WorldwideDX Amateur Radio Forums

Adriano I got an email from Sam Lewis today about your problem, if you can give me your email address I can put you in touch with Sam about your problems, send me your email to tucker4422@verizon.net and I will foward it to Sam Lewis, is is very concerned about your problems

My 257HP has bad SSB TX audio brand new out of the box. The SSB TX audio sounds distorted and raspy. It sounds alot like RF getting into the modulation. However, I don't think it's an RF problem. Even reducing the RF output to only a few watts still produces the probllem. The SWR into the IMAX 2000 antenna is 1.1 @ 28.450MHz. Swapping in another HF radio into the antenna connection does not have the problem; so that removes the RF as the cause of the problem.

I did a google search on "Magnum 257HP Poor SSB TX audio" and found that I'm not only one having this issue. Some people think the top-gun modulator is the culprit because the previous version of the 257 did not have this problem and the AM TX audio of the 257HP is excellent.

I'm open to any suggestions, otherwise I have no other choice than replacing my 257HP with a different 10 meter rig.

send it to Chris at the Radio Shop in Ontairo Ca. he is the warranty guy and a great radio tech for magnum radios, if it's new the repair will probably be free if not then his prices are very good and not a lot of down time. If that doesn't work just list in on Ebay for like an hundred bucks someone will buy it even with an issue for that money

The blue display non-RFX-75 radio's had the Top Guns for several years with little or no problems. To be honest you hardly ever heard of a 257 go bad until this newest version with the RFX-75, which is the HP version.

That said it's not the RFX units but rather, I think, some kind of a production or quality control issue. I have never seen a firestorm if problems with Magnum radio's until this newest 257. I wish I knew what the deal was.

it always amazies me how many people have a 1.1 to 1 swr, either everybody had a crummy meter or they just have no output power. I am creeping up on 58 yrs old, have had almost any antenna made that is under 100 dollars and have never ever had a 1.1 to 1 swr. My best has been like a 1.2 and a little bit meaning like 1.25 or more most of them have been 1.3 to 1.5 with different coax configs or just different coax at different lengths but never had a 1.1 so why don't you 1.1 guys either get a better meter or just go around the band to see it get higher on other channels that you have cuz ALL bs ASIDE not all these people have a 1.1 swr antenna unless they are like doing 2 watts

There is NO TopGun Modulator in a Magnum 257HP!
lol!

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BASE: Kenwood TS-2000 w/Alpha Delta DX-CC, 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.
"...2 WR-011..."

You mean you don't key up and turn that litle knob until the meter reads 1.0:1??

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A radio is only as good as the person operating it . . .

This is off-topic to my issue, but here's how I get the low SWR on 10 meters:
1. Start with a new IMAX-2000 antenna and trim length according to instruction to tune it to center freq of 28.4
2. Since my coax run is 85' I decided to use LMR400 coax.
3. Antenna is mounted on telescoping fiberglass mast so it can be lowered during severe weather.
4. This base installation gives me an SWR of 1.2 @ 28.45MHz on my DAIWA SWR & POWER METER even with RF output at 50W.
5. To further reduce the SWR, I installed a quarter wave coaxial sleeve inside the fiberglass mast, just below the antenna feedpoint. The coax runs through the sleeve which is attached to antenna ground at the feedpoint. The coaxial sleeve acts as a counterpoise and further reduces the SWR to below 1.2