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Author Topic: Heathkit AT-1  (Read 966 times)
KC2YQY
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Posts: 40




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« on: October 28, 2009, 03:20:01 PM »

I recently acquired a Heathkit AT-1 w/ a VF-1 VFO. My question is what is the output of the transmitter on 40M? Should I see a difference between a crystal and using the VFO? Any help is appreciated. Thanks. -Bill- (working on my ticket!)
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KA5N
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« Reply #1 on: October 29, 2009, 04:58:42 PM »

A working AT-1 should give around 15 to 20 watts output.  The power output is not related to whether a VFO or crystal is used for frequency selection.
Before you ask there is no simple way to increase the power output.  The AT-1 is a good beginners radio and should not be modified.  In comming years a good restoration will be worth more and more.
Allen
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KC2YQY
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« Reply #2 on: October 30, 2009, 08:45:44 AM »

Allen
Sorry for being a such a moron concerning the AT-1 xtal v VFO question. I have a very nice AT-1 and VF-1. I replaced a few parts in the AT-1 (caps and resistors) but it is pretty much stock. My add was an AC lamp. I certainly do not want to increase the output. It's a great entry-level transmitter and I have no intentions in augmenting the output. Thanks for the note.  -Bill-
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N2EY
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« Reply #3 on: November 17, 2009, 09:29:28 AM »

The output of a stock AT-1 is only about 9 watts on 80, 40 and 20 meters into a 50 ohm load. There are two reasons for this:

1) The rig has fixed output links with no means of adjusting the loading

2) The rig operates the 6L6 final as a doubler on all bands except 80.

There's a good article about the AT-1 in QST for October, 1955.

73 de Jim, N2EY
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W8JI
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« Reply #4 on: November 18, 2009, 07:23:29 AM »

The VF1, because it has no output buffer stage, often it a bit short on excitation. It also pulls frequency a bit from the external load.

The VF1 is only a simple single stage pentode that is a standard Clapp oscillator with the output taken from the plate.

It also output 1.750 to 2 MHz when on 80, so the input stage of the radio has to act as a doubler.

Don't be surprised if it reduces the output quite a bit! I had to build a buffer into my VF1's.

Tom
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