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SR-75 Coil Winding Data
¿ªÔÆÌåÓýThanks Don, ? The SR-75 coil data is as follows: ? Form length is 2.375¡± Diameter 1.375¡±, Thickness is .05¡± ?4 holes are drilled to accommodate 6-32 screws, two on each end at the spacing of the jacks on the chassis and two more to allow for the insertion of a small solder lug? that the coil wire is attached to. A spacer bar is also used for the 80 and 20 meter coils where a cap is attached t the center banana pin. It¡¯s not used on 40 and 10 meters. ? The banana plugs are Pomona #3265 available from the usual suppliers. I bought mine from Mouser. ? 10 meter coil is 1.28 uh and 6 turns of #18 tinned copper 20 meter coil is 4.3 uh and 12 turns of #18 ¡° 40 meter coil is 10.3 uh and 20 turns of #18¡± 80 meter coil I have no means to measure but it is 26 turns of #22 enameled copper wire ? The inductance was provided by Chris Farley who provided pictures which I can forward to anyone who needs to see the construction. ? The 80 meter coil I made has the correct number of turns but the original seems to have had some wider spacing however both work the same as near as I can tell. ? I have extra coil forms already drilled if anyone needs them. I have extra screws and 3/8¡± nylon spacers as well. I built a coil winder out of scrap material which seems to work pretty well. The coils were sealed with polyurethane. ? I hope this provides enough info for anyone to reproduce them. My email is nj2r@... ? 73, Roger, NJ2R ? From: [email protected] <[email protected]> On Behalf Of don Root
Sent: Tuesday, August 23, 2022 10:47 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-17 and SR-75 Coil Data ? Roger congratulations on your ingenuity? and perseverance? ?too! you guys are in the real ham spirit... spread it around! I once saw a real SR-75 at a swap, but a minute later when i got to the table, it was gone ! I hope you give it some work to do. ? From: [email protected] [mailto:[email protected]] On Behalf Of Roger Shultz via groups.io ? Hi Randy, ? I picked up a SR-75 in May with only the 80 meter coil. With the help of Chris Farley who had the 40, 20 and 10 meter coils I was able to determine the turns count and wire size.? ? I then bought Bakelite tubing exact size, the solder lugs, spacers, and Pomona banana plugs. I wound coils using enamel wire but just bought the tinned copper to make the coils again to look more original.? ? I have a good number of additional forms and hardware except for the banana plugs which are readily available.? ? When I get to my desktop I can send pictures, wire size and turn count. The 80 meter coil I made works identically to the Hallicrafters original. The 40 meter coil also works well.? ? I¡¯ve recapped my SR-75 and it does as the manual reads on transmit. The voltages are now nearly exact as shown on the tone socket chart in the manual ? ? What has me baffled is how to connect or transform the transmit output to 50 ?ohms. I have no idea how much power it¡¯s really putting out at this point!? ? BTW I sourced the 4 pin plug for the key and 50L6 plate current/light bulb indicator. I have a couple of those. ? I¡¯d love to hear from others who have experience with this unique transceiver.? ? 73, Roger, NJ2R ? ? On Aug 23, 2022, at 7:50 PM, Randy (VE6RGU) <rmorden@...> wrote:
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