[AMPS] Bargain basement broadband tetrode amp

[Jeff Wolf]

I wrote:
>The 4CX250 amp looks like a CB amplifier Skipp.

Skip must have replied:

>Why would Skipp have to reply with the below statements?


> >>>Actually, it looks like a Pride DX-300.  A tuned input, 80 to 10 meter
> >>>amateur radio amplifer.  One of the cleanest amps I have seen come from
> >>>a production environment.  App 20 dB gain, clean, parasitic free,
> >>>completely adjustable bias...  Yep, seems like the average CB
> >>>amplifier.

Unregulated screen voltage is an absolute no-no, as is the lack of a
screen meter.


>>So you say, but the Pride design has been in use for 20 years (going on 
>>30), doesn't blow tubes, is one of the cleanest amplifiers I have ever 
>>operated, and has no known problems.



Collins got away with an unregulated screen in an amplifier by
building a beefy screen supply and using heavy negative feedback
with a cathode driven tetrode, but this tube is a grid driven 4CX250.


>>Yes, and Collins used a tube with a smaller grid than the 4CX250.

4CX250's are poor enough for IMD when operated correctly.

>>I haven't had that problem.  The 4CX250/350 seems to work well in the 
>>circuits I have built them around.  Telestar also made some nice multiband 
>>/ multitube 4CX250B amps in the 80s.  I imagine you don't like those 
>>either?



> >>>Why not?  Because it has high gain?  If you don't want the gain, Pride
> >>>made another (to compliment the FT 101 and similiar series of radios,
> >>>called the KW-1 (1 Kw input).  It used an untuned grid, just swamped
> >>>with R.  THAT seems more like a CB amplifier to me.

Pride was in the business of selling CB amplifiers under the guise
of amateur radio amps.


>>I suppose you have proof of that statement?  Or are you slandering a 
>>company that is no longer in business and cannot defend themselves?


They cared less about linearity.


>>I know that to be untrue.


They also sold components and devices that allowed CBers to operate on
frequencies outside the CB band.


>>And you manufacture and sell amplifiers that have a simple wire clip 
>>modification to operate on 10/11 meters.  When the Pride was built, it was 
>>built to tolerance and spec of the day.

>>I wonder what the amplification level of the AL800H is when driven with a 
>>standard 20w PEP CB radio is?  I have seen a surge in the popularity of 
>>that amplifier on 11 meters, since it makes such a nice driver for triodes 
>>with handles, when driven with the "Modulator" type of amplifier.  Guess 
>>that puts you in the same boat as the people who built Palomar, Pride and 
>>the rest of the multiband early 70s tube amps, eh?


To me, that is like printing you own money and bragging about how
skilled you are at making money.


>>What?  You honestly believe that an amplifier manufacturered 25+ years 
>>ago, to tolerance and spec of the day, should be equated with someone 
>>commiting the acts of "Funny Money"?


>It takes 1-5 watts of drive, and worse yet has no screen regulation,
>current limiting, or metering.
>
>
> >>>People could say the same of the current amateur amplifiers that don't
> >>>have parasitic suppressors, replace tubes an inordinate amount of
> >>>times, and the such.

I'm not sure anyone who considers a tetrode with no screen
regulation, no feedback, and no screen or grid metering is a top-
notch amplifier would make a good judge of design quality in other
systems.


>>And it has gone around and around about people who design and build 
>>amplifiers that have little or no parasitic suppression and eat tubes, 
>>too.  Nice way to skirt the issue, Tom.  Notice:  Lack of response other 
>>than attacking the person making the original statement.  This is the 
>>common method people use to defend themselves when they are in the wrong.


> >>>The Pride amplifiers have metering jacks on the back.  The front panel
> >>>has nothing but a wattmeter.  If you want metering, you have grid
> >>>current, plate current and screen current metering on the front.  The
> >>>Pride also has a LED Screen current indicator on the front panel.  I
> >>>was leary of this at first, but after studing the schematic, I have
> >>>found that it works quite well.  On the air reports indicate the same.

I guess that would work if you have a light meter, that converts light
from the LED into a screen current reading.

