Daily GLOWBUGS
Digest: V1 #134
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Purpose: building and operating vacuum tube-based QRP rigs
Subject: glowbugs V1 #134
glowbugs Saturday, October 11 1997 Volume 01 : Number 134
Date: Fri, 10 Oct 1997 15:39:22 +0100
From: BOB DUCKWORTH <bob@atl.org>
Subject: push pull 2 x 807 xtal tx.
My brother found a copy of the 1938 RCA air cooled transmitting tube
manual at the flea market. In the 'circits' section is a nifty
2 x 807 push pull xtal tx. 30W. It's still a cheap tube.
Now to scare up a big xtal.
- -bob
Date: Fri, 10 Oct 1997 16:38:33 -0400 (EDT)
From: rdkeys@csemail.cropsci.ncsu.edu
Subject: Re: Plate plucking vs. series capacitors
> I plucked the plates from a capacitor last night to reduce it to a single
> plate tuning cap for the UY-227 detector and one step that I will start
> building this weekend. I started to think that maybe I should have just
> put a 25 pF trimmer in series with the tuning cap and that way I would have
> variable band edge setting capability.
>
> Anybody have experience one way or the other?
Both ways work fine. The former requires only one capacitor, the latter two.
IFF the tuning capacitor is valuable or historically important, or otherwise
non-replaceable, then use the series cap to set the range and run with it.
Since your regen set is assumingly ``period'' with '27's in it, I would not
be against plate plucking. I don't like to pluck plates in early period
caps of historic interest. They are too rare. For generic caps, pursue
accordingly.
If you are just experimenting, but don't have a good singleplater cap, for
tuning purpose, try the series pair as an expedient. If you are shooting
for a 10pf tuning cap, then find a 25pf or so series cap and set it
accordingly (roughly 3/4 meshed) or a 50pf cap and set it about half mesh
for starters. Twiddle until the range is where you want it. Then pad with
external padding or adding/subtracting coil turns.
For junk box caps, and things I know are going to be specifically regen or
narrowband Hartley fodder, I will pluck plates if the plates are not too
many in number (i.e., caps about 100pf or less, only, since larger caps
are used elsewhere, as in throttle condensers, Hartley bandset condensers,
etc.). I don't usually pluck plates if there are more than 10 or so plates,
because that is a tad wasteful (unless I can recycle the plates, as on big
transmitter tuning capacitors with the bolt-in plates). I save any plates
that look like they might be useful elsewhere.
For regens, I find the junk 35-50pf things that seem to abound at hamfests,
and pluck those. Ditto for Hartley narrowbander tuning caps (it is nice to
have a 3500-3600 tuning range on Hartleys).
I usually prefer one cap rather than two, but have used the large multiplate
caps with a series cap in both Hartleys and regens with good success.
For series caps in regens, you can use small trimmers or use fixed caps.
In Hartleys, find a good fixed cap of the air plate kind or a good quality
variable. Junkers cause squirrelly Hartleyitis.
That is all I can offer now.....
Bob/NA4G
Date: Fri, 10 Oct 1997 16:40:09 -0400 (EDT)
From: rdkeys@csemail.cropsci.ncsu.edu
Subject: Re: Plate plucking vs. series capacitors
Another thought for low value variables --- use a split stator cap, seriesed.
That will put the rotor above ground, so use an insulated shaft coupling and
space it well away from the front panel if unshielded.
Bob/NA4G
Date: Fri, 10 Oct 1997 16:43:52 -0400 (EDT)
From: rdkeys@csemail.cropsci.ncsu.edu
Subject: Re: Sliding Coil Coupling and NEW FUNKY TUNING CAPS
> I'd suggest using 1/4-20 nylon bolts and nuts to set up a permeabilty
> tuning system. Most good hardware stores have them and they give you a lot
> more control over the nature of the fit.
>
> --Jeff Duntemann K7JPD
Good thought, Jeff..... Also, why not make a capacitor in the manner of
a plate neutralizing capacitor, for tuning purposes, using one of the
1/4-20 bolts or threaded rods, and a nutplate on the front panel with
a turns counting crank....... complex, but might work pretty well.
Bob/NA4G
geee.... the list is an idea mill, today.....(:+}}.....
Date: Fri, 10 Oct 1997 16:46:18 -0400 (EDT)
From: rdkeys@csemail.cropsci.ncsu.edu
Subject: Re: Hartley Using an 813
> 73 de W5EGP
> - Steve -
> ***********************************************************
Steve.... for the fun of it, refresh the list's collective memory
of your regen detector experiments using an <<<<< 833 >>>>> detector!
Bob/NA4G
Date: Fri, 10 Oct 1997 14:10:09 -0700
From: Walt Turansky <turansky@xroads.com>
Subject: Re: Plate plucking vs. series capacitors
>> I plucked the plates from a capacitor last night to reduce it to a single
>> plate tuning cap for the UY-227 detector and one step that I will start
>> building this weekend. I started to think that maybe I should have just
>> put a 25 pF trimmer in series with the tuning cap and that way I would have
>> variable band edge setting capability.
>>
>> Anybody have experience one way or the other?
>
>Both ways work fine. The former requires only one capacitor, the latter two.
>IFF the tuning capacitor is valuable or historically important, or otherwise
>non-replaceable, then use the series cap to set the range and run with it.
>
>Since your regen set is assumingly ``period'' with '27's in it, I would not
>be against plate plucking. I don't like to pluck plates in early period
>caps of historic interest. They are too rare. For generic caps, pursue
>accordingly.
