I hate FANS

Discussion in 'Amplitude Modulation' started by W2NBC, Nov 16, 2019.

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  1. W2NBC

    W2NBC Ham Member QRZ Page

    I’m sure most of us can relate to this scenario:

    Perhaps you’ve constructed a low power project with nice audio and intend to drive a linear for that extra and needed power on the bands.. But the reality is noise, heat, and ultimately a pain to interface if the linear uses tubes that require forced air (as in most).. Our on-air presence and signature is all about the sounds that make it to YOUR receiver..

    Which leads me to this statement :

    I HATE FANS . Yes, the sound of fans, the look of those plastic or metal blades ready to push the air into our linears, and into our audio chain..

    Yes, fans suck (or blow) but are needed especially in any high-duty service like AM !

    I have quite a few linears around here including a Johnson desk RF section that now uses 3-500’s in grounded grid with a homebrew supply at 3.8K volts. It’s a great unit to get over 250 watts and headroom but requires lots of AIR .. = F A N S which = NOISE ..

    So, here’s my question to the group..

    I have this closet behind my operating position, and I’m thinking about mounting the linear and supply behind that closet door... The problem of course will be the actual ventilation inside with the door closed.


    -Drill a hole and a hose through the closet floor into the basement to suck the heat out?

    -Let the heat build up and open the door once and a while?

    -Forget the whole deal and get on 2 meters (don’t answer that) ..

    Come out of the closet and share your noisy FAN experience ..
  2. N1BCG

    N1BCG Ham Member QRZ Page

    I use circulating water from a cooling pond outside the shack to keep El Valianté cool. Totally silent outdoor pumps.
    N2EY likes this.
  3. AC0OB

    AC0OB Subscriber QRZ Page

    W2NBC likes this.
  4. W2NBC

    W2NBC Ham Member QRZ Page


    Oh yeah, is that the cooling pond that your Boy Scout group fishes for Coney Island whitefish???
    N2EY, KF5FEI, WR2E and 1 other person like this.
  5. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    Most hams (and other 'lectronics folks) greatly overestimate the amount of air movement necessary to keep things cool. In most cases, you can drop the fan speed in half, which GREATLY decreases the noise. Keep an eye on the differential temperature...if it's within bounds, you're moving enough air. Also, be sure there's enough humidity! It is the humidity in the air that provides the cooling....the specific heat...and heat capacity of dry air is just about nil.
    W2NBC likes this.
  6. KK4NSF

    KK4NSF Ham Member QRZ Page

    you could use a water cooling set up like computer gamers do. You'd have to make the heat exchanger, but that could be a simple coil of small copper tubing just friction fitted onto the tubes. You'd still have the pump noise, but they are pretty quiet.

    OR you could vent the bottom of the case, fit a 6ft stovepipe to the top, and let the rising heat in the pipe suck cool air in from the bottom. That's how many furnaces work.

    OR you could install a LOT of small peltier modules, and cool it with thermoelectric processes.

    I can think of several more.... but to be honest, IF your amp is fixed in place, the stovepipe idea would probably work the best, especially if it were vented to the outside. I've actually seen several broadcast amplifiers with just such a set-up.
    W2NBC likes this.
  7. N2DTS

    N2DTS Ham Member QRZ Page

    I just built a rig that does not need fans.
    I have two, the pair of 4-125's modulated by a pair (they do not need forced air) and the 3X4D32 rig, runs three 4D32's modulated by 811's at 1200 volts.
    Both run over 300 watts carrier.
    I used to have a KW version of a globe king 400, 812a's in push pull modulated by a pair of 811a's using KW components.

    You have to build a silent transmitter over about 100 watts or get a globe king or Johnson 500 I guess.
  8. W2NBC

    W2NBC Ham Member QRZ Page

    I have quite a few very quiet transmitters and some homebrew too Brett.. But as the original post suggests, I was referring to noise from linears being driven with lower power drivers .. Consider it the “Nouveau 75 factor”..
  9. N2DTS

    N2DTS Ham Member QRZ Page

    I don't know of any silent amps although I guess you could build one.
    It just needs to be overbuilt to be able to run legal limit type power without needing forced air cooling.
    Or run at very low power output.

    But why use an amp instead of running a rig that does not need an amp?
    Any time I tried an amp, I was very displeased with having to tune another thing in the chain, plus the low power output
    for the heat generated.

    I once built a quad of 813 tubes in grounded grid. It would do 200 watts carrier and blow off huge amounts of heat.
    A single 813 will do 300 watts without cooling in plate modulation!

    On ssb, they make sense, the low duty cycle means they can be very wimpy.

    If you had to, putting the blower someplace else will lower noise in the shack.
    The KWS 1 had it in the power supply cabinet...

    And remember the 4wx300 tubes? Like a 4cx250 but water cooled?
    Bill Orr handbooks had an amp that used them and a fuel pump pumping distilled water through the tubes.
    4 of those tubes might be cool to run in more ways then one....
    W2NBC likes this.
  10. WR2E

    WR2E Ham Member QRZ Page

    But... your fans love YOU! :p
    AC0OB and W2NBC like this.

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