Mast Mounted 2m Preamplifier Recommendations......

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by K3GM, May 25, 2015.

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  1. KA9JLM

    KA9JLM Ham Member QRZ Page


    If that is the case, I would use the control cable, and ditch the RF keying.

    I never was a big fan of preamps, unless you use a very narrow filter on the frontend, they can make things worse.


    Have Fun.
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I wouldn't rely on RF keying unless I liked climbing up to service the preamp pretty often.

    I've used masthead preamps lots of times over the years but always with hard keying and a sequencer. Saves a lot of service.
     
  3. K3GM

    K3GM Ham Member QRZ Page

    Thanks for your suggestions. What I've decided to do is run a 4 conductor cable to power the preamp and manually key it. Steve, I've heard other people say that about RF keyed preamps. I tossed around making a pair of bias-T's that were stout enough to handle the power, but it's just as easy to hard wire it, and I don't have as many connectors inline as someone else mentioned. The cable arrives today, and I can get busy. The Heliax and rotator lines to this tower are hung from a messenger wire which is anchored several places along the 125' run out to the site. I'm moving in about a year and didn't want to pipe it. Adding another cable is a very easy task. In place of a sequencer, I'm invoking the delay transmit option on my K3.
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Yes, that should work if the PTT line closes 20 mS (or more) before the RF envelope is generated, and vice-versa going back to receive. My Ten Tecs have that option also.
     
  5. KA9JLM

    KA9JLM Ham Member QRZ Page


    Sounds like another missed contact.

    That is to long. :rolleyes:
     
  6. N2SLO

    N2SLO XML Subscriber QRZ Page

    I was advised not to bother with a mast mounted pre-amp for 2m. I just added a 1296 & 432 SHF (Germany), that work great. For 2M, no need for mast mounted preamp. Jut make sure you use LMR 400 minimum for Coax run.
     
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    A 2m masthead preamp could be valuable for those having antennas pretty far away.

    That takes 'property,' but some have a lot of that. If your cable loss is more than 2 dB, a masthead preamp isn't a bad idea...but I'd never use 'RF keying' for one. Hard key it, and use sequencing.

    I had an e.m.e. station temporarily installed in upstate NY where the feedline had to be 400 feet long or so...LMR400 would have lots of loss in that. We used 1/2 inch hardline, which is a bit better, but still in 400 feet it had about 3.5 dB loss and killed a lot of signals. A masthead preamp made it all work. With a sequencer.
     
  8. W0AAT

    W0AAT XML Subscriber QRZ Page

    On EME a mast head preamp is a must, .5db loss is to much when you are trying to squeeze every last bit out of your system. Same on meteor scatter where a ping might be way down in the noise floor, that .5 db gain in the system might be the difference between a good decode and contact and no contact.
     
  9. KB0TT

    KB0TT Premium Subscriber QRZ Page

    Just do what Steve ( WIK ) says ....

    He knows about the pre-amp business... As with all , he has done it and everything
    else regarding amateur radio .....

    It is what it is ...... What he says is correct ..... Save yourself
    aggravation and wasted time ..... Do it right the first time...
     
    Last edited: Jun 1, 2015
  10. K3GM

    K3GM Ham Member QRZ Page

    Follow-up

    Thought I'd post a follow-up. Here's the first of two preamp mounted in a NEMA. I decided to add a 6m preamp as well, and I'm waiting for that to arrive. To save time, I'm going to use a diplexer until I'm at my new QTH when I'll run separate runs of Heliax. 20150620_102553.jpg
     

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