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Question for techs about keying a solid state amp with a key line...

Discussion in 'Amplifiers' started by Bushmaster, May 7, 2011.

  1. Bushmaster

    Bushmaster Member

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    I run a Kenwood TS-480SAT, and I want to use it to drive an RM Italy HLA-300 solid state amp. I know that this amp can be keyed with simple RF sensing, but it also provides a dedicated keying input on the rear of the amp, which is the way I'd like to go about keying the amp. The input is a simple RCA plug jack.

    There is an 8-pin mini DIN connector that plugs into the TS-480, and looking at the pin chart in the owners manual, I see that pin #2 is labeled as "COM", and is the common terminal for the internal keying relay in the radio. Pin #4 is labeled as "MKE", and the chart indicates that it "connects to "COM" (pin #2) when the radio transmits".

    So, does anyone know if that is the way that the HLA-300 amp is keyed? By basically shorting the the two keying line conductors (using the internal relay in the radio)? Just wire up a keying line, with an RCA plug on the end that goes to the amp, and then connect the ground from the amp (on the key line) to pin #2 on the DIN plug, and the other conductor to pin #4 on the DIN plug, which goes to the radio?

    I am asking because I haven't wired a keying line before, and do NOT want to damage the radio or the amp. I know there is more than one method used to key an amp, in various makes and models, so I want to make sure that this is correct for this solid state amp.

    Thanks for any help anyone can impart.


     
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    Last edited: May 7, 2011

  2. Bushmaster

    Bushmaster Member

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    Found this on another forum:

    "The RM Italy HLA 300 series has three ports on the back side besides the red and black power leads. Radio input, Antenna output and a Key line which is a RCA connector. If you use the SSB sense the keying has a 1 second delay or you can use the key line which connects to your PTT on your transceiver. The key line is jumper programmable to positive voltage or grounded keying."


    So I take it that there is a switchable jumper inside the HLA-300, and that there is more than one option for keying the amp. The relay inside my TS-480 which switches pin #4 to ground (pin #2) when the mike is keyed, would mean that I need to make sure that the "programmable jumper" is in the "grounded keying" position, in the HLA-300 amplifier...

    Correct?
     
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  3. Captain Kilowatt

    Captain Kilowatt Professional Amateur Staff Member

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    You are spending a lot of cash to gain 1/2 an S-unit not to mention the output will be cleaner just from the TS-480 but that's your business until it starts to splatter.

    http://www.worldwidedx.com/amplifiers/37058-rm-italy-hla-300-10-160m-amp-4.html#post281363

    You will have to look up the keying voltages and current required by the amp and see if the exciter can handle it. Typically all you have to do is connect a straight cable from the amp keying line input to the exciter's key line output. It's just a simple contact closure.

    I just reread this part " The relay inside my TS-480 which switches pin #4 to ground (pin #2) when the mike is keyed, would mean that I need to make sure that the "programmable jumper" is in the "grounded keying" position, in the HLA-300 amplifier...

    Correct?"

    The answer is yes, correct as long as the keying transistor in the radio will handle the current. I believe it uses a transistor as a switch and not a relay in the radio. Good old relays have long since been replaced by much less robust transistors in keying circuits.
     
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  4. MrSuburban

    MrSuburban Guest

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    What Band do you plan on using the amp?



    "If the HLA 300 is anything like the HLA 150, here is what you can expect:


    RM HLA-150 test

    RM Italy clearly lies about the power rating. On SSB, the HLA 150 is only clean to about 100 watts, even though they claim it is a 300 watt PEP amplifier. The HLA 150 BARELY makes 155 watts when totally saturated. So if someone splatters enough, they can get 155watts PEP from an HLA150.

    It's my experience that a company that boldly lies about the ratings of one thing can't be trusted for anything else.

    Since you report 450 watts from an RM-300 that they say is 600 watts, it makes sense to assume they lie about equally for all product ratings. This means to have a reasonably splatter free signal you would probably need to run the RM300 at about 220 watts or so.


