A review on the Radio Shack TRC-485 AM/SSB CB radio

A review on the Radio Shack TRC-485 AM/SSB CB radio

Post by <72527.01.. » Sat, 18 May 1996 04:00:00

TRC-485 REVIEW

   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
most?

    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
the TRC-465.

    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
change them.

    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
intelligibility.

    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

 
 
 

A review on the Radio Shack TRC-485 AM/SSB CB radio

Post by Codys » Mon, 20 May 1996 04:00:00


Greetings...

While cleaning out the files using KITTYLTR.COM and using Windex<TM> for


>   If anybody comes up with any more information about the TRC-485, I
would
>appreciate it if you forward the information to me.

Sounds like a neat little radio, how's the display at night?

You did an excellent job of telling us about it BTW!  :->

What I'm curious about, is it's layout.  Any ideas on the type of finals
or the AM modulator primary driver?  Does it use a 2SA1012 still or did
they upgrade to another type [Like the 2SD1143 or older 2SA473]? 2SA2312
for final - or something more ***?

Does it still generate tons of heat while transmitting? Does it affect
match on an antenna that was tuned using a different radio?

I'm sorry I don't have any answers for you, just questions.  I had a
chance not too long ago, to choose between the 148 F or the TRC 485 - I
now know which one I should have bought in the first place. ;-)

Great job on the presentation...it would make a good archive somewhere...

Thanks,
:+> Andy <+:

 
 
 

A review on the Radio Shack TRC-485 AM/SSB CB radio

Post by John Wilkers » Tue, 21 May 1996 04:00:00

: Greetings...

: While cleaning out the files using KITTYLTR.COM and using Windex<TM> for

: >   If anybody comes up with any more information about the TRC-485, I
: would
: >appreciate it if you forward the information to me.

: Sounds like a neat little radio, how's the display at night?

: You did an excellent job of telling us about it BTW!  :->

       He did a superb job....   I see the radio was undertuned, per RS
and their typical paranoia.  When I get one, I'll also have to invest in
a modulation meter, in order to get about 95% max modulation.  I tune a
radio personally to my own specs... I do not trust Inbred Radio Mechanics.

_MY_ question.... is on the receive side.... Any noise generated by the
radio itself?  Midland did a disaster on their multifunction radios.  
Lots of noise generated by the internal CPU.

--


   "Political Correctness is for mindless sheep... Speak what _you_ want
to say... not how others say you should"

    "Only after all the "Political Activists" are silenced, can we build
a better society."

 
 
 

A review on the Radio Shack TRC-485 AM/SSB CB radio

Post by rwil.. » Mon, 27 May 1996 04:00:00


>    If anybody comes up with any more information about the TRC-485, I would
>appreciate it if you forward the information to me.

Due to your review, I went out and got one of these today.  Not a bad
price, either.  It was...I think $129.  Haven't hooked it up yet, but
will have it hooked up tomorrow. :)

Anyone know if it can be opened up for extra channels?

 
 
 

A review on the Radio Shack TRC-485 AM/SSB CB radio

Post by Codys » Tue, 28 May 1996 04:00:00

This is a supplement and addition to the previous posts regarding the
radio...

Greetings Everyone, Including Steve...

Over the weekend, [hope everyone in the USA - and world, had a Memorable
Memeorial], I purchased the TRC-485.  Already it performs far beoynd my
original expectations and I've got some answers...some of the things were
already covered by Steves' initial posts regarding this radio - I am only
accentuating the features this radio has...

Radio was on sale for 129.99, and sells retail at 199.99. They do offer
TSP.
The radio has an all black case, with a dark grey matching front panel -
all required brackets, screws and connectors are supplied with a spare 3
amp in-line fuse. A lightweight microphone is also included.


writes:

Quote:>What I'm curious about, is it's layout.  Any ideas on the type of finals
>or the AM modulator primary driver?  Does it use a 2SA1012 still or did
>they upgrade to another type [Like the 2SD1143 or older 2SA473]? 2SA2312
>for final - or something more ***?

