HW-101 for PSK31?

[Wilson Lamb]

A crucial part of hot rodding is to use a good big capacitor at the relay 
coil.  Then the high voltage charges the cap, which supplies the surge to 
zap the relay in quickly.  Remember that the energy stored in the cap goes 
up as V^2,  so don't go overboard...Twice normal voltage and a few uF should 
do it.  With the resistor and no cap, the relay will be slower than normal.

The 400V story sounds a little high.  The drain would be pretty high on the 
supply (coil current) and there would be a lot of dissipation in the 
resistor (coil current ^2*R).

Wilson
W4BOH
----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at VERIZON.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Sunday, September 02, 2007 7:24 PM
Subject: Re: HW-101 for PSK31?


> On 2 Sep 2007 at 6:58, Paul Blumhardt wrote:
>
>> In regards to using the other gear on the newer digital modes, the
>> area that is of most concern is T/R cycle time.
>
> Yes. However, supposedly if your setup makes at least 20
> mS or less, that is amply adequate.
>
>> The old relays take
>> too long to go from Receive to Transmit and vise-versa.
>
> Not necessarily. It depends on how they are set up. My HW-
> 101/SB-200 combo JUST makes 20 mS, but I have "hot-
> rodded" the relays in the HW-101 just a bit by changing the
> value of one resistor to 1K from 10K. I'll have to dig out the
> info.
>
> For the HW/SB-101 series, you also have to reduce the
> AGC delay, but this is easily done.
>
> The receiver recovers very fast, usually in under 5 mS.
>
> The method used in research facilities to "hot-rod" a relay is
> really rather simple: use a pretty high voltage to the relay,
> with a dropping resistor in series so that after the relay
> starts drawing current, that current will not be above the
> rated current, and thus the rated voltage will not be above
> the rated voltage.
>
> Say, use 150 VDC and the necessary resistance to drop the
> voltage to 12 VDC when the relay is drawing steady current.
>
> The initial burst of higher voltage causes the relay to pull in
> very quickly.
>
> In one case with which I am familiar for a research device in
> our Chemistry department, a solenoid rated at 2.25 VDC
> was connected to a 400 VDC source. Although I don't now
> remember the exact figures on opening-time, it was in the
> microsecond range. Normal opening time with 2.25 VDC on
> it was in the 100 mS range.
>
> Ken Gordon W7EKB
>
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