Performance Test Of The DX 2547

This is the first base station in the line of Galaxy CB radios. In these days of converted 10-meter radios, companies like Cobra, Midland and Uniden seem to be trimming their CB radio lines. Cobra with the elimination of their base station radios. Midland back in the hay days was one of the first manufacturers with a line of true single sideband radios now with only one mobile in their SSB lineup. Uniden earlier dropped the PC122, a low cost AM/SSB mobile. More recently they have eliminated the rest of the SSB line with the removal of the Grant mobile and the Washington base. The only other SSB brand with an AM/SSB base station CB radio is Texas Ranger. Cherokee has a base radios on their web site, but they aren’t to be found in the real world.

With all the manufacturers moving away from base station and SSB CB radios, it was a surprise to me when I learned of the new Galaxy DX 2547 CB base radio. It sure made me wonder what might be so special about this radio that would make sell in the current marketplace. Will it be the replacement for the Uniden Washington or the Cobra 2000 GTL? Or is it somewhere in between? These are the reasons for picking this radio as cover story of the first web edition of CB World Informer.

The radio is made for Galaxy, to Galaxy specifications by RCI. The photos on the Galaxy site and the photos on the box, although very professionally done, don’t do the radio justice. I wasn’t able to capture the true appearance of the radio face with my camera either. I tried many lighting sources and camera settings. The radio just looks so much better in person. A customer came into the store and said “I saw the new Galaxy base on the web, I wasn’t impressed.” I then showed them the radio and they immediately said “I like that, it’s a nice looking radio.” I’ll do my best to describe the face of the radio. The face color is a metallic platinum color with charcoal gray accents and knobs. The indicator area is black giving a high contrast for the LED and meter display. The face has black lettering on the platinum background while there is white lettering on the charcoal and black backgrounds. It is much more impressive to view the real radio.

Looks may be very important, but the performance and functionality is paramount. The DX 2547 has all the features of the past top of the line CB base radios of the recent past and then some. Little things like front legs that flip down tilting the radio for better viewing don’t add to the cost of the radio but make a difference in making it user friendly. Sometimes it’s simple well thought out features like this that make a radio stand out from the competition.

Below is a picture of the radio with all the listed control and indicator functions so you can familiarize your self with the radio. Click on picture for close-up view.

