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Acceptable feedline loss for satellite operations?

Discussion in 'Satellite and Space Communications' started by WA7F, Nov 4, 2019.

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  1. KS1G

    KS1G Ham Member QRZ Page

    You mean like this:

    I got ideas from the Rohn catalog and built a zero-pen base from big-box store angle iron bolted together for our recent ARISS QSO. Mast is 1 1/4 iron pipe threaded into a floor flange on a hinged based, braced as shown. Rubber roof mat underneath. Concrete block ballast. Held up quite nicely through a strong frontal passage with wind and heavy rain over the weekend before the contact.

    Observations: A 6'x6' base is very stable and wasn't too heavy by itself (under 5o lb) but hard to transport w/o use a good-size pickup truck or trailer. 14 gauge angle iron is easy to work with but not cheap at big box stores and too bendy under load if it isn't well-supported along the lengths. A thicker-gauge angle iron welded and painted would be more rugged and better for long-term use.
  2. K3RLD

    K3RLD Ham Member QRZ Page

    Here's an artists rendering of it sitting in my driveway (wheels not modeled yet, and this is shown as 10ft tall - that upper section will only be a foot or two taller than the pyramid part).


    [edit] I currently have the pyramid about half way done (have to fishmouth the top interface and then start welding). The lower horizontal braces will probably be smaller diameter tubing than shown (everything in the picture is 1.5" diamter).
    WE4B likes this.
  3. WA7F

    WA7F Premium Subscriber QRZ Page

    Iā€™m glad to see all of great innovation. It would be fun to see a trailer mounted satellite system for mobile ops. Anybody have one?
    NH7RO likes this.
  4. K9JKM

    K9JKM Ham Member QRZ Page

    I always liked this one from G6LVB
    NH7RO likes this.
  5. WA7F

    WA7F Premium Subscriber QRZ Page

    The steering wheel is on the wrong side.
  6. WA9SVD

    WA9SVD Ham Member QRZ Page

    I'm not clear. :confused: If you are running LMR240 from your preamps to radio, that is probably OK. But what are you using from the antenna(s) to the preamp inputs? And where are the preamps located? (I.e., at the antenna it/them selves, or at the shack?
  7. WA9SVD

    WA9SVD Ham Member QRZ Page

    That's the Brits (or Aussies) for you. :( Go figure.:rolleyes:
  8. K3RLD

    K3RLD Ham Member QRZ Page

    There is 5 or 6 feet of LMR-240UF between the M2 Antenna feedpoints and the the mast mounted ARR pre-amps. There are also MFJ diplexers in the pre-amp enclosure (but for the life of me, I cannot remember if they are before or after the pre-amps..... although I did research to figure out where I should put them). There is also a 1 ft LMR240 jumper between the diplexer and the pre-amp.
  9. WA7F

    WA7F Premium Subscriber QRZ Page

    I would guess that your diplexers are between the antennas and preamps if they are being used as Bandpass filters. This placement improves preamp operation by reducing unwanted signals prior to amplification. Iā€™m hoping to avoid Bandpass filtering with the antennas spaced on an 11ā€™ boom versus the 8 or 9ā€™ boom that comes with the Leo-Pak.

    If the diplexers are used to combine 2m/70cm onto a single feedline then placement is typically between the preamps and radio.
  10. NH7RO

    NH7RO Ham Member QRZ Page

    I would think something along the same lines could be DIY'd with angle aluminum, tube or bar stock bolted together---and weighted with a bucket of sand or rocks if necessary. Add 10" pneumatic tires/wheels from Harbor Freight and voila!

    While aluminum might be costlier than steel many of us don't have steel welding gear or skills, hence my suggestion above.


    KS1G and K3RLD like this.

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