Transverter to 2,4 GHz with 28MHz input for the uplink TX, does a product or kit exist?

  • To be able to use a HF transceiver that has no 144 or 432 MHz capability I am looking for a tTransverter to 2,4 GHz with 28MHz input, does such a product or kit exist?

  • You should ask Darko if he had tested the BU-500 up converter on 10m Input. The LO is able to cover 10m.. I am running this with 2m input and this works.. also 70cm input

  • To be able to use a HF transceiver that has no 144 or 432 MHz capability I am looking for a tTransverter to 2,4 GHz with 28MHz input, does such a product or kit exist?

    Probably not. The problem with upconversion by mixing is that the output of the mixer does not only contain the wanted product Fosc+Finput but also the Fosc-Finput (the mirror) and the Fosc itself.

    When the ratio of mixing is too large, like when going from 28 to 2400 MHz, these products are relatively close to the wanted frequency and more difficult to filter.

    Remember the entire 13cm band is from 2320 to 2450 and so a single fixed filter would not do anything at all, it would have to be a tunable filter.

    Even when you restrict the use to only Es'hail-2 there would still have to be a filter that passes 2400 MHz and strongly rejects 2400-28 and 2400-(2*28) MHz.

    While that of course is possible, it makes such a transverter harder to construct than one with an IF of 432 MHz, where the unwanted products are 2400-432 and 2400-(2*432).

    (even using 144 MHz as a first IF is something I would rather avoid when starting with zero requirements)


    When you really want to start with small budget it may be better to look at SDR solutions. While an SDR suffers the same limitations, the unwanted frequencies are so close (the IF is normally near zero) that it is okay when they are down by at least the S/N ratio of the signals on the transponder plus some margin, say 30dB total. That is achievable with an I/Q system as used in such SDRs.


    Ready made SSB transmitters for the Es'hail-2 uplink will likely be developed and become available, but right now there already are stations that use something like the ADALM PLUTO with a small 13cm pre-amp and a WiFi booster as a final amp, requiring at most some filter for really clean signals.

    Such a construct would cost ~300 euro in total, plus of course a computer to run the software.

  • Hello

    .........but right now there already are stations that use something like the ADALM PLUTO with a small 13cm pre-amp and a WiFi booster as a final amp, requiring at most some filter for really clean signals.

    Where can i find more Infomation using an ADALM PLUTO for TX ing to QO-100 ?

    tnx

    herbert

  • Mike5000 There are quite a few people active on Es'hail-2 / QO-100 with 28 MHz as IF. However, they use an 'inbetween transverter' to convert 28 MHz to either 144 MHz or (preferably) 432 MHz or other

    frequencies.


    Here you find a cheap 28/432 MHz transverter. Of course it is not 'top of the bill', but good enough for your purpose and/or to play with (for that little amount of money). You can interface this transverter to e.g. a SG-Labs transverter or Kuehne upconverter to produce the 2400 MHz uplink signal.


    For the receiving end you can either use a RTL-stick (TCXO) and a PLL LNB, or upconvert the 739.5 MHz (10489.5 - 9750) to 2400 MHz (with another converter ; -) so you can use the receiving part of e.g. the SG-Labs transverter as well, or ... you can downconvert 739.5 MHz to 432 MHz with a home brew converter. Such a 'in between -in between-' converter can be very simple as it's only purpuse is to serve you 'in between'.


    If this all is too complicated, then consider buying an all mode 70cm transceiver and save yourself the hassle ; -)

    (however, it IS possible, like I said, several stations use the aboven mentioned setup succesfully).

  • The BU500 has a to high LO level (-3dBm) on the output side.


    To be in the given specs here in DL you must use a additional filter after the BU500 to get the LO signal to a acceptable level.


    Better >= 50dB from the 2,4GHz to the 1,970 LO must be achieved.

    Without additional filter the difference is only abt. 30db!


    A friedly OM told me about that issue.


    I was suprised as the BU500 has already 3 filters after the mixer on the PCB.


    VY73 DB8TF

  • Measured today, sig on 2,4GHz abt 27dBm (0,5W) and LO on 1,97GHz -3dBm (0,5mW) as soon as the BU500 is powered on.


    I inserted a filter from a old FritzBox after the BU500 and the LO is gone.


    vy73 DB8TF

  • I will do my measuments again and then post it as well.. may be there was a change on the BU-500 and there are at least two versions in use.. I also will ask Darco this..:thumbup:

  • Where can i find more Infomation using an ADALM PLUTO for TX ing to QO-100 ?

    tnx

    herbert

    These stations are usually using the newest version of SDR-RADIO which has support for the ADALM PLUTO.

    It generates about 0dBm at 2400 MHz so you first need to amplify this a bit (say 10-15dB) with one of those generic amplifiers, probably insert a simple filter centered on 2400 MHz, then a 5W or 10W WiFi booster. Those items are available from our Chinese friends for bargain prices.

    The frequency stability of the ADALM PLUTO is not great, it is better to replace the 40 MHz TCXO with a better one or a GPS-stabilized source e.g. the Leo Bodnar Mini GPS clock or some home-made thing.

    But frankly it would be best to replace the ADALM PLUTO with something that is specially designed for this purpose (better TCXO, 2400 MHz filter included, a bit more output so it can drive a WiFi booster or even with integrated PA).

    Such a box will undoubtedly appear on the market.

  • In my opinion the hobby is experimental radio research. So you're allowed to make some (accidental) 'mistakes' while experimenting. If ones goal is to get across the transponder on microwaves (2400 MHz up) more 'degrees of freedom' are valid

    (and then a good antenna may be also a good filter).


    So ... let's not talk .. but build! (and increase the activity because it's too quiet for such a 'game changing' payload with spectral impact in the amateur bands on a commercial broadcasting satellite!