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Old Jun 07, 2004, 10:28 AM
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Boston, MA USA
Joined Jun 2003
38 Posts
DIY TX for DIY Micro AM RX

I keep on looking at the DIY Micro AM RX. Why carry the weight of a superhet unless it is narrow band. If it is not narrow band then go for simplicity of the super-regenerative design.

One restriction is the desire for the convenience of a computer TX. These tend to be 72MHz in the US and FM. I don't want to hack my computer TX but want to add 27MHz AM while disabling the 72MHz FM.

This seems possible with the buddy box connector. Plugging in the buddy plug disables the RF and taps the computer signal output. I have the original RC Classic system from 1968 and built a couple of copies of that system. All that is necessary is to use the buddy jack output to run the Classic modulator and I have the required TX.

Has anyone done this? I am interested in knowing what problems will be encountered. In particular the potential damage to the output stage of the existing 72MHz RF stage?
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Old Jun 09, 2004, 03:32 AM
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QLD, Australia
Joined Sep 2003
1,543 Posts
vaughan,
I cant see how you could damage your tx . I would put a ferrite bead over the buddy cord lead just to be sure no RF is fed back .
Stewart
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Old Jun 09, 2004, 10:10 PM
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Boston, MA USA
Joined Jun 2003
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Quote:
Originally Posted by clipclop
vaughan,
I cant see how you could damage your tx . I would put a ferrite bead over the buddy cord lead just to be sure no RF is fed back .
Stewart
I am concerned about 27MHz RF being received by the final stage of the 72MHz TX driver. I am thinking about mounting the 27MHz module to the 72MHz plastic case or clipping it(mechanically not electrically)directly on the TX telescoping antenna.

I suppose I can just try it and look for smoke.

Brian
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Old Jun 09, 2004, 11:10 PM
Registered User
QLD, Australia
Joined Sep 2003
1,543 Posts
Brian,
I would remove the antenna from the 72mhz Tx , this would reduce the chances of it getting RF from the 27mhz TX .
Stewart
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