Sensitivity Tests on a Modified
Icom IC-2SAT VHF FM Transceiver
A few weeks after posting the below message to USENET,
I posted a later message
describing further modification details.
Click here to see that later article.
Later, I wrote an article explaining
how to modify the Icom IC229H
for extended receive.
Click here
to see that article.
From: cromwell@xoanon.ecn.purdue.edu (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 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
cromwell@ecn.purdue.edu
