Posts by DL5CN

    Hallo,

    I had the chance to have a look at the intermodulation distortion of a "Chinese Pluto". It was disappointing a bit. Originals and LimeSDR Mini do much better.
    Can anybody confirm this?
    There is no idea where the reasons are. The Chips are the same. Power Supply, layout
    Don't panic, we will go further.
    73
    Andreas

    Hallo Achim,

    I know the datasheet. But are there amateur constructions which confirm this really? Unfortunately nobody does IMD-Measurements. Between my small result and what the datasheet says is a difference. I would like to know where the mistake is. From my point of view, the chip seems to small for 27 Watts SSB-PEP. This means two carrriers with 38 dBm. Does the above diagram show what we call linear operation? More Spacing of the single carriers gives less dissipation. A two tone measurement with the usually small spacing signal from a Pluto or Lime would be appreciated.
    73
    Andreas

    Hallo,

    What is the difference between a WIKI and a FORUM? One have to read it otherwise it will not help. In a WIKI it is better structured probably. But the informations are the same nearly.
    After some measurements and discussions about amplifiers, I think, first we need a paper about intermodulation distortion and how to reduce it in praxis. I often read and listen to informations about single carrier output. Without results about the linear operation range of an amplifier it has no releveance. In the past there were no easy to handle two tone signals. Now with digital systems it is simple.
    73
    Andreas

    Hallo,

    I am looking for a reliable information which intermodulation distortion can be reached with a Freescale MW7IC2725. My result is approx. 30dBc at 8 to 10 Watts PEP. I don't know if this is the end already. Optimizing the idle current of the two stages does not give a general improvement. Single tone power is not interesting but together with linearity two tone measurement.
    Thanks
    73

    Andreas

    Hallo,

    if there are any ideas what we can do further to organize more and better knowledge transfer please publish it. This year all the meetings didn't take place and we missed the chance for talks and presentations. Probably there are many papers and informations we can share?
    Good cops help old Ladies crossing the street. Let's do this with the Newbees if wanted.

    73
    Andreas

    Hallo,

    which tool is useful to predict the max. elevation of the moon? As far as I know it will reach 28,6 degrees. Will it be possible to receive the DL0SHF without adjusting the dish to a lower elevation? Some former tests in my court with a prime focus dish were negativ. I am not sure to see the cold sky, it seems like much noise from different directions. Weak signal experts like to use SpectraVue for receiving such signals. The vertical resolution can be reduced and there is a signal history mode also. It must work with other systems too, the receiving result is generally defined by the LNB and dish size.
    Thanks
    73
    Andreas

    Hallo,

    we don't need a qrp-day. I agree with Achim fully. Some guys don't know what intermodulation means and how to avoid it. That's it what we should talk about. All transmitters all amplifiers are not intermodulation free. As more stages are in the transmit chain as more intermodulation distortion can happen. Theory says a given stage should be 6 db better in intermodulation than the following one not to generate more distortion. If there are mixers and many amplifiers in a cascade, a correct leveling is important. SDRs and the software with a two tone option can do this easily. It is missing in many TRXs. May be an audio file with a two tone signal is possible like in the IC7300. This is not the best way but helps. An expensive spectrum analyzer is not nessecary. The satellit itself can show how the own signal looks like. If one don't have a duplex station which is strongly recommended, look to a WebSDR when transmitting to check the signal. It should show sharp limits without any products out of the filter in the water fall. I am afraid, stations with intermodulation products don't see a spectrum and probably don't work duplex. That's a pity. A free of charge WebSDR is a duplex receiver....

    Don't hesitate to ask if something is not clear. Good linear signals are our visiting cards.

    73
    Andreas

    Hallo,

    don't mix the Console Settings with the Plutos. The Adalm Pluto has a LINUX-System with some environmental variables that are changeable.

    There a two different ways to connect the Pluto with a host. Using DHCP with a router don't modify anything. In case of direct connection to a host, fix IPs for the Pluto and the host are necessary, see above example. Modify ippaddr_eth only. Additional at the host the Pluto's IP is required as standard gateway in the settings.

    After a restart, the Pluto-system uses default values. In normal operation this doesn't happen.

    Hallo,

    it is strongly recommend to use an external soundcard, especially in case of laptops. Some internal systems are not separated in input and output clearly. A simple external USB-Card will help. Probably the internal system must be deactivated completely.
    First, look at the Win-Setup. Check all the settings in the sound system carefully. If there is an AGC, don't activate it. If you find a level control slider in the sound system adjust it in a way that the VOX GAIN slider in the Console doesn't show overdrive. The VOX Gain slider shows the audio level input to the Console given from Windows. All this must work correct, the audio spectrum in the transmit window shows it without transmitting also. If there is less audio level given from Win to the Console something is wrong. At the lower right side in the transmit window there is a audio monitor. Some time ago, there was a recommendation to install a virtual audio cable to avoid distortions when using this monitor. Don't know why but it worked.
    If all this is running, use the equalizer to adjust more gain at higher audio frequencies and turn the compression on. Audio gain sliders shoud be at 50, compression at 30 for example. Set the booster to 5dB. If you need more, search the reason for it.
    At least it will be a very clear signal with high linearity and good frequency response. The RF Gain slider should not exceed 90. Don't hesitate to ask for more help.
    73s
    Andreas

    Hallo,

    here is a picture of a dish with beams (read lines) from the mirrors to the focus point. The mirror pieces are cracked from a bigger mirror. Take care not to get injured.

    The reason for this method was a false mounting. The wholes in the dish allowed to mount it wrong, the upper side was at the right side. It didn't work at all, no focus, much frustration. With the mirrors I found my misteake easily. With the top side on top, all is fine.
    It is a little bit difficult to hit the sun but with some trials it will be ok. Follow the beams from the mirrors to the focus, the correct position can be found. It can be used also with a dish and unknown focus point.

    73
    Andreas

    Hallo Jabi,

    take 3 very small pieces of a mirror and glew it in the dish at different places. The mirror surfaces must be parallel to the dish. With thin double-sided adhesive tape it will work. Turn the dish to the sun. With a sheet of paper you will see, where the sun beams meet. With this method it can be seen also , if the dish surface and the paraboloid shape are correct still.

    Have fun.
    73
    Andreas

    Headshaking Modus on

    What a strange discussion?
    Don't look at the bandwith. Take care about the audio frequency response to generate SSB with good readability. Many signals waste much power closed to the carrier. In the literature there is a clear information to increase audio gain with 6dB /Octave. In wireless communication the power densitiy spectrum must be filled everywhere constant to get good reports even with low power and noise. Another question is compression. One can found literature information there also. The readability increases with a specific degree of compression. I don't mean clipping but level control without additional distortion. At least the linearity of the transmitter chain should be good enough for a clear signal with the same bandwith as the SSB-Filter has. Carefully leveling and level control help a lot. All this is implemented in a SDR. Believe me or not, digital technology can be very senseful in transmitters.
    Of course there are newcomers. That is what we want. They need help to optimize their stations.
    Headshaking Modus off

    Let's be good Oms and give support in a friendly and hamlike way. To go forward as an example I wrote a paper (German) about my radio. Send me an email if you like to get it.

    73
    Andreas

    Hallo,
    after playing around a bit with the SAA_2N, I found, the firmware works. It is difficult to calibrate the touch display. After finding the right button and sticking the upper left and the lower right corner, all is fine. Putting the device into DFU, press the left cursor button and switch on. Connecting QT leads to the update menue.
    But, don't update anything until there is more clear information. At present we have some confusion about the display size and the corresponding firmware.
    73
    Andreas

    Hallo,
    please don't talk about power without any information about linearity. Even with a Pluto there is a very useful two tone generator. And with the receiver itself you can have a look to the output spectrum. Use a dummy load and attenuators to feed the signal back to Rx. It is very easy. You can use it as a perfect spectrum analyzer. The absolute power is not important but low intermodulation distortion. It is a good sign to do a sharp limited band in the waterfall display. And it will be estimated from others.
    73s
    Andreas

    Hallo,

    I measured 800ms delay between pressing the PTT at Console Input or clicking on TX-Button and Pluto- GPO-Signal. This was confirmed by Evariste, F5OEO. Hew wrote me, this is the round trip of his firmware_031. He wrote also, this can be reduced to some milliseconds but I don't know if this is done already. Meanwhile, I found the POE-Adapter-Solution and it works well and very fast. And was copied by some friends.

    To avoid missunderstandings, the delay was not caused by the Console or the method how to activate the transmit mode. Keeping the amplifier in TX-Mode, the delay was very low also. So, the Pluto was ready to transmit but the Amps were switched on and off with 800ms delay. Using the Ethernet-Line is very simple and cheap and there is no distance limit.

    73s
    Andreas

    Hallo Christian,

    using the Plutos GPIO-Port to get a PTT-Signal means a delay of 800ms. Look at my report about PTT over Ethernet.
    It is just some postings before. The POE-Adapters are very cheap and can simply be sticked between the Ethernet-Connectors.

    800ms delay are not problematic for DATV but for SSB and CW.
    Beside this the USB-Relays for PTT-Input and output allow a hardware switch may be integrated in a microphon. From my point of view it feels better then pushing the TX-Button with a mouse.

    73s
    Andreas

    Hallo,

    look to this thread.
    PTT over Ethernet

    SDR-Console supports PTT-IN (USB to TTL Adapter) and PTT-OUT (HID kompatible USB-relay).

    The USB to TTL-Adapter should contain a FT232 Chip from FTDI. A status line can be configured and used with a microfon button. It works with VOX also.
    The output relay must follow the HID-Rules (Human Interface Device).

    To bring the PTT-Signal to the amplifier use two POE-Adapters on each end of the Ethernet cable. There is no distance limit.


    The GPIO-Port of the Pluto gives a PTT-Signal also. This requires firmware from F5OEO. Unfortunately there is a delay of about 800ms between Tx on and PTT-out at the GPIO-Port. Evariste, F5OEO told me, this can be reduced.
    There is no matter for DATV. But fast SSB-Talking is much better without this delay.
    That's why, I prefer the POE-Adapters.

    73s
    Andreas

    Hallo,
    CN0417 Cool Down.
    With the help of a very kindly Applications Engineer of AD the Rev C of the CN0417 is clear to me now. The additional chips are a temperature switch U2 and a tri state buffer. The buffer U3 has an output enable pin. It is clamped to 5P.


    This is the backside of CN0417. Remove R6.

    Patch 1k from Pin1 of U3 to GND. Patch a pull up from Pin4 to 5P. The PTT-Signal to pin1 of U3 changes between 0 (Rx) and 5P (Tx).
    The current consumption goes down from 600 mA to 40mA and is good for stby.


    Again, the help of the Applications Engineer from Analog Devices must be higly appreciated.

    Save current, avoid heat.
    73s
    Andreas