A remote Power Supply for the SB-220

Discussion in 'Amateur Radio Amplifiers' started by WA6MHZ, Apr 26, 2017.

ad: L-HROutlet
ad: l-rl
ad: l-BCInc
ad: Subscribe
ad: L-MFJ
ad: Left-2
ad: Left-3
  1. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    Well this is supposed to be a full length program. No program runs 7 min, at that itsa WHY BOTHER! Hams want the full show and most of my programs run about 45min within the standard FORUM SESSION timeline they have at ARRL Conventions and Dayton. The Audience is kept well entertained as long as I keep talking.
    The ONE BOMB i did do was "DAYTON, the MOVIE" That ran long and included tours of the Route 66 Museum in Elk City, OK. That put the audience asleep and in a later version I had to cut it. It was wonderful, so I thought. full of YANNI backround music, made with WINDOWS MOVIE MAKER and I had fun making it. But the Audience snoozed. So that bombed. I went back to powerpoints after that and they are all well received.
     
    AF6LJ likes this.
  2. AF6LJ

    AF6LJ Ham Member QRZ Page

    Let us know what you find out.
    not knowing how you hooked up the 4011, it is hard to say...
     
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    You don't need a preamp on 6m using the 736R.

    First thing I do with my Mirage amps is bypass their internal preamps -- they all suck anyway and the 736R doesn't need them. Just one more thing to fail (actually, three more things -- the FET and the two relays that switch it in and out of line).

    I have four Mirage brick amps here (50/144/222/432) and have bypassed the preamps in all of them.:p
     
    AF6LJ likes this.
  4. AF6LJ

    AF6LJ Ham Member QRZ Page

    The 736R he has that I worked on had no trouble hearing -140DBM.
    And that is so damned quiet.
    No preamp needed, at least not a preamp that old.
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The best, lowest-noise preamp in the world won't help a 736R on 50 MHz. When you connect an antenna, atmospheric noise takes over and if the noise figure of the preamp was "zero," it wouldn't make the receiver any more sensitive.

    The 736R even on 432 MHz is very sensitive and a typical 0.5 dB GaAsFET preamp really does about nothing for it, unless the preamp is at the antenna and overcomes transmission line loss. I have a "stack" of ARR GaAsFET preamps all noise optimized and have tried them with my 736R: They bump up S meter readings by 20 dB (!) but don't improve S+N/N in any way I can find.
     
    AF6LJ likes this.
  6. K2XT

    K2XT Premium Subscriber QRZ Page

    The talk in Dayton about 4-5 years ago, on restoring vintage gear, was outstanding. Pat is a great presenter. Very confortable with a mic in one hand and a remote control in the other.
     
    AF6LJ likes this.
  7. AF6LJ

    AF6LJ Ham Member QRZ Page

    The 736R has a hot receiver, and from what I have seen it is well designed.
    I might have to get me one of those some day.
    :)
     
    WE6C likes this.
  8. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    Things aren't going well with the Lunar. We smoked a CD4011 and now am redesigning the mod circuit. It seems that the Schematic for the amp is ALL WRONG!!! There are actually 2 Power amps in the box and they are combined somehow. But the worst is the 2N4401 is wired completely different than the schematic shows.

    So the new plan is to tear out the relay and install a DPDT relay and put another GATE output to key that transistor.
    Maybe it will work.
    Maybe not.
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    One thing that keeps it "hot" and also quite immune to junk/crap/garbage that plagues many VHF-UHF receivers today is it has no "out of band" coverage, at all. Front ends are tightly resonant and just barely cover each ham band, plus the tuning doesn't allow you to dial 1 kHz outside the ham bands.

    Helical resonators between front end FETs and following stage preamps. The 70cm module has triple aperture-coupled helical resonators between a pair of 3SK164s; the 144 MHz module has a sealed helical resonator between a pair of 3SK122s, in each case before the first mixer. First mixers have roofing filters. Second mixers have selectable bandwidth crystal filters. Everything is optimized for the ham bands only with no concern for how it would perform out of band, since it doesn't cover anything out of band.

    Really good design.
     
    WA7PRC, N2EY and AF6LJ like this.
  10. AF6LJ

    AF6LJ Ham Member QRZ Page

    exactly which also allows for more overall system gain.
    My attention was focused mainly on the 33cm module, same set up helicals in the front end, a decent compound loop synthesizer, a well thought out thermal design and (if you have the test equipment) fairly easy alignment.

    I wasn't able to measure the actual receiver sensitivity, however the radio had little trouble hearing the third harmonic of my 8640 which I measured on the spectrum analyzer at -120DBM I wouldn't put that much stock and faith in any accuracy of what I measured since I don't have anything I could actually use to check the spectrum analyzer at that signal input level.
    But..
    Hey that is good enough.
     

Share This Page