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MAGNUM 257 HP Review

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Old 05-04-2010, 02:51 AM
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Arrow MAGNUM 257 HP Review

Stealthy, Sleek, and Small...

When I was first called on the phone by Sam Lewis of RF Limited/Magnum International to review this radio a few weeks back, I had to admit to him that my curiosity was already aroused from what I'd recently heard. That is, that they had upgraded it with the RFX-75 MOSFET amplifier. I was about to call him to ask if I could review the 257 HP anyway - so he sent one out to me.

For those readers who don't know who Sam Lewis is, I'll give you a brief idea. Both Sam and his father were the original designers/manufacturers of Palomar Electronics. They made tube linear amplifiers that are still sought after to this day, as well as other various radio equipment. It didn't stop there either, as Sam went on to help develop the AR-3300 and 3500 radios that are a legend in themselves. Today both Sam and his son Eric build export radios, cameras and radios for motocross use, and microphones for CB radio applications. They even make a special camera with software to help one improve and correct your golf game. Not to mention, they manufacture the EKL brand of semiconductors - the MOSFET's that are the aftermarket solution to repair and upgrade of older radio bipolar final transistors...

I have heard so many different stories - both pro and con - about the Magnum 257. I had never used one before. Indeed, I had never even seen one up close for that matter. That alone was enough for me to question both sides of what I'd heard. Those that own these radios seemed to be quite pleased with its performance, and the critics seem to say much the same thing - except that its receive is noisy and prone to picking up even more noise when installed in a vehicle. Now that it is available in the amplified and non-amplified version - it was high time I gave it a spin and put it through some paces and some close scrutiny. It arrived a week after the phone call, so I quickly put it on my Diamond 40 amp power supply, Dosy TC 4002 SW meter, and IMAX antenna. Now that I've had it for awhile, its mysteries to me have been revealed.

The picture on the box is accurate, except for the fact that the LCD digital readout is blue; not yellow.

To begin with, it is both very small and fairly lightweight. The HP version is about 1/4 pound heavier than the non-HP version. It is not built using the typical round resistors, disc capacitors, glass diodes, and epoxy transistors. It is built with Surface Mount Technology; or 'SMT' for short. These SMT parts are much smaller and lighter, so it can be made more compact. It is also more cost-effective to do it this way, as machines can control nearly the entire manufacture process and eliminate more errors. Many European electronic products these days are being built in this fashion. Including many computer components that you probably are using right now - unaware.

It measures only 6 inches wide, 2 1/4 inches tall, and 10 inches deep.

Left to right: The Magnum 257 HP next to a Yaesu FT-8800R 2 meter Ham radio.
As you can see, small enough to mount most anywhere a small 10 or 11 meter radio is required

This radio comes from the manufacturer set for 10 meter operation. It can be easily modified - by the purchaser - for frequencies between 25.165 to 29.699mhz. One does not need a shop to do this as other radios require a radio tech to perform this kind of conversion. Which can save the buyer the added expense - usually $30 or more. All one needs to do is remove the cover and move a 'jumper' to any one of four locations on a small board mounted on the frame near the front of the radio held in by a single phillips screw. Older versions of the 257 had only two positions to choose from.

1. Make sure Magnum 257/257 HP is turned off and disconnected from power source!
2. Take off speaker-side cabinet.
3. Find the CPU Reset Board located near the front panel on the side frame of the radio.
4. On the CPU Reset Board are 4 jumper positions (CON 1 - CON 4).
5. After selecting the desired frequency range and configuration, press the CPU Reset Switch (SW1) for 5 - 10 seconds.
6. Reassemble the radio, turn on and test.

(Each jumper position provides a different frequency range and configuration. From the list below, select the desired frequency range and configuration, and move the jumper shunt to the corresponding CON.)