Below are a list of controls and indicators with comments about each of them

POWER SWITCH Independent power switch. allows the radio to be turned on and off without disturbing the volume setting. Also reduces wear on the volume control and panel around the volume knob for those who rub the front panel while turning the knobs, 
SIGNAL/MODULATION/
SWR/POWER METER
This 4 function meter is easy to see and reads up to 60dB on the S-meter scale. It reads modulation in the AM mode as well as all mode power output and SWR with auto calibration, but is most accurate at full power. All functions were very accurate for an internal meter. Some operators will be disappointed that there is only one meter, but accuracy is more important than quantity.
LED CHANNEL INDICATOR This is a standard easy to read red LED 40 channel display selected directly by the channel selector switch.
6 DIGIT FREQUENCY COUNTER Fast update constant readout 6 digit frequency counter reads down to 100Hz. It is quite accurate, although the last digit sometimes seems lazy by change a little slowly while changing the clarifier position. When adjusting  the frequency to 27.4051 then slightly move the clarifier just until it reads 27.4050 then turn the mode switch to another mode and back again then it might read 27.4049. This isn't a major concern, just an observation. This also happens in the other RCI products using this frequency counter board.
TALK BACK VOLUME CONTROL The talkback volume control also has an off switch position. Talk back works in AM and SSB with plenty of clear volume and minimal RF modulation distortion.
HEADPHONE JACK This is the typical 1/4" headphone jack. Not a heavily used option, but some operators wouldn't be without it. Also a good position for an additional switch.
4 PIN MIC CONNECTOR Standard 4-pin microphone connector. Wired the same as all the Galaxy radios. Cobra/Uniden 4-pin mics will work on this radio. Also the mic jack will supply power to the RCI SRA-117 echo mic.
POWER OUTPUT CONTROL A feature only found on Galaxy CB radios. And one that in the past the FCC wouldn't approve in a type accepted radio. It works in both AM and SSB giving the radio a very flexible range.
MIC GAIN CONTROL Controls the gain from off to full with very gradual and even control. Very useful when using an amplified mic like a D104 where the gain control is on the bottom of the mic. Gain adjustments can be made at the radio.
RECEIVE GAIN CONTROL Smooth receiver gain control and very low distortion at low gain settings. Reduces a S-9 signal to S-0 and a 30dB signal to S-9. Works very well.
METER FUNCTION SWITCH Select the desired meter reading you wish to display. The SWR meter automatically calibrates as you transmit.
DIMMER CONTROL Adjusts all the LED displays and meter light to your desired brightness.
TONE CONTROL Adjusts the receiver audio tone. Can be used to clean up hard to understand transmissions by turning it clockwise increasing the high frequency response. Or it can reduce the amplitude of noise spikes by turning the control counter-clockwise decreasing the high frequency response and increasing the low frequency response. It has a very good range.
ROGER BEEP SWITCH Turns the roger beep on and off. The roger beep is not over powering and very short in duration. Galaxy seems to have tried to appease the many that have been annoyed by the piercing elongated beeps of the past.
PA SWITCH Public Address On/Off switch.
CHANNEL SELECTOR SWITCH A real channel selector switch, not a rotary Up/Down encoder. When the radio is set to a channel it stays there, unlike some of the newer radios that if the memory supply is interrupted they revert to channel 9.
MODE SELECTOR SWITCH Select Upper Sideband, AM or Lower Sideband with this switch. My personal preference is LSB/AM/USB instead of the USB/AM/LSB order of selection on this radio.
AUTOMATIC NOISE LIMITER SWITCH This is used to reduce noise in the AM mode. It seems the ANL is on all the time when the NB (noise blanker) is off. With the NB on there is a definite deference when the ANL is switched on and off. Checking the schematic, it doesn't appear to be the intended operation of this feature.
NOISE BLANKER SWITCH Reduces noise in both AM and SSB. Works by reducing or removing noise spikes at the first IF. The noise blanker in this radio is very effective, one of the best I've used.
GALAXY NOISE FILTER SWITCH Cuts the high frequency response reducing the amplitude of noise spikes. There is no documentation on this circuit in the Service Manual. I can only guess that it's a active audio Bandpass filter with a cutoff point somewhere around 1Khz.
CLARIFIER ON/OFF SWITCH Switches the clarifier out of the circuit. Puts the receiver on center slot. Also comes in handy once the clarifier is unlocked.
CLARIFIER CONTROL Controls the receiver frequency ±.1Khz.
VOLUME CONTROL Adjusts the volume to a suitable level. Works well with plenty of volume.
SQUELCH CONTROL Adjusts the threshold for squelching deferent signal levels.
ACCESS SWITCH TO CHANNEL 9 OR 19 Auto access to channel 9 or 19 no mater which channel your channel selector is set to.
ADJUSTABLE FRONT FEET Not actually adjustable, but folded under, the radio sits flat for placement on higher levels like on a shelf. Flipped down the radio is angled upward for easier viewing on lower level locations like a desk or table top.

Now for the performance test of the DX 2547. First, this radio came from a distributor and no one Knew this was going to be tested and reviewed by CB World Informer. There is no reason to expect any radio to perform differently from this on tested, although this one has a quirk in the ANL function which is covered above. I've submitted and E-mail to Galaxy tech support about this and will add their response as soon as it's received.

UPDATE: Galaxy returned my E-mail and confirmed the problem by checking some older and newer DX 2547 radios. The problem is that the J6 connector on the main circuit board is reverse on my radio and others at their site. It's unclear how many radios are involved, but the solution is simple. Unsolder the three pin J6 connector from the main circuit board then rotate it 180 degrees and re-solder it.

Checking the frequency stability from cold to warm, I found it took about 15 minutes for the radio to warm up and it settled down close to center slot after changing about 250Hz . This may vary from radio to radio, but I would expect it to be close. The frequency from the factory was within 100Hz of center slot and the counter alignment was on the money.

As far as transmitter performance, both AM and SSB audio are very high quality. The stock mic is adequate, but it sounded better with an EC-2018 turbo echo mic from RF Limited with or without echo. It will sound great with an Astatic amplified mic, especially a D104 type base mic. Out of the box the AM modulation peaks around 50% and the power readings are listed below.

Output Power Power Control Down Power Control Up
AM TX Dead Key  .5 Watts 3.75 Watts
AM PEP 1.5 Watts 8 Watts
SSB PEP 4.75 Watts 13.75 Watts

Testing the receiver with the signal generator, the radio seemed to meet the specifications. It performed as well as or better than most radios on the market. The sensitivity is very good and adjacent channel rejection is also impressive. But the true test is on the air with peaked and over modulated radios in close proximity. Being located in the middle of a wholesale produce market, there are hundreds of over the road drivers running power delivering in the area and in the building that my shop is located in. This is one of the best test beds for receiver performance.

