PLUG-IN Coil Forms are BACK (National RF)

Discussion in 'Homebrew and Kit Projects' started by W9GB, Mar 6, 2009.

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  1. W9GB

    W9GB Ham Member QRZ Page

    National RF now manufactures NEW plug-in coil forms.

    These forms are machined of high-impact plastic and mounted to a standard 8 pin “octal” plug. The form measures just slightly over 2 inches in height with a coil diameter of 1.5 inches. An area of 1.3 inches is machined for the actual coil, or coils, to be wound. In addition, a groove is machined in at the top that provides a convenient finger grip for inserting or removing the coil from a socket. And with a total of 8 pins available, the customer can bring out numerous taps, or wind separate “coupling” coils on the form. Matching octal sockets are available as well.
    A note to vintage radio buffs: these plug-in coils are not intended as restoration forms for older equipment. They are made new, and intended for the experimenter or radio enthusiast who needs to insert different coils for different frequency operation of home-made receivers or transmitters.

    They are also making the old National analog dials (again)

    National RF’s HROII-PD and PDA precision dials

    National RF, Inc
    7969 Engineer Road Ste. 102
    San Diego, CA 92111
    Phone: 858-565-1319
    Fax: 858-571-5909
    Last edited: Mar 6, 2009
  2. AC0OB

    AC0OB Subscriber QRZ Page


    Sorry GB, your inks don't work for me.
  3. W0BTU

    W0BTU Ham Member QRZ Page

    Links work ok for me

    The site or DNS must have been down. I was able to access the site.

    73 Mike
  4. N4LTA

    N4LTA Guest

    Being real honest - The picture of these in Electric Radio didn't impress me at all.

    Looked like a piece of PVC Schedule 40 with a tube base fitted ito it a with a couple of sheet metal screws, The machiining did not look good either.

    You need to post some better pictures if this is not the case.
  5. KC2UGV

    KC2UGV Ham Member QRZ Page

    I might order a couple of these. Could come in handy :)
  6. K9STH

    K9STH Ham Member QRZ Page

    They are a "little" more than just a cut piece of PVC stuck on an old tube base. However, it is very possible to make your own by doing just that.

    Also, for those of us who have to restock our home pharmacy often (that is who have a number of prescription medicines) the various pill bottles make excellent coil forms. They come in various diameters and various lengths.

    The dials are nice. Fortunately, I have several original National and Millen dials that I can use if I need one. However, using such a dial can certainly "dress up" a homebrew project.

    Glen, K9STH
  7. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    I might have to start going back to the doctor again, I am running low on pill bottles...

    They have some interesting stuff there, and they are right up the road from here.
  8. K9STH

    K9STH Ham Member QRZ Page


    How many pill bottles do you need? My wife gets tired of all those that I keep (she has been caught throwing them away against my wishes). Having rheumatoid arthritis and a couple of other maladies means that I have a constant supply of pill bottles.

    Glen, K9STH
  9. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    Lately I've been using Altoids boxes for everything that will fit.
    Unfortunately the pill bottle I kept all my small alignment tools in
    broke, no wonder it was over 25 years old and had been rattling around my tool box for ages.
    I have no problem with the smaller sizes, that's what my hormone replacement comes in, it's the really big ones that are hard to come by.
    My roommate has been raiding my stash of Altoids boxes lately for her silver jump rings.
  10. W9GB

    W9GB Ham Member QRZ Page

    IF you are looking for repalcement of the old 5-pin American Phenolic Corp. (Amphenol) coil forms (1-1/4” dia. x 2-1/4” high), Cat. No. 24-5P;
    Larry Baker, WB5OFD is now making and selling these coil forms.
    His coil forms are high-quality, hand-made, and are visually near-identical to the originals. Keep Larry in mind if you need to wind your own coils for your Ocean Hopper; restoration project, OR if you just want to experiment with different frequency ranges.
    These coil forms were used on some Heathkits, Allied Knight-kit Ocean Hopper and the Ameco AC-1.

    You can see a photograph near the bottom of David Ishmael, WA6VVL restoration of the Knight-kit Ocean Hopper (749).

    WB5OFD Coil Forms

    These forms are modeled after the American Phenolic Company (APC) Polystyrene coil form Catalog No. 24-5P which was used by Ameco for their AC-1 transmitter and also for the Allied Knight Ocean Hopper receiver. My forms are hand made using 1/8 inch wall thickness Polycarbonate hollow tubing and have the standard five pin base pattern using nickel plated pins. There are three pieces to each assembly; Base pin disc, Coil form body and the Collar. Polycarbonate liquid cement is used to assemble the component pieces together.

    Each form is approximately 1-1/4 inches in diameter and 2-1/4 inches in height not including the height of the base pins. There is a 1-1/2 inch collar at the top of each form to assist in inserting and extracting the coil from its socket without disturbing the wire coil itself. The forms are not predrilled for the entrance/exit of the coil winding.

    Should you wish to purchase these forms please keep the following in mind:

    1. Polycarbonate is easily scuffed or scratched. (*Note: but no more so than the original AMECO forms)

    2. There will be slight (thousandth's of an inch) variation in each coil. It would take an inordinate amount of time and waste of material to produce a large number of these forms exactly the same since they are individually HANDMADE.

    3. Due to sizing tolerances of the inside and outside diameters in the Polycarbonate tubing, as a result of the Tubing Manufacture's process, it is not always possible to obtain a snug fit of the collar at the top of the coil form. Because of this, a small air gap may exist and the cemented joint can assume a milky colored look to it; however, it still a strong joint.

    4. During final assembly I mix and match component pieces to minimize this effect and also take as much care as I can to prevent cosmetic blemishes.

    If you wish to place an order please Email me.

    Pricing per form is $10.00 each plus Shipping and Handling for orders of four forms or less. For orders of five or more forms, pricing remains $10.00 each; However, I will pay the handling and shipping cost which will be by U.S. Postal Priority Mail.

    Thank you for your consideration.

    73 Larry Baker
    Last edited: Mar 13, 2009
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