CON 1:
10 Meter Only (28.000 - 29.699 MHz)
*Default mode
*All functions operate normally

CON 2:
10 Meter & Expanded Mode
*At turn on, the radio defaults to 10 Meter mode.
*For Expanded mode, press FUNC and then press CALL for 3 seconds.
*To return to 10 Meter mode, repeat above steps.
(For information on Expanded mode operation, see CON3)

CON 3:
Expanded Mode Only (25.165 - 29.699 MHz)
*In Expanded mode, the frequency range is divided into 10 bands of 40 channels each
"Bands are shown on LCD display by letters (A through J) - Band E is regular 40 channel CB. To switch bands, press the CALL button (do not hold down for 3 seconds),
*In Expanded mode, either the frequency or channel can be displayed on the LCD. To switch between frequency display and channel display, press the FUNC button and then press the CALL button (do not hold down for 3 seconds).
*On the channel display, the small number (0 - 9) to the right of the Band letter is the 1 kHz frequency display. Example: If the frequency is 27.405, then the channel display will indicate 40 E5. "40" being the channel, "E" being the Band, and "5" being the 1 kHz position of 27.405.
*In Expanded mode, the RPT and SHIFT functions do not operate

CON 4:
40 Channel CB Only (26.965 - 27.405 MHz)
*Only operates on the regular 40 CB channels

I ran it in the 'CON 3' position. This made the regular CB/40 channels available as well as every frequency between 25.165 and 29.699mhz. In this mode, the repeater function will not operate. If I put it on 'CON 2', I can use either full Ham/10 meter operating capacities and switch over to 'expanded mode' by pressing 'FUNC' then press 'CALL' for three seconds. This is called 'Stealth Mode'. I will set it up like this the next time I pop it open. In the 'expanded bandwidth', the radio can access bands 'A' through 'J' by pressing the call button. This allows some 400 channels. 10 bands @ 40 channels each.

Please Note: Do NOT use any frequency 28-29.699mhz without a Ham license, unless you wish to draw attention and receive retributions from the Ham community.


Although small in size and weight, it has a number of functions and capacities. No; it does not have a talk-back, echo, or even a roger beep. It has soft-touch button controls, as well as regular analog knobs. The knobs on these controls are made of rubber, much like the Yaesu FT-8800R does in the above picture. It doesn't have a built-in PA function either - which I consider a plus. The controls themselves feel a little bit loose - not tight or stiff. They are back-lit with the same blue LED lamps.

One feature it has is the ability to scan frequencies. Or, you can program up to five different commonly used frequencies (regardless of what band it may be) and the chosen mode (USB, LSB, AM, or FM) and it can scan them as well. I found this a constantly used feature - really quite handy. I can listen to all of the frequencies that I normally listen and operate on. I just let it run in the background until something interests me and I can go right to it.

This radio also includes a speech processor/compressor that makes the transmit audio more effective. This is a recent addition to the 257. A compressor will make a subtle audio signal nearly as loud as a stronger signal. This gives detail to the finer points of speech and the human voice. On the other hand, it will also temper voice peaks so they aren't as loud. One can look at it as a kind of volume equalizer when transmitting. This will have the effect of bringing the average output power of the radio up a little bit, as well as being made clearer to those that receive your transmitted signal. More radios should have these installed. Most radio mfr's unfortunately - don't. Many Magnum radios do have this feature.

The radio has the usual 'ON/OFF-Volume', 'Mic Gain', 'RF(receive) Gain', 'Squelch', 'RF Output' (output power), 'Clarifier' (unlocked:1.5kc each way from center position), and 'Frequency' controls. There are six soft-touch buttons; five of these buttons have dual functions. To access the second function, one needs to merely press the 'Clarifier' knob once, and then select either 'Step/Noise Blanketer', 'Scan/Shift', 'LCR/RPT', Mode/T-Low', or 'M-Load/M-Save'. I have included a .pdf file at the bottom of this review if you wish to examine -in detail- how to operate these functions.

The 'Call' button serves only to change the band you choose, or to change the LCD to read either channel numbers (such as '19', '39', or whatever...) or frequency readout (such as '27.185' or 27.385' or whatever...). This not a frequency counter per se; but a frequency read-out. This radio employs a CPU driven VFO. This CPU also governs a great number of functions that keep it chosen frequency and mode extremely accurate. Only the Magnum and RCI/Ranger radios use this technology at present. In the default 10 meter mode, changing repeater shifts requires 100kc shifts. This is simply accomplished by pressing the 'Shift' button twice to move the cursor to the 100's position. Additionally, the clarifier is unlocked and tracks receive and transmit at the same time. I like that too.

