[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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