Loading ...
Sorry, an error occurred while loading the content.

Re: [softrock40] SR impedances

Expand Messages
  • Bill Dumke
    How about a unity gain cascode circuit? You could set it up so the common base stage would give a nice 50 Ohm match. Bill
    Message 1 of 8 , Mar 31, 2006
    • 0 Attachment
      How about a unity gain cascode circuit? You could set it up so the
      common base stage would give a nice 50 Ohm match.

      Bill

      FRANCIS CARCIA wrote:

      > Emitter follower would have a higher Z input. I like to stay at 50
      > ohms to make testing easier. I'm thinking the most stable performance
      > for the mixer would be a pad setting the input Z resistive. I'm yet to
      > connect a SDR directly to an antenna letting the whole world into the
      > mixer. I have a nice prepost selector that would make a nice front end
      > for a sdr. Still tend to want to use a stage ot IF with a roofing
      > filter here. But keeping an open mind....
      >
      > */Bill Dumke <billd@...>/* wrote:
      >
      > Kees,
      >
      > One thought I had was to use an emitter follower. It would be unity
      > gain, so it would not mess up the intermod, and it would have 100%
      > negative feedback so it should be quite linear. Of course, for it
      > to be
      > unity gain the output would look like a very low impedance. (If you
      > stuck a 50 ohm resistor in series with the output you cou ld get a
      > good
      > match, but also 6 dB of voltage loss.) I don't know if the low
      > impedance of an emitter follower would mess up the switch or not.
      > Maybe
      > it would improve the performance?
      >
      > Bill
      >
      > windy10605@... wrote:
      >
      > > With the two 10 ohm resistors on each side of the transformer and
      > > assuming a few ohms for the switch, how well do we maintain a
      > good 50 ohm
      > > termination (considering all the switching, overlapped
      > switching, etc)
      > > for the transformer so the BPF filter on the other side works
      > correctly ?
      > > Any thoughts on how this might be improved ?
      > >
      > > 73 Kees K5BCQ
      > >
      > >
      > ------------------------------------------------------------------------
      > > YAHOO! GROUPS LINKS
      > >
      > > * Visit your group "softrock40
      > > " on the web.
      > >
      > > * To unsubscribe from this group, send an email to:
      > > softrock40-unsubscribe@yahoogroups.com
      > >
      > >
      > > * Your use of Yahoo! Groups is subject to the Yahoo! Terms of
      > > Service .
      > >
      > >
      > >
      > ------------------------------------------------------------------------
      > >
      >
      >
      >
      > Yahoo! Groups Links
      >
      >
      >
      >
      >
      >
      >
      >
      >
      > SPONSORED LINKS
      > Ham radio
      > <http://groups.yahoo.com/gads?t=ms&k=Ham+radio&w1=Ham+radio&c=1&s=15&.sig=t8IpznzYq-E2LbCrDXaGPQ>
      >
      >
      >
      > ------------------------------------------------------------------------
      > YAHOO! GROUPS LINKS
      >
      > * Visit your group "softrock40
      > <http://groups.yahoo.com/group/softrock40>" on the web.
      >
      > * To unsubscribe from this group, send an email to:
      > softrock40-unsubscribe@yahoogroups.com
      > <mailto:softrock40-unsubscribe@yahoogroups.com?subject=Unsubscribe>
      >
      > * Your use of Yahoo! Groups is subject to the Yahoo! Terms of
      > Service <http://docs.yahoo.com/info/terms/>.
      >
      >
      > ------------------------------------------------------------------------
      >
    Your message has been successfully submitted and would be delivered to recipients shortly.