DTV LNB Mod; Ku Conversion, Part One

[Hermitman]

I modified a couple of LNBs using a slightly different technique, specifically in the adding ceramic to the puck and also the tuning area. For adding more ceramic to the puck, I used the ceramic puck out of an old, noisy c-band LNB. (They're all over the place for nothing) The pucks in these LNBs are donut-shaped. Using all possible safety precautions (disclaimer), I used a dremel tool to enlarge the center hole so it would tightly fit around the KU-band ceramic puck. I trimmed the outer ring area with the dremel tool till it was about 1/16 to 3/32 thickness. I then superglued the newly made ceramic ring to the puck. As far as tuning goes, I connected this modified LNB to my FTA receiver and pointed it at the floor. I then would input different L.O. frequencies and look at the signal readings (not quality but just signal noise). I found the highest signal reading happened at the frequency the modified LNB was resonating at. I would then grind a little off the puck till it came close to the 10750 frequency. Slight adjustment of the tuning slug would get it real close, about plus or minus 2 mhz. I've had one of these LNBs pointed at 123 degrees for going on 3 years now with no problems and good stability. Good luck and have fun.

 

[sidha]

Well I have managed to convert 1 LNB without resorting specialized equipment although I was really tempted with the LO setting. As I am in Europe at the moment I set my dish on Arabsat 26 east which has a massive signal and was pleasantly surprised with the quality, on a weaker sat 12w I still got good quality. It suffered some frquency drift at the top of the scale and could not reach all the european Ku higher frequencies but it was a really worthwhile project. //....

I was impressed with the performance on 18" - 20" Dish 500 reflectors. Especially when used on a Primestar, where the dish to feed illumination is a mismatch.

 

[sidha]

I modified a couple of LNBs using a slightly different technique, specifically in the adding ceramic to the puck and also the tuning area. For adding more ceramic to the puck, I used the ceramic puck out of an old, noisy c-band LNB. (They're all over the place for nothing) The pucks in these LNBs are donut-shaped. Using all possible safety precautions (disclaimer), I used a dremel tool to enlarge the center hole so it would tightly fit around the KU-band ceramic puck. I trimmed the outer ring area with the dremel tool till it was about 1/16 to 3/32 thickness. I then superglued the newly made ceramic ring to the puck. As far as tuning goes, I connected this modified LNB to my FTA receiver and pointed it at the floor. I then would input different L.O. frequencies and look at the signal readings (not quality but just signal noise). I found the highest signal reading happened at the frequency the modified LNB was resonating at. I would then grind a little off the puck till it came close to the 10750 frequency. Slight adjustment of the tuning slug would get it real close, about plus or minus 2 mhz. I've had one of these LNBs pointed at 123 degrees for going on 3 years now with no problems and good stability. Good luck and have fun.

I'm suspicious about how safe the DRO ceramic dust is, once ground into fine particles and airborne. Besides, I'm not patient enough to grind and sculpt away at those pucks, when I can just shatter the puck inside a thick plastic bag, remove a few fragments and epoxy to the DRO to be modified, with enough puck debris left over for several more. I've got it down so I can almost eyeball the required amount, on the first attempt, done in about a minute. I suppose one could weigh the pieces to measure what's required, too.

I like your signal level peaking method for tuning the puck mass. I've used a sat finder meter that is far more sensitive than the signal readings on a receiver. But my comparisons were done alongside quality readings, and for another reason. Sometimes I would notice an unusually high signal level, which I suspect was more a result of phase noise, as the quality percentage would dip at the same time. Maximum quality did not necessarily coincide with a 10750 LO. Which suggests that a low quality reading, borderline transponder situation could be improved if the LO is other than 10750. Introducing a transponder frequency offset matters less in this case.

Even in a standard KU LNBF, the IF band isn't linear with respect to each transponder. Sometimes the lower half performance is better -- assuming the coax run doesn't interfere. Not that it matters much, unless you're able to manipulate a critically weak transponder up or down the IF segment by broad tuning the DRO. Like what was also done during the era of remote tunable LO downconverters, before block converters allowed for a fixed stable LO married to the LNA. An added feature in LNBF mods is that one can steer things around to peak for results per a specific transponder, and with some satellites in certain situations, it might be significant. This is more interesting than just buying a KU LNBF for a plug & play experience. It's more fun to explore inside the case and discover what's possible by working with the variables; tweak it to do some special tricks, so to speak. Nice to have that opportunity once in a while; component level hardware to human interaction is becoming a lost art.


-sidha

 

[Cadsulfide]

I know that in transmitting and microwave tubes the ceramic contains beryllium oxide which is extremely toxic if the dust is inhaled, don't know the composition of the ceramic in a lnb but would'nt chance grinding it.

 

[sidha]

Most likely not highly toxic beryllium oxide in the mix; no need for high temperature thermal conductivity. But since the composition is unknown, along with traces of foreign contaminants... being cautious is being berylliant.

 

[Cadsulfide]

That's too punny! LOL

 

[scrungy_doolittle]

dish pro

I have a couple of dishpro dual lnbs and some singles, as well as a working 36 inch dish with it's lnb.
I am wondering of I can mod the dispro dual so that I can pick up both AMC4 and Galxy25 like the glorystar setup.

When I clicked on the picture links in the first page of this thread, they come up as 404's
Can you please update the links?
no one described where to put the ceramic on the puck, nor what the purpose of adding it is, and without a visual I can't even get started.


Cheers
Woody

 

[Anole]

I have a couple of dishpro dual lnbs and some singles, as well as a working 36 inch dish with it's lnb.
I am wondering of I can mod the dispro dual so that I can pick up both AMC4 and Galxy25 like the glorystar setup.

Two points for imagination! - :up - :up

Unfortunately, the spacing between LNBs is too far apart for those satellites, if used on the original 20" dish.
... and the dish is too small, as well.
LNB spacing is dependent on the focal length of a dish, so ....
I'd have to calculate what the DishPro 110/119 would do if used on your 36" dish.
But I'm pretty sure they're still too far apart.

 

[sidha]

Using my oval Primestar I was able to do 8 degree spacing for the two satellites mentioned, but it was necessary to trim away a fraction of the scaler ring from the KU converted single feed.

I never completed my conversion project on a solid twin feed where one DRO is a shared LO for both LNBF's. I planned to make it KU and change the SW-21 switching on Legacy heads to 22K. Unlike the SuperDish, the twin feed head isn't a good candidate for co-feed separation reduction surgery.

I have my DRO conversion photos that once existed inside this project thread. I'll try to put them back up soon. Maybe even find some time to pursue new ideas, but outdoor projects are more enjoyable on warm summer evenings.