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Author Topic: RM HLA 300 V Plus hf amplifier  (Read 25606 times)
K1ZJH
Member

Posts: 901




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« Reply #30 on: March 22, 2012, 07:20:15 PM »

If they cared about IMD, it would be impossible to market FCC accepted Class C amplifiers.
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ZENKI
Member

Posts: 906




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« Reply #31 on: March 23, 2012, 02:24:53 AM »

Poor CB bias circuits, wrong amplifier class and generally poor inherent  IMD performance also should be added to your list.

Lets face it CB amplifiers are the worst possible   solid designs available on the market and even suggesting that you can drive them cleanly is ludicrous. If all hams  were of your Caliber K6AER I would not be so worried, however when we have hams who dont even understand that using a class C amplifier is wrong on SSB we will soon have 10 meters sounding like the CB hand with 50khz  to 100khz of splatter as a norm.

Every  ham that i hear on the air that uses a RM italy amplifier splatters a lot, that anecdotal evidence suggests that its going to most hams problems.
.

The largest problem, “crudding the band”, are not reworked CB amplifiers. Half the hams on the air would not know where to start in connecting an amplifier.

Your on the air crud comes from;

•   To much mic. compression.

•   To high a mic. gain.

•   Over emphases low end audio response.

•   Excessive wide SSB transmissions.  (3KHz is plenty)

•   Overdriving the amplifier and expecting the ALC to remove the distortion.

•   Trying to get the last 5% out of the amplifier output.

•   Loading a 50 ohm amplifier output into ladder line.

•   RF into the audio because your G5RV is just above you in the attic.

•   Leaky coax connection (bad connectors) which were not a problem at 100 watts but now are at 1KW.

I will bet you dollars to donuts there are 10 more I forgot.

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ZENKI
Member

Posts: 906




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« Reply #32 on: March 23, 2012, 02:32:09 AM »

Well Mike is wrong and using RM Italy CB amplifiers on the ham bands is recipe for disaster. The problem is that most hams and it seems some experience just  just dont get it.

Its amazing that we even have to have this debate, it clearly points to the poor technical understand of this issue. This is hardly a surprise, our hobby has lots most of its technical ability in RF science. It is then no surprise  that  we have CB'ers promoting crap CB equipment of poor technical standard on the ham bands.

Frankly there is no shortage of affordable decent amplifiers on the market, why go looking in the  technical garbage dumpster for CB products?

Hi,

1.  Mike is absolutely right on with his list.
2.  I am surprised it took ZENKI four days to post one of his name calling rants against RM Italy.

73,

John
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K6AER
Member

Posts: 3483




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« Reply #33 on: March 23, 2012, 06:02:30 PM »

You have 350,000 CBers who have passed ther ham license and now the ARRL sees gold. Only a small portion will buy an amplifier and even a smaller portion will take the time to understand the technical issues in using them.

I just wish they leave the CB lingo on 11 meters....roger that!

Quite franky RM Italy is the least of the band problems. It's Friday night and the WPX contest is in full swing. Not a single signal has better than 6 dB of dynamic range. Every one is distorted, over modulated except for 17 meters.

Looks like a good weekend for a motorcycle ride.
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KE3WD
Member

Posts: 5694




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« Reply #34 on: March 23, 2012, 08:39:17 PM »

Looks like a good weekend for a motorcycle ride.

Welcome to my world. 

When yer setup to go MotorcycleMobileCW, I'll be out there waitin' on ya. 


73
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KW6LA
Member

Posts: 91




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« Reply #35 on: March 23, 2012, 10:19:47 PM »

 <<  It's Friday night and the WPX contest is in full swing. Every one is distorted, over modulated except for 17 meters. >>

Mike-   Had to have a quick listen to WPX 20 meters and WOW can you screw up the quality of a SSB transceiver more ? Roll of at 500 on the low and 2K on the top.
Then compress it so you might as well be running AM. Under load the Amp with the Heil HC-4 mic and you have contest nirvana . Oh.. don’t forget to scream into the
microphone so they hear you better. Worry about CB amps killing the hobby?  Not any time soon and like you Mike, might be a good weekend to give it a rest.
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WB2WIK
Member

Posts: 20543




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« Reply #36 on: March 24, 2012, 05:28:11 PM »

Steve,

No IMD, its not on the FCC RADAR. They only care about out of band harmonics, case emissions and operation (positive gain) in the 26-28 MHz band.

Case emissions is strange. They must think we don't use antennas.

If that's the case, Andy Leimer at the FCC who wrote me the earlier correspondence must be all wet, as he stated they do measure IMD.  I wasn't sure about that, and now there's a disconnect.  I should probably ask somebody else at the FCC. Cheesy

Re the case emissions, that does seem weird but I think that wasn't intended to address in-band emissions.  Some amps do have microprocessors and stuff in them (in fact, any certificated amp to meet the 26-28 MHz lockout requirement would need to have a frequency counter in it, as I can't think of any other way to do that and still allow operation on 10m), and that stuff might have case emissions that are way out of band.

I don't like amp designs that are "too well" shielded, myself, they're just a PITA to service.  Even the SB-220 has way more internal shielding than makes sense.
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GM3SEK
Member

Posts: 46




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« Reply #37 on: March 25, 2012, 12:34:20 AM »


I don't like amp designs that are "too well" shielded, myself, they're just a PITA to service.  Even the SB-220 has way more internal shielding than makes sense.


To offer a contrary view, I hate 'open plan' amplifiers where everything - RF and non-RF components alike - is bathed in strong RF fields.

Yes, we all know it's amazing what you can get away with... but please don't call it good RF engineering.


73 from Ian GM3SEK



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OH7PS
Member

Posts: 22


WWW

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« Reply #38 on: April 14, 2012, 02:30:01 PM »

Hi

Nearly 10 years ago I had my first RM amp for 2m (2nd hand) - and at the same time the very last one.
It was oscillating and killed ft-897 finals.
Factory gave instructions how to fix it but I did not bother to do their job....

Maybe nowadays the quality is somewhat improved.

73 Ben

« Last Edit: April 14, 2012, 02:39:24 PM by OH7PS » Logged
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