[IRCA] Tuning 1-KHz splits with 2-KC bandwidth (R-390A)

[Charles A Taylor <MWDXer@xxxxxxx>]

At 07:43 PM 5/6/2007 -0400, you wrote:
>Hi Charles,
>
>Yeah I did, I've been using the 1 KHz filter for that, I'll try your 
>method and let you know how it works for me, thanks.
>I find that most people don't really differentiate between 390's and 
>390A's especially if they don't own them, that's part of the reason why I 
>assumed Patrick meant a 390A, also in private correspondance he mentioned an A,
>
>Bob

Bob,

The 1-KC bandwidth is too "tight" for AM work, in my opinion, It
precludes being able to hear 2 and 3-kHz voice components which
are very helpful...maybe essential, for intelligibility.


                 ________
                 |   2   |
                 |  kHz  |
________________|       |__________

-----------------------------------
1510            1520            1530
   |               |  |            |
                     |
                    1521

Above is how I think you're tuning BKBSA-1521. The 2-kHz
passband centers on 1521. As you can see, 1520 carriers
are going to be audible as they are inside the passband.




                    ________
                    |   2   |
                    |  kHz  |
   ________________|       |__________

-----------------------------------
1510            1520            1530
   |               |  |            |
                     |
                    1521

Above, you've "slid" the R-390As frequency up so that it
reads something like "1522" on the dial. 1520 carriers
are outside the passband.

In slowly tuning across 1520 upwards, you should note
that the 1521 het appears rather abruptly, As you
continue to tune upward, the het should disappear
abruptly. That's the sharp-sided shape factor of the
R-390A mechanical filters working. The R-390 doesn't
have that shape factor.

As a matter of fact, the 1-kHz passband is shaped more
like a sinewave. Only a crystal lattice filter
replicates the shape factor of the mechanical filter.

Cheers!

Chaz-O


Charles A Taylor, WD4INP
Greenville, North Carolina  


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