[ARC5] TRF - RAK "Q-5er"

Kenneth G. Gordon kgordon2006 at frontier.com
Fri Jul 6 15:33:33 EDT 2012


On 6 Jul 2012 at 14:39, Geoff wrote:

> While a TRF may require 3 RF amps a TRF-regen does not unless there is a lot 
> of circuit loss. The added front end selectivty of either 1930's design is 
> minimal.

RAK has enough selectivity at RF to exhibit single-signal (one side of zero-beat) throughout 
its tuning range. RAL, of course, isn't as good as that, but it is completely adquate.

> The RAK/RAL use tubes designed in 1933 which are actually 6,3V versions of 
> the ones designed in 1931.

And which were followed by octal versions: i.e.,the characteristics of the 6SK7 (or 6K7) is 
almost identical to the 6D6. National used the 6SK7 in their RBL which is a close copy of the 
RAK.

> Even so the CW sensivity of the RAL is easily .5uV thru 14MHz for a 10dB SNR 
> (NOT MDS) when the input is well matched to the signal generator.

Thank you for that info. I never did measure mine, and always wished I had. I wonder what 
MDS would be?

> With an adaptor and a 6SG7 in place of the first 6D6 it would likely do well 
> on 15M or even go with a 7 pin miniature such as the 6BZ6 or 6GM6,

Very interesting! I had not thought of that.

> The RAL covers up to 23MHz.

Well, the reason I originally traded my BC-348 for an RAL-7 was so that I could work 15 
meters...which I did with it regularly.
 
> The RAK/RAL also have an excellent audio limiter which works excellent for 
> storm static as well as a sort of audio AVC. The selectable audio filters 
> also do a good job on CW QRM.

Yes.

> OTOH the tuning and lack of calibration is far from user friendly so its not 
> a band scanner.

As far as I was concerned, that was the only place the RAL could have been improved. I 
even bought an Eddystone 898 once to correct that, but could never figure out how to mount 
it, so I didn't. I really didn't spend very much time on it though.

> Both are around 70# plus

Closer to 80#; 79 lbs in the case of the RAL, 81 lbs for the RAK.

> another 40# for the remote PS

Closer to 65#, I think.

> but a HB one is very 
> simple as long as its well filtered. I use an original on the RAK and a SS 
> all regulated DC version on the RAL where it is usually used on 30M.

I use a much smaller SS supply with my TRFs too. Takes up less room and gives off less 
heat.

I had thought, once, of using an RAK as a "Q-5er" for any of my single-conversion receivers, 
but thought better of it later. Having a second-IF twice as big and 5 times as heavy as the 
main receiver seemed kinda weird...even for me. ;-)

Besides, the BC-453 was quite adequate in that service.

Ken W7EKB




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