[ANSS-netops] radio frequencies

[VLF]

I have seen some chatter recently regarding loss of VHF channels due to NTIA
reallocation operations. I would propose that any who wish to continue
analog operations consider the 217-220 MHz spectrum. CERI at the University
of Memphis has used these frequencies for the past 35 years in the analog
New Madrid network (65 stations). The band is pretty free of competition,
however channel 13 TV is right below the band with typically maximum power
of 316KW. It is clearly the thousand pound gorilla in the room. Vertical
polarization of antennas and cavity filters are required on telemetry paths
that are anywhere near one of these transmitters. In rural areas it is
usually clear sailing though. Our company has teamed up with Hamtronics (a
long term ham equipment supplier) to produce a radio specifically for
telemetry use by modifying the modulation circuitry of their equipment for
low distortion transmission( <1%) of analog signals. The current radio is a
synthesized unit with the three programmable frequencies and a  variable
power design that operates over a 100 to 1500 mW output power range.  The
receiver noise is around .3uV and the modulation bandwidth i2 300 to 3500
Hz. Frequency stability is typically better than 200Hz over a temp range of
0 to 120 degree F. The radio does not require custom crystal (or crystal
compensation)

If there is sufficient interest, we will produce a new custom, frequency
agile, 217-220 MHz  analog radio system that will meet FCC emission masks
while allowing full 25 KHz bandwith NBFM operation, thus allowing for
unhindered use of all standard IRIG analog telemetry frequencies, This radio
can also be made available for 12.5 KHz bandwidth use if necessary. We will
try to market these radios in as cost effective way as possible which will
depend on the quantity required. Small samples of the current radio in
production are available for evaluation for $1200 per pair. 

 

VLF Designs

1621 Bella Vista Dr.

Jackson, Mo. 63755

573-204-1286

vlf at cablerocket.com

vlfdesigns.com

 

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