The 'RPT' and 'Shift' buttons will not work in any other 'CON' position other than CON 1 or CON 2. They are used to set repeater offsets for 10 meter operation. The 'Step' button will allow the user to change the frequency readout from, say 27.385 to 27.384, 27.383, or any number between 0 and 9 for the last digit. Combine this with the fact that the clarifier will slide 1.5kc - and you can go anywhere between.

There is no analog S/RF meter; but there is a digital meter built into the LCD screen. It will also display LSB/USB/AM/FM, the noise blanketer "NB', low tone 'Tone', 'RPT', 'Save', 'Scan', or 'Load' if programmed in. Either the channel can be displayed - or in the numeric equivalent frequency in megahertz. It is easy to read and the blue back-lit LCD is easy on the eyes. 'TX' or transmit will also display when the mic is keyed up.

Either in SSB or AM mode, this radio has audio talk power - with or without the RFX-75 amplifier - which depends on the model you might get. The non-HP model is rated at 30 watts peak power output in AM and SSB modes. While the HP model suggests that it can produce 90 watts peak power on AM, 60 watts SSB, and 15 watts FM. FM was also clean from reports from local friends as AM was very nice too. Tough crowd to please - BTW. The following two pictures show SSB power output and AM power output in watts - respectively.

When I opened up the case the first time, I noticed that they added a toroid choke to the incoming power, as well as two disc capacitors for additional noise filtering in the power feed section. This is also a recent addition to this radio. Perhaps adding an electrolytic capacitor would increase its ability to filter more noise? It is something that I will look into and report later on.

The upper scale on this meter shows '1, 2, 3, 4, 5', and then '10', '15', and '20'.
Each number is representative of 10 watts.
As one can see, SSB power was 60 watts, and AM performance was ~90 watts peak power.

Actually, I saw more than 60 watts output on SSB. More like 90; but I keep the level to the recommended levels and by doing so preserve the life of the radio output transistors. I was surprised that it could do so. I don't recommend the practice of turning any radios power output all of the way; it just isn't prudent. This radio has plenty of power for most conditions. The RF Output knob was never turned up past half way. More like 1/3 the way up - and I never felt the need to turn it up any higher - except to see what it was capable of. When kept at the recommended levels, the heat sink only got a little warm. Don't let them get hot; or you may damage the radio and need repair.

The RFX-75 MOSFET Amplifier

This is what separates the Magnum 257 from the 257 HP model. This little but versatile amp can be found on a number of Magnum radio products, such as the Magnum OmegaForce S-45 HP and others. They are also sold individually from various CB shops as an add-on to other brand-name radios on the market, such as Cobra, Galaxy, and so on. So long as they are set up correctly and aren't allowed to overheat, that can last indefinitely.

What can damage these units in the fastest possible manner? Having a poor SWR match and a poor ground in your system. Make sure and check these aspects thoroughly and make corrections as necessary before operating any radio that you use. The RFX-75 employs one ERF-2030 and one ERF-7530 MOSFET device that can produce up to 100 watts of output power.

The not-so-stock mic

The mic that comes with the 257 is certainly not a slacker. In fact, to purchase another aftermarket mic is a consideration, but I have no idea why one would want to. This mic is an electret condenser mic that has its own preamp and excellent dynamic frequency response. If heard when transmitting, one would assume that an aftermarket mic was being used. It really is just that good, and I felt no need whatsoever to use anything different. It has an adjustment in the mic, and the adjustment can be turned up if you like. But it isn't really necessary to do. Seldom does any radio manufacturer make a mic worthy to keep and use. Again, Magnum made this happen. Wise engineering - IMO. The early mic cords used to be made of the same cheap vinyl that Cobra mics have. The new mic cord for the 257 is made of genuine Buna rubber and has a 4 ft use length. This also saves an additional $40-50 for not having to buy another mic.

On the front of the mic where the word 'Magnum' appears, there are two arrows to either side of it. When either up or down arrow is pushed, it will change the channel up or down by one channel. If you look at the picture of the mic taken apart, you will notice a small round hole near the center of the mic printed circuit board. This is where the mic gain can be turned up or down from the mic amp itself. As previously stated, the mic works quite well right out of the box and no adjustment is really necessary...


