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 Post subject: Hallicrafters S20-R SO-239 Mod
PostPosted: Nov Thu 29, 2018 12:22 pm 
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Location: Laflin, PA
The S20R I am working on came with this old modification to allow the use of a coax. I have not come across this mod documented in my travels. It seems strange to me that they are not using any kind of shielded wire going into the RF section. I would be interested in comments on this.
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S20R SO 239 mod.JPG
S20R SO 239 mod.JPG [ 62.93 KiB | Viewed 333 times ]

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 Post subject: Re: Hallicrafters S20-R SO-239 Mod
PostPosted: Nov Thu 29, 2018 12:36 pm 
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 Post subject: Re: Hallicrafters S20-R SO-239 Mod
PostPosted: Nov Thu 29, 2018 7:17 pm 
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That connection to A1 terminal does not look right. The schematic show it going directly to band switch SW7A being the only connection. I wonder that red wire is supposed to be fore.


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 Post subject: Re: Hallicrafters S20-R SO-239 Mod
PostPosted: Nov Thu 29, 2018 8:04 pm 
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AJJ wrote:
That connection to A1 terminal does not look right. The schematic show it going directly to band switch SW7A being the only connection. I wonder that red wire is supposed to be fore.


Good question! I was hoping someone might have a clue about the modification, it looked pretty ugly. The radio works pretty decent just using a random wire antenna. I had not bothered to hook anything to the SO-239.

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 Post subject: Re: Hallicrafters S20-R SO-239 Mod
PostPosted: Nov Thu 29, 2018 8:38 pm 
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The radio has been hacked, so it may be worth the time to find all the mods in your set. If you can trace the mods and identify them on the schematic, people here might be able to help with figuring out why/what they're for.

There's nothing special about the SO-239 addition; it's just a convenient way to connect up to an existing coax cable.


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 Post subject: Re: Hallicrafters S20-R SO-239 Mod
PostPosted: Nov Thu 29, 2018 8:48 pm 
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AJJ wrote:
The radio has been hacked. The S-20R works well as designed; so it may be worth the time to figure out how/why all the mods are implemented.


This does not seem to bother the radio in any way, it still is receiving well on all the bands. I have not heard anything on band 4 but I can hear the signal generator so I know it works. I am sure the radio will benefit from a alignment.

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 Post subject: Re: Hallicrafters S20-R SO-239 Mod
PostPosted: Nov Fri 30, 2018 1:44 am 
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I removed that red wire and the BC band got a lot more sensitive. The wire went from the A1 terminal to the CB(BC band) trimmer in the converter coils. I am not sure what the mod was suppose to do but without it the BC band really improved.

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