Posts by om0aao

  • console crashes

    I am using Atom n270 with 1GB RAM under W7. Bandwith 1MHz. Crash occurs if satellite stabilisation together with NR is used. Maybe other app running on the background is causing problem. Turn off everything You can and try

  • What TX amplifier do you plan to use?

    Hello Roberto iw5bsf , thanks for suggestion! I am now using only test configuration. I need to solve some things, the main is BIAS because it varies a lot with a temperature change. Will try BIAS with LP2951 IC.


    The 2nd thing is match with a driver, agree!

  • What TX amplifier do you plan to use?

    I ak using modified Andrew PA with MRF. Measured gain around 10,5dB with possible match till 2360MHz. Tried several tweaks but witout luck.


    Works on 2400MHz with not good match but Can deliver around 12 - 15W from 2W. Bias 0,5A at least! With lower bias amplifier lost gain.

  • Would a 744MHz filter help?

    G8UGD Hi Adrian, one more thing that I can suggest... I have tried various bandwidths with RTL-SDR and SDR Console. Reception with 250kHz bandwidth was signifinatly worser than with 1MHz bandwidth. Let's try to adjust that.

  • SDR bandwidth change gain and SNR

    G8UGD Thanks Adrian, but the surprise is that, I got better resulst with a wider bandwidth. Achim DH2VA has probably right that it depends how Simon calculates noise.


    I have tried:

    • 250 kHz bad results
    • 1MHz good results
    • 1,5MHz the same as 1MHz
    • 2MHz the same as 1MHz


    I have not tried 500 kHz yet.


    It's good to know for somebody that the reception with SDR could vary with the bandwith differently that in analog world. Thanks!

  • SDR bandwidth change gain and SNR

    Hello,



    did anybody notice that the bandwidth of SDR radio noticably change sensitivity and SNR? I am using SDR Console with a newgen RTL2832 dongle with standard setting of bandwidth 1 MHz. If I set 250 kHz, the gain, sensitivity and SNR change. Why?

  • Polarization Losses on QO-100 Uplink

    I have tried to make a circular feed based on the idea of DC2TH with a 2x 4el. PCB yagis from LZ5HP. I found that one yagi gives me good result so I decided to try this feed. Used 100cm offset dish.


    I make similar construction like this one:



    But I have make a small experiement with 1 yagi only. If the yagi was horizontal (above or bellow LNB), the signal was noticable stronger than I try vertical (left or right). The difference was abt. 4dB.


    Question - it is due that the feed is not absolutely in the focus point or due that the offset dish push the energy not consequent?

    Did anybody observe similar results?

  • DX information in Shoutbox

    What do You think about writing QRZ + QRG in the forum? Of course, EL2DT similiar DXCC are quite interesting for anybody. But in past SAT HAMs were making an experiments - building stations, antennas, accessories, trying to excess distance records going portable etc.. It was good for someone who is interested in science and Eart-something-Earth communication but does not have a room for solid EME antennas.


    DX hunting was something mostly dedicated to HF with all behaviors of operation.


    I wonder is somebody can run on the transponder with homebrew setup, developing software, make realy QRP contacts etc. But that's my opinion. What's Yours?

  • Let's build a PA for 2,4 GHz

    Quote from PY1SAN

    OUT: 21W

    IN: 2W

    24VCC


    Hi Sandro,


    Is that right, please? What's the Idq please? If I know, it is needed around 0,3 to 0,5A idq at least. So there is max. 0,6A of active current as photo shows.


    24V x 0,6A x 50% eff. = 7,2W out


    I am running 28V with Idq 0,5A. The output is modified by idea DK5DN

    and input is my idea - make PCB line (add wire and solder) thick as I can. I am reaching 28V/2,2A in key down. There is 2W input (or less!) from LZ5HP transverter. I dont know the output. No power meter SRI.


  • Which feed for f/D 0.25?

    Unfortunately the dish was damaged in transport. But Santa (in June, hi) brings me a present - D6 analyser. Not calibrated yet, but it helps me a lot.


    There are 2 screens, one is before aligment, second after. It was tuned toho high.



    Did anybody try to Fred deep dish with a moxon? Or 2 moxons phased fór circular polarisation?

  • Which feed for f/D 0.25?

    PA1EW Hi Ed, thanks for suggestions! You have rights, the N-connector body stands off the reflector a little bit. Good point!


    It is small picture - the black material is 3mm drill used for correct spacing. There is nothing, the plate is soldered and holded by the live pin of the N-connector.


    Probably this type of feed is not suitable for f/D 0.25, the parabolic dish effeciency is only 50% depending on the study:


    [Blocked Image: http://2ingandlin.se/432_MHz_ES5PC_patch_feed_in_dish.gif]


    Probably the dish was designed originaly to feed with a dipole and rod reflector spaced 0.24 lambda or so. There is teoretical effeciency more than 70%

    http://www.w1ghz.org/antbook/chap6-2.pdf


    I rather changed my plans and order 100cm TV dish with higher f/D and will try helix. Think that it should work.


    Thanks!

  • Which feed for f/D 0.25?

    @dk0kp Hello Heiner, yes, the screews can impact to the patchfeed but I don't think that they make -6dB.


    Studying materials about the feeds as SM6FHZ comparsion or W1GHz. It seems that with f/D 0.25 have patchfeed low effeciency. The most suitable f/D is 0.4.

  • Which feed for f/D 0.25?

    Hi folks,



    I have tried to improve my uplink with a 120cm dish. This is an old commercial dish with a low f/D 0.25.

    Now I am using linear polarised WiFi grid antenna PW 24 dBi,


    Due the low f/D I have choose K3TZ patch feed. I was calculating with a gain of 3dB for circular polarisation and 6dB for mechanical dimensions.


    Test shows only +3dB.


    I can confirm that th feed was placed correctly in focal point and SWR was not bad (indication on LZ5HP's XVRT), The reason why I did not reach the estimated gain is probably that the feed has not so wide radiation angle as I need for f/D 0.25.


    To imagine that 120cm dish has 30.8cm depth and focal point is 29.2cm from it depth.


    Has anybody an idea for circular feed for this parabolic dish, please let me know.