For the money spent for a single radio, one should consider this as a first-buy for the new radio hobbyist. Even the seasoned radio vet may consider this a viable choice due to its outstanding SSB performance. I ran it as a base radio for a couple of weeks, mostly on LSB/SSB. It never got hot; but I never pushed it. Didn't need to. The mic gain is set at the 2 o'clock position and the RF output was set at the 10 o'clock position. Ran cool and never had a single problem.

Talking skip today was a real breeze. Canada, Australia, Mexico, and all over the US of A. Of course, this has more to do with skip conditions than the radio or the antenna. But still - a very dominant little radio without the needs for further modifications of any kind. It's all in there - folks! The power cord is an interlocking type plug using 12 ga stranded wire, Pretty heavy duty - nice touch.

The receive was next to remarkable. I had just gone from my Icom IC-718 the week before and thought that I liked the receive in the 257 better. You have no idea how much it pains me to say that. The audio output is punchy and very clear, as the receiver was able to pull things in my friends couldn't. I actually needed to use the RF gain knob to control strong local stations. That was a first in my book.

The ability to lock into a frequency while on SSB and stay there without any discernable drift is a pretty important thing to me personally. If I put it somewhere - it stayed that way indefinitely. If one is getting into radio and wants a low priced ultra solid SSB rig for $180; then the Magnum 257 is the ticket. If one wants to spend a little more and have some additional power, then the HP model is the best way to go.

For the Ham who doesn't want an export radio, this radio might change their mind. I think they can really appreciate this radio. Never heard a single bad thing from other operators when using it on 10 meters. The opposite was true, it was also unsolicited. It doesn't have the CB 'toys' in it. I think you might forget about what others say about these radios and try one yourself. I think you will be pleasantly surprised. The repeater functions are far easier to program than any 2 meter radio I've used. They can appreciate the receive audio and stout transmit. In fact, this radio didn't interfere with my computer at all. All of my other radios would shut off my mouse and keyboard due to 'splattering' and proximity to the equipment. This radio did not, and I found that surprisingly refreshing as well.


I have some that Magnum could change for the better. The knobs are impossible to read. I had the hardest time trying to figure out where the Clarifier, RF Power, and Mic Gain were at. Even in a well-lit room it is impossible to determine.

The on-board speaker cannot be relied upon to make the audio understood in a way that this radio is fully capable of producing. You must use an external speaker to fully appreciate the receive and audio here. I used an old computer speaker (with a midrange and tweeter speaker) - because it used the same 1/8 inch jack plug. Probably sound even better if I used a real hifi speaker on it.

The noise blanketer - like so many other radios - is really useless as well. The 'Low Tone' is also useless. Cobra radios have that feature and I never used it in those radios either. Just muffles otherwise nice audio.

The digital S/RF meter doesn't have enough gradients for my tastes either. If/when I give a signal report for someone, it only shows up in increments of 1, 3, 5, 9, and +30. Same is true for modulation. It would be better if it had a more defined scale. Of course, other radios brands have this feature too, and I don't like those radios for the same reason. Again - personal taste.

Also, I am not a fan of SMT technology either - but that tide is coming folks and it cannot be helped.

I don't consider any of my personal dislikes a real 'deal-breaker'. But that is up to you. For the money and what you get, I consider it a bargain and this radio can be recommended to add in one's arsenal. Or, if a first-time radio operator looking for a radio that will provide accurate SSB performance and enjoyable AM performance - this radio comes up with the goods. Made a fine base station - IMO.

I have yet to use it in a car. This is where many of the arguments concerning this radio exist. I will update this review and use it in my car for a week and see if it is as noisy as some claim. It behaved like any other radio that I own and use, as far as being used as a base station radio. The rest remains to be seen...

"4 1/2 out of 5 stars possible"

*This radio has been given to the author for the expressed purpose of reviewing the manufacturer's' product. The author retains the right to express whatever views he sees fit for said product*

Jumper board showing CON 2 thru CON 4 (right side of board) and reset switch (bottom center of board)
Attached Images
File Type: jpg 8.jpg (95.5 KB, 1569 views)
Attached Files
File Type: pdf magnum_257_om.pdf (323.8 KB, 165 views)
BASE: Kenwood TS-2000, GAP Titan DX, Diamond X50A, Sirio SY27-4, and IMAX 2000.
MOBILE: Galaxy DX99V w/RF Limited CR-577 mic, Sirio Z-180. Yaesu FT-8800R & Diamond NR-770.

