Receiving system not based on Octagon LNB

  • I have been checking out today the receiver I intend to use for the NB transponder. This uses an EME quality preamp (ca 0.5dB noise figure) at the feed with coax feed to the downconverter at the back of the dish. The feed is a simple 22mm copper pipe squeezed down at one end to fit inside a WG16/WR90 waveguide flange.


    I have two preamps available, from DU3BC and F1OPA. They perform very similarly on EME, but I wanted to check first their gain response at 10.706GHz, since they both use internal bandpass filters. The results are given below. The DU3BC has slightly higher gain and was selected for initial tests.


    The downconverter is an old WDG002 design, which has a two stage preamp (tuned for 10368) and a pipe cap type image filter (tuned to 10488). Performance at 10706 is degraded compared to 10488, mainly due to the attenuation of the image filter at 10706. LO injection is at 2586MHz from an LMX2326 synthesiser, locked to 10MHz.


    Even though it is operating well above 10488, good signals were received from the 10706 beacon at an IF frequency of 362MHz - screen capture from HDSDR is attached.

  • Hi Charlie,


    I'm impressed with the signal strength you've of the 10706 beacon. Is that with your EME-dish?


    Btw, I'll inform Ron that his LNA outperforms ; -)

    Yes, that's with the 3m dish. Will try something smaller soon!


    The F1OPA preamp is a two stage design, hence less gain that Ron's.

  • Hello,

    I have an Octagon LNB for myself but, for new starters, it seems ebay and amazon is out of stock for octagon lnbs..


    Is there any other stable (no need for modification) LNBs that you found?


    Prefered aliexpress lnbs .. ebay (paypal) is not valid in TA.. so we can not shop via ebay..

  • I have tested now 4 different low cost LNBs (WITH PLL, not the type with DRO as they drift even more). All of the LNBs with PLL drifts a lot so all needs to be modified for any serious downlink work at least. Unless you like to adjust the VFO every 10 seconds or so. There also seems to be some short term drift / wobbling.

  • Found some renamed chinese lnbs on market.. ordered some models and i will open them up to see if they have pll or dro..

    I got one of those SR-3602's and on the box and LNB there is NOWHERE the mention of PLL so I complained at the store and the assured me it was PLL.

    So I opened one and indeed it is true!

    (this LNB cost me only 7.50 euro including shipping... what times are we living in?)

  • I've tested two more, from amazon : The Ompticum twin lnc lpt-04h and the Inverto twin universal premium idlp-twl410-premu-opn.

    They seem to work ok, although the last could be tricky to disasemble due to it's packaging, I haven't tried that yet.


  • Well, it is still kind of disturbing for me that we can order such things in China, with free shipping by airfreight, for half of what it would cost to only *ship* the same item to somewhere inside the country.

    (not to mention that we paid 10 times as much for a simple DRO LNB not so long ago)

  • pe1chl You kill a lot of dealers when ordering in china direct. all these products are smuggeld into EU without any tax. no certificate of compliance, no ROHS, no return

    Well, it is not really smuggling. We can receive packages up to 22 euro in value without paying tax, above that we have to pay VAT and import duties, plus a 13 euro handling fee. So it is only attractive to order things < 22 euro and > ~50 euro.

    Frankly I do not care about ROHS, it is for careless consumers only. I do not dump my electronic waste into the environment, and like most amateurs I have more than enough stock of non-ROHS-compliant electronics (and solder) to make this little LNB insignificant. When it is discarded it of course goes to a recycling depot and the lead will not end up in the environment.

    Other compliance may be a factor, e.g. unwanted signal radiation.


    However, that is not my main concern. What I worry about is how it is possible to make and ship things so incredibly cheap. It likely involves non-environmental-friendly production, underpaid workers, people running their business but barely making sufficient income to live and eat, shipping things through systems that are only possible due to unjust exceptions (airlines paying no tax on fuel or fares, packages delivered for free in destination countries according to ancient reciprocal agreement) etc.

    It isn't (cannot be) a fair and sustainable system.


    And indeed, in the meantime it affects our local shops and dealers. They operate on a completely different regime. They have to charge VAT, and they cannot ship anything without charging at least 10 euro for shipping&handling realistically due to much higher shipping and wages here.

  • I have tested now 4 different LNBs (WITH PLL, not the type with DRO as they drift even more).


    All of the LNBs with PLL drifts a lot, so all needs to be modified for any serious downlink work at least.


    Unless you like to adjust the VFO every 10 seconds or so. There also seems to be some short term drift / wobbling.