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New AGC mod #ubitx

 

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I used that same line of thought, but replaced Q10 in the uBITx with a dual gate FET¡­ the second gate doing exactly what your Q2 does.? The advantage is that there is no loss¡­ and in fact the FET has more gain than the 2N3904.? My AGC generation is a little more sophisticated too¡­ variable RF gain and integration time (variable AGC time reaction) and a filter¡­ but the idea is the same.

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Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

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Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

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Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

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Moderator ¨C North American QRO Group at Groups.IO.

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email:? bill@...

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From: [email protected] [mailto:[email protected]] On Behalf Of Don, ND6T via Groups.Io
Sent: Sunday, April 15, 2018 11:44 AM
To: [email protected]
Subject: [BITX20] New AGC mod #ubitx

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I have a new, low insertion loss (0.6 dB), wide dynamic range (>50 dB @ 3.5 MHz, 34 dB @ 30 MHz) and fairly simple design. It works! The particulars are posted on . 73, Don


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Bill, do you have it posted somewhere?
 

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I have not posted it yet Don.? It¡¯s still just modeled in spice and crudely cobbled into my ¡°test uBITx¡±.? I have only limited time to work on all of these projects so it comes in bits and pieces.? I¡¯ll get it posted with some test soon.

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Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

?

Owner - Operator

Big Signal Ranch ¨C K9ZC

Staunton, Illinois

?

Owner ¨C Operator

Villa Grand Piton ¨C J68HZ

Soufriere, St. Lucia W.I.

Rent it:

Like us on Facebook!

?

Moderator ¨C North American QRO Group at Groups.IO.

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email:? bill@...

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From: [email protected] [mailto:[email protected]] On Behalf Of Don, ND6T via Groups.Io
Sent: Sunday, April 15, 2018 12:45 PM
To: [email protected]
Subject: Re: [BITX20] New AGC mod #ubitx

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Bill, do you have it posted somewhere?


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Your original setup is working quite well for me. I'll have to try your
new one! I put mine on a little surfboard and plugged it in on the
headers soldered across the break in the receive line. Having a long
ground lead doesn't seem to affect it much. I'll have to find a better
way to ground the new one.

Good job.

tim ab0wr

On Sun, 15 Apr 2018 09:44:14 -0700
"Don, ND6T via Groups.Io" <nd6t_6@...> wrote:

I have a new, low insertion loss (0.6 dB), wide dynamic range (>50 dB
@ 3.5 MHz, 34 dB @ 30 MHz) and fairly simple design. It works! The
particulars are posted on ND6T.com ( ).
73, Don
 

Don,

WoW!

This version works great. With the original I could never actually hear
the noise level drop as strong signals would come on. You can certainly
hear it now! You can hear the receive sensitivity actually come back
after the strong stations disappears. I might go to a 500K resistor to
make it discharge just a little quicker.

I basically only work on 80m and 40m and I can't tell any actual loss
of sensitivity on either band. Minimum signals are determined by the
noise, not the receiver sensitivity.

I'm impressed. Good work!

I'm not sure I'm going to even play around with the PIN diodes I bought!

tim ab0wr

On Sun, 15 Apr 2018 09:44:14 -0700
"Don, ND6T via Groups.Io" <nd6t_6@...> wrote:

I have a new, low insertion loss (0.6 dB), wide dynamic range (>50 dB
@ 3.5 MHz, 34 dB @ 30 MHz) and fairly simple design. It works! The
particulars are posted on ND6T.com ( ).
73, Don

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