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

Marijan Miletic, S56A artinian at siol.net
Fri Dec 7 17:37:42 EST 2001

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
  multiple Hi-Q, RF stages with distributed gain that track the tuning
  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

  > 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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