W0UN -- John Brosnahan wrote:
>At 05:45 AM 3/8/2006, Paul Christensen wrote:
>
>> > I don't believe an amp with vacuum relay T/R
>> > switching can be considered a full QSK amp. Yet Alpha advertises the
>> > 99 and the 9500 as full QSK. I run my 99 in semi-breakin only. How
>> > long can a vacuum relay last in full QSK mode?
>>
>>The vacuum relay in my Alpha 70V has lasted 36 years. A vacuum relay with
>>an appropriate accelerator circuit can switch nearly as fast as a PIN diode.
>>
>>Paul, W9AC
>
>
>Paul, I think your experience with relay lifetimes is pretty typical
>of amps used
>on a regular basis in normal operation and is shared by many of
>us. But I suspect
>that if an amp is operated in a CW contest every weekend and used during the
>week by a high-speed CW merchant for a lot of rag-chewing then the relay life
>may not be nearly as great.
>
>I do quibble with your statement on speeds. Vacuum relay speeds are
>measured in
>milli-second switching times whereas PIN diodes can be switched in
>micro-seconds.
>The fact that PINs are not switched that fast for typical ham amps is
>more of a function
>that they don't need to be rather than that they cannot be switched
>that fast. Of course
>it all boils down to the operating frequency and the carrier lifetime specs.
>
>73 John W0UN
For a very effective single-band solution using low-cost diodes, see:
http://www.sm5bsz.com/pindiode.htm
This switch will handle 2.5kW and is fast enough to hear the station's
radar echoes:
http://www.sm5bsz.com/aurora.htm
SM5BSZ's design is for 144MHz, but it could be adapted for any one HF
band using LC networks to replace the coax stubs. However, it is not
suitable for multiband operation.
Somewhere in a drawer, I even have the diodes...
--
73 from Ian GM3SEK
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