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Preamp Question

Discussion in 'Satellite and Space Communications' started by N1EN, Oct 11, 2021.

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  1. N1EN

    N1EN Premium Subscriber QRZ Page

    So, I'm toying around with the idea of adding some satellite capability to the shack.

    I know that SSB and Applied Research are the two brands of mast-mounted preamps commonly recommended for satellite work, but I was wondering: I know that Mirage (MFJ) has mast-mounted preamps as well, at a considerably lower price than SSB preamps.

    However, I'm having trouble finding online reviews for Mirage preamps, and I've had issues with some examples of Mississippi's Finest Junque before.

    So, I wonder...does anyone have experience with the Mirage pre-amp that they'd be willing to share?
     
  2. KS1G

    KS1G Ham Member QRZ Page

    What kind of antennas are/will you be using, how long will your coax runs be, and is your QTH electrically quiet or noisy? You might try w/o preamps and see if your results are acceptable to you. IMO, a preamp may be of marginal benefit on 2M. I use one depending on how bad the RFI is at the time (varies with time of day, day of week, and which neighbor is in the way). It definitely helps on 70cm (unless neighbor to the NNE has a pulsing (dog fence or critter annoyer?) running). Setup is M2 LEOPack, 50ft LMR400UF. ARR (70cm) and Landwher (2M, ancient from mid 1990s) RF-switched. Back in the AO10/13/40 days, a downlink preamp was pretty much a given. Not so much with the current LEO birds. YMMV.
     
    VE4MM likes this.
  3. N1EN

    N1EN Premium Subscriber QRZ Page

    Antennas -- Eggbeaters. Yes, I know they're less than ideal, but:
    • My horizon is blocked in most directions by vegetation or terrain
    • The antennas will replace a Jpole used for local repeaters and packet, and I'd prefer not to lose access to some of those repeaters/nodes due to an antenna aimed the wrong way + polarization losses
    • I have a spouse that detests the appearance of conventional yagis, tolerated a hexbeam, and hasn't expressed an opinion about an eggbeater (because I haven't asked). I won't antagonize her by putting up a yagi given her expressed opinion; but I'm not above standing on plausible deniability when it comes to other forms of antennas
    Coax will be LMR 400, with runs of less than 50 feet (probably 30-40; I tend to just cut cables to the needed lengths without actually measuring the final results).

    I've had fun in the past chasing FM birds from the yard with an Elk and an HT, despite the limited open sky. However, new physical limitations, combined with how my operating time is frequently just "a few minutes here/ a few minutes there" as quick breaks during work or chores, has me interested in setting up to play from my shack, despite the less-than-ideal location. I suspect given the compromises/constraints I'm working under, I'll want/need mast-mounted preamps to maximize my fun.
     
  4. KO4MA

    KO4MA Ham Member QRZ Page

    If you are concerned about polarity mismatches and repeaters, you should know eggbeaters are horizontal at zero elevation, and only circular overhead.
     
  5. N1EN

    N1EN Premium Subscriber QRZ Page

    Well, that would be annoying....but thinking about it, it does make sense.
     
  6. W5OXL

    W5OXL Ham Member QRZ Page

    I have two kits from Mini-Kits in Australia, one for 2 M and one for 70 cm. They look high quality and have switching relays on the boards. I have yet to build them as I have been busy with some other projects. The price including shipping was not bad but does depend on the current exchange rate from $Aus to $US. They do sell the preamps assembled and I believe they are still less expensive than the brands the OP posted.

    Bill, W5OXL
     
  7. KO4MA

    KO4MA Ham Member QRZ Page

    Eggbeaters with the radial kits are actually directional straight up from the top. If you tilt those over at an angle (generally 15-30 degrees, depending on surrounding terrain) and put them on a tv rotor you'll hear much better and more of the pass. That's the idea behind K5OE's Texas Potato Mashers. That also puts the circularity more towards the horizon, which helps with using repeaters and other vertical polarized targets.
     
  8. N4UFO

    N4UFO Ham Member QRZ Page

    I don't know about the mini-kits... but I tried building some kit preamps for my first home setup. It did not go well at all... made things WORSE. Few of those cheaper preamps are desgined to operate in a hot RF environment such as a repeater site or where you have another antenna right there next to the 'receive' antenna. They don't have the filtering and if they don't come in a RF proof enclosure, don't expect much. That is what you are paying for with the ARR and SSB preamps, etc. They can handle 50 watts on another band 'right next door'. - As always, your mileage may vary. Just saying, in case you run up against what I did and are scratching your head. o_O

    And thanks for the explanation Drew. I first saw K5OE's TPMs back in the 90s when I worked him on RS-12/13. I kept trying to figure out the point of leaning them over and it never dawned on me until I read what you said. I didn't get the advantage over a yagi, etc. Was not thinking 'CP'. Always wanted to build some and try them, but never had the right situation. Ended up going full yagis instead. Hmmm... wonder if I can find a cheap TV rotor. ;)
     
    KO4MA likes this.
  9. K4BAD

    K4BAD Ham Member QRZ Page

    Howdy Kevin: I had similar problems with cheap preamps.

    Tilting egg beaters and using a rotator might make an interesting experiment.Do wonder how performance compares to fixed elevation Elk beam and small rotator for azimuth changes…Any advantages one way or the other? Of course the difference in cost for commercially made egg beater vs.beam antenna could be significant.
     
  10. N4UFO

    N4UFO Ham Member QRZ Page

    Between the two, I'd think the Elk would be the better performer, especially at lower angles... more gain. Unless you lose the bird completely when overhead, then the eggbeater (or potato masher) might have an advantage.

    BTW, if anyone is interested, the Texas Potato Masher design/plans can be found archived here: https://web.archive.org/web/20070312005627/http://members.aol.com/k5oe/tpm.htm

    I wonder if that page can be downloaded/copied and hosted/listed on amsat.org? Drew? Afterall, it originated in the AMSAT Journal.

    from the webpage: "The folowing is excerpted from the Jan/Feb 1999 issue of The AMSAT Journal:"

    :)
     
    Last edited: Oct 13, 2021

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