Or, if you use the LED to ensure that you are not pulling negative screen 
current, and use the jack on the back of the amplifier to measure screen 
current, huh?  Notice, once again, the amplifier has the capabilities, but 
Tom chose to ignore those.  Some people don't want 5, 6, 7 or even 8 meters 
on the front of their amplifier.


>I certainly hope not many are used on amateur bands!
>
> >>>Why?  Looks a H3LL of a lot more stable and harmonic free than the DAF
> >>>series of amplifiers, and I am a fan of the DAF design.  Or some of the
> >>> homebrew amps I have heard on the bands.

Because:

1.) Many or most modern exciters "dirty up" when turned way
down. At low levels, you get into cross-over distortion in the
transistors


>>And that was also addressed.  Use the Pride KW-1 which uses an untuned, 
>>swamped grid input.  Will take near 200 watts PEP input and amplify it 5 
>>to 8 times (depending on band)


2.) Most exciters already have overshoot on leading edges, the
problem is aggravated at low output settings. One of my ICOM's
puts out a 170 watt leading edge, and does so whether set at 10
watts or 100 watts.


>>And when the Pride was designed, built, and distributed, that transciever 
>>was on the market?  Not highly likely.


3.) Many hams can't tune a GG triode correctly, let alone a tetrode.
IMD increases more rapidly in a tetrode than a GG triode when
mistuned.

>>Tune by watching screen current.  No wattmeter needed.  Seems to me, that 
>>if you tune by watching the LED brightness (It does have a nice peak to 
>>it), you have done the same thing as when using a screen current meter.


4.) The amp has no mistuning protection.


>>With the 4CX250 series of tubes, that hasn't been an issue..  At least, 
>>not that I have found in the 15 years of operating the Pride amplifer.


5.) The amp uses 4CX250's which are very poor IMD performance
tubes.

>>Poor tubes, but widely used.


Even well designed tetrode amps often can't match modern GG
trodes in SSB performance. Look at measured IMD in tetrode
amps available today compared to GG triodes like 3CX800's.

>>I do agree here.  But, again THIS AMPLIFIER IS 20++ YEARS OLD.


> >>>Actually, Pride was a manufacturer of amplifiers and VFO's, as well as
> >>>frequency counters and the like.  They where owned (all or in part) by
> >>>Palomar Electronics in Escondido, California.  They where also heavily
> >>>influenced by a member of this reflector, and a current day businessman
> >>> that works in the RF field, still.

I'm very sorry to hear that. Please don't ever tell me who that
person was, that made a living selling equipment that allowed
CBers to operate out of band..


>>He made his living selling amplifiers, test equipment and other radio 
>>related accessories.

>>Would you care to peruse the ebay system, or rec.radio.cb and find out how 
>>many of your al-811 amplifiers are in the hands of CBers?  Your in the 
>>same boat, my friend, and people in glass houses don't throw stones.

including on ten meters. I might like
the guy, and wouldn't want his past to color my opinion.


>>You sound like a politician here.


> >>>Bottom line is that the Pride was and still is, one of the best high
> >>>gain, ceramic tube amplifiers EVER produced.  The power output, gain,
> >>>reliability and other things have proven that it is a capable little
> >>>powerhouse, and it was cheap.
>
> >>>Have a nice day Tom.  Maybe your company should investigate the 4CX250
> >>>or 350 series of tubes.  They are darn near idiot proof.

I care less what CBers run inside the CB band, as long as that is
where they and the equipment they use stays.

>>How about an amateur running a DAF design amplifier on 40 meters, 
>>destroying the band around them?  That make you stand up and take notice?


I personally think anyone who helps CBers operate outside the CB
band deserves the maximum penalty of the law. The grief they have
cause amateurs, and other services, is amazing.

>>Then I expect to see your low budget amplifiers pulled from the shelves, 
>>as well as a better method of getting to 11 meters other than "Cut the 
>>green wire".


What a horrible thing they promoted for the sake of a buck.

>>All I can say to that comment is "AL-811 anyone?".


73, Tom W8JI
w8ji@contesting.com

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