[1000mp] IMD improvement

Tue, 16 Apr 2002 14:10:06 -0400

Interesting. 

On the next rig that comes through for Product Review, I will see if we can
look at the 20 M IMD at different power levels. It might prove to be of
interest.

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

> -----Original Message-----
> From: John [mailto:[email protected]]
> Sent: Tuesday, April 16, 2002 1:25 PM
> To: [email protected]
> Subject: Re: [1000mp] IMD improvement
> 
> 
> The reason for the constantly bad IMD on the new rigs is mosty due to
> manufactures are using the industry standard Toshiba 2SC2879 
> in the finals.
> The MP use's it , the FT-990, 757 ,   the late model Kenwood 
> 450 ,850, 870,
> do to. It's a inexpensive transistor that is durable. The 
> Icom's are using
> other types. There have been other rigs made in the mid 80's 
> that have been
> very clean with 12 volt finals. The high volt rigs using the MRF422
> ...1000D, TS-930,TS- 940, FT-767 & other mosfet final radio's have no
> problem getting low IMD of -35 or better. The IMD of tested 
> rigs is at rated
> power, but if you turned the radio down ,( 40 watts)  to say 
> drive late
> model amp's with ceramic tube's ... the IMD go's out of 
> sight. You should
> look at the data sheet on the 2sc2879 at lower power levels 
> ... The IMD is
> scary !!! and thats were most people run there rigs to drive 
> their legal
> limit amps .........
> 
> 73's john
> 
> 
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