[David Dunlop]

The third piece of the puzzle for fabricating a suitable Leads, Aerial 25-3/4 Inch was to be able to source a suitable central pin assembly for the tips. This is where the modern Motorola Pin Connectors come into play. The vast majority of these have a ½-inch pin fitted (the necessary length), but not all. Most venders on line do not provide much information regarding the pins on the products they offer, so you have to email them and ask. The more critical issue regarding the pins today is the construction of them. It is not always evident from the photos provided. Three methods of manufacture are used for making the pin components.

The cheapest method, and the most likely one to produce garbage, is an attempt at rolling a small rectangular strip of metal which results in a series of three and a bit longitudinal folds for the length of the pin, and the two longitudinal edges end up overlapping one another to some random degree. The finished pin should have a .125-inch diameter. The problem with these pins is the sides of the folds are rarely equal; so one measurement across the pin will be in excess of .125 inches, causing the pin to jamb in whatever it is plugged into. I would avoid this type of product at all costs.

The second means of pin making, uses equipment that produces a true rolled pin body cylinder, with the two longitudinal edges butting up smoothly and evenly against one another. The cylinders are then cut to the required length and the rounded tip and flared base formed. They cost more than the first type, but are more commonly found and the diameters consistently measure very close to spot on .125 inch.

The last type of pin production involves extruding the pin metal to produce a long closed tube. Pieces are then cut to length and formed as per the second option above. Specs are very high tolerance and the products these pins are fitted to are the most expensive. Just remember to always ask for the specifications of the pin before buying.

The first photo attached shows the off the shelf Motorola Pin Connector I purchased from an eBay Store called ‘Antenna World Inc.’, based in Miami, Florida. The Seller goes by the name ‘platech1’ and the Item Number was 361514744308. The item is described on the site as follows:

10 Lot Motorola Male Car radio antenna connector Crimp Solder RG-58 RG-59 RG-62

The second photo shows how the crimping end of the outer sleeve can be bent to the side and the sleeve spread open to release the inner plastic insulator assembly holding the pin. A very pleasant surprise at this point was to find the diameter of the pin base is just one half mm smaller than the end hole of the brass sleeves I purchased. Also, in these first two photos you can see the longitudinal seam down the side of the pin. This should allow good solder penetration from the tip and side of the pin and also allow the base of the pin to be soldered effectively to the end of the sleeve when the time comes. So the sleeves will be “hot” on these fittings, just like the originals.

The outside diameter of the plastic insulator is at a maximum of 7.5 mm, so the insulator needs to be thinned down to the point where it is a snug 7 mm. I want to avoid any wobble in the final product if at all possible. Lacking a lathe, but having a drill press, the drill press gets the job assignment. I found a 13/64-inch drill bit shank is a snug fit when inserted into the cable end of the insulator. It would probably not be snug enough to resist slipping when any load was applied to the outer surface for long, when the drill was powered up. The solution was to place two layers of saran wrap between the drill bit shank and insulator when inserting the drill bit shank. Very snug now…yet removable in the end. The plan is to use thin strips of fine, to very fine, sand paper against the side of the spinning insulator to slowly trim it down to the needed diameter.

The third and last photos show the fitting of the Saran Wrap, before and after trimming away the excess.

Will let you know how that turns out.

David