    73 Tom "



    "
    That all sounds good, but filters have absolutely NOTHING to do with splatter. I don't know where people get the idea that an output filter can clean up splatter, but it is a pretty silly idea!!!

    The RM Italy HLA 150 is very clean for harmonics, but fails FCC radiation limits for the microprocessor inside!!!

    The splatter comes because the transistors they use are too small for the power they try to run, and the bias system is not that good. Also it uses 12 volt transistors, bad for higher power levels. To fix the splatter you would need bigger transistors and better bias, NOT a better output filter. The output filter is fine.

    You intend to clean up what is not broken, and fix what does not affect splatter...and splatter is the main problem. :)

    I think an RM150 would probably be acceptable as a 120 watt PEP mobile, and a 90 watt home amplifier. This means an RM 300 would probably be good as a 180 watt home amp on a big antenna, and a 240 watt mobile amp on a small antenna.

    They are not good amps for splatter. Most 12 volt amps are not.

    73 Tom "
     
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  5. Captain Kilowatt

    Captain Kilowatt Professional Amateur Staff Member

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    BTW for those that don't know, Tom W8JI that did the above report is the designer of most of Ameritron's amplifiers. If anyone should know about the proper operation of an amplifier and it's ratings it would be him.
     
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  6. Bushmaster

    Bushmaster Member

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    Quote:

    "You are spending a lot of cash to gain 1/2 an S-unit not to mention the output will be cleaner just from the TS-480 but that's your business until it starts to splatter."

    Actually, the difference between 100 Watts and 400 watts is 6 dB, which equates to a full S-unit. Seems kinda silly to maintain the idea that going from 100 watts to 400 watts simply isn't worth it. Obviously, it depends on what situation a person is in. There have been many times when I am right at the noise level with 100 watts, but would have been perfectly readable with 400. And when a person has done all that they can do with their antenna and feed (like I have), which is the right order in which to do things, then the next logical step is to bump up the output, at least a bit. And in my view, 6 dB gain is 6 dB gain better than 0 dB gain. Fair enough?

    But I do appreciate the opinion. 73's...
     
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  7. Bushmaster

    Bushmaster Member

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    Quote:

    "What Band do you plan on using the amp?"

    Whichever band I want. I have an Extra ticket. And using the amp isn't illegal in the USA. Just manufacturing and distributing them, without certification.

    And yes... I am more than familiar with Tom, and his credentials. I have seen a million and one of his posts, reviews, and articles over the years. I've also seen plenty of people with equal (or even better) credentials who disagree with him on some things. If I took everything that he says as absolute, undisputable, gospel hardline fact, I probably would end up running nothing. Just because someone regards themselves as a purist, doesn't mean they are infallible.

    I can easily understand why Tom is so vehemently down on these amps, even though other people have tested them with good results, and plenty of other people are absolutely happy with them. After all, Tom has been affiliated with designing for other manufacturers. Of course, there are also those who have never owned one, who are quick to say disparaging things about them, as well as the fact that almost ANY piece of equipment is going to have people who had a bad experience with it. But I happen to know a number of folks that use these all the time, on 40M and 75M and every one of them have nothing but good things to say about them. 2 people I know even went and bought another one.

    Maybe that, in itself, wouldn't be solid evidence for quality, but when I repeatedly hear (with my own ears) an amplifier with good, clean audio, and it isn't splattering, or blasting out harmonics, and then when someone affiliated with the designing of a competitive manufacturer's amps, has all kinds of horrendous things to say about it, I have to consider motive and pride into the equation.

    I am not saying Tom isn't right about most things, and I'm sure he's a good, decent, and all around nice guy. Only that he isn't infallible, like some people make him out to be. As I said before, there have been plenty of people who have gone rounds with him over the years, and who I personally think won the arguments.

    I am not a purist. I also don't have wheelbarrows full of cash to throw around. If an amp has reasonable specs, and sounds excellent on the air, then that is all I am really interested in. There are more people who have tested this amp as reasonable and clean, than there are who have tested it, and found undesireable emissions.

