[Amps] Available Class A in Yaesu
Alek Petkovic
vk6apk at bigpond.com
Sat Aug 18 05:44:14 PDT 2012
I don't know. You tell me.
I just know that if you run the Mark V at less than 75 Watts (full
power) out in Class A, things get really really hot and things let out
all their smoke and things don't work any more.
The technicalities of how or why that happens elude me and don't really
interest me.
Running my Mark V at 10 Watts out in Class A into an amplifier resulted
in the destruction of the output transistors. Many other owners have
reported the same thing. Since the event, I have not done it again and
the radio lives happily ever after.
Cheers,
Alek.
On 18/08/2012 8:03 PM, Peter Voelpel wrote:
> Hi Alek,
>
> What extra dissipation by reduced power?
> In class A current and voltage is constant whatever the drive is.
>
> 73
> Peter, DJ7WW
>
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Alek Petkovic
> Sent: Samstag, 18. August 2012 13:37
> To: amps at contesting.com
> Subject: Re: [Amps] Available Class A in Yaesu
>
> G'day Charles.
>
> A small correction.
>
> Do not run a Mark V in class A at less than 75 Watts full power. The extra
> dissipation in the finals when you run class A at reduced power, tips the
> BLF147's over the edge. The radio will run day and night at 75 Watts out,
> class A. Ya wanna run class A, ya gotta run full grunt.
>
> Most of us Mark V owners have learned this lesson, the hard way.
>
> 73, Alek
> VK6APK
>
>
> On 18/08/2012 7:22 PM, Charles Harpole wrote:
>> Correction: xcvrs with choice to xmit Class A are, at least, the
>> following: FT-1000MP Mark V, FT-9000Contest, FT-9000d, and FT-9000MP.
>> The latter three also have a bias adjustment on the front panel to
>> slide Class A downward away from pure Class A in SSB or CW modes. I
>> burned up a Mark V by running it full Class A (only choice on that
>> rig) and at about 40 watts... great techs tried to fix it and it blew
>> two more sets of finals before I lost track of it. Morale, do not run
>> a Mark V in Class A. Today, I own K3f, FT-9000d, and IC-7800, as well
>> as KWM-2A, and several other rigs. Very fun to compare them.GL 73
>>
>> Charles Harpole
>> k4vud at hotmail.com
>> > From: jim.thom at telus.net
>>> To: crc at cyberlink.bc.ca; amps at contesting.com
>>> Date: Sat, 18 Aug 2012 00:09:29 -0700
>>> Subject: [Amps] Re K3
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: Fern
>>> Sent: Friday, August 17, 2012 9:11 PM
>>> To: Jim Thomson ; amps at contesting.com
>>> Subject: Re K3
>>>
>>> Jim:
>>> Where in the world are you getting your misinformation from re the
> K3?
>>> You don't own one so quit running the darn radio down. Most of us ham
>>> don't run any more than the legal power of 1500 watts so there's no
>>> need for a 200 watt exciter. I happen to have Icom, Kenwood and Yaesu
>>> rigs and by far, the
>>> K3 has them all beat without a doubt. It would be nice if people
>>> would quit running down equipment that they don't even own.
>>>
>>> ### good info Fern. Tell you what I will do. I will buy one next
>>> week....with the
>>> provisio if I don't like it, I can get a full refund for it. I'm
> getting
>>> tired of one flop after
>>> another after another for every xcvr that comes out. I have yet to own
> any
>>> of em, that work right,
>>> designed right... outa the box.
>>>
>>> ## since u have all the fancy test gear, do us all a favour and
>>> measure the
>>> 2 tone TX imd at
>>> 120 w pep out, ( or what ever max power on ssb is), and do it on all
>>> bands, including warc.
>>> Do it the correct way, not the arrl fubar method either. IE: db below
> one
>>> tone of a 2 tone signal.
>>> Then give us the results for imd 3-5-7-9-11-13.
>>>
>>> ## while you are at it, measure the RX audio THD and max po of the
>>> k3's audio section.
>>>
>>>
>>>
>>> I've been in the
>>> communications business for over 50 years with owning my own business
>>> for over 25 years so I think that I have a bit of an idea as to what
>>> I'm talking about as I have on my disposal all of the test equipment
>>> to check this all out.
>>> The output power on the K3 is just over 120 watts dc (key down
>>> on mine) not 100 W pep as you stated. 99% of legal hf amplifiers
>>> don't require any more than 100 watts to drive them to full 1500 W
>>> allowed power. No offense Jim, I'm just stating the facts.
>>> Fern
>>>
>>> ### allowed power is 2250 w pep... AFTER feed line loss. IE:
>>> measured at the ant feed point. With just .5 db loss= 11% loss, the
>>> amp has to put out 2528 w, just to get
>>> 2250 w pep at the feedpoint. 1db loss = 21% loss. Now we require 2850 w
>>> out.... to
>>> get 2250w at the ant.
