Daily GLOWBUGS
Digest: V1 #106
via AB4EL Web Digests @ SunSITE
Purpose: building and operating vacuum tube-based QRP rigs
Subject: glowbugs V1 #106
glowbugs Sunday, September 7 1997 Volume 01 : Number 106
Date: Fri, 5 Sep 1997 15:18:27 +0000
From: dlwade@pacbell.net
Subject: Workbench ideas
Greetings glowbuggers and VSS'ers
After buying a house earlier this summer, the time has come to set
up an BA/GB/VSS workshop in a corner of the garage.
I am calling on your collective wisdom to get and idea on do's,
don'ts and whatever else you may think would be useful to know before
building a work area, including size of the work area, arangement of
test equipment and lighting ideas.
Test equipment so far consists of a Tek 545 scope (on a cart),
HP-412 DC voltmeter and TS-497C and Measurements model 66-B sig gens.
High on the want list for the next Foothill swap are a general purpose VTVM and audio osc
(HP-200 type). (would a power supply be useful, suggestions?)
Uses will be mostly BA repair, and GB/VSS experimentation.
Any and all ideas are welcome! If the response warrants,
I'll repost a digest of the ideas I get.
Thanks,
Dennis
Dennis L. Wade
KG6ZI
Sacramento, CA
Repy to: dlwade@pacbell.net
Date: Sat, 6 Sep 1997 18:10:51 -0500 (CDT)
From: Bob Roehrig <broehrig@admin.aurora.edu>
Subject: Cheap/easy/effective AGC
I was playing around with the navy RCH receiver recently obtained and.
as with all pre-product detector receivers, I get frustrated by trying
to use it in the CW mode with no AGC.
In this particular unit, there is conventionally derived rectified IF
AGC in the AM mode, but in CW, the AGC bus is shorted directly to
a negative bias supply (derived from a 50 ohm resistor in the HV
xfmr center tap to ground). In most receivers, the AGC would simply
be shorted to ground.
Not wanting to really modify this unit, I thought I'd try audio-derived
AGC, and it is outstanding. This simple circuit could be applied to
anything from an ARC-5 to a HRO.
The circuit is simply a conventional half-wave voltage doubler. I used
a pair of 3.3uf 50V caps and a pair of 1n4001 diodes. I tack soldered
a 2K pot across the 600 ohm output transformer terminals (one is grounded)
and that feeds the circuit. The output is loaded with a 470K resistor
and connected to the AGC bus. In this receiver, that is accomplished
by removing the wire to the mode switch that comes from the fixed
bias source and connecting the detector output to that switch lug.
I tuned in a fairly strong SSB station on 40 meters, then cranked up the
gain until the signal started to distort, then adjusted the 2K pot
until I started to get AGC action. Thereafter, the gain could be cranked
up all the way with no distortion and all signals in the round-table
sounded identical in level.
AS I said, this same scheme should work with a great many receivers.
The pot value should be a few times higher than the output impedance
to prevent loading. This circuit has a time constant of around 1.5
seconds decay, which works great for both CW and SSB.
E-mail broehrig@admin.aurora.edu 73 de Bob, K9EUI
CIS: Data / Telecom Aurora University, Aurora, IL
630-844-4898 Fax 630-844-5530
Date: Fri, 5 Sep 1997 17:25:22 +0000
From: dlwade@pacbell.net
Subject: Re: ISDN to DNS down and secondary DNS down at the same time, f
Hello Bob,
Although your message says the problem is fixed, I have been
trying (over the last half hour or so) to post a message to:
glowbugs@www.atl.org
10-15 min later, I get a message from:
Administrator_at_ushmm@inetgate.ushmm.org
saying the message is undeliverable, with no other information.
Is something wrong, or is my address wrong?
Thanks,
Dennis
Dennis L. Wade
KG6ZI
Sacramento, CA
Repy to: dlwade@pacbell.net
Date: Fri, 5 Sep 1997 16:46:01 +0000
From: dlwade@pacbell.net
Subject: (Fwd) Workbench ideas
- ------- Forwarded Message Follows -------
From: Self <Single-user mode>
To: glowbugs@www.atl.org
Subject: Workbench ideas
Cc: vss@mlist.access.digex.net
Reply-to: dlwade@pacbell.net
Date: Fri, 5 Sep 1997 15:18:32
Greetings glowbuggers and VSS'ers
After buying a house earlier this summer, the time has come to set
up an BA/GB/VSS workshop in a corner of the garage.
I am calling on your collective wisdom to get and idea on do's,
don'ts and whatever else you may think would be useful to know before
building a work area, including size of the work area, arangement of
test equipment and lighting ideas.
Test equipment so far consists of a Tek 545 scope (on a cart),
HP-412 DC voltmeter and TS-497C and Measurements model 66-B sig gens.
High on the want list for the next Foothill swap are a general purpose VTVM and audio osc
(HP-200 type). (would a power supply be useful, suggestions?)
Uses will be mostly BA repair, and GB/VSS experimentation.
Any and all ideas are welcome! If the response warrants,
I'll repost a digest of the ideas I get.
Thanks,
Dennis
Dennis L. Wade
KG6ZI
Sacramento, CA
Repy to: dlwade@pacbell.net
Date: Sun, 07 Sep 1997 10:30:21 +0100
From: BOB DUCKWORTH <bob@atl.org>
Subject: Re: Workbench ideas
Workbench ideas.
Comfortable but not carpeted floor.
Height for standing work and a bar stool with telephone insulators
to eliminate 'through the butt' currents. (unless you're really
keen or rolling around while seated).
