[Milsurplus] RAK/RAL Muting

[Kenneth G. Gordon]

On 30 Mar 2016 at 18:22, William Props wrote:

> 
> Was there any type of muting used with the RAK/RAL on ship installations when used with a 
> transmitter or was the receiver expected to handle strong local signals? I've tried using my RAL 
> with a separate receiving antenna for full QSK, and the transmitter just blocks the oscillator like 
> expected. How was it done on the ships?
> 
> Chris

Hmmm....well, I used an RAL-7 for at least 12 years as my main station receiver and 
operated full-QSK CW with transmitters up to a KW input. I was first licensed in 1956, and 
go the RAL-7 about a year later.

I used separate tx and rx antennas.

>From my experiences with it, I consider the RAL to be the finest HF TRF receiver I have 
ever used. Mine was very sensitive, stable as a rock, plenty selective enough for me, and 
extremely reliable.

I was very much involved in CW message-traffic handling at the time (1960s), and at this 
late date, I don't remember ever havning any sort of problem with blocking such as you 
seem to describe.

On the other hand, my RAL-7 was NIB when I got it, so maybe that has something to do with 
your issues: I don't know.

I DO know that many Navy Sparks preferred the RAK/RAL to the later RBB/RBC receivers 
because the RAK/RAL was less subject to interference from nearby transmitters than the 
later receivers. The RAK/RAL were unusually well filtered for RF ingress by means 
other-than the antenna.

You say that the transmitter blocks the oscillator: how long does it take to recover? Is the 
oscillator (detector) pulled off frequency? What, exactly, happens when you hit the key on 
your transmitter? Have you gone through your RAL and tested or replaced the caps? Many 
of those are bad by this late date. Are you setting the regeneration control on the very edge 
of oscillation, or deeper into that? I always set my regen control on the very ragged edge of 
oscillation. What sort of power supply are you using? At the time, my power supply and 
cables were all stock and original. 

I will repeat that the RAK/RAL had every single lead that went into and out of the receiver 
very well filtered with RF chokes and bypass caps, so that the only way RF could get into 
the receiver was by the antenna connector, and even THAT was filtered in a way that 
allowed RF to the 1st RF amp grid but to no where else.

The power-supply cable is double-shielded and bypassed at both ends, as is the AC line 
into the power supply. The audio output connections are also filtered, and the front-panel 
phone jack is in its own shielded box with RF chokes and bypass caps in it. 	The cabinet 
has a springy thing around the periphery of the box which ensures an RF-tight contact 
between the receiver chassis and the box, and the box has a large can in the rear 
containing another filter through which the power supply cables and audio to an external 
speaker or audio control were fed.

Ken W7EKB