>>>
>>> ## I only have one grid driven amp here, (its being sold),
>>> the rest are GG. The hb 3x3 will do 2.5 kw pep out with real low
>>> IMD..with just 100 w
>>> pep drive. But that is a moot point if the xcvr is not up to snuff.
> The
>>> arrl lab tested
>>> the k3 at -29 db pep for IMD3. That's -23 db below one tone of a 2
>>> tone signal.
>>> That doesn't meet any standard, ITU, mine, or anybody else's.
>>>
>>> ## what's the point of me having an amp capable of -59 db pep for
> IMD3....
>>> if I don't
>>> have the mating clean xcvr to drive it with.
>>>
>>> ## fact is, a 55 year old KWM2 will eat the k3 for breakfast, as
>>> far as TX imd.
>>> Your typ 200w SS xcvr, when run at 100-120w pep out, is fairly clean.
> The
>>> only class A
>>> 100 w pep out xcvr out there is the yaesu 400w version of the 9000.
> And
>>> even that xcvr
>>> has enough problems.
>>>
>>> ## BTW, can you put the K3's sub rx on a different band than the main
> RX.
>>> Jim VE7RF
>>>
>>>
>>>
>>>
>>>
>>> ----- Original Message -----
>>> From: "Jim Thomson" <jim.thom at telus.net>
>>> To: <amps at contesting.com>
>>> Sent: Friday, August 17, 2012 7:57 PM
>>> Subject: [Amps] K3 spike problem
>>>
>>>
>>>> Date: Thu, 16 Aug 2012 14:11:02 -0700
>>>> From: Jim Brown <jim at audiosystemsgroup.com>
>>>> Subject: Re: [Amps] K3 spike problem
>>>>
>>>> On 8/16/2012 5:59 AM, Joe Subich, W4TV wrote:
>>>>> In addition, if Charlie is using external ALC (he does not say) and
>>>>> has the K3's power control set too high, he will see the spike due
>>>>> to ALC time constants*in the amplifier*.
>>>> It should be noted that when high quality rigs like the K3 are used
>>>> to drive a power amp, amplifier output power should be set by using
>>>> just enough drive power, NOT by setting drive power higher and using
>>>> ALC to reduce it. For at least 30 years, Ten Tec has recommended
>>>> AGAINST using ALC with their rigs and power amps in this manner. The
>>>> only good reason for using ALC between a power amp and a transceiver
>>>> is to protect the amp in case of a failure in the antenna system.
>>>>
>>>> ### Unless the amp has a front panel adjustable ALC control knob,
>>>> it won't work anyway. Also, the alc time constant in the amp HAS
>>>> to match the alc time constant in the XCVR..and NONE of em do..
>>>> so don't waste your time.
>>>>
>>>>
>>>>
>>>>
>>>> In an excellent applications note on the topic, Tom, W8JI, noted
>>>> that many rigs produce a spike of their full power output when their
>>>> drive level is set well below full power. For those rigs Tom
>>>> recommends a passive attenuator between the rig and the amplifier.
>>>> The K3 is NOT one of those rigs -- indeed, it is quite well behaved.
>>>> It's also one of the cleanest rigs on the air.
>>>>
>>>> ### IOW, if the amp requires 50 watts of drive, then use a 3 db pad
>>>> between
>>>> the xcvr and amp, then run the xcvr at 100 w output. IE: the pad is
> used
>>>> to
>>>> control the power output, and not any control in the amp. If 25w
>>>> drive required,
>>>> then a 6db pad is required. Any pad is a PITA. The 3db pad has to
> be
>>>> rated
>>>> for at least 50 w CCS. The 6 db pad has to be rated for at least 75
>>>> watts CCS.
>>>> Then you also lose 3-6db on RX... which is the last thing you want.
>>>>
>>>> ## a simpler approach to adjustable po is to just put -9vdc across
>>>> a 50 k
>>>> pot...then feed 0-9 vdc (neg) into the alc buss on the xcvr. Crank
> po
>>>> control on xcvr to max... then adjust pot for desired output..from
> 0-max.
>>>> No alc time constants to mess with, since you have already developed
> the
>>>> alc voltage with your -9vdc source. And no spike problem.
>>>>
>>>>
>>>>
>>>> ## The K3 is NOT a clean xcvr on ssb. It has typ lousy imd... like
> -29
>>>> db pep
>>>> for IMD3. That's on a par with sweep tubes from the 70's. It only
> does
>>>> 100 w
>>>> pep out, and I require a 200-250w pep put xcvr..so no K3 on my desk.
>>>> Ten tec needs to go back to the drawing board, and build a
>>>> competitive xcvr.... not one that's suited for cw only + grid
>>>> driven tetrodes.
>>>>
>>>> Jim VE7RF
>>>>
>>>> 73, Jim K9YC
>>>>
>>>> _______________________________________________
>>>>
>>> π
>>>
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>>
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