LF source to generate 10-60Hz at 10-25V. It works well at 1/2 speed (25Hz) by gets a bit feeble and/or shaky at 1/5 (10Hz) speed. 1/3-1/2 speed is a good compromise. To switch the motors from +/-36V I used 4x zero-volt switching solid state relays and some diodes etc. The zero volt switching reduces the thumps a bit when starting and stopping. The 36V is only low current in this set up. I tried it using a Uniden UST-771 and it works fine.

 

[Terryl]

Check out the Yaesu G-5500 Azimuth and Elevation rotor, it's a bit pricey but has been used to turn a 3 meter mesh dish. (with counter weights)

Will do a 360 by 90 degree AZ and EL.

 

[s-band]

I boxed the interface - the grey box at the base of stand in pic. It worked well with the RC2000 once I'd set up the mount parameters. Without the counterbalance, it was inclined to over-run with dish face vertical (a nonsense position as the beam would be pointing into the ground). The optimum speed is 1/2 (i.e. 25Hz) which is a compromise between it shaking when starting and stopping, having enough power and not taking ages to get anywhere.

I replaced the CM polar mount tube adapter with one from a Prodelin fixed az-el. The pan/tilt bolts don't line up so I added a piece of 120mm square box section between the tube adapter and the pan/tilt.

Until it happened, I didn't realise that the RC2000 counters are always live. So, if the dish moves without being commanded, the controller keeps in synch but shows an alarm.

The total weight of the dish, feed & counterbalance is about 22kg i.e. within the 25kg limit of the pan & tilt for a balanced load. I don't expect it to stay put in a wind so it will need to be parked on its back.

 

[John]

I boxed the interface - the grey box at the base of stand in pic. It worked well with the RC2000 once I'd set up the mount parameters. Without the counterbalance, it was inclined to over-run with dish face vertical (a nonsense position as the beam would be pointing into the ground). The optimum speed is 1/2 (i.e. 25Hz) which is a compromise between it shaking when starting and stopping, having enough power and not taking ages to get anywhere.

I replaced the CM polar mount tube adapter with one from a Prodelin fixed az-el. The pan/tilt bolts don't line up so I added a piece of 120mm square box section between the tube adapter and the pan/tilt.

Until it happened, I didn't realise that the RC2000 counters are always live. So, if the dish moves without being commanded, the controller keeps in synch but shows an alarm.

The total weight of the dish, feed & counterbalance is about 22kg i.e. within the 25kg limit of the pan & tilt for a balanced load. I don't expect it to stay put in a wind so it will need to be parked on its back.

View attachment 109920

Nice work and looking the biz

 

[s-band]

The lighter pan & tilt is fine for the CM 1.2m but I wanted something that could take the Prodelin 1.2m which weighs 25kg for the reflector alone. Pelco make units that can take 40kg and have worm drives. I could only find 115VAC versions at a reasonable price, so that's what's here. I used the original technique to add the optical feedback. This time with only 2 spokes on the choppers as the RC2000 can not keep up with pulses <10ms. I had to drill & tap the motor shafts to fit the choppers. (1st pic) The motors have PTFE brakes that rub on disks to prevent over-run. These had to be refurbished. There were a few bits that needed adjustment & re-greasing as the unit must have been quite old.

The 2nd pic shows the pan & tilt with the original for comparison. The RC2000 interface (+/-36VDC to 115VAC switching) at the bottom. The 3rd pic is where I was in the process of balancing the thing (I'll add a 2nd rear arm later). It needed 7.5kg once the feed support was added and will need another kg or so when the electronics is attached.

Getting closer to an Egis;-) It could take a 1.8m Laminas but I'm not going there.

 

[s-band]

To set this up I needed a Ku KNB with skew control. The Octagon single PLL LNBF is very light and I fitted it to the servo assembly that originally had a Ka LNB. It was easy to fix using self-tapping screws into the back of the Octagon's plastic case. RG6 or thicker cable is too inflexible so I used a short length of thin coax for the rotating part. If you want to scrape the last dB from a system, I highly recommend adding skew control, even with a polar mount. It is especially important when there are transponders on the same frequency on both polarisations. The LNB feeds are not always precisely orthogonal and there are small variations between satellites.

 

[John]

To set this up I needed a Ku KNB with skew control. The Octagon single PLL LNBF is very light and I fitted it to the servo assembly that originally had a Ka LNB. It was easy to fix using self-tapping screws into the back of the Octagon's plastic case. RG6 or thicker cable is too inflexible so I used a short length of thin coax for the rotating part. If you want to scrape the last dB from a system, I highly recommend adding skew control, even with a polar mount. It is especially important when there are transponders on the same frequency on both polarisations. The LNB feeds are not always precisely orthogonal and there are small variations between satellites.

View attachment 111858

>>If you want to scrape the last dB from a system, I highly recommend adding skew control, <<

Seconded . Lets get it pointed at something now G and give it a good testing

 

[s-band]

Lets get it pointed at something now G and give it a good testing

OK, boss.



7E - Top plots are the Prodelin with Octagon, lower plots are an IRTE PF 1.5m with Inverto Black C120 with "wide band" IRTE feed. In theory, the Octagon will over-illuminate the Prodelin, despite that, it's the same or better than the IRTE 1.5m on most TPs. The original IRTE feed with domed PTFE only worked for FSS and the new one (used here) was supposed to be full band. However, I've always been suspicious of the IRTE at the top end. It looks like I need to spend some time fixing more than one aspect of it!



This one is high band on the vertical probe skewed to be horizontal. Compare to high_H.GIF

 

[John]

OK, boss.

View attachment 111865

7E - Top plots are the Prodelin with Octagon, lower plots are an IRTE PF 1.5m with Inverto Black C120 with "wide band" IRTE feed. In theory, the Octagon will over-illuminate the Prodelin, despite that, it's the same or better than the IRTE 1.5m on most TPs. The original IRTE feed with domed PTFE only worked for FSS and the new one (used here) was supposed to be full band. However, I've always been suspicious of the IRTE at the top end. It looks like I need to spend some time fixing more than one aspect of it!

View attachment 111861 View attachment 111862 View attachment 111860 View attachment 111859

This one is high band on the vertical probe skewed to be horizontal. Compare to high_H.GIF

View attachment 111863

>> OK, boss. <<
Like it lol.

Nice to see the 'ol RC2000 in action as well Graham