"It was the best of times"
"It was the worst of times" - isn't that always the situation, Charles Dickens ?
Recently I was reminded of a failed VFO project presented in the ARRL book: Understanding Amateur Radio on page 152:
source: https://archive.org/details/understandingama00geor_1/page/152/mode/2up
I actually wanted to build this for use with the HW-16 in 1973 so I could abandon the previously required crystals. At first I borrowed a Knight VFO from the Nicolet ARC but brought it back before graduating in 1973. I got as far as etching and drilling the boards for the VFO and also a friend gave me an old Millen dial/drive and I had the dual 365 variable cap and power transformer. But it never really progressed beyond that point. Eventually I gutted my Hallicrafters S-120 and used the bandspread cap along with an MFJ 7 MHz VFO board with the HW-16. I also added a divide by 2 flip flop for 80 meters. I also tried an HW-16 transceive project from Ham Radio magazine (another fail - couldn't get that to work).
So what killed the project from the ARRL book ? I can't quite recall but probably one factor was getting the parts with the money I had. The project had a bandswitch made from a Centralab customizable switch:
Recently I was reminded of a failed VFO project presented in the ARRL book: Understanding Amateur Radio on page 152:
source: https://archive.org/details/understandingama00geor_1/page/152/mode/2up
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| Centralab custom switch |
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| JW Miller coils |
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| Schematic |
I actually wanted to build this for use with the HW-16 in 1973 so I could abandon the previously required crystals. At first I borrowed a Knight VFO from the Nicolet ARC but brought it back before graduating in 1973. I got as far as etching and drilling the boards for the VFO and also a friend gave me an old Millen dial/drive and I had the dual 365 variable cap and power transformer. But it never really progressed beyond that point. Eventually I gutted my Hallicrafters S-120 and used the bandspread cap along with an MFJ 7 MHz VFO board with the HW-16. I also added a divide by 2 flip flop for 80 meters. I also tried an HW-16 transceive project from Ham Radio magazine (another fail - couldn't get that to work).
So what killed the project from the ARRL book ? I can't quite recall but probably one factor was getting the parts with the money I had. The project had a bandswitch made from a Centralab customizable switch:
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| this is the mechanical part of the switch |
source: https://www.ebay.com/p/782894064
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| this is a switch wafer - three were needed for this project |
Source: https://www.ebay.com/itm/295399257866
It also required JW Miller slug tuned coils - and those weren't that easy to come by either - this was about the time that the sellers like Allied started to split into hobby and commercial divisions making it harder for hobbyists to access those Miller coils and Centralab switches. Also this VFO was pretty overbuilt with a lot of buffering and filtering and with an on-board power supply. With a keying circuit it could have been a 2 watt transmitter ! And as a relative newcomer to ham radio, I probably wanted to use the exact parts specified rather than substituting. Finally the cost had to be kept fairly low or it would be easier to just buy a commercial VFO.
Nowadays the bandswitch (especially with only 2 positions) would be replaced by relays. The JW Miller coils would now probably be replaced by toroids with trimmer caps for adjustment. Or of course just synthesize the frequency using a PLL like the SI5351.
So I guess all I am saying is that 21st century builders are complaining about surface mount, unobtanium and inflated prices while ignoring easy information availability and counsel along with multiple marketplaces for parts.
"It was the best of times, it was the worst of times" :)
Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm
Nowadays the bandswitch (especially with only 2 positions) would be replaced by relays. The JW Miller coils would now probably be replaced by toroids with trimmer caps for adjustment. Or of course just synthesize the frequency using a PLL like the SI5351.
So I guess all I am saying is that 21st century builders are complaining about surface mount, unobtanium and inflated prices while ignoring easy information availability and counsel along with multiple marketplaces for parts.
"It was the best of times, it was the worst of times" :)
Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm
