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 Post subject: Hallicrafters S40A Antenna Question
PostPosted: Dec Wed 05, 2018 1:52 am 
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Joined: Jan Sat 02, 2016 4:45 am
Posts: 45
Location: Clayton, CA 94517
Hello,

I'm having trouble finding the antenna input impedance for my Hallicrafters S40A. Anyone happen to know this offhand or know of a resource for finding it? Thanks for any help.

Karl


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 Post subject: Re: Hallicrafters S40A Antenna Question
PostPosted: Dec Wed 05, 2018 2:47 am 
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Joined: Jul Thu 29, 2010 5:35 am
Posts: 1124
Location: Simonton, Texas
It is my understanding that since your receiver works on so many frequencies the input impedance would not be constant. I would just experiment with different antennas an find the one that works best for your set.

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 Post subject: Re: Hallicrafters S40A Antenna Question
PostPosted: Dec Wed 05, 2018 2:49 am 
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Joined: Oct Fri 09, 2009 9:25 pm
Posts: 321
Location: Cleveland, Ohio
That front end is pretty broad at 50 to 600 ohms impedance. Performance really depends on the antenna and it's resonance.

Typically, if you are going with unbalanced line (i.e. 50 ohm coax), connect the inner conductor to # 1 and the outer shield to # 2. Ground # 2 to the ground terminal (jumper). Otherwise, balanced line (i.e. 300/400 ohm etc) to 1 and 2 with no jumper. Single wire typically to #1 with a ground to 2.

Depending on what you are using for an antenna and the band you are choosing, variations on the above (i.e. no jumper from 2 to ground with 50 ohm coax) may prove to be better....

Todd
ka8gef

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Last edited by KA8GEF on Dec Wed 05, 2018 3:01 am, edited 1 time in total.

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 Post subject: Re: Hallicrafters S40A Antenna Question
PostPosted: Dec Wed 05, 2018 2:54 am 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 6677
Karl,

The input impedance of the S40A (and pretty much all classic communications receivers) will vary wildly across its coverage range. generally the target range was around 70-400 ohms so it isn't critical. Your S-40A will be happy fed with a long wire, coax, twin lead, etc. Most antenna connections will require shorting terminal A2 to ground, if using a balanced feed connect it to the A1 and A2 terminals with the short from A2 to ground removed, otherwise (for coax, single random wire, etc.) connect the "hot" lead to A1 and short A2 to ground.

Especially for receivers like the S-40 series where there is no antenna "trimmer" or compensator the best alignment of the input coils occurs with the antenna connected during alignment with the signal generator lightly coupled to it.

And on edit, I see Tod already addressed your question :)

Rodger WQ9E


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 Post subject: Re: Hallicrafters S40A Antenna Question
PostPosted: Dec Thu 06, 2018 4:02 pm 
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Joined: Jan Sat 02, 2016 4:45 am
Posts: 45
Location: Clayton, CA 94517
Thanks folks. New antenna is inbound. I had to go with a powered loop due to my location. I'm still trying to work out the best longwire solution, but that may have to wait until the summer at this point.

Karl


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