I hate FANS

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

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  1. W2VW

    W2VW Ham Member QRZ Page

    Hi Jeff,

    My main linear power amplifier is a Collins 30S-1. It was not designed for legal limit AM but it will handle that fine with an external air handler.

    I use a tv transmitter cabinet exhaust fan mounted to basement ceiling joists and sealed to same.

    There's a hole in the floor which leads up to one 14-1/2" wall cavity. Same idea as most forced air residential HVAC. Their return ducts are usually just wall cavities married to tin in the basement or crawlspace.

    The AMplifier sits on the first floor against the wall cavity which has a large piece of cheatrock cut out.

    The rear of the amp is mated to a frame lined on one side with weatherstrip on one side and sealed to the wall on the other side.

    This allows for enough negative pressure to aid the existing blower to keep the amplifier happy at 1500 watts peak output on AM with no time limit.

    Almost zero extra noise in the shack.

    I am reducing my carbon footprint in cool months as the exhaust air heats my basement and takes some load away from the heating system. I do not wish to discuss summertime.

    Obviously, your glass tubes are going to be slightly less demanding than my ceramic one which relies entirely on good airflow.

    Have you installed a camera within the RF deck so you can see the firebottles?

    AG5CK and W2NBC like this.
  2. K8ERV

    K8ERV Ham Member QRZ Page

    I just use naked native girls waving palm fronds for cooling. Very quiet.

    TOM K8ERV Montrose Colo
    AC0OB, K9ASE, W2NBC and 1 other person like this.
  3. W2NBC

    W2NBC Ham Member QRZ Page

    Very interesting Dave on your 30S-1 set up! I won’t be getting that elaborate, but the hole in the floor and a remote exhaust fan might do the trick to get rid of the ambient heat with the closet door shut.. The door itself is a standard solid six panel type, but that will be changed out for one with glass panels to see inside for plate color and for reasons to use the fire extinguisher..

    The most common glass tubes in linear service (3-500, 4-400, 4-1000, etc) require some air on and around the pins and more is better..

    And Tom, if I had naked girls in my shack, they wouldn’t be quietly blowing air on my AMP..:D
  4. WD0BCT

    WD0BCT Premium Subscriber QRZ Page

  5. K4KYV

    K4KYV Subscriber QRZ Page

    Some slopbucketeers intentionally make sure they include plenty of fan noise from their leen-yar on their on-air signal, because they think that makes them sound BIG.
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    That is funny.:eek: My big boy amp blows and sucks thru a air filter. That kills a lot of noise.

    My amp has remote control, And if I wanted it in the closet I would run a dryer vent out thru the wall.

    You may need to get rid of all the boxes of Playboy magazines to make room in the closet. o_O
  7. N1BCG

    N1BCG Ham Member QRZ Page

    It’s the tips of the blades turning at high RPM that generate the most noise so using larger fans that turn slower (yet move the same cc of air) would help.

    This is the same noise reduction principles that make turbofan engines quieter than the early turbojet engines on commercial jets.
    W1TRY likes this.
  8. K5UJ

    K5UJ Ham Member QRZ Page

    The older tubes are great in that they were mostly made to be convection cooled: the xxxTH and xxxTL series, 813s, 833As, anything in the twist lock sockets like 810s, the HFxxx series, and so on. The air cooled glass internal anode tubes were pretty much an Eimac invention. And Eimac in many types prescribed the proper cooling as forced air up through their sockets and through glass chimneys. The better ham leenyars used chimneys and the cooling can be less noisy that way. That hammy value engineered method of blowing air across the tubes may be okay for low duty cycle modes but I am not so sure about it when it comes to RTTY and AM. Some manufacturers for broadcast and ham AM rigs put the tubes in compartments with air being forced into the tube chamber or cabinet and drawn out. Others like WRL didn't do any forced air cooling which may mean that your transmit time on a stock globe king 500 may be limited.

    Once you operate with a quiet rig you can't go back to a screamer.
  9. N2DTS

    N2DTS Ham Member QRZ Page

    All you have to do with almost any tube is run it at reduced ratings to eliminate a lot or all of the air requirement.
    The distortion will likely be lower and tube life longer.
    Turning the amp down from 300 to 200 watts out would likely not be detectable even if the person was looking for it.

    And what about the power supply? Most amps are wimpy there also.

    I have a pair of 4X150's rf deck, 500 watts of plate dissipation.
    200 watts carrier in screen modulation is ok and normal, but when I plate modulate them at 300 watts carrier,
    they are running about 50 watts dissipation each, very slight air flow is all that is needed and they run cool.

    Budly has a viking bud that has a single 4x150 (or 4cx250b) in it.
    It needs almost no air.
  10. AA7QQ

    AA7QQ Ham Member QRZ Page

    I use surplus LDMOS pallets. 2-MRF157s for HF (1KW), 6-BLF278s) for 2M & a BLF574 for 70cm (400W. All bolted to spreaders, then an old 5 circuit bar soda cold plate(Used to go in the ice well to cool soda) that I machined & lapped for many hours.
    Water is circulated by a RV water pump that is PWM'd by an Arduino for temp control in a 7 gallon resiviour through a Hyundai radiator. Pump, resiviour & radiator are outside. THe fan on the Hyundaiy radiator was used somewhat, but not often. Not bad for Las Vegas.
    All of the RF components are housed in a MAC G5 case I do use 2-12VDC fans in series, fed by 12VDC just to quietly vent the G5 case.
    This is all broken down due to moving, but will be operational in a month or so.
    Yes, I know that it's not tubes, but runs clean & sits right beside my TT Pegasus on the desk.
    The only non water cooled amp is a Larcan 1.5KW VHF-LO (6-BLF-278s) for 6 meters. It uses little air, so, again, 2-12VDC fans in series, run on 12VDC. It loafs at 1.2KW.

    I have not done much HF AM, but after getting the TT Pegasus dialed in, I was complimented by some of the Southwest regulars on the audio. Amps were clean & nothing need adjustment after turning it on.

    6M & 2M AM are not as good, as I have an IC-7000 & IC-7100. AM is just not great with them.
    Working on an SDR system to replace the need for the Icoms.

    Yeah, I know, all solid state. Just trying to give cheap surplus alternatives.
    I have $1,450 in all amps, switching, cooling & filtering.
    I run them all well below specs. All amps have attenuators built in & radios are at full output to prevent spikes.


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