[Milsurplus] RAK-7

[Kenneth G. Gordon]

On 23 Jul 2016 at 20:50, Richard wrote:

> I measure 25 ma at 180 volts from a regulated supply to the RAK, with no 
> VR tube

The Navy's 35 mA specification is with a 600 ohm load on the audio line and the RF gain 
control set at maximum. If you were to try to operate the receiver at this setting with 
headphones on, any decent signal would deafen you.

Your 25 mA is far more typical of what the receivers draw in normal operation.

And I agree with you, Richard: 30 mA drawn through the 874 for a 1 mA load at the oscillator 
is ridiculous.

The RAK/RAL has no audio gain control: AF gain is set essentially wide open and gain is 
controlled only at RF.

Adding an audio gain control is very simple, and well worth the effort. Richard has done it, as 
have others. The only problem is where to mount it, since there really isn't any open "real 
estate" where one could put it.

I think someone here, possibly Richard, removes the DC switch and puts the AF gain pot 
there.

BTW, in every RAK or RAL I have here, all the wiring is a rubber-covered type. That rubber is 
getting very brittle in several of my receivers. If it is in yours, be very careful to NOT move 
any of it unless you absolutely have to.

I am not one bit surprised at Richard having big audio oscillation problems when he 
attempted to widen the audio bandpass. There is essentially no shielding whatever in the 
audio stages.

I'm glad you got it fixed, Richard. Good job.

Ken W7EKB
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