[1000mp] QST Product Reviews whitewash

Tue, 16 Apr 2002 11:55:38 -0400

Since previous radios going back to well designed rigs using 
tube finals were capable of < -35 dB third order products, I 
do not clean signals an "optional" improvement.  Failure to 
meet that standard is, quite simply, cheapening the product. 

That aside, what would it cost to "clean up" the driver and 
final stages in one of these radios?  I suspect simply using
larger transistors ... something like a pair of 160 Watt rated 
devices in push-pull biased into class AB1 instead of a pair 
of 80 Watt rated devices biased into class B ... would go a 
long way to solving the problem.  The added cost should be 
relatively minor ($5 each for the larger transistors plus a 
larger heat sink?) ... say $50 at retail.  

The IC-706MKIIG makes -33 dB third order on 20 and below ... 
the Kenwood 570 holds -33 dB third order through 6 meters ...
even the relatively ancient Alinco DX-70T shows worst case 
-29 third order.  Those are a good start and none of the radios 
are exactly "high dollar."  -33 dB (even -29 dB) third order 
IMD would be a major improvement over the -23dB numbers of 
the 746 Pro. 

For something like this the product reviews need to do more 
than say "we would like to see improvement."  The need to say, 
"while there may be no FCC standards for third and fifth order 
IMD, we consider these results completely unacceptable." 

73, 

   ... Joe, K4IK 

> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Hare,Ed, W1RFI
> Sent: Tuesday, April 16, 2002 10:18 AM
> To: '[email protected]'
> Subject: RE: [1000mp] QST Product Reviews whitewash
> 
> 
> > It would be refreshing to see: "the transmit IMD of this product is 
> > simply not acceptable for a modern radio.  We would expect to see 
> > third order IMD results at least -36 dB and fifth order products  
> > at least -46 dB.  Any manufacturer that releases a product which 
> > fails to achieve that standard simply does not care about the 
> > amateur market!" 
> 
> And you are willing to pay how much for this improvement?
> 
> 73, 
> Ed Hare, W1RFI
> ARRL Lab
> 225 Main St
> Newington, CT 06111
> Tel: 860-594-0318
> Internet: [email protected]
> Web: http://www.arrl.org/tis
> 
> 