[ARC5] ARC5 Digest, Vol 115, Issue 6 VTVM (Message:1

Sun Aug 4 03:35:03 EDT 2013

Hi Mac

I have got a similar RCA WV-77E.

Tired of replacing the battery every 3 to five years, 
I replace dit with a little stabiliser circuit containing 
a Zener diode. Since instrument always has to be calibrated
before measuring Ohms, I did not make a big effort for this
Circuit.

In addition I changed the tubes with special quality ones
and hope, that will outlive me...

73 de Peter  HB9RUZ   

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Gesendet: Sonntag, 4. August 2013 04:37
An: arc5 at mailman.qth.net
Betreff: ARC5 Digest, Vol 115, Issue 6

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Today's Topics:

   1. Re: Meter Calibration (D C _Mac_ Macdonald)
   2. Re: Meter Calibration and HV probe (Kenneth G. Gordon)
   3. 3A5 Filament Voltage Question (J. Forster)
   4. ARC-5 ANT Matching (tbs50a at aol.com)
   5. Re: 3A5 Filament Voltage Question (neilb at ihug.co.nz)
   6. Re: 3A5 Filament Voltage Question (J. Forster)
   7. Re: [Boatanchors] 3A5 Filament Voltage Question (Dave Harmon)

----------------------------------------------------------------------

Message: 1
Date: Sat, 3 Aug 2013 16:38:27 -0500
From: D C _Mac_ Macdonald <k2gkk at hotmail.com>
To: KM1H Carl H. <geoffrey at jeremy.mv.com>, K9STH Glen Zook
	<gzook at yahoo.com>, 	Brooke Clarke <brooke at pacific.net>, ARC-5
Mail
	List <arc5 at mailman.qth.net>
Subject: Re: [ARC5] Meter Calibration
Message-ID: <BLU170-W196A29FE633A1EBCA60F92F1520 at phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"

Somewhere in the recesses of my memory I seem to remember that the 11 Megohm
rating of so many VTVMs "back in the day" consisted of 10 Meg in the
instrument and another 1 Meg resistor in the probe!

I still have the original Heathkit "Bench" VTVM with 6" meter I built back
in 1963 or so!  I HOPE I took the battery out of it!

* * * * * * * * * * *
* 73 - Mac, K2GKK/5 *
* (Since 30 Nov 53) *
* k2gkk at hotmail.com *
* Oklahoma City, OK *
* USAF & FAA (Ret.) *
* * * * * * * * * * * 

> From: geoffrey at jeremy.mv.com
> To: gzook at yahoo.com; brooke at pacific.net; arc5 at mailman.qth.net
> Date: Sat, 3 Aug 2013 15:40:32 -0400
> Subject: Re: [ARC5] Meter Calibration
> 
> Thanks, its listed at 10M so 1M has to be added to use a Fluke probe.
> Not bad for the price of $45 unless Fleabay has similar cheaper.
> 
> Carl
> 
> 
> ----- Original Message -----
> From: Glen Zook
> To: Geoff ; Brooke Clarke ; arc5 at mailman.qth.net
> Sent: Saturday, August 03, 2013 11:21 AM
> Subject: Re: [ARC5] Meter Calibration
> 
> 
> The manual for the 98674 DMM can be found at:
> 
> 
> http://images.harborfreight.com/manuals/98000-98999/98674.pdf

> 
> 
> 
> With just a quick "look", I did not find the input impedance. However, 
> that figure may be somewhere in the manual.
> 
> Glen, K9STH
> 
> 
> 
> Website: http://k9sth.com
> 
> 
> 
> 
> From: Geoff <geoffrey at jeremy.mv.com>
> To: Glen Zook <gzook at yahoo.com>; Brooke Clarke <brooke at pacific.net>; 
> arc5 at mailman.qth.net
> Sent: Saturday, August 3, 2013 8:23 AM
> Subject: Re: [ARC5] Meter Calibration
> 
> 
> I wonder if that DMM will work with a Fluke HV probe? Is the input 
> impedance listed?
> 
> Those cheap meters are in every vehicles glove compartment, garage, 
> toolbox, etc. Fine for the basics and Ive fried a few also (-; I 
> bought a case lot of 20 for something like $50 at a local fleamarket 
> several years ago. Tossed the junk batteries and leave batteries out of
the unused ones until needed.

------------------------------

Message: 2
Date: Sat, 03 Aug 2013 21:58:03 -0000
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: ARC-5 List <arc5 at mailman.qth.net>
Subject: Re: [ARC5] Meter Calibration and HV probe
Message-ID: <51FD7CEB.8910.BE16C20 at kgordon2006.frontier.com>
Content-Type: text/plain; charset=US-ASCII

On 3 Aug 2013 at 16:38, D C _Mac_ Macdonald wrote:

> Somewhere in the recesses of my memory I seem to remember that the 11 
> Megohm rating of so many VTVMs "back in the day" consisted of 10 Meg 
> in the instrument and another 1 Meg resistor in the probe!

You're absolutely correct, Mac. I have two Heathkit VTVMs here, which I use
regularly, and both are set up the same way: 10 meg in the instrument and 1
meg in the probe.

Someone some time ago published on the web a modification to include the 1
meg inside the instrument instead of in the probe. However, that turned out
to not be such a hot idea after all.

Also, I have two Heathkit HV probes here (up to 30 KV) and a Simpson
version. I have used those with a couple of different versions of DMMs and
the voltage readout was always very close to the readout when connected to a
Simpson 260. In fact, it was close enough that I never bothered about
"calibrating" it any closer. The difference between 10KV and 10.1 KV isn't
enough to worry about at that level.

