Fw: [CQ-Contest] Fwd: [FCG] riding the RF gain...

Marijan Miletic, S56A artinian at siol.net
Sat Dec 8 16:30:13 EST 2001

P.S.  Beware that the situation is much worse on noiseless DX 2 m band...

----- Original Message -----
From: Marijan Miletic, S56A
To: Dennis OConnor
Sent: Saturday, December 08, 2001 4:22 PM
Subject: Re: [CQ-Contest] Fwd: [FCG] riding the RF gain...

"Contesting is extreme radio" is someones motto on this reflector...

RX levels in M/M environment might be in Watts range and we are back to
relays technology.

Market dictates general coverage HF RX with all modes and that brings us to
15 kHz first IF filter.

So we end up with K2 solution...

73 de Mario, S56A, N1YU
  ----- Original Message -----
  From: Dennis OConnor
  To: artinian at siol.net
  Cc: cq-contest at contesting.com
  Sent: Friday, December 07, 2001 9:57 PM
  Subject: Re: [CQ-Contest] Fwd: [FCG] riding the RF gain...

  Mario, I wasn't intending to discuss the hardware, but since you bring it
  up...  Remember, we are talking receive power levels here... Creating
  capacitances on a chip is super easy and efficient... Inductances are
  tougher, but the smaller ones can be done on chip surfaces, and the larger
  ones can be screened onto glass boards..  Doing the selecting can be done
  with FET arrays as line drivers.... And, of course a microprocessor doing
  the logic decisions...
  Not tough at all... You do have a point that the immediate ham market
  doesn't justify R&D costs, but the chips/technology would seem to have
  other uses once it is a shelf item and offered to RF design engineers
  products for mass markets...
  The MK-V uses mini relays, BTW....


  > There seems to be a brand new concept proposed to "unpeak the immediate
  > frequency with not particularly sharp LC filter" .
  > Multiple Hi-Q requires large L and C without varicap diodes.  Hamradio
  > HF market does not justify such a technology investment...
  > 73 de Mario, S56A, N1YU
  >   ----- Original Message -----
  >   From: owner-cq-contest at contesting.com
  >   To: tree at kkn.net
  >   Cc: cq-contest at contesting.com
  >   Sent: Friday, December 07, 2001 1:51 PM
  >   Subject: Re: [CQ-Contest] Fwd: [FCG] riding the RF gain...
  >   Tree, this is a topic that W8JI and I have discussed in this forum in
  >   the past.. There were bad trade offs made when amateur transceivers
  >   went to up converting, band pass front ends that are 500 kc+ wide...
  >   Given todays cheap processing power, there is no reason, cost or
  >   technology, to not
  > have
  >   multiple Hi-Q, RF stages with distributed gain that track the tuning
  > across
  >   the band... Yeasu has gone part way there on the MK-V which has a
  >   tuneable LC filter that can be inserted before the First RF
  >   amplifier/mixer stage, but it is not particularily sharp and requires
  >   the operator to manually peak it as he moves up and down the band...
  >   However, it also has the ability to unpeak the immediate frequency
  >   which can have benefits at times so the Yeasu engineers did do some
  >   thinking outside of the box...  We have driven the technology of
  >   receivers forward with our demands for better contest receiver
  >   performance, but there is lots of room for improvement
  >   Denny>
  >   >
  >   > Sorry for the confusion generated by my post.
  >   >
  >   > When I said "in band" I was thinking "in passband" as opposed
  >   > to signals within the amateur band.
  >   >
  >   > Actually, I consider the "in band" IMD performance of most
  >   > receivers today to be really disappointing.  I think that when you
  >   > have lots of noise, this distortion makes it really hard
  >   > to copy signals near the noise level.  It might also explain
  >   > why some receivers sound bad when there is a big pileup.
  >   >
  >   > The IMD graphs show two signals mixing - but that isn't real
  >   > life all of the time!
  >   >
  >   > Backing off the RF gain quickly attenuates these products by
  >   > another 20 or 25 db.
  >   >
  >   > You can see a graph of this IMD distortion at this URL:
  >   > http://www.arrl.org/tis/info/pdf/k2.pdf on page 19 under the
  >   > title "In-Band Receiver IMD Graphs".  The K2 actually looks
  >   > about 10 db better than my TS850 and some other radios I have
  >   > looked at (including the MP).  Perhaps this helps explain why
  >   >some people think this receiver responds to pileups better.
  >   >
  >   > I did some work with AC6T to try and get better results with
  >   > the 850, but we weren't able to come up with anything after
  >   > about a month of work.
  >   >
  >   > You can make your own measurements if you are interested.  You will
  >   > need two XTAL oscillators about a few hundred Hz apart
  >   > with pretty much the same output.  You can download software
  >   > to use with a soundcard to turn your PC into a spectrum analyzer.
  >   > Then, you can play with your AGC and RF gain settings to see the
  >   > difference.
  >   >
  >   > Ask anyone who has a direct conversion receiver to bring it
  >   > over - and you will be amazed at the difference!!
  >   >
  >   > 73 Tree  N6TR
  >   > tree at contesting.com
  >   >
  >   >
  >   > --

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