I just purchased a TRC-485 AM/SSB from Radio Shack, mostly out of curiosity
because of some of the posts that have appeared on the newsgroup about this new
radio. The radio is similar inside to the TRC-465, which is the AM/SSM radio
that the TRC-485 replaced, but looks different on the outside. The unit is about
the same size as the TRC-465.
The major difference is the nice LCD front panel display that the TRC-485
has. The display shows both the channel number and the frequency in Mhz that you
are tuned to. There is a six segment LCD display that shows received signal
strength. This replaces the 5 segment LED display on the older model. The
segments are calibrated S-1, S-3, S-5, S-7, S-9 and 30db over. When comparing
the S-meters between the two models, they seem to agree with each other. Since
the older TRC-465's first LED is labeled "S-3", the received signal has to be
at least that strong before you can give a reading. The TRC-485 also has an S-1
segment, which is better.
The last LED on the older model is labeled "OVER", while the newer unit
reads "+30". I noticed that it takes a tremendous amount of signal to light the
+30 segment, even more than it took to light the "OVER" LED on the TRC-465. I
had to be within two blocks of my house to light the +30 while I was talking to
my wife. This might be useful to tell you when you are right next to a trucker
on the highway, or to track down that annoying carrier thrower in your
neighborhood. I wish the unit had an extra segment that indicated +15 or so
because after my wife's signal reached S-9 as I headed home, there was a long
distance before it lit the +30 segment.
The unit also has digital switches for dual channel watch, instant
channel 9, scanning, noise blanker, last channel recall and mode changing
between AM/USB/LSB. I cannot stand radios that have an instant channel 9 switch.
Most of the people in the Philadelphia area use channel 19 for emergencies
because we can never raise anybody on channel 9. This feature is next to
useless. When will radio manufacturers dump channel 9 priority switches in favor
of a programmable priority switch that you can program the channel you want the
I have found the dual channel watch (labeled DW) to be the best feature. I
like to use channel 33 to talk to locals, but my wife likes to monitor channel
30, while in the mobile, because it is quieter. With the dual channel watch I
can talk on channel 33, while still monitoring channel 30 in case my wife calls
me. Every few seconds the receiver will switch to channel 30 for a fraction of
a second to check for activity, and stop on channel 30 if it is active. This
feature works similar to the priority channel feature found in most scanners.
The scanning feature on a CB radio is OK, but since most of the channels in
my area are busy until very late at night, the unit will stop at just about
every channel. The one good thing about the scan feature in this radio is that
the radio will pause on an active channel for only 5 seconds, and then resume
scanning again. This could be useful if you are trying to find somebody who
frequents several channels, or if you are just looking for the best conversation
to get into.
The last channel recall is another useful feature. "LCR" is nice if you
decide to channel hop while somebody is making a long transmission about their
medical problems or is naming all the species of insects in Latin, and then you
forget what channel you were using originally. Just hit the "LCR" button and you
are instantly back to the original channel. This is also useful if you are on
the highway, monitoring channel 19, and decide to channel hop. By pressing the
"LCR" button, you are back on 19 again. The original channel is stored into
"LCR" memory until you transmit on a newly selected channel. Once you transmit,
the new channel becomes the "LCR" channel.
The noise blanker seems to work as good as the one on the TRC-465, but I
have only had the unit for a short time and have not experienced all kinds of
noise situations yet. The noise blanker worked well at eliminating the popping
noise from my automobile ignition, though.
Most Radio Shack rigs are set way to low on both modulation and power
output, so I decided to check the rig on my station tester. While hooked to an
Astron 35 supply, the rig put out 3 watts into a dummy load on AM. On single
sideband, while talking in a normal voice, I only averaged about 5 watts output,
which jumped to about 10 watts with a whistle. The modulation percentage on AM
was a little higher than most RS rigs out of the box and peaked 75 to 85% while
talking in a normal voice. Most RS rigs I have tested only peaked 40 to 50%,
with some a little lower.
I decided to open the radio to find out where the AMC (automatic modulation
control for AM) and ALC (automatic level control for SSB) were located so I can
adjust them for maximum performance. After removing the four screws that held
the bottom cover, (speaker side) I noticed another advantage to the new radio
over the older model. The speaker wires had a small, easily removable plug
attached to them while the older model had the wires soldered directly to the
board. I have broken these wires several times while trying to make adjustments
to the older rig, so this is a welcome change!
While looking into the bottom of the radio with the front panel of the radio
toward you, you notice 5 adjustable potentiometers grouped fairly close to each
other near the antenna jack. The one closest to you is labeled "RV6" and affects
the single sideband ALC. I adjusted this until my average power came up to 8 or
9 watts, with my voice peaks going up to 12 watts. When I turned this control
all the way up, this radio put out a tad over 20 watts with a whistle, but I
elected to keep it legal and not peak over 12 watts.
Next I adjusted RV5 which is to the right and further back than RV6. RV5
affects the AMC and allows you to adjust your modulation percentage. I decided
to keep it legal and adjusted it so my modulation peaked at 100 % without going
over. Out of curiosity I turned it all the way up and it easily pegged my meter
at over 125%. This is much higher than the older TRC-465 which had to be turned
all the way up just to peak 100%.
Even though the frequency response of the transmit audio is the same on the
specification sheets for both of these radios, the older TRC-465 sounded much
bassier and even muffled when using the stock mike. The newer TRC-485 has much
cleaner and less bassy sound when using the stock mike. When I tried my "Night
K Eagle" D-104 on both radios, I am told that I sound cleaner, punchier and more
professional on the TRC-485, even though I always got decent audio reports on
Next I discovered that the pot right above RV5, which is labeled "RV10",
affected the AM carrier power output. When I turned the pot all the way up, I
noticed that the radio put out a maximum of 6 watts. I reset the pot so I got
4 watts output, the full legal limit. Since the AM carrier power was changed,
I re-checked modulation percentage, which can change slightly when you adjust
carrier power. I found that I was back down to 90% peak, so I re-adjusted RV5
so I got 100% modulation on my voice peaks.
There are two pots to the left of RV10 that are labeled RV7 and RV1. They
both seem to affect the S/RF meter. RV7 seems to affect the maximum allowed
value on both transmit and receive, while RV1 seems to affect the received
signal level only. I returned these pots to their factory stock setting,
figuring that the S-meter readings agreed with the TRC-465 so I don't need to
There are two other pots in the left hand, back corner that affect the
driver and final bias settings. Do not touch these at all. They are pre-set at
the factory and should not need adjustment.
There are also two pots near the left hand front panel. Not having a
schematic diagram, my educated guess is that the one closest to the front, RV2,
affects the transmit frequency and the one closer to the middle, RV3, affects
the squelch control sensitivity. Do not adjust the transmit frequency unless you
have a frequency counter.
In closing I will recommend that the factory settings of all the pots be
marked with a black marking pen so you can "line up" the marks again should you
not feel comfortable with your adjustments. I would also not recommend that
anybody touch any adjustments without using a good watt/modulation meter and a
dummy load. Raising the modulation beyond 100% will cause excessive splatter and
bleed over to those using adjacent channels and cause distortion and less
If anybody comes up with any more information about the TRC-485, I would
appreciate it if you forward the information to me.
73 from Steve, Havertown, PA