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W7TFO Hints & Kinks: "Fear & Loathing in the land of Engineering"

Discussion in 'Amplitude Modulation' started by N6YW, May 31, 2016.

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  1. W7TFO

    W7TFO Premium Subscriber QRZ Page

    I was part of a team that recently rebuilt the KOOL-FM transmitter site for CBS (now Entercom).

    Shown is a transition from 6" Heliax down to 3-1/8" rigid line. The 6" was originally longer, and carried 52kW @ 95.5 MHz up to the antenna.

    I cut it shorter, and installed a new female connector ($!), then made up a gas-stop adapter plate to hook up to the 3" line from the output switch matrix. A new, more efficient antenna now requires just under 30kW, so 3" rigid will handle that.

    The Heliax is pressurized at around 4PSI, but the indoor lines are not. Note the common-mode protection ferrite ring on the line.

    Rigid is not very forgiving if you are off in your measurements...

    73DG 6 inch 001.JPG 6 inch 002.JPG 6 inch 003.JPG
    WC5P, AE7BT, N6YW and 4 others like this.
  2. W7TFO

    W7TFO Premium Subscriber QRZ Page


    1..Take an old Bakelite octal tube socket and cut all the pins off short and push them out.

    2...Secure a 1/4" or 5/16" bolt of sufficient length, washers, & nuts.

    3...Punch, drill, or saw the proper size holes in your bulkhead or other location. Mount with suitable hardware.

    4...Place the bolt thru the center locating hole in the socket as shown, connecting your heavy gauge wires. Tighten securely.


    73DG bushing 001.JPG bushing 002.JPG bushing 003.JPG bushing 006.JPG bushing 007.JPG
    W7UUU, W1TRY, AC0OB and 5 others like this.
  3. W7TFO

    W7TFO Premium Subscriber QRZ Page

    Lots of vintage electronic gear has Bakelite parts; knobs, handles, bezels, panels.

    This stuff called Lustra works well at bringing back the shine:

    You have to really get all the dirt & grime off first, but it is best to use hand soap & water. 409 cleaner and the like will ruin the surface irreparably.


    K4KYV, WA1ZMS, W1TRY and 1 other person like this.
  4. W7TFO

    W7TFO Premium Subscriber QRZ Page

    I've found painting threads on stainless steel fasteners with milk of magnesia will ease removing without so much of the usual galling.

    This is especially effective when those bolts are used in a high-heat environment.

    Graphite, powdered mica, oils, and greases just don't do as well.

    W1TRY, KA4KOE, AD5HR and 3 others like this.
  5. W7TFO

    W7TFO Premium Subscriber QRZ Page

    A cheap 'Greenlee' radio chassis punch at IKEA. Yep, there is one fer $13.

    It goes by the name "FIXA", comes with a little tubing cutter as well.

    Nicely made, punches a hole just under 1-3/8", perfect for most tube sockets as shown.


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    WA1ZMS, W1TRY, N6YW and 1 other person like this.
  6. W7TFO

    W7TFO Premium Subscriber QRZ Page

    If you build via panels and cabitnets, a good finish is desirable. I have found a source for a really tough spray paint, marketed for touch-ups on powder coated items.

    Available in hundreds of colors. I've used some of this and had excellent results over hardware store aerosol cans. And they mention Faraday cages!

    W1TRY likes this.
  7. W9GB

    W9GB Ham Member QRZ Page

    Lustra (Luster Sheen) uses Toluene (methylbenzene) as the solvent for the hard European waxes.
    Chemical Safety Facts : Toluene

    I prefer to use White Mineral Oil (paraffinum perliquidum in UK) for initial application to Bakelite knobs & materials. Then, depending on the Bakelite product, apply hard waxes (softened with heat gun) as part of the polishing process.
  8. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    NEVER EVER use a household cleanser like Fantastik or 409 to clean Bakelite. It's very effective in dissolving away the crud, along with the thin "skin" of phenolic, exposing the filler underneath which is usually fine sawdust or something similar, permanently removing the sheen which can't be polished back. Learnt that the hard way when I ruined a very nice pair of National Type A Velvet Vernier dials. I remember another ham describing a similar disaster with the dial escutcheon on a KW-1.
    K0OKS likes this.

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