2,4GHz transmission check

  • Hi All,

    thought I would share my plans for station monitoring in case somebody finds this useful. My approach is maybe a bit heavy duty for some, but this is how I am ;-)

    I have been scrounging bits and pieces from my junk box to put together a "Loop Test Translator". This is essentially a box that takes a sample of the 2.4 GHz uplink and downconverts it directly back to the downlink band on 10 GHz. For Es'hail-2 this means a local oscillator of 8089.5 MHz. This was something I already did many years ago when we (AMSAT-OH) were still developing the P3E/P5A linear/ranging transponder - it made testing the linear transponder a breeze.

    So far I have put together a 40dB RF sample port on a 2.4 GHz load that will absorb my uplink power (you could simply use a directional coupler in the antenna line and point the antenna to zenith for safe testing). This sample is further attenuated and fed to a surplus microwave mixer (Anaren 74129) and the LO is a modified PLL multiplier "brick" that I have retuned for 8.1 GHz output and uses a reference crystal of about 96 MHz that I found in my junk box (this experimental crystal is still about 3 MHz off at X band). Ideally, this should be 96.30357 MHz (84x) or preferrably 101.11875 MHz (80x, in my particular case) to achieve 8089.5 MHz exactly. The upconverted 10 GHz signal is then filtered, attenuated further and coupled to the input of my modified PLL LNB (SPC Electronics) using a waveguide directional coupler, just after the antenna feedhorn.

    In this way, it is possible to make a very quick test for overall station end-to-end performance, also on the WB transponder.

    Michael, OH2AUE


    "If you have data, you have something, if you do not, you have nothing." (Bengt Hultqvist, SK 24.02.2019)

  • Good old AOR5000 receiver with a SDR connected to the 10 MHz IF output. The BW is 10 MHz of the receiver.

    My old one is reaching 2,6 GHz. The last generation of the receicver can receive up to 3 GHz.

  • My plan is to use a Drake 2880 MMDS that I used for AO-40. This will be connected to a Directional Coupler via attenuators as not to overload the Drake. This will them be connected to a dongle, to give visual and audio indication, or to a receiver for just audio. The were a quite a number of these sold when AO40 was operating, along with a number of other MMDS converters. With this set up I will leave the coupler inline and will be able to monitor my signal continuously.

  • A very good and respectable motivation for sure, but if we are honest 99% of all hamradio operators don't do this. Going full duplex as suggested for satellite operations is very helpful here but the round trip time is messing with the brain. It needs a bit of practice to cope with a delayed version of own voice.

    You need experience of politics - speak regardless of what you hear is the secret.

  • Hallo zusammen,

    im Augenblick werden bei ebay aus Thailand für 14,- US$ (allerdings plus 24.- US$ shipping) „Norsat 2500 2.4 ghz to 144mhz Satellite Down Converter“ angeboten. Ich habe mir vor 3 Wochen einen bestellt, er ist vorgestern gekommen.

    Der Konverter macht einen sehr guten Eindruck und ist meiner Meinung nach den Preis plus Porto wert. Er setzt 2400,00 MHz auf 122.00 MHz um, ist also ideal geeignet als Erweiterung für bestehende SDR-Empfänger. Es finden sich im Internet relativ einfache Umbauanleitungen aus AO-40-Zeiten um den Empfänger im Amateurfunkband empfindlicher zu bekommen (Teflon-Klebeband auf das Bandfilter kleben). Für meine Zwecke reicht die Empfindlichkeit aus, ich kann damit mein eigenes Signal abhören und mit dem RSP1A eine einfache Spektralanalyse durchführen. Mit einer Kombination von Dämpfungsgliedern und Kopplern sollte sogar eine (relative) Leistungsmessung möglich sein.

    Short English-version: have a look on ebay for „Norsat 2500 2.4 ghz to 144mhz Satellite Down Converter“, sold from someone from Thailand. Converts from 2400,00 MHz to 122.00 MHz. Cost is 16 US$ plus 24 US$ shipping. In my humble opinion very good value for money.

    Vy 73

    Holger, DK8KW

  • In the attachment of this article you will find a detailed modification description of the xtal and input filters for 2300-2450 MHz.


    Success, Cor