Retro-fitting C-band to an old IRTE 1.5m PF

[s-band]

I’m just getting back into satellite stuff and refurbishing my 1988ish IRTE 1.5m PF dish. I tried a Titanium C1W LNBF taped to the side of the Ku LNB and it wasn’t too bad so I decided to make a more permanent mount..

I took a photo of the Ku feed with the camera back on the rear of the dish. That was printed 1:1 to use as a template to cut the scalar ring to avoid the tripod rod and to mark out the fixing positions. I aligned the new feed using a line parallel to the two top tripod rods. The scalar ring is mounted using one of the existing feed bolts (torx screw in photo) and an M3 fixing drilled and tapped into the Ku feed clamp.

The scalar ring is not really in the right position relative to the focal point of the dish but it works ok adjusting the LNBF position for best signal and ignoring the setting for f/d of the dish. The offset is about 5.5 degrees (orbital position) relative to the Ku feed. The photo looking directly at the feeds was taken with the dish pointing to 55.5W on C band. Only the narrower bandwidth signals manage to crawl through the trees but it works.

I’ve attached couple of xml files from EBSPro for 40W & 55.5W. 40W is reasonably clear of the trees. I think the performance is probably 1-2dB below what it should be if the C band feed were at the prime focus. I can’t lock anything that is much lower than 38dBW eirp. I used to have a 10ft Winegard on C band (and regret selling it!) which could manage around 30dBW with a lot of sparklies. That sort of ties in with -6dB loss for 1.5m vs. 3m and 2dB for the bodged feed position.

 

[archive10]

Hey S-band, welcome to the Forum.
Great results from a little modding.
If I remember the IRTEs are 6 petal things.
Would it not be possible to turn the dish, so that two feed arms were 60 degrees from horizontal, and thus allow you to mount the LNB without cutting 25% of the feedhorn?
I'm sure there's an obvious reason, but I am curious.,,,

 

[archive10]

If I remember the IRTEs are 6 petal things.

No, wait, that's the bigger ones...
What's the 150 like??

 

[s-band]

Hey S-band, welcome to the Forum.

Thanks

If I remember the IRTEs are 6 petal things.
Would it not be possible to turn the dish,

The 1.2m & 1.5m were one piece stamped aluminium, the 1.8 was 6 petal, the 2m a 1.5 + extensions and the 3m was spun aluminium. No, I'm not sad enough to remember but I still have a 1990 Micro-X catalogue.

I wanted a quick fix and until I refurb it, I can't remove the dish face to turn it as the bolts are rusted. I don't think it makes much difference, maybe adds a bit of ground noise having the scalar ring chopped and a bit offset. I've made quite a few compromises.

 

[John]

Thanks


The 1.2m & 1.5m were one piece stamped aluminium, the 1.8 was 6 petal, the 2m a 1.5 + extensions and the 3m was spun aluminium. No, I'm not sad enough to remember but I still have a 1990 Micro-X catalogue.

I wanted a quick fix and until I refurb it, I can't remove the dish face to turn it as the bolts are rusted. I don't think it makes much difference, maybe adds a bit of ground noise having the scalar ring chopped and a bit offset. I've made quite a few compromises.

Hi S-band & welcome,
Is Ku at focus on the 1.5 essential to your Ku viewing needs ?, when the weather warms up and you get into a more serious tinkering mode, could you not mount your C-band lnbf at focus and suffer the slight Ku loss with side mounting the Invacom. Looks like you had some serious bud's in the past

 

[s-band]

Hi S-band & welcome

Thanks, John. I'd prefer to keep the Ku peaked and get something bigger for C again. The Fortec 2.4m seems cheap & interesting but I'm not sure about the bad press it gets. I still have a Chaparral co-rotor but was never happy with its Ku performance. If I got a Fortec I could try it again, its advantage was that it could be set to do linear & circular polarisation remotely.

 

[John]

Thanks, John. I'd prefer to keep the Ku peaked and get something bigger for C again. The Fortec 2.4m seems cheap & interesting but I'm not sure about the bad press it gets. I still have a Chaparral co-rotor but was never happy with its Ku performance. If I got a Fortec I could try it again, its advantage was that it could be set to do linear & circular polarisation remotely.

>> If I got a Fortec I could try it again, its advantage was that it could be set to do linear & circular polarisation remotely.<<
Strangely i'm just doing some evaluations on my recent C-band home -brew multi polarity project thingy on my 1.8 CM as opposed just using a single feed, to determine how efficient it was against the single feed.

Your intended C-band projects sounds good, look forward to your reports on your re-builds.

 

[Channel Hopper]

The IRTE 1.5m in almost every case outperformed the 1.8m Precision dishes I installed many years ago. The letdown was the first polarmount, the aluminium feed /feed arms that rot internally in UK weather so they have to be cut apart, and the thickness of the reflector that has to support the LNB(s) on its own. The reflector eventually distorts and loses some 10% of its efficiency.

If you have a straight reflector (a few dents are fine, just the edges need to be undamaged) then treasure it and don't hang a heavy scalar ring and LNB off the centre unless you give the reflector some additional support by strapping some braces from the feedarm supports to the latter six point backplate.

Oil/grease the polarmount bearings once a year and stick a carrier bag or three around them with cable clips.

