Discussion in 'Amateur Radio Amplifiers' started by WA4SIX, Jul 3, 2017.

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  1. WA4SIX

    WA4SIX Ham Member QRZ Page

    Thank you, Sue. I was thinking that way, but have not found (Or understood) how to calculate that in all of the articles I have read. Receiving Chinese junk every day dow.
    My intent is to put the 90* 50 ohm phase line right at the output of the board, internal to the casing. The heatsinks will move towards that end a bit to support the 100 ohm flange mount resistors. Then, 1/4W 75 ohm lines to a final combiner/relay/LPF/SWR coupler box, which will be mounted on the shorty heat sink from the MASTR II amp & water cooled, with a fan backup, of coursse. The input will be a mirror image & I will use a couple of the dozens of PC heatsinks for the input combiner resistors (30W flange mount).

    So, the topography is to have the 90* 50 ohm phasing lines in the amplifier case, along with their 100 ohm resistors. 2-75 ohm splitter lines from input/output, each, to the final combiner box, where there will be a final splitter/combiner (With 90* 50 ohm phasing lines, or not?) on a water cooled heat sink. The LPF & SWR board will be there.
    I have some great Med grade 600W power supplies, gratis from work, that will feed each pallet (Along with 1.5A 5VDC to feed the bias). All parameters of the power supplies are monitored & controlled by an Arduino. It will show volts/amps of each module & their bias supplies.
    I have some .375X.754 copper HO4 grade (Hardened) copper barstock to machine for bridges over each LDMOS. They will provide a tough of center clamping force in the center of each device with a #10 allen set screw. Also, the temp sensor for bias, and another temp sensor for monitoring each device (Arduino monitored & displayed). If the temp goes high, I will have backup fans on the heat sinks. If it goes too high, bias & power will be shut down. The 50V- line will also atattch to these bridges for a solid current source (LDMOS heat sink base is 50V-).
    I may add input SWR/power monitoring, just because I have a sensor for it.

    This weekend, I will post pictures of all of the parts. I will have to figure an anclosure for RF tightness & I have 25 feedthru capacitors for sense & control lines to each area needed.

    Any other suggestions would be appreciated,
  2. AF6LJ

    AF6LJ Ham Member QRZ Page

    This is coming along really good Ed.

    Coolness Abounds. :)
  3. WA4SIX

    WA4SIX Ham Member QRZ Page

    Working on a chiller.... We'll see if that happens, or not.

    AF6LJ likes this.
  4. WA4SIX

    WA4SIX Ham Member QRZ Page

    So.... On the local repeater (1 of 320,000), a friend that is in the hotel maintenance business & I were talking. I may be taking a different route on cooling the amp.
    7 circuit soda gun cold plate & a refrigerated air dryer.
    The cold plates used to go in the ice well to chill the soda in bars & other places. The refrigerated air dryer will have a distilled water/proylene glycol mix. I might still have a radiator for winter use. Yeah, I do change mi mind a lot, but these would be cheap to free surplus items that still fit my need to be cheap...

    AF6LJ likes this.
  5. AF6LJ

    AF6LJ Ham Member QRZ Page

    I looked at those chilling plates, they are nice. and may be just what the doctor ordered. :)
  6. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page


    Now We're Talking!
  7. WA4SIX

    WA4SIX Ham Member QRZ Page

    I had thought about them years ago, but they were very expensive. Now, they are surplus, due to health department regs.

    KD2ACO and AF6LJ like this.

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