[TenTec] Circuit question - Omni VI type 563

[Dr. Gerald N. Johnson]

On Fri, 2009-07-17 at 09:37 -0600, David Feldman wrote:
> I'm investigating a problem in my Omni VI type 563, possible diode failure
> in the antenna T/R path. The low-pass filter board (81592) shows three
> diodes in the main receive path from antenna to front end (D6, D7, D8) as
> 1N4007 rectifier diodes (but they appear to be used for RF switching.)
> 
> Is the 1N4007 still the normally used part for service, or should I look for
> another device type.
> 
> Thanks,
> 
> 73 Dave WB0GAZ
> 
The 1N4007 because of its high voltage rating is a PIN diode. That makes
it a little bit better RF switching diode than a 1N4148 silicon high
speed diode. It is very rugged which is an advantage, it does introduce
more distortion than a true RF switching diode.

The best article on the choice of RF switching diodes was in VHF
Communications about January 1994. A copy was on line at:
http://homepages.ihug.co.nz/~jaking/TS-940_02.htm#_Toc155846465 the last
I checked (and posted on this forum last January). Its still there but
its still a long page with many large images and is slow to download,
even with broadband.

73, Jerry, K0CQ