Here is a link to an appropriate transformer design:
http://www.aytechnologies.com/TechData/9-to-1_XFMR.htm
This design will work well at 630m. It's a lot like the binocular core
design with 73 material.
Gary, K9AY
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ue.
>
>
> Two turns is of the edge of the cliff. Better to use 3 turns I believe.
>
>
> Chuck.
>
>
>
>
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> From: Tim Shoppa
> Sent: Monday, July 16, 2018 5:07 AM
> To: Chuck Hutton
> Cc: kd9sv; topband@contesting.com
>
.
Two turns is of the edge of the cliff. Better to use 3 turns I believe.
Chuck.
From: Tim Shoppa
Sent: Monday, July 16, 2018 5:07 AM
To: Chuck Hutton
Cc: kd9sv; topband@contesting.com
Subject: Re: Topband: Beverage transformers tht work down to 630 m
I
d 107 Ohms. 3 turns is 77 uH and 242 Ohms.
>
>
> So theory seems to tell me I need 3 turns.
>
>
> Chuck
>
>
>
>
> From: kd9sv
> Sent: Sunday, July 15, 2018 4:43 PM
> To: 'Chuck Hutton'
> Subject: RE: Topband
There are a couple of good articles on this subject by John Bryant with Bill
Bowers and Nick Hall-Patch , VE7DXR and the other by Mark Connelly WA1ION which
are worth taking a look at.
The first article includes measurements from 100kHz up to 7MHz.
Yup! Amidon BN-73-202 (Fair-rite 2873000202) is good stuff! Very high
permeability.
W8JI himself kindly introduced me to 73 material back in the 1980s. Back
then we just used Beverage antenna transformers made from stacked ferrite
beads made from that that stuff, but those binocular cores were far
and 107 Ohms. 3 turns is 77 uH and 242 Ohms.
So theory seems to tell me I need 3 turns.
Chuck
From: kd9sv
Sent: Sunday, July 15, 2018 4:43 PM
To: 'Chuck Hutton'
Subject: RE: Topband: Beverage transformers tht work down to 630 m
Guys, the 4x rule is to my
sfy the 4X rule. Yet my 3 turn windings measure 108 uH and 120 uH. That
explains a good bit of the low end response.
Chuck
From: Tim Shoppa
Sent: Sunday, July 15, 2018 3:50 PM
To: Chuck Hutton
Cc: topband@contesting.com
Subject: Re: Topband: Beverage transformer
Chuck,
I used the BN73-202 transformer exactly as shown on W8JI's website
and it work very well on 630 meters. I wish my Beverage were
2000 feet long instead of 580 feet...
73
Frank
W3LPL
On Sun, Jul 15, 2018 at 6:29 PM, Chuck Hutton wrote:
> The commercially available Beverage
I agree the usual rule of thumb (Transformer winding Z should be several
times larger than nominal line impedance) would cause you to think you
should have more turns.
The old Clifton Labs website is no more. But an archived page of
measurements of transformers shows that the frequency response
The commercially available Beverage transformers I have seen are like the W8JI
model: 2 primary turns on a BN73-202 core.
My calculations say 4 turns are needed at 630 m.
Does anyone know of commercially available transformers with isolated windings
that operates well down to 630m?
Chuck
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