[Hammarlund] HQ-129-X Mixer Noise

[Kenneth G. Gordon]

On 22 May 2019 at 9:27, `Richard Knoppow wrote:

>     If the noise disappears with no antenna its coming from 
> outside the receiver.

Correct.

> While the mixer is a noisy one the RF gain 
> should overcome it.

And in the HQ-129X, it does just that.

>     The RF tube is relatively noisy but replacing it will require 
> re-designing the AVC. The 717 was an octal base prototype of the 
> 6AK7. Its a sharp cut-off tube that does not work well in AVC 
> controlled stages.

And this is another reason to be wary of using the 6AC7: it is also a sharp-cutoff type.

> Note that below about 20Mhz the atmospheric noise will be 
> greater than receiver noise.

Yes, but even there, there are times when the atmospheric noise is at a very low level. 
Which is why I have always worked for as low receiver noise as possible.

> You need a calibrated signal generator and known dummy load 
> to check the receiver sensitivity. That is, how much output it 
> has for a given signal strength. From that you can figure out the 
> amount of noise.

Agreed, and if you don't own such gear, someone near you surely does. Ask them to help 
you with this.

Ken W7EKB