I wrote:
> The 4CX250 amp looks like a CB amplifier Skipp.
Skip must have replied:
> >>>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.
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.
4CX250's are poor enough for IMD when operated correctly.
> >>>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. They cared less about linearity. They also
sold components and devices that allowed CBers to operate on
frequencies outside the CB band.
To me, that is like printing you own money and bragging about how
skilled you are at making 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.
> >>>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.
> 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
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.
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.
4.) The amp has no mistuning protection.
5.) The amp uses 4CX250's which are very poor IMD performance
tubes.
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.
> >>>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..including on ten meters. I might like
the guy, and wouldn't want his past to color my opinion.
> >>>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.
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.
What a horrible thing they promoted for the sake of a buck.
73, Tom W8JI
w8ji@contesting.com
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|