The tip to receive was to use the USB 3 port of my laptop. Using USB2 no luck !!!
Posts by SV1BDS
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Hi,
I have received for the first time using Pluto and 2.0.16 . But the signal is not stable. Any ideas ?
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SV1BDS I'm using a design similar to yours, it is sold in DL by DH1ND (see his QRZ.com page)
Another design and an extensive discussion can be found at https://www.helitron.de/dj0abr/index.html "Helix Feed für es'hail-2", (unfortunately in german only but with many pictures )
My combination of Helix-feed and LNB works well, a little bit better than a POTY feed for RX and a little worse than separate TX and RX antennas. By "a little" I mean differences less than 3db in RX, I noticed practically no difference for TX. When transmitting in SSB I sometimes see a "ghost signal" on the waterfall but my receiver is never desensitized.
73 de Greg
Maybe the diference is due that my antenna has a plastic tube that has no effect at 2.4 but it may have significant loss at 10.5 GHz. Also the Amiko L108 may desensed from 2.4 GHz. I will make some lab tests to find the reason for both problems. Also I plan to try a dual feed antenna (patch & LNB). I will keep inform for results.
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Also this effect I've observed with my Winkler-helix. Offset your helix a little bit to left seen from antenna to dish. Post an actual photo pse.
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The proposal is to have the LNB and Helix not together but offset from one another, e.g. the helix above the LNB. This will impact TX efficiency because the beam is no longer precisely towards the satellite but hopefully not by too much as the beam at 2.4 GHz is 4 times as wide as it is at 10 GHz.
OK I got it. I have try this and I have seen the Tx drop.
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Sorry, I can not understand! I have a Rx signal drop , more precise SNR drop about 10 dB. The Tx is OK. What is your proposal?
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HB9SKA The LNB is inside the helix.
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The only way TX should be able to desense RX is for there to be significant 10/12 GHz energy from harmonics of 2.4 GHz. The 2.4 GHz fundamental will not get through the waveguide - (as long as it is long enough, which it should be). Does the same desense occur with a patch rather than a helix?
Hi,
I do not have try patch yet. I have a 10.2-15GHz bandstop filter that may solve the problem, it has about 0.5 dB loss at 2.4 GHz.
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Hi,
The conclusions from testing dual feeder are :
1) No important Tx signal drop exists due to LNB lens that exist inside helix.
2) Rx is desensed while Tx-ing and is not usable (in my case is not a problem as I plan to use only half duplex).
3) SNR (while not Tx...) is reduced by more that 10 dB comparing to LNB standalone operation. The obvious explanation is that helix blocks the Rx signal.
Any similar experencies from others for 2 & 3?
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But keep in mind to add a lo-pass filter after the last Amplifier to keep the signal sine form and not to "send out" harmonics.
25 MHz x 3 = 75 MHz (security Band) and 25 MHz x 4 = 100 MHz (Public radio Band).
Also you may disturb yourself in the SAT IF.
73s
Armin DF1QE
If you use a MMIC it does not need a low pass filter as far as it is below 1 dB compression point and the 25 MHz is clean.
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Hi,
A dual feeder using modified Amiko L108. SWR is about 1:1.5.
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Hi,
Modification of Amiko L108 LNB for external 25 MHz.
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Hi,
I use a MAV11 MMIC for boosting 25 MHz reference. The advance of using MMIC is the 50 ohm in/out termination. You can of course use any similar one.
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Hi,
A PE4302 parallel step attenuator was added to the 28/430-739 transverter. Two BCD switches was added, omitting 8 on both switches as 6 bit (3+3) is required.
Project is now consirded closed !!!
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Has the design and code for GPSDO this been published anywhere ?
Hi, this is : Lars GPSDO , I finally use updated code (variable TC) from PA3FYM modified by me.
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yes, but driver and pre-driver get 3,3V instead of 5V.
all measurements on the datasheet are taken with VCC1, 2 and 3 at 5V.
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Hi Claudio,
This mean that it takes 5V at the final stage and not 3.3V.
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Hi i2NDT can you tell me the voltage at pins 4,11?
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„i2NDT“ sent you a message on AMSAT Deutschland e.V. Forum:
hi George,
I measured my amplifier and found out that its power output is only 25dBm for 0dBm input.
power supply was 5V and consumption 500mA.
I guess that the difference (they said 30dBm output) is due to the fact that the amplifier is powered with 3,3V (on board LDO regulator) instead of 5V as per the datasheet...
BTW there is no need for a big heatsink as the sky65135 doesn't heat!
best 73
de
i2NDT Claudio