The cap whose plates I plucked was an 8-26 pF transmitting variable that I
obtained from Fair Radio. They are surplus trimmers from the TU-# series
tuning drawers and make very nice bandspread caps. I'm using one on my 80m
Hartley. Fair still has them; I called this morning and ordered a few
more. They look like they would make very good neutralizing caps with a
plate or 2 plucked out.
73 de N7QFN,
Walt
Date: Fri, 10 Oct 1997 14:05:38 -0700
From: Walt Turansky <turansky@xroads.com>
Subject: Re: Plate plucking vs. series capacitors
Bob,
Great idea.
>Another thought for low value variables --- use a split stator cap, seriesed.
>That will put the rotor above ground, so use an insulated shaft coupling and
>space it well away from the front panel if unshielded.
I have some NOS Millen 25 pF per section split stators that I am planning
to use in a mulit-band Hartley or TPTG rig (I've been studying the 1929
H'book recently). I had planned to use the both sections in parallel on
80m and one section on 40m. Putting the sections in series ought to be
just right for 30m. With the right coil sizes and some creative padding I
think I should be able to get 0-100 on the dial for 3500-3600, 7000-7100,
and 10100-10200.
73 de N7QFN,
Walt
Date: Fri, 10 Oct 1997 14:36:13 -0700 (PDT)
From: Ken Gordon <keng@uidaho.edu>
Subject: Re: push pull 2 x 807 xtal tx.
On Fri, 10 Oct 1997, BOB DUCKWORTH wrote:
> My brother found a copy of the 1938 RCA air cooled transmitting tube
> manual at the flea market. In the 'circits' section is a nifty
> 2 x 807 push pull xtal tx. 30W. It's still a cheap tube.
Could you scan/copy the schematic and mail it to me ?
> Now to scare up a big xtal.
You may not need a big crystal. Put a pilot lamp in series with the
crystal and adjust feedback for minimum brilliance with good keying.
Ken W7EKB
Date: Fri, 10 Oct 1997 21:32:10 -0500
From: w5hvv@aeneas.net (Rod Fitz-Randolph)
Subject: Re: Hartley Using an 813
>Steve.... for the fun of it, refresh the list's collective memory
>of your regen detector experiments using an <<<<< 833 >>>>> detector!
_____________________________________________________________________
Wow, I bet he wasn't bothered by front end overload!!!!
73
Rod, N5HV
w5hvv@aeneas.net
Date: Sat, 11 Oct 1997 12:42:25 +1000
From: Murray Kelly <mkelly@powerup.com.au>
Subject: Re: Sliding Coil Coupling
Thanks, Jeff. I thought I might need to put a loop of
teflon tape thru the hole. Nothing like trying - as you
did.
I don't think I made clear the toroid was to supply a
'slug' and not to wind coils on.
Jeff Duntemann wrote:
>
> At 10:39 AM 10/10/97 +1000, Murray Kelly wrote:
> >I have been looking at a couple of glue stick formers that
> >caught my eye. They are the 'paste stick' type and there is
>
> >This would perhaps be the basis for a PTO oscillator, or
> >without the toroid an antenna coupler - just a thought.
>
> I actually tried this a few years ago, and while it worked there is the
> problem that the fit of the screw into the device is very loose, and
> there's no easy way I could devise to tighten it up. (The glue stick
> itself provided a sort of self-lubricated friction brake--but once the glue
> is gone it's just a loose screw/nut fit.) The slightest vibration causes
> the toroid to move around. I'd trust it for an antenna coupler but NOT for
> any sort of oscillator frequency determination.
******************************************************************
* Murray Kelly vk4aok mkelly@powerup.com.au *
* 29 Molonga Ter. / Graceville/ QLD. 4075/ Australia *
* ph/fax Intl+ 61 7 3379 3307 *
******************************************************************
Date: Sat, 11 Oct 1997 12:29:58 -0400 (EDT)
From: rdkeys@csemail.cropsci.ncsu.edu
Subject: Kilroy was there on 3579..... were you?????
I had the gear up on 3579 last night from about 0000Z to 0400Z, but no
joy, no smoke, no etherzaps, and few dittlededumdedits. A couple of weak
ones were there, but nil BAGB QTC. I will fire it up again tonight, and
mebbie sees a few o' ye fine bottleburners about on watch......?
73/ZUT DE NA4G/Bob UP
Date: Sat, 11 Oct 1997 11:03:47 -0700 (PDT)
From: Ken Gordon <keng@uidaho.edu>
Subject: Re: Kilroy was there on 3579..... were you?????
I was listening from about 0000 to 0400...all __I__ could hear was noise.
On Sat, 11 Oct 1997 rdkeys@csemail.cropsci.ncsu.edu wrote:
> I had the gear up on 3579 last night from about 0000Z to 0400Z, but no
> joy, no smoke, no etherzaps, and few dittlededumdedits. A couple of weak
> ones were there, but nil BAGB QTC. I will fire it up again tonight, and
> mebbie sees a few o' ye fine bottleburners about on watch......?
Around here, 80 and 40 are clear until about 0000, then this buzz starts,
gets stronger and stronger until by 0400 it is at least S-9, stays that
way until early in the morning, then suddenly stops.
I thought at first it was local noise: now I am convinced that it is some
form of atmospherics.
Ken W7EKB
End of glowbugs V1 #134
***********************
Created by Steve Modena, AB4EL
Comments and suggestions to modena@SunSITE.unc.edu