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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 19th Oct 2011, 11:28 am   #1
Gi4CZW Cliff
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Default ATU from ShortWaveMagazine April 1987

Fred on our 80m net, has dusted down an atu that does not seem to work. He says it is marked SWM April 1987 and has a three way switch marked " LC CL DT ". At the back, are three connectors marked " rec single-wire wm " . The " DT " and " wm " are confusing us. Would somebody have the article/circuit diagram ? Cliff.
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Old 19th Oct 2011, 11:54 am   #2
ms660
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Default Re: ATU from ShortWaveMagazine April 1987

I am guessing LC & CL are the impedence matching elements and combinations thereof, and DT = Direct? not sure of WM.

Lawrence.
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Old 19th Oct 2011, 12:47 pm   #3
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Default Re: ATU from ShortWaveMagazine April 1987

Perhaps he used it with a BC221 or similar wavemeter, and this connector was to inject a signal of known frequency to either measure the tuned frequency or to perform a calibration check?
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Old 19th Oct 2011, 12:56 pm   #4
G8HQP Dave
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Default Re: ATU from ShortWaveMagazine April 1987

wm=wattmeter?
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Old 19th Oct 2011, 4:10 pm   #5
Gi4CZW Cliff
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Default Re: ATU from ShortWaveMagazine April 1987

with " rec " perhaps for receiver, rather than transmitter, and " wm " for a BC221 could this not be an ATU but some sort of tester/bridge to balance L&C or C&L.
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Old 19th Oct 2011, 4:17 pm   #6
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Default Re: ATU from ShortWaveMagazine April 1987

I have the original article by George Dobbs, G3RJV. It is an L-match tuner. Lawrence (pwdrive) is correct. The LC and CL switch positions refer to the two configurations of the tuner. "DT" is direct or direct through.

The circuit diagram shows three connectors: the first is a coaxial connector for the receiver, the second is for the antenna, and the third is for the ground. The article describes the latter as being plug and socket connectors.

HTH and 73

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Old 19th Oct 2011, 8:05 pm   #7
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Default Re: ATU from ShortWaveMagazine April 1987

WM - Water main?
Rob.
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Old 19th Oct 2011, 10:26 pm   #8
Gi4CZW Cliff
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Default Re: ATU from ShortWaveMagazine April 1987

by way of explanation our Fred is a " Kc/s, aerial, valve and condenser " man, not yet a regular eMailer but a whiz on 807's. So on tomorrows QSO, I'll skip the water-main and pass on the other goodies. Trust Fred to have a George Dobbs unit. Thanks to all. Cliff.
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Old 21st Oct 2011, 12:56 pm   #9
Gi4CZW Cliff
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Default Re: ATU from ShortWaveMagazine April 1987

Update for the interested. Fred has resoldered a dry joint and it now works. He's to upgrade a 200/300 pF variable condenser to take transmitter voltages. Thanks to all. Cliff.
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Old 21st Oct 2011, 1:32 pm   #10
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Default Re: ATU from ShortWaveMagazine April 1987

Quote:
Originally Posted by glowinganode View Post
WM - Water main?
Rob.
Water Main as in Earth connection.
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Old 21st Oct 2011, 2:28 pm   #11
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Default Re: ATU from ShortWaveMagazine April 1987

Maybe wm = windom?

Adrian
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Old 21st Oct 2011, 7:00 pm   #12
Gi4CZW Cliff
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Default Re: ATU from ShortWaveMagazine April 1987

windom ? ouch ! not my favourite, I did try to think of a funny, but gave up. No problem GlowingAnode, I did pick that up, no offence intended by leaving you out, just I have to be careful with the words I use during QSO. So much PC every where, compared to the time my parents taught me how to express myself. Cliff.
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