    Truth be told, I never intended to get into all of this, considering that my thread was intended to get information on a key line for my amp/radio combination. I also find it somewhat amusing, that with the number of people who really ARE running filthy amps at this forum, that it would be a bone of contention to try and garner info on an amateur amp, with proper biasing, switching, filtering, etc... albeit a foreign manufacturer.

    I'm not looking to run a 2KW illegal CB amp here. Or even 1K. Just a puny few hundred, on a filtered and biased amateur amp. I'm licensed to run 1,500. No need for the drama, really. A very good percentage of the amps currently being used on the amateur bands, are not FCC certified, and yet are just as clean (and legal) as those which are. With the very low number of amateur amps that RM Italy exports to this country, I can fully understand why they wouldn't want the expense of certification, even when the product would pass. There are a number of other reasons that I can imagine, which have nothing to do with whether the amp would pass or not.

    73's to all...
     
    #7
  8. Bushmaster

    Bushmaster Member

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    #8
  9. Captain Kilowatt

    Captain Kilowatt Professional Amateur Staff Member

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    You will never get a spectrally (word?) clean 400 watts out of four SD1446's. I mentioned about the 1/2 S-unit based on your other thread that I linked to above where you stated that you just wanted to run it lightly at 200 watts output. Don't blame me for what you said. Here it is again in case you forgot.

    http://www.worldwidedx.com/amplifiers/37058-rm-italy-hla-300-10-160m-amp-4.html#post281363
     
    #9
  10. hookedon6

    hookedon6 W9WDX Amateur Radio Club Member

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    #10
  11. MrSuburban

    MrSuburban Guest

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    LOL exactly he is a product of the no code testing. If he knew so much about what Tom said he wouldnt have bought the amp.
     
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  12. Beetle

    Beetle Well-Known Member

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    Get a good footswitch -- one that has two separate switches that actuate at slightly different times just a few milliseconds apart. Wire the switch that closes first to the amplifier and the other one to the radio.

    This way, the amplifier is turned on and ready just 5 - 10 msec before the radio can send any RF its way. It's a lot easier on just about any amplifier to be keyed like this rather than having the radio keyed first and then sticking the amplifier into the mix.
     
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  13. jazzsinger

    jazzsinger Bullshit Buster

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    No-one is infallible, but from what i've read of Tom Rauch, the vast majority of his advice is pretty sound, and i doubt very much his opinion on rm amps is based on his loyalty to ameritron, more the fact that rm italy bullsh!t constantly, as do their competitors in italy zetagi.cb manufacturers that tell the truth are easier to find than bin laden was, but if you have a spare odd ten ten years, i'm pretty happy to wait till you find me one that is honest.

    i think you'll find the chances of rm's amps passing certification are about equal to rosie o donnel winning a slimming contest. its nothing to do with their lack of imports, if they were quality products at those prices they'd be exporting plenty to the states, even most cb'ers know rm's amps are grossly overrated, not only for output power but also input power as they splatter so easily.
     
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  14. eagle1911

    eagle1911 Active Member

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    They are overrated by the manufacturer.. but if you drive them at the levels the transistor's datasheet ratings suggest (which is always FAR less than what RM says), they seem to do alright. The rating stated by the manufacturer has little to do with the circuit design, which is pretty much standard and used by lots of manufacturers, not all of which are CB amp makers. Push-pull amplifiers aren't rocket science and there's not a whole lot to them really.. most of the designs that are out there are based on the Motorola engineering bulletin designs anyway, so what difference does it make who builds it?
     
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  15. spickus

    spickus Member

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    Yes, that solid state amp can be keyed directly by your radio. I have no idea which pins you need to use on the Kenwood. Plug an RCA plug into the amp and short the other to the body of the amp. Did it key? Good, wire up a cable and use it but pay heed to manufacturers rated output of the devices. That was my amp that Tom used to perform the tests. I hope the auto band switching circuitry doesn't give you birdies every 20 KC on every band like it did me.
     
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