Let me know about lighting. It's a constant problem here.
Flourescents are too noisy and Halogens too hot.
Also need a good quality, glass, large, easy to move, lighted
magnifier. If you find a source, let me know.
The big decision is, do you want to bring the test gear to the work
or the work to the test gear. Once this decision is made the rest is
pretty straight forward.
You'll never have enough:
space, bench top, power, light, time
- -bob
wb4mnf
Date: Sun, 7 Sep 1997 08:46:04 -0700
From: "John Burch" <occupant@ns.net>
Subject: Re: Workbench ideas
- ----------
> From: BOB DUCKWORTH <bob@atl.org>
> To: dlwade@pacbell.net
> Cc: glowbugs@www.atl.org; vss@mlist.access.digex.net
> Subject: Re: Workbench ideas
> Date: Sunday, September 07, 1997 2:30 AM
>
> Workbench ideas.
>
> Comfortable but not carpeted floor.
> Height for standing work and a bar stool with telephone insulators
> to eliminate 'through the butt' currents. (unless you're really
> keen or rolling around while seated).
>
> Let me know about lighting. It's a constant problem here.
> Flourescents are too noisy and Halogens too hot.
> Also need a good quality, glass, large, easy to move, lighted
> magnifier. If you find a source, let me know.
>
> The big decision is, do you want to bring the test gear to the work
> or the work to the test gear. Once this decision is made the rest is
> pretty straight forward.
>
> You'll never have enough:
> space, bench top, power, light, time
Or CATS!
>
> -bob
> wb4mn
de John
wb6gha
Date: Sun, 07 Sep 1997 16:07:04 +0100
From: BOB DUCKWORTH <bob@atl.org>
Subject: Re: Workbench ideas
John Burch wrote:
>
> Or CATS!
with preserved mustard greens. mmmmmm caaaats
Date: Sun, 7 Sep 1997 18:43:15 -0500 (CDT)
From: Bob Roehrig <broehrig@admin.aurora.edu>
Subject: Re: Workbench ideas
On Sun, 7 Sep 1997, BOB DUCKWORTH wrote:
> Let me know about lighting. It's a constant problem here.
> Flourescents are too noisy.
I think this has been discussed before. My shop is also my hamshack
and I have both fluorescent and incandescent lighting. When I need
bright lights for the benchwork, the fl-- lamps come on. When I am at
the rig, they are usually off and the goosneck 75watt job comes on.
I have not in recent years had trouble with noisy fl-- lights.
If the bulbs are in good shape and the ballast is not leaking to frame,
they should be quiet enough.
> Also need a good quality, glass, large, easy to move, lighted
> magnifier. If you find a source, let me know.
Absoultely agree here. Don't mess with the cheapos - get a Luxo!
I also have a normal goosneck type lamp on the other end of the bench
so I can get concentrated light from 2 angles, both movable.
> The big decision is, do you want to bring the test gear to the work
> or the work to the test gear. Once this decision is made the rest is
> pretty straight forward.
My bench setup consists of a sturdy formica-topped top 2 1/2 by 4 feet
fastened between two 6 foot Bud enclosed relay racks. There are two
equipment shelves above this and one below (just above floor level)
which are not as deep. Both racks are on rollers so the whole thing
can be swung away from the wall if necessary. That way both rackmounted
and shelf-type test equipment is within reach and visible.
For the real tough bench work, like drilling, sawing,and grinding, etc, I
have a separate bench in the garage made from an old oak library table
top sitting on an old set of kitchen sink cabinets. The doors/drawers
are great for storing the SKill saw, jig saw, router, etc.
For lighting out there I have several 200 watt bulbs in a row on the
ceiling plus a 75 watt flood aimed at the drill press. I don't use
fl-- lamps in the garage because they don't start in the winter
temps.
E-mail broehrig@admin.aurora.edu 73 de Bob, K9EUI
CIS: Data / Telecom Aurora University, Aurora, IL
630-844-4898 Fax 630-844-5530
Date: Sun, 7 Sep 1997 21:39:51 -0600 (MDT)
From: Shane <toyboat@freenet.edmonton.ab.ca>
Subject: RS transformers
Hello All,
RS has a transformer rated at 25VAC C.T. and 3A. That would work
out to 75VA for primary and secondary windings. The primary should
handle about (75VA / 115VAC = .652A). Right so far?
If I fed in 115VAC to the secondary, the primary should deliver
about 529VAC, according to the turns ratio. Since it's center
-tapped, I could get 264VAC out by just using one side of the
secondary as my 115VAC primary.
Here it gets a little confusing. Common sense tells me that, from
the size of the transformer, it should be good for about 60 or 70
mA output at around 250VDC, loaded. However, if each winding is
good for 75VA and the wire gauge in the intended-for secondary winding
is good for 3A, then this winding used as the primary should be able to
handle 75VA / 115VAC = .653A or 653mA with no problem. Likewise, the
intended-for primary winding has a rating of 653mA, so should be able
to handle this as a secondary at either 264VAC or 529VAC. At 75VA /
264VAC = 284mA, this is more than my common sense guess of 60 or 70mA.
I realize that phase-shifting might play a factor here that I have
not accounted for, or does it? Did I screw up in some basic way
here?
It would *seem* that this transformer would make a good little power
supply component for a small CW transmitter, when run in reverse.
Would it? What would its maximum current output be in the cases above?
Regards,
Shane Wilcox
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Shane <toyboat@freenet.edmonton.ab.ca>
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End of glowbugs V1 #106
***********************
Created by Steve Modena, AB4EL
Comments and suggestions to modena@SunSITE.unc.edu