 

[archive10]

The Fortec 2.4m seems cheap & interesting

...and is piece of cr*p. It is flimsy and made from thin powder coated steel sheets. It is tricky to get assembled so that all petals are well-adjusted, and it will rust from the day you stick it up outside. Anywhere you fit nuts, washes or bolts, you will scrape of the thin powder coating, and the dish will rust and rust.
I had the 180cm, and it was a real disappointment (but cheap).

It may serve well as a single-or-two-season C-band reception dish, but if you expect more longevity and performance, get a large mesh-dish or - even better - a larger used IRTE dish...
(Best is of course a large Prodelin or Channel Master, but these are expensive from new, and scarce as used...)

 

[amdade]

Hi S-band
very interesting mods on the IRTE 1.5, I also have the 1.5m, but replaced the whole feed mount with custom made support for C band Titanium LNBF. For Ku I use a channel master 1.2 on a technomate motor. I replaced the nuts and bolts with stainless ones some time ago.

I have a new motor on the 1.5 controlled by an old Pace positioner

What I would really like to find is some original IRTE petals to take it to 2m. Thinking about trying some home brew petals :-)

I also have the Fortecstar 2.4m which picked up for £195, while I can understand some of the negative comments I must say works well with c band, build quality better than I expected for the money. I have this one parked on 55W. Im thinking about getting this onto a polar mount in the summer.

Of course the US style mesh dish option would be good too, not sure where these can be purchased in the UK ?

 

[s-band]

Thanks for the comments.
John, when I used the co-rotor there were only circular polarised TPs so I did not get a chance to test its circ/lin feature. The KU has a loop coupling to the WG and a dipole in a corner reflector that rotates to set polarisation. I'm sure that lost a few dB.

Channel Hopper, Yes, it performed well and has been a bit like Trigger's broom. I replaced the original PTFE narrow band, domed, feed with a later IRTE one. Even with the Titanium I think the current arrangement is lighter than the original magnetic polarotor and SMW LNB but I like the idea of fixing to the back plate. Whilst the fixings are bad, the plate has survived reasonably as I Waxoiled it inside. I bought a new plate a few years ago which I have yet to fit.
I never liked the declination adjustment but the bearings are still good as I always oiled them when passing on the way to oil something else. I plan to take it apart (probably having to cut bits), replace fixings with SS and fit the new plate. I'll think about the feed tripod.

ST1, it was the cost that attracted me vs £fewk for a new ali dish. I tried the bodge fitment to the IRTE just to see what was around now. I suppose if it lasts a few years it may be worth it - unless someone has a 10ft Winegard they want to sell. I only want it for C band and below.

amdade, I saw your write up which almost persuaded me. 55W is of interest to me and that's in the trees for the IRTE. I want to keep the IRTE for Ku & Ka. I use a Uniden UST771 controller - they don't make stuff like they used to!
I don't think there ever were many big mesh in the UK. Mine came from Alston Barry. I like the look of these: RF HAMDESIGN - 4.5m on full Az-El anyone?

 

[John]

Thanks for the comments.
John, when I used the co-rotor there were only circular polarised TPs so I did not get a chance to test its circ/lin feature. The KU has a loop coupling to the WG and a dipole in a corner reflector that rotates to set polarisation. I'm sure that lost a few dB.

Exactly >>I'm sure that lost a few dB.[/QUOTE]<< ..... initial comparison tests on my old / new C-band poloriser showed at least one and a half dB increase . There are some very nice pieces of kit on that link btw

 

[amdade]

S-band thanks for the link very impressive.

I spent quite a while with my 1.5 IRTE trying to find 55W or 58W without any luck at all. The other pain of course is these two are linear where most of the arc is circular polarisation. Im still not 100% if trees were the issue or just not enough gain from the 1.5

So for now the old IRTE has the dilectric plate in, the fortecstar I have no plate. Im using an external switch with one cable feeding the three dishes into my Technomate RX. much more convenient than muddy feet taking plate in and out :-)

On the fortec star the bottom edge of the dish is almost touching the ground for 55 and 58. Both come in well, I was wondering about doing a dual feed 55 and 58....

Yes there will be some issues of rust but I have a tin of well known antirust paint on hand :-)

 

[renibacterium]

I have a 1.5 m IRTE and a 2.0m IRTE ( a 1.5 m dish with six added petals). First of all the 1.5m stand alone dish and the 1.5m dish with petals (to make 2.0m) are not the same. I don't think you can add the petals to a stand alone 1.5m IRTE dish ( at least not without some major work). Secondly, the tripod arms with the stand alone 1.5m IRTE dish are not ideal for C-band, they are ideal for Ku band. I bought longer tripod arms designed for C-band use from IRTE for the 1.5m dish many years ago for this purpose. Hope this helps.

 

[amdade]

Hi renibacterium
Thanks for the info, very interesting. I have extended my tripod arms slightly to allow me to get a more optimum focus point for the C band lnbf. Would need to come out further with extension petals :-)

My 1.5 has four fixing holes on the rim at 90 degrees to each other, I was assuming (maybe wrongly) these were fixing points for the 6 extension panels ?

If you could post some pics of the 2m back where the petals connect to the 1.5 would be great

 

[Channel Hopper]

It would be good to look at Evan's thread on Christina and the work required to construct extender panels from scratch. I have a couple of segments of a 3m fibreglass dish here. If I had time and enough incentives, I would be making sets of them for fellow enthusiasts.