[Milsurplus] BC-229, RU selectivity

[Jack Antonio]

On 8/1/2014 3:38 PM, Hue Miller wrote:
>How about using a converter from the 80M band down to say, the 300-400 
kcs range, and then using an
> LF coil in the rec?

I've done this.

The biggest problem with most of the WWII radios is selectivity.
When on AM, it always seem there is a strong SSB QSO 10kc up
or down that takes over the passband. The strongest signal wins.

The BC-348's crystal filter is a big help, but I find it is
actually a little too narrow for AM, receiver has to be
retuned if stations are only few kc off freq.

I built up a couple of converters, one using a 6BA6 RF amp, 6BE6 
osc/conv, another one using 6BJ6 and 6BH6 with a 6AB4 oscillator,
both of them crystal controlled. Both the RF and mixer are tuned
so images are way down(sorry didn't measure).

And using a BC-453 or BC-946 (and their ARC-5 relatives) it works well.
Also the low frequency RAX and the ARB on its two lower
ranges make good AM Q5ers.
(Remember that in the ARB, the two lowest ranges use an IF down
in the 150kc region, the two upper ranges use 915kc).

But when trying this with an RU, the results were not nearly as
good. Although better than the trying the RU "on frequency", the
rejection of signals 10 to 15 kc away was just not enough, the
weaker on frequency stations were still covered up.

Dave Stinson has reported success with regeneration to improve
RU selectivity, (and I applaud his efforts), but that approach just
never appealed to me.

Jack Antonio WA7DIA/4