[Elecraft] Why no IF shift ?

[Siu Johnny]

Hi Group,

PRESS your delete button now if you don't like long winded arguement.

For the price paid for K2, we have the chance to enjoy exceptionally RX 
performance near the top end transceivers. Naturally, we have to give up 
something e.g. band scope specturm, manual notch within AGC loop, IF shift, 
band pass tuning, FM mode and general TX/RX coverage etc

Part of the price paid for K2 is for customer services and support.  
Elecraft has to be profitable in their business in order to survive.  
Bearing in mind, quite a portion of the ham population is fond of multiband 
multifunction all mode rigs.  It is nothing wrong for them but competition 
in the ham rig market is keen.  If we are NOT prepared to give up something 
for such a high performance K2, the price for K2 could be much higher and 
not affordable by most of the hams.

Just taking IC7800 as an example, only 25% of the sale goes to the ham 
market whereas 75% goes to the institutional users.  ICOM earn most of 
their profit from corporate users.  Therefore, you can imagine how many 
hams can afford high end rigs at high price.  For what we got from the K2 
is quite a good balance among performance, functions and pricing.

Clearly, if there were a new K3 with all the missing functions mentioned in 
para. 1 above and at similar price tag, I would be delighted to jump into 
it.  However, we have to be realisitc and Eleraft has to make his profit  
to survive.

I share the 'miss' of IF shift and did ask similar question about 4 years 
ago when I first built my s/n1146.  Eventually, I accepted it as a 
compromise.  I  have the luck to own / play around most of the top end rigs 
but I still love my K2.

73

Johnny Siu VR2XMC


From: "Don Wilhelm" <w3fpr at earthlink.net>
Reply-To: w3fpr at arrl.net
To: <N2EY at aol.com>, <gmk at gm4esd.fsworld.co.uk>,<elecraft at mailman.qth.net>
Subject: RE: [Elecraft] Why no IF shift ?
Date: Tue, 8 Aug 2006 20:39:34 -0400

Folks, (long philosophical response - delete if not interested in my
opinion).

Some very good points mentioned in this thread, but the reality of all of 
it
is compromise.
For any given price target, some tradeoffs must be made.  If I can 
interpret
the K2 design goals loosely, the dynamic range was considered uppermost, 
and
good sensitivity and IP3 performance running a close second.  To achieve
that in a kit product, single conversion IMHO is the only realistic way to
go.

Yes, there ae very good designs out there for multi-conversion receivers 
and
they have their costs and limitations, but the K2 is a compromise of all
that.  It is single conversion because that is the way to contain the
dynamic range and good IP3 characteristics within the chosen price range.
It is well known that one must get into the $3K+++ transceivers to achieve
those receive parameters that K2/100 owners have achieved for less than 
half
that price.

Certainly, IF shift is not an easy acomplishment with a single conversion
transceiver.  Answering one question posed in the thread which asked why a
BFO frequency knob would not do the deed - the answer is  YES, BUT - if 
only
the BFO frequency is changed, the displayed frequency would no longer be
correct - the firmware currently corrects for both the BFO and VFO
frequencies and displays the correct carrier frequency, so while passband
tuning might be accomplished simply by changing the BFO, the VFO would have
to be altered manually to compensate for the BFO shift, and the resulting
frequency on the dial would be incorrect.  We used to do exactly that on
receivers with a variable BFO, but then we did not have digital dials that
were good to the nearest 10 Hz (but I digress).  When CAL FIL is run, all
that is taken into consideration in the firmware, and the EEPROM values
contain the result of that calibration run which produces correct carrier
frequency dial readings - you have to give up one thing to gain another in
any design process unless 'price is no object'.

If the world were perfect, we would all have receivers with a 120+ dB
dynamic range, straight sided selectivity curves (with perfectly flat pass
band shapes and no change in group delay across the passband), MDS figures
in the -160 dB range and all that at a cost of less than $100 - of course I
am dreaming based on today's technology and price/performance criteria that
would be within the budget of the majority of hams.  There is no sense in
developing a superior design for production that would sell only one unit
because of the cost involved - that is the stuff that extreme designs can
produce, but those are currently the stuff of advanced homebrewers - they
are the designs of tomorrow when the price of such designs comes down to an
affordable level suitable for production.


73,
Don W3FPR