With the radio connected to a Solarcon I-Max 2000, I scanned around listening  for familiar voices. After monitoring AM for a couple of hours, I found the receiver to be quite sensitive and exceptionally clear. With the tone control set at mid-way the audio frequency response was the best I've heard from solid state equipment. Transmissions from the regular operators I'm used to hearing sounded fuller with just enough bass response.

The sideband receiver was equally clear. The radio has a natural sound on sideband that's easy to listen to. Tuning into a station is easy with this clarifier. Turning the clarifier off worked well on most signals and I think this feature may convert some operators to sideband. In time with more frequency stable radios on the market, the need to constantly tune in stations may be a thing of the past eliminating the most common reason people won't use sideband.

Testing the squelch, I found it very smooth cutting in and out. There was no pop or click as signals came in breaking the squelch. It also worked very well on sideband. I'm not a squelch user myself because most of them are erratic and at times choppy. I find more often than not, calls get missed or parts of conversations are cut out because the squelch can't be properly set. This one works pretty well. It's one worth giving a try.

On air transmission reports were very good. The audio was clear on both modes and at all power settings. The modulation wasn't super compressed at the lowest power settings as it is on some radios.

The auto calibrating SWR meter is very convenient, no more keying up at either end of the band and calibrating the meter before you get your reading. Just go to the channel, key up and there it is.

During the on air tests I didn't encounter any interference that impeded communication. There was slight interference from stations within a quarter mile the next channel over, but I would expect this from any other radio and far worse on most.

The Galaxy filter did reduce the noise level at the audio end. You won't see a reduction in S meter reading but it smoothes the audio out reducing harsh spikes from reaching the audio amplifier. There is a cost to this. Weak signals become difficult to understand with the high frequency removed from the audio signal. This filter cuts the high frequency out so well, the tone control has almost no effect on the audio. Many signals seem muffled, but under extreme noise conditions, this may be worth getting use to.

Galaxy DX 2547 Specifications

GENERAL   
Channels 40
Frequency Range 26.9650 - 27.4050 MHz
Emission AM/USB/LSB
Frequency Control Phase-Lock-loop (PLL)
Synthesizer Frequency Tolerance 0.005%
Frequency Stability 0.003%
Temperature Range -30°C to +50°C
Antenna Impedance 50 Ohms
Antenna Connector Standard SO-239 type
Meter Function RF output Power/Antenna SWR/Received signal strength/MOD % 
Input Voltages AC 120V, 60Hz or DC 13.8V
   
TRANSMITTER  
RF Power Output  AM 4W; USB/LSB 12W PEP
Antenna Connector UHF Type, 50 Ohms
AM Modulation up to 100%
Spurious Emission Better than -60 dB
Unwanted Sideband Better than -60 dB
   
RECEIVER  
Sensitivity for 10 dB (S+N)/N AM: 0.5 mV, USB/LSB: 0.15 mV
Adjacent Channel Rejection -60dB Image Rejection -50dB
AGC Figure of Merit 50 mV for l0dB Change in Audio Output
Audio Power Output 2.5W @ 10% Distortion
Audio Response 300 to 2500 Hz 

This radio comes with both a detachable AC and DC power cord. It's not a bad size for a camping trailer where the DC cord will come in handy. In addition to a user manual, Galaxy includes a service manual. This manual is complete with schematics (except the Galaxy noise blanker PCB), exploded parts drawing, PCB drawings, mic wiring, parts list, alignment procedures, adjustment location drawing, test equipment setup, and block diagram. This hard copy manual is worth a $20.00 bill, and more when you need it. Galaxy warranties the radio for 2 years from the date purchased or if you lost your receipt, 26 months from the date of manufacture. A little note from the warranty policy page may be of interest to the readers. Galaxy uses a "R" as the first character of the serial number  to denote a refurbished radio. Always check for this when you make or receive a new purchase.

One thing I would change, a small one but an important one, the knobs should have a light colored pointer. The position of the knobs is difficult to see even in decent lighting.

Although priced in the $320.00 to $360.00 retail range, it does have many features for the money. This radio like other Galaxy models seems to be designed by radio operators, not just hatched from an engineer’s desktop. It certainly appears Galaxy did their homework on the user and engineering level. The features that are desirable are there and work very well. Time will tell if there’s room for a high quality 40-channel AM/SSB base station CB radio in this seemingly 10-meter radio market. A market, ironically that Galaxy was very instrumental in helping to create with their 10–meter line of radios. ©CBWI

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