[NJARC] Voltage Drop, Ham Radio...

[Scott Roberts]

Hi John-
While I am still considering the tube type dow key switch, I found some info on the internet stating that the t-r type using the tube has an issue with adding some noise. It can be cleared up by adding a bandpass filter.

I realized I had a homebrew Dow-Key switch of the conventional relay type one a homebrew rig I poicked up last year. I pulled it apart, and can get it in operable shape for 110AC, and the HT-37 has provision for operating that one(it is switched through the HT-37, and has a separate power plug).

I can also build a few, now I have a pattern :)

Interestingly, I found the HA-2 & HA-6 transverters have a 6 or 12VDC Dow-Key switch BUILT IN! Just noticed it in the pics- so worst comes to worst, I can always borrow one out of the HA-6, and use it with a power supply.

I MAY just have the radio On The Air this week, If all goes right!

Scott


--- On Tue, 7/28/09, John Ruccolo <jr6v6gt at yahoo.com> wrote:

> From: John Ruccolo <jr6v6gt at yahoo.com>
> Subject: Re: [NJARC] Voltage Drop, Ham Radio...
> To: "NJARC Radio Club" <njarc at mailman.qth.net>, "Scott Roberts" <ng19delta at yahoo.com>
> Date: Tuesday, July 28, 2009, 4:20 PM
> 
> Hi Scott,
> 
> OK, I *think* I have this right. Any others feel free to
> chime in.
> 
> You've got 150V and you want to drop it to 120V to feed a
> load that draws 25 mils. (.025 ampere).
> 
> So the voltage drop is 30V
> 
> Ohm's Law: I=E/R
> 
> R (the dropping resistor) = E/I
> 
> R = 30/.025 = 1200 ohms (great -- that's a standard
> value!)
> 
> Now, your next question: how big should R be?
> 
> P = I * E
> 
> P = .025 * 30 = .75 watt
> 
> So, a 1-watt resistor would be OK, but just to be safe,
> good practice would be to use a 2-watt resistor
> 
> 
> Regards,
> 
> John
> 
> 
> --- On Mon, 7/27/09, Scott Roberts <ng19delta at yahoo.com>
> wrote:
> 
> > From: Scott Roberts <ng19delta at yahoo.com>
> > Subject: [NJARC] Voltage Drop, Ham Radio...
> > To: "NJARC Radio Club" <njarc at mailman.qth.net>
> > Date: Monday, July 27, 2009, 1:10 PM
> > Just remember 
> > Reply = Poster
> > Reply All = Everyone
> > 
> >
> _________________________________________________________
> > 
> > Well, I am very close to getting my Hallicrafters
> HT-37 on
> > the air. Great Thanks to John Ruccolo for getting
> together
> > with me after the swapmeet Saturday at InfoAge(Great
> > Swapmeet!) and going through the HT-37. We got it to
> a
> > decent point where it was showing great signs of
> life,
> > especially after some tube replacement(Thanks to Al
> Klase
> > for locating a few tubes for us)
> > 
> > It now looks like I should be on HF this week.
> > 
> > Voltage Dropping Question- In order to use the HF
> sets, I
> > need to get my vacuum tube Dow-Key powered. It takes
> > 90-120VDC & 6VDC. I would like to pull the power
> from
> > the receiver- it has a 150VDC available, and so i need
> to
> > know how to drop it to 110-120 or so... I know I can
> add a
> > couple power resistors, but not sure how much. Can
> anyone
> > give me any ideas? 
> > 
> > I am still lousy at these calculations still... On of
> these
> > days!
> > 
> > Thanks!
> > Scott
> >
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>