2 wrote:
>>I was particularly interested in their equivalent to
>>the Jennings RJ1A, the GH1-12Vdc, which comes with a 12 volt coil. This
>>meant I didn't have to build an additional power supply for 26
>>volts.
>
>*** In order to speed up a GH1-12vdc sufficiently to use with a modern
>transceiver, one would need a 50 - 70 volt PS and an appropriate
>series-R.
>
The RJ1A is rated at 8 milliseconds max open or close, and the Kilovac
HC-1 at 6ms max. The GH1 is rated at 6ms but it doesn't say whether this
is maximum or typical.
All these figures are when operated from the rated coil voltage, and
neither speeded-up nor slowed-down electrically.
Rich's highly successful circuit uses a high-voltage supply and a series
resistor. Recalling earlier posts from Rich, this will speed up typical
24V relays (RJ1A and HC-1) to about 1.5ms closing. This level of speed
means that relay closing time is not a significant factor in your QSK
timing.
However, you don't actually *need* a high voltage supply to achieve this
speedup. You can do almost the same from the existing relay voltage, by
using the one-transistor circuit developed by K1KP. Using this circuit
with the normal 24V rail, I've had 1.5ms closure times from a number of
HC-1 relays... pretty much the same as Rich gets.
Adding a 'universal' 12V low-current PTT interface to any transceiver,
the circuit expands to a whole three transistors - see:
http://www.ifwtech.co.uk/g3sek/in-prac/best-of.htm#speedup
Click on the "April 2002" link for more details of how it works.
It's an easy mod to almost any amplifier, and will also speed up an
existing open-frame antenna relay. Bringing the closure time down from
about 30ms to more like 15ms can sometimes cure hot-switching problems
without needing to change the relay.
BTW, my favorite source for vacuum relays is:
http://www.mgs4u.com/relay.htm
Allen Bond is a straight guy, and very easy to deal with.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
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