They did a good job of the layout, and the radio is in two parts.  The
front panel contains the users controls, RF-gain, Clarifier, Volume,
Squelch and Channel selector and the Mike 5-Pin DIN of typical radio shack
microphone wiring. The RF PCB has all the more discrete components for RF.
 While the front panel, which mounts vertically, has all controls, LCD
display, and CPU.  The front panel has small grain of wheat lamps that
mount through holes on the board with their wires soldered to the back of
the front panel - if you wish - these lamps can be changed by simply
unsoldering them from the board and with this versatility - you can use
different colors for a custom effect.[Blue LED's for example - you need a
dropping resistor though].  The Panel can be removed with the knobs not
needing to be removed, by small plastic tabs and 4 small countersunk heads
that keep the panel in place.

On the Squelch knob, turning it fully counterclockwise engages the PA, and
ON/OFF power is through the volume knob. All variable adjust knobs use a
translucent grommet that is part a fiber optic plastic panel support for
the selectors and serves as a spacer for styling. The potentionmeters are
mounted through holes on the CPU PCB and are arranged in all corners and
the panel switches are small carbon button types.

There is a series of six buttons just under the LCD channel display and
status panel labled DW [Dual Watch], Scan, NB [noise blanker/ANL is
automatically on all the time], LCR [last channel recall - used for last
channel you TX'd on, engaging will bring you back to the channel], CH 9 -
Instant channel 9 switch, and Mode [AM/LSB/USB] pressing these buttons
will toggle the features on or off.  Then the radios power is off, the
radio will remember the last channel and any other status you have set
when the power is turned back on via the volume control.  However, it
forgets everything and resets to channel 9, with all enabled features off
and resorts to AM mode - except for PA which is hardware controlled by the
squelch knob when the power to the power cord is switched off for more
than 1 minute.

The front panel/CPU section contains the LCD panel that is side-lit
illuminated by the lights and shows indications for operation and features
using NB, SCAN, TX, AM/USB/LSB. The S-RF uses 6 large width LCD segments
that are displayed on the bottom showing relative RF bargraph and the S/dB
level as they are turned on - versus older panel plastic silkscreening of
the numbers and other status indicators.  It displays the channel number
using a dual 7 segment layout, with the frequency of the channel is
smaller 7 segment configuration. This part shows an accuracy of 5 digits
with the configuration of XX.XXX - this is generated by the CPU and wil
not change or fluctuate while TX'd or adjusting clarifier on RX. One note,
there is no zero blanking of the display, if your on a single numbered
channel 1-9 it will display the leading 0, like 01, 02...09. Just so you
know.

When the radio is off, the LCD panel is completely blank. There is no dim
feature, and it is really not needed, for everything is adaquately
illuminated in all lighting conditions - it does generate some heat from
the lamps so remember this on hot summer days. By turning the squelch
control fully counterclockwise until it clicks, will engage the PA feature
and the display then changes to show PA in the channel indicator.

Another side note to the lamp illumination is stability and temperature -
on colder days it doesn't take too long to warm up and keeps frequency
synthesis better due to the heat generated by the lamps - and helps remove
and keeps the LCD panel from fogging and slow reaction times for the
polycarbonates in the display are kept to a minumum. SMD's [Surface Mount
Devices] are used exclusively in the front panel - all components are of
this type on the panel, except for the potentionmeters and buttons.

The RF PCB is connected through a series of solder bridge connections that
are balanced to ground via a series of chip resistors on the panel to
reduce noise and improve shielding. The RF sections are mounted on a PC
122 style chassis and all components are mounted horizontaly, parallel to
the ground plane of the board and this board is mounted at a right angle
to the front panel. All discrete conponents are used on the RF PCB.
Resistors are 1/6 watt with a few exceptions for power supply and
driver/final area.  The Mirror board is soldered in place and is best left
alone - there are parts underneath that can short to the board.

