[Heathkit] (Fwd) Re: HW-101 for PSK31?

[Kenneth G. Gordon]

On 3 Sep 2007 at 12:27, Wilson Lamb wrote:

> 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.

Yup.

> 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).

You should see the power supply: it weighs probably at 
least 50 lbs
and has 4 huge capacitors on it, in addition to several (6?) 
large
heatsinked solid-state switches.

I had to replace two of the solid-state switches once.

I'm the Electronic Instrument Specialist for the University of 
Idaho's
College of Science.

Yes, it really is 400 volts to a 2.25 volt solenoid. Honest.

Ken Gordon W7EKB

> 
> 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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> 
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