finally the 500w 2,4ghz ready fo DVB-S2 tests. Designed by myself with Ampleon USA supports.
Produced by Fausto Coletti.
See the pictures.
Next Sunday DVB-S2 portstdown streaming tests with 250w new PA 105cm uplink dish.
- 500w-3.JPG (271.03 KiB) Viewed 1617 times
- 500w-2.JPG (250.35 KiB) Viewed 1617 times
- 500w-1.JPG (286.16 KiB) Viewed 1617 times
Nice job! I have a question: is the LDMOS soldered or only maintained by the teflon bar?
I have sucessfully used this sort of fixation for my 20 W 2.4 GHz amp, and was wondering if I could do the same with the Ampleon 250 W LDMOS?
Yes, only the bar not soldered but using a bit of
white thermal past. I’ve not soldered it bevause
I’ll use it at 200w maximum power.
I’m current using the 250w ampleon pallet witch has
the ldmos soldered to the pallet and the pallet
it is screwed to the case with thermal past.
an italian colleague used the bar only whith the ldmos
using the bar at 80w and i works.
How much power do you get out with -50 dB shoulders? At VHF I have found with standard LDMOS about above 10% of the maximum output the shoulders start to grow. That means a 500W PA is only really good for 50W on 4m and 2m in the special allocations where we have to be very careful not to radiate out of band. That's already above the power limit so its fine, unless we get a higher limit. Increasing the bias helps a bit but probably DPD is the answer.
About thermal past we've used non conduttive, we have not seen and kind of instabilities.
Abaout the power and shoulders I'll measure it as soon as I'll Made dvbs tests.
Currently I'm using the 250w ampleon pallet and getting around 80w with 40db shoulders.
As a rule of thumb to è stimate the shoulders I use cw maxi power minus 6db for 40db shoulders
and half of the power to get 35db shoulders.
For sure if you are using Umts amplifiers on 2,4ghz the rule is not valid.
I've also one other ldmos pallet on uhf having 500w but not used for dvbs, at max power I've mesured -60db at
first 500w Ampleon Pa tests, first changed PA to 105cm cable to 1/2inches Cellflex to stand up to 700w at 2,4Ghz as in attacched 105cm-ofset.jpg.
First dattv tx trial at 1Msymbol immediately stopped due to over power.
Second tests 2Msymbol see pictures 2Msymb.jpg.
Last but not least new upstation see Upstation.jpg.
Power around 130w shoulders 50db.
- Upstation.jpg (540.16 KiB) Viewed 1238 times
- 105cm-ofsset.JPG (824.69 KiB) Viewed 1238 times
- 2Msymb.jpg (909.48 KiB) Viewed 1238 times
- 1Msymb.jpg (828.15 KiB) Viewed 1238 times
the bottle is a curiosity killer…
I've done an hole in the roof exactly over the up station, I've than placed a pipe directly going to the roof offset dish.
It rained a lot during last month in Italy, sometime I had rain drops getting in, so I've decided to place a plastic box
to avoid the drops going to the PA.
Originally the bottle and syringe was to fill out the water…
Finally I've found the rain infiltration and solved the problem..
I'll leave everything just in case of Great Flood