Now, that we are on to the meat of the radio, here are some specs that you
might find interesting....

The RF PC board uses 3 tunable tanks for AM/LSB/USB, and one single
tunable tank for AM carrier balance and initial frequency synthesis
[16.240], and the CPU generates the offsetts for the balanced modulator
[it's not an AN612 - it's house numbered] and the VCO section is located
in one side closer to the ground of the chassis and ties into the 3 tanks
for voice and uses a crystal [10.697] for voice filtering/mixing. A series
of PC mount style potentionmeters are used for adjustments of ALC/AMC/S-RF
bias/S meter fine adjust/AM Power and TX adjust. Two other potentionmeters
are used for Final and Driver bias. There are two 1/8 mini plug jacks for
both external speaker and PA speaker on the rear panel.

I won't tell you the exact labeling due to the nature of it being a new
radio and it shouldn't be messed with. It does what it is supposed to do
and any attempts to re-adjust the radio shouldn't be done without more
test equipment than that which is normally available to a user.

The radio uses a 2SC2166 driver, 2SC1969 for Final - and the Tank coil for
suprious emmission and tuning is epoxy - not wax - sealed.

The NB, RF amp, and IF amplifier sections are layed out in similar
configuration to a PC 122 style and all adjustments can be done
accordingly.

The AM modulator amp/driver is a 2SB834 - all transistors listed are
TO-220 style and the Varistor diodes are epoxied to the plastic cases of
the two RF transistors.  It does not use Thermapad type heat transfer
mounting for the TO-220 styles, only a polycarbonate spacer before being
mounted to the chassis/heatsink. There is no heatsink compound used.

The chassis is isolated from ground and uses RF bypass caps for use on
Positive/Negative type ignitions.

Radio - out of the box, will do 3 watts - no modulation, maximum of 6-8
watts with modulation - factory set at 75%, and will RMS SSB to 4 watts
with audio peaking at 8 watts, using a wistle will swing to 12 watts. The
Microphone uses an Electret Condenser and uses 1.3 volts for powering the
element.

Quote:>Does it still generate tons of heat while transmitting? Does it affect
>match on an antenna that was tuned using a different radio?

Yes, it still sufferes the same fate as that of the older PC 122 styles -
so any attempts at adjustments to make the radio do more is not
recommended.  And due to impedance of the unbalanced matching network -
the users antenna should not need retuning. There is no SWR feature, or an
AWL indication - so the user needs to rely of S-RF indications for
trouble.  The heat generated is much less than the previous versions. And
although it is a heat producer, if the settings are left alone and
installed properly - it will not pose a problem.

Quote:>I'm sorry I don't have any answers for you, just questions.  I had a
>chance not too long ago, to choose between the 148 F or the TRC 485 - I
>now know which one I should have bought in the first place. ;-)

Yes, I'm slamming myself here, but for good reasons...

I need to interject something here.  Many of you out here use Uniden
products. Although the radio does not specifically say is from Uniden, I
see many of their types of products inside and the layout and components
used are a dead giveaway.  It works much like the older PRO 6XX - 8XX
series radios, both mobile and base, that had backlighting and solder
piggyback connections - there were many manufacturing problems associated
with it because of mechanical failure and undue flexing in a harsh
environment when subjected to excessive vibration.  Much of these problems
has been addressed with lighter yet stiffer materials, redesigned layouts
to reduce damage from flexing, and continuous solder rows versus small
areas separated by large gaps that would set up vibrations that weaken the
electrical joints between the two sections.  Plus, with the type of
mounting on the chassis, there is more strenghtening due to physical
contact on the chassis that runs lengthwise - reducing the bowing or
additional harmonics that are caused by vibration. The small rivets that
held solder tabs to the board are gone, no more failures due to the rivets
that either oxidized or separated from the board. They have been replaced
by actual bolts and nuts on the ...

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