Sensitivity Tests on a Modified Icom IC-2SAT VHF FM Transceiver
IC-2SAT Sensitivity Tests
The ham community has a lot of interest in modifications,
"mods" or tweaks in hardware or software to extend the
frequency coverage or mode capabilities of a radio.
A few weeks after posting the below message to USENET, I posted a later message describing further modification details.
Later, I wrote articles explaining how to modify the Icom IC229H and IC-3220 for extended receive.
From: firstname.lastname@example.org (Bob Cromwell) Newsgroups: rec.ham-radio Subject: Icom IC-2SAT Date: Thu, 28 Jun 90 22:10:19 GMT Organization: Purdue University Engineering Computer Network The Icom IC-2SAT definitely does some things not mentioned in the manual. I've got some questions, maybe someone can fill me in. But first, what I've found. I'm sure most everyone knows this, but just in case: Power-on with <light>-B-# held down until self-test ends: Open up VFO for wider frequencies (be careful, also enables transmit on 140.000-150.000 MHz). Power-on with <light>-3 held down: First keypad entry is 100 MHz digit (<light>-2 and <light>-3 are ditto for 10 and 1 MHz). With that done, and an old HP 608 signal generator, I made the below sensitivity measurements. Caveat emptor. There are no good as absolute measurements, but should serve for comparisons: Frequency S1 S3 S5 S7 S9 S9+ 90.000 MHz (50 uV was just detectable) 100.000 20 uV 110.000 10 120.000 2.3 138.000 0.38 0.48 0.65 0.95 1.7 2.6 147.000 0.23 0.34 0.46 0.70 1.2 1.9 173.995 4.6 6.5 8.0 12.0 174.000 50.0 175.000 65.0 176.000 70.0 177.000 72.0 178.000 >100 Yes, it goes clear down through the FM broadcast band (although BC deviation is too wide for legibility). What's more, it demodulates the AM signals in the aviation band just fine. What a deal, a pocket 2m transceiver and aviation/public service scanner, all in one.... Note the *really* sharp drop-off right at 174.000. Using the VFO knob to tune between 173.990 and 174.000, I hear a distinct "ping" on the transition from 174.000 to 173.990; is the result of some built-in filter to prevent wider coverage? Is this almost a two-band radio?? Will we see the IC-23SAT soon??? It seems kind of suspicious that it dies off that fast going up, but trails off slowly with lower frequencies. I have three questions for the most knowledgable: 1 -- Is there a way to open up receiver sensitivity above 174? 2 -- Is there a way to speed up the scan rate? 3 -- What does it mean when, in VFO mode, the memory channel display shows "U"? Bob Cromwell KC9RG email@example.com