Ken W7EKB

------------------------------

Message: 3
Date: Sat, 3 Aug 2013 17:18:55 -0700 (PDT)
From: "J. Forster" <jfor at quikus.com>
To: ARC5 at mailman.QTH.net, boatanchors at mailman.QTH.net,
	Milsurplus at mailman.QTH.net
Subject: [ARC5] 3A5 Filament Voltage Question
Message-ID:
	<7199.12.226.214.5.1375575535.squirrel at popaccts.quikus.com>
Content-Type: text/plain;charset=iso-8859-1

I'm playing with an ART-4 Transmitter. This unit is for reporting the blast
intensity near an airplaned towed target tube (sock), hence the closeness of
the shell to target can be estimated.

Anyway, after tracing the circuit, it has an oscillator and an amplifier
stage.

The filament on the 3A5 is parallel wired.

The spec sheet says 1.4 VDC, Max. A current alkaline battery will put out
significantly more than that.

I want to run the thing off an adjustable DC supply, and allow some margin.

Does anyone know roughly what the minimum DC filament voltage to apply for
enough emission to work reasonably well? I just want to test the operating
frequency and get a rough idea of the modulation deviation.

Thanks,

-John

===================

------------------------------

Message: 4
Date: Sat, 3 Aug 2013 21:18:21 -0400 (EDT)
From: tbs50a at aol.com
To: arc5 at mailman.qth.net
Subject: [ARC5] ARC-5 ANT Matching
Message-ID: <8D05EC7A4F66B91-B5C-21CA2 at Webmail-m104.sysops.aol.com>
Content-Type: text/plain; charset="us-ascii"

Does it make sense to maybe post diagrams of these circuits on Ken's site?
I'm a neophyte and don't have good math skills so a diagram would be very
helpful in order to put something together for ant matching.
TNX Guys
Terry N3GTE 

------------------------------

Message: 5
Date: Sun, 4 Aug 2013 13:27:41 +1200
From: <neilb at ihug.co.nz>
To: "arc5" <arc5 at mailman.qth.net>
Subject: Re: [ARC5] 3A5 Filament Voltage Question
Message-ID: <8FA94B4CF8E6486E96E00949F17B611A at NeilB>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
	reply-type=original

> The filament on the 3A5 is parallel wired.
>
> The spec sheet says 1.4 VDC, Max. A current alkaline battery will put 
> out significantly more than that.
>
> I want to run the thing off an adjustable DC supply, and allow some 
> margin.
>
> Does anyone know roughly what the minimum DC filament voltage to apply 
> for enough emission to work reasonably well? I just want to test the 
> operating frequency and get a rough idea of the modulation deviation.
>
> Thanks,
>
> -John

Is your problem how to obtain 1.2 - 1.4 VDC from a power supply?
What about two 1N4007's in series, fed from a dropping resistor?
About 1.2 - 1.3 volts will appear across them, and this voltage will remain
constant, much like a zener diode circuit.

Sorry if I've misinterpreted your question. I found it difficult to see what
you're driving at.

73 de Neil ZL1ANM

------------------------------

Message: 6
Date: Sat, 3 Aug 2013 18:42:07 -0700 (PDT)
From: "J. Forster" <jfor at quikus.com>
To: neilb at ihug.co.nz
Cc: arc5 <arc5 at mailman.qth.net>
Subject: Re: [ARC5] 3A5 Filament Voltage Question
Message-ID:
	<65320.12.226.214.5.1375580527.squirrel at popaccts.quikus.com>
Content-Type: text/plain;charset=iso-8859-1

Not at all. I can set the PS voltage to anything, and current limit it
anywhere.

I'm trying to find out the minimum operating filament voltage, to allow as
much headroom as possible so as not to accidentally blow the filament.

-John

=============

>> The filament on the 3A5 is parallel wired.
>>
>> The spec sheet says 1.4 VDC, Max. A current alkaline battery will put 
>> out significantly more than that.
>>
>> I want to run the thing off an adjustable DC supply, and allow some 
>> margin.
>>
>> Does anyone know roughly what the minimum DC filament voltage to 
>> apply for enough emission to work reasonably well? I just want to 
>> test the operating frequency and get a rough idea of the modulation 
>> deviation.
>>
>> Thanks,
>>
>> -John
>
> Is your problem how to obtain 1.2 - 1.4 VDC from a power supply?
> What about two 1N4007's in series, fed from a dropping resistor?
> About 1.2 - 1.3 volts will appear across them, and this voltage will 
> remain constant, much like a zener diode circuit.
>
> Sorry if I've misinterpreted your question. I found it difficult to 
> see what you're driving at.
>
> 73 de Neil ZL1ANM
>
> ______________________________________________________________
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------------------------------

Message: 7
Date: Sat, 3 Aug 2013 21:07:58 -0500
From: "Dave Harmon" <k6xyz at sbcglobal.net>
To: <jfor at quikus.com>, <ARC5 at mailman.QTH.net>,
	<boatanchors at mailman.QTH.net>,	<Milsurplus at mailman.QTH.net>
Subject: Re: [ARC5] [Boatanchors] 3A5 Filament Voltage Question
Message-ID: <002c01ce90b7$743a8450$5caf8cf0$@net>
Content-Type: text/plain;	charset="us-ascii"

Decades ago the 3A5 was one of the tubes used in model airplane radio
control transmitters.
We used 1.5v batteries for the filament and I don't remember any of them
burning out.
Just use a battery and it will last for a looong time.

Dave Harmon
K6XYZ[at]sbcglobal[dot]net
Sperry, Ok.

-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of J. Forster
Sent: Saturday, August 03, 2013 7:19 PM
To: ARC5 at mailman.QTH.net; boatanchors at mailman.QTH.net;
Milsurplus at mailman.QTH.net
Subject: [Boatanchors] 3A5 Filament Voltage Question