given that the 4W boosters sell for 20 USD, using one as a driver stage for any 8W booster is probably easiest.. and if driven so far away from its limit, it will be linear enough for sure.
Posts by DH2VA
-
-
I was planning to carve a lens to be fitted in front of my LNB, to improve efficiency. The material I was planning to use is wax. Candle wax. Wax being a good dielectric, losses should be low, I hoped.
High frequency dielectric is characterized by both dielectric constant (the famous epsilon) and the dissipation factor or dielectric loss tangent (often quoted as tan-delta).
I would be very surprised to see a measurement for candle wax as its composition is anything but well defined. At best you could try to find it out for paraffin, but given its low melting point of 37degC, I would not recommend it for use in a feed.
Teflon is easily available, is well documented and has excellent properties at high frequencies. Try to carve a lens based on Willi's drawing.
https://rfantennas.wordpress.c…-dualband-feed-vergleich/
I just did so and upgraded my home setup to a POTY type with a teflon lens. No drop in RX performance compared to LNB-only setup (transponder noise still ca. 4dB above thermal noise on my 88cm dish) but I have now a TX feed in focus (wasn't the case up to now). More news next weekend at the UKW-Tagung in Weinheim.
-
kontaktiere bitte office@amsat-dl.org
-
The key phrase is here:
for NB, a 60cm dish with optimal alignment and suitable feed
we have seen many instances where a botched setup (bad feed, misalignment, ...) lead to bad performance which people believe that a big dish is required. Or even worse, they complain about downlink not working and just use any WebSDR.
On the other hand (and this pleases me a lot!) many OMs recognize that improvements are possible and tweak the living daylights out of their system. That's what hamradio is all about.
-
to summarize: for NB, a 60cm dish with optimal alignment and suitable feed will just be maxing out the downlink SNR (TP noise visible). For WB, I believe a 1m-1.20m dish is required. But for the latter some of the DATV experts should chime in.
-
The hardware solution was chosen because SDR Console actual is not able to mute audio if not using a limeSDR or so. (V 3.0.12).
I have a PLUTO and the mute function works really nice.
-
But if a station sends a weak signal to the satellite, let's say 100 mW and a 60 cm dish.
The transponder will output it with a small signal/noire ratio. Let's say 5 dB,
Will I be able to decode this better with a larger dish?
no because the received signal will be uplink-limited and not downlink-limited.. Nothing you can improve here even with EME-type antenna on downlink.
-
Ach ja, Du bist ja auf H Polarisation..
Tip: Verdreh das LNB jetzt so dass die Bakensignale minimal werden und dann schaltest Du auf 14V.. das sollte es sein.
-
Die RF-Verstärkung ist fast auf 0 gestellt, AGC aus.
Warum denn? AGC ein und RF Gain solange hochdrehen bis das SNR nicht mehr besser wird. Ob das Rauschen bei S0 oder sonstwo liegt ist nur Kosmetik.
-
G0MJW we do have a link budget with is in very good agreement with the observed performance. But as you feared, this has too much NDA'ed information in it and for the sake of staying clean, I will not publish any numbers myself (sorry for being paranoid).
However, if anybody else is generating a spreadsheet which can be verified by the QO100 community, there is nothing we can do about...
-
My guess: dBFS (full scale). Whatever your RX is, 0 dBFS is ADC just saturating so you want to keep well clear of that. In general, dBm scale for QO100 is rather meaningless, as there are too many variables which influence it.
-
Just a remark on the Tc: having the GPSDO optimizing its Tc is a great thing but the conclusion that higher Tc automatically means 'better OCXO' is only partly true.. it can also mean 'shitty GPS receiver' as the control loop needs to average longer to benefit from the GPS information.
When developing such a system myself some time ago, I could easily go down 10x with Tc (while keeping performance) once I included the sawtooth correction from a proper timing receiver. See also www.gpstime.com from Rick Hambly W2GPS (former AMSAT-NA president).
-
Please do not contact BAKOM directly but rather get in touch with Bernard HB9ALH who is the USKA contact. He has been extremely helpful in the past with such requests.
-
-
according to Figure 6 of the datasheet, 1200mA is the sweet spot. More Idq makes things worse.
-
140W CW is single tone performance.. call it P1dB. 30W is W-CDMA performance with a specified ACPR (adjacent channel power ratio) of -41dBc (according to datasheet). So the 30W is more likely the usable DVB-S2 power in our situation.. which incidentally is about -6dB of the CW output power. Seems to be a good rule of thumb according to the BATC experts.
-
steady MER here on my 88cm dish, no changes
-
Do you have a photo of your suspected joint? Input or output connector?
-
Is the yellow mating piece electrically conductive? It should be otherwise you lose quite some signal.. there has to be currents flowing in the walls of the waveguide..
-
Thanks for your predisposition PA3FYM and DH2VA!
More less! The exact description would be: Developing a link budget tool and use DH2VA spread sheet and ES' Hail Sat 2 to validate it!
I have been working with this famous spreadsheet! Right now I am stuck because I do not really know what is the the current state of QO-100: Output power, back-off, #of channels... Do you know where I can find this data?
Thanks
!All credits for this spreadsheet go to Jan King, W3GEY... I am a mere user. About the QO-100 data, I am afraid all of these parameters are confidential due to NDA.
