Thanks for all your replies. I should have explained the reason for my
question. I've become interested in SID (Sudden Ionosphere Disturbance)
monitoring: http://www.aavso.org/solar-sids
This basically involves monitoring the signal strength of various VLF
stations that transmit a 50-baud RTTY signal. Knowing nothing about the
spectrum of these signals I build a receiver that has a bandwidth of about
200 Hz and it works reasonably well on one station that transmits on 21.4
KHz. I would like to use it to also monitor a signal on 25.2 KHz.
However, I happen to live about 50 miles from a 500 KW station
that transmits on 24.8 KHz and that signal swamps everything within 600 to
800 Hz. So I thought a narrow bandwidth might be better and was about to
start construction of one when I learned the nature of the transmissions so
I thought I had better get some information on the actual bandwidths
involved. Hence my query.

I would appreciate your comments regarding the design of my VLF rig: The
antenna is a shielded, tuned loop www.febo.com/time-frerq/wwvb/antenna. The
receiver is a direct-conversion type. I use a FST3125 quad FET bus switch as
a mixer with the LO derived from a DDS source. The mixer output is amplified
(60 dB) and fed to a 5-pole 120 Hz Butterworth LP which also provides about
27 dB of gain. The filter output is rectified and integrated (5.4 sec TC)
and is the input to the ADC on a microprocessor (on a separate board) that
collects and stores the data for later download to a PC. The construction is
a mixture of through-hole and surface-mount parts on a two-sided PC board.
Is it possible that I have a shielding problem when tuned near the nearby
station? Is it likely that I would have better results if my receiver was in
a shielded enclosure?

Thanks in advance for your coments and advice.
Gary Richardson, AA7VM


"garyr" wrote in message
...
Anyone know what the bandwidth of a 50 baud RTTY signal might be?