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Old 05-04-2010, 07:15 PM
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thanks for the review. how ya compare it to the omega hp both tx rx
BASE-magnum delta force, emperior 5010, AR 3500, sirio 2016
MOBILE-ss3900, uniden grant xl, z180, 636lS.E.

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Old 05-05-2010, 10:20 AM
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I had one of the original Magnum 257's. I liked the radio and used it extensively on 10 meters. The biggest gripe I had was that the front end (receive) was too hot and it picked up everything in the mobile. Have you put this radio in the mobile and used it yet?

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Old 05-05-2010, 10:42 AM
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I have the late 257 in my Jeep, and it works great except that it is badly disturbed by STOP LIGHTS in my area. Great in the country or on the road, though.
Incentives are important.....I learned that in rehab!

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Old 05-05-2010, 11:49 AM
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robb you obviously put a lot of time and effort into this review . thanks for sharing your opinions of the radio with us

hey packrat , i see you have a few old school classic cb radios in your siggy .
have you compared your 257 in the house with your 2000/139 or D-201 ? i know the 257 has more channels , but on 11 meters how does it compare to them rx wise ?

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Old 05-05-2010, 12:22 PM
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I been playing around with a 257HP as well. Things I noticed was that the quality has improved. Buttons still feel a little loose however overall it's improved from before. This may be because they are from the Philippines now. Receive was good on the base. There is some white noise on AM but it was more pleasant on the ears than the Icom7k but not as good as a well tuned HR2510. Used it on all modes with great reports. Was able to hold a qso with a local station that I usually have difficulty with on FM! That surprised me. Distant local stations said that AM was loudest of all modes. Noticed the heat sink did get hot with heavy FM use but that is to be expected. I did notice a few things and did some minor mods more for peace of mind. I replaced the power wires on the input filter and to the RFX with a size larger and installed a small fan on the rear heatsink. At the low setting around 2-3dk and around 15w on high. As far as swing, at 3w dk swing to 12w avg/80pep. On SSB at max around 70w. This all done at 13.5v and a 43P. I'm sure the SSB watts could be improved with ALC adjustments. The highest amp draw I seen was at full power FM, around 10 amps constant. As far as modulation goes this is a hot performer. As in older 257's I increased the modulation in the mic and on the radio when I did the expansion. This caused a OM signal and I ended up back to near stock settings. Noticed the board has changed some what and i'm sure there will be a chart soon to the locations and pot numbers and as to what they control. With a good tune you might be able to squeeze out a few more watts. The same should apply with the rx. Be warned that unless you know what you're doing, trying to adjust these will probably result in screwing up a great little radio. There is also the ch. selector on the mic and a nice scan that will change modes as well. If looking for a all mode radio for the price, size, watts and features of this radio I don't think it can be matched.

Overall I'm glad I got mine.

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Old 05-05-2010, 03:00 PM
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The Radio Shack HTX-10 is made by Magnum. It is actually the Magnum 257 - but with less features (no RF Output control, etc...). Here is a page to build a outboard CW to plug into the microphone jack. For those who contest CW on 10 meters, here is an easy/small add-on project to play with:
KB2LJJ Radio Mods Database and Manuals
Attached Images
File Type: gif cwadpt20.GIF (25.7 KB, 36 views)
File Type: jpg 59800_04.jpg (5.6 KB, 1524 views)
File Type: jpg 59800_06.jpg (19.5 KB, 1527 views)
BASE: Kenwood TS-2000, GAP Titan DX, Diamond X50A, Sirio SY27-4, and IMAX 2000.
MOBILE: Galaxy DX99V w/RF Limited CR-577 mic, Sirio Z-180. Yaesu FT-8800R & Diamond NR-770.

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Old 05-05-2010, 03:11 PM
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Are the front 6 buttons the same as the old ones? You might have to pull the face off to see. I broke those on two different versions of this radio because they were fragile. I'm curious if they've addressed this issue.

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