Portable offset dish with dual feed

  • I want to present my design for a single-dish portable station as described below and partly shown in the pictures. For me it should meet the following requirements:

    ·       Easily detachable construction (transport by car)

    ·       Single offset dish 60cm, dual band feed

    ·       Stable tripod mounting

    ·       Comfortable adjustment of dish heading

    ·       Compact “radio-box” to carry two full-duplex transceivers + SDR

    ·       12V operation (battery) possibility

    A new adapter bracket (picture 1) was constructed to mount the Triax 64 dish in a stable way to the tripod pan-tilt head. The dish's own (elevation)adjustment is fixed and not used. Another bracket (left side in picture 4) is added to carry the plastic box with Mini-GPSDO 27,841846MHz + 30MHz low-pass filter + battery pack 5V.

    As my modified Octagon LNB was readily available to be combined with the 5,25 turns LHCP Helix, I choose this for the moment above the patch-feed to be used as dual feed. The Helix/LNB mounting has been improved from the quick-and-dirty tape-construction to the detachable- and adjustable Helix-reflector mounting as shown in picture 2 & 3.

    The construction allows also for LNB skew-adjustment rotation at any time. Releasing the two wingnuts (pictures 2 & 3) on the sides will then allow for LNB –focus adjustment, the Helix reflector is moved too. The Helix reflector is held in place also by the front-section of the Octagon LNB.

    Last item to be finished is a compact housing for the FT817 (144MHz TX driver) and a TM-455E (435MHz RX). The modified MKU2424A (=B) up-converter will be placed on top. A compact 13.8VDC/22A SMPS supplies the power when 230VAC is available, when not, a 12V gel-battery could be used. Hook-up for SDRplay RSP2 is also foreseen. Hope to work you soon via QO-100 with this portable station!.

    I am curious who has similar- or totally different portable constructions, please let us know and show.

    73 Ed PA1EW/P

  • Work-in-progress on the plastic "Portable Box". Fitting of the 144MHz driver (Yaesu FT817ND) and 435MHz IF-receiver (Kenwood TM-455E) on a metal sub-frame.
    Some smaller parts, like Bias-T, splitter and attenuator, will be placed inside as well.

    73 Ed

  • i2NDT Hello Claudio. The (very old) box is made out of a lightweight "plastic" and was available many years ago at a local electronics shop. I am not sure if this still can be found.It was unused by me for a long time, but now I finally found a good use for it...!.

    It measures 22 x 22 x 31cm.

    73 Ed

  • My idea:

    BU500 pre-programmed to make up conversion in 432.Very stable . Chinese 8w Wifi Booster , Mini-Kits EME225 modified relay (NC&NO) connected to ACC rear connector FT818. TX with 13v signal pin.

    The LNB is a TXCO 432 down high-stable PLL 1ppm from OK2ZAW.

    Semiduplex like a conventional equipment. Little adjustment with RIT in RX. BU-500 programmed as to almost perfect coincidence TX up frequency with RX down frequency. Tested . Just need to mechanise a box in tripod leg .

    No PC.Just a battery 12v or a little power supply, tripod and 60cm dish.



  • First field test at a demonstration last Friday at our VERON Maastricht Radio Club with the portable QO-100 full-duplex setup was very succesful.

    Initially tuned the 70cm RX to 435,800MHz (EB-frequency 10489,800MHz) and the beacon could soon be received with a clear and strong signal.

    Clear view to the sat with 20W from the MKU2424A into the 60cm offset dish producing respectable Up/Downlink signals. Even just on battery-power!.

    Fellow HAMs were surprised about the very good quality, like a local repeater hi,hi.

    73 Ed PA1EW/P

  • Tnx Heiner!. I am very happy with the setup. As expected the Kuhne MKU upconverter is perfect for this purpose and the Helix-dualfeed does also a good job. There is a RF-splitter in the box that will be used to connect to a SDRplay RSP2, but not used here to keep the setup simple as can be seen.

    Hope to work you and many others during my upcoming vacation when I will take the portable station along.

    73 Ed

  • The last picture did not fit in anymore(?). So, I'll show it here again.

    I have added also pictures of the latest status with improved mic-input to the FT817ND (lefthand side input via ethernet cable). This is much more convenient...

    73 Ed PA1EW/P

  • Hi, what size did you make the reflector in mm? and relative distances

    73 of iw5bsf Roberto

  • Hi, what size did you make the reflector in mm? and relative distances

    73 of iw5bsf Roberto

    iw5bsf Hi Roberto, the helix + Octagon LNB reflector dimensions are 120mm wide - 150mm height. The aluminum sheet I used is 1,5mm but 2mm would be fine as well. The LNB opening in the lower part is 58mm in diameter, this diameter is for Octagon OTLSO model. The LNB hole is at 10mm from the bottom of the reflector.

    The 5,25 turns helix, with 43mm diameter, is positioned just above the LNB (should have been in the middle, but mine came a bit offset to the side). You can see the construction in the pictures below. Also visible here is that the focal point can be adjusted at the same time for both helix and LNB.. The LNB skew rotation can be adjusted easily as well.

    P.s. I found that using a non-metallic (Teflon/Nylon) centre-support inside the helix provides less attenuation to the LNB signal.

    Good luck en see you on QO-100!.

    73 Ed PA1EW

  • Hello PA1EW,

    i am also build a portable station with 60cm Dish.

    IF all will work, i hope i am qrv at the end of Novemebr from EA7 near Cadiz IM66VO,

    See also ur Camper Car. If i am ready there i will post a picture on qrz.com

    vy 73 Klaus

    DL2FP Hi Klaus, looking forward to work you from your camper holiday location near Cadiz.

    Wishing you good operations with your portable setup, it is real fun!.

    73 Ed PA1EW

    • Official Post

    The 5,25 turns helix, with 43mm diameter, is positioned just above the LNB (should have been in the middle, but mine came a bit offset to the side).

    In principle I have the same dish setup as you with the (new) 5 turn Winkler helix above an Opticum LNB. With the helix centered to the dish I had a lesser strong signal than with a little offset to left, reflected to right, seen from helix to dish.

    This is an interesting observation I think. Who can explain this effect ?

  • thanks Ed PA1EW I try to build it while I wait for your answer, I realized that I was inspired by your photo but using a reflector I had the propeller 125x125 and centered but slightly above the return loss of 28 db trying a second transponder with 2watt and dish offset of 80 cm the return signal s7