Carl, there's nothing at all wrong with posting to both forums in this
instance as the subject matter here about the problematic dearth of current
production Tx tubes is equally pertinent to the interests of both; albeit
perhaps more so to the home brew amp focused ham_amplifiers group.
I'm not sure what you mean by your abstruse and presumably sly derogatory
reference to "CB style QRO amps"...certainly none of the amps I own, or have
built, or modified have technical performance that's less than superlative.
All deploy engineering best practice and would be on par with the finest in
any technical benchmark performance competition; whether on the lab test
bench or on-air assessment.
Some of these high performance amps use Russian mil-spec SSB Tx tubes :-)
Cheers,
Leigh
VK5KLT
("that pompous pinhead" from down under that you refer to Carl Huether) :-)
________________________________________
From: ham_amplifiers@yahoogroups.com [mailto:ham_amplifiers@yahoogroups.com]
On Behalf Of Carl
Sent: Tuesday, 31 July 2012 11:50 PM
To: ham_amplifiers@yahoogroups.com
Cc: amps@contesting.com
Subject: Re: [ham_amplifiers] RE: [Amps] 3CX1500A7/8877 vs el cheapo GS-35B
Leigh, the last I heard is that the AMPS reflector is highly concerned with
the use, reliability, and maintenance of commercial ham amps.
If you just want to talk about your CB style QRO amps with your good buddies
then quit cross posting to both reflectors.
Carl
KM1H
----- Original Message -----
From: Leigh Turner
To: ham_amplifiers@yahoogroups.com
Cc: amps@contesting.com
Sent: Tuesday, July 31, 2012 8:32 AM
Subject: RE: [ham_amplifiers] RE: [Amps] 3CX1500A7/8877 vs el cheapo GS-35B
Hi Carl,
But this is a technical forum for homebrew amplifier builders and
experimenters, so why do you continually make repeated reference to
commercial amplifier companies in your posts?
I agree that commercial amp companies absolutely must use new current
production tubes in their products.
Hams buying expensive $6000 to $10,000 commercial amps and increasingly
expensive new CPI/Eimac tubes in this day and age of economic downturn is
the province and domain of only the well-heeled appliance operator; most
folk are content and prefer to build their own with low-cost surplus parts
from the junk box and hamfests. The cost of the two remaining ham radio Tx
tubes from CPI/Eimac, the 3CX1500A7/8877 and 3CX800A7 are VERY expensive as
evidenced by the list pricing from Alpha spares and authorised CPI dealers.
Many countries outside of the USA are not blessed with a steady stream of
cheap tube pulls from MRI equipment, etc, and must instead improvise with
their tube and RF component sourcing as Bob VK3ZL has mentioned below.
As for the commercial ham amplifier manufacturers, they are stuck between a
rock and a hard place nowadays when it comes to the difficult choice of tube
to launch a new amplifier product with an OEM tube that's assured to be in
production for years to come...there are so few viable options for sourcing
new and warranted Tx tubes. China has become the source of choice for many,
as it is for affordable vacuum caps, vacuum relays, HV xfmrs, RF caps, etc.
As for the European commercial amp manufacturers, they choose the Svetlana
St. Petersburg tubes; whereas the European and aussie ham home brewers tend
to choose the lower cost super-value for money NOS military surplus tubes.
This is the reality today....
Leigh
VK5KLT
________________________________________
From: ham_amplifiers@yahoogroups.com [mailto:ham_amplifiers@yahoogroups.com]
On Behalf Of Carl
Sent: Tuesday, 31 July 2012 2:24 AM
To: ham_amplifiers@yahoogroups.com; amps@contesting.com
Cc: ham_amplifiers@yahoogroups.com
Subject: Re: [ham_amplifiers] RE: [Amps] 3CX1500A7/8877 vs el cheapo GS-35B
I doubt if any respectable amp company will get bit by Russian surplus
again. It may be a great ham tube but unless there is current production its
a loser for an OEM.
I could care less what country a tube comes from. If its reliable and cost
effective its a choice.
Carl
KM1H
----- Original Message -----
From: Leigh Turner
To: amps@contesting.com
Cc: ham_amplifiers@yahoogroups.com
Sent: Monday, July 30, 2012 6:56 AM
Subject: [ham_amplifiers] RE: [Amps] 3CX1500A7/8877 vs el cheapo GS-35B
Good comments here Bob; you've nailed some relevant points here.
The GS35B does indeed need a higher plate voltage / plate load impedance to
achieve parity in efficiency with the 8877; complaining about achieving
circa "only" 55% efficiency and a few extra watts of exciter drive is
splitting hairs; particularly in a GG AB2 SSB linear.
At circa $120 the NOS GS-35B represents the best bang for buck in the 1500W
plate dissipation triode tube class; costing a meagre 10% of that of a new
8877 from CPI/Eimac, or 15% of the cost of an excellent Chinese clone.
Most affordable key RF components for building QRO amps like tubes, vacuum
capacitors, vacuum relays, doorknob capacitors, roller inductors, etc are
all made by non-USA countries. If it weren't for the China tube companies
producing affordable clones of the popular ham-radio tubes and Russian NOS
surplus parts, then readily available tube amplifier components would be a
thing of the past...or the exclusive domain of the wealthy ham.
Cheers,
Leigh
VK5KLT
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Robert Briggs
Sent: Monday, 30 July 2012 5:11 PM
To: amps@contesting.com
Subject: [Amps] 3CX1500A&/8877
Interesting comments re the two types of tubes 8877/GS-35B...I have
built six amplifiers using the GS-35B four on 160 meters and two on 6
meters...I have found that to make the 35B reasonably efficient you need
at least 3500 volts under load...
I live in VK and we don't have the opportunities to buy 8877
pulls...When one considers cost then the GS-35B is way ahead at
$120..The efficiency at 3500 volts is around 55%....You must use a tuned
input to get the best from the tube..Who cares if you need a few more
watts to drive the 35B....Pretty well all transceivers these days have 100
or 200 watts output..
There always seems to be a bias on here by some people regarding
anything that isn't made in the US...Hams are generally looking for the
cheapest way to build amplifiers and other gear and there is a ready
market out there of excellent quality components made in other countries
other than the US...
I spend much of my time custom building amplifiers for VK hams and a
large majority of the components come from suppliers like Dr Alex Gavva
UR4LL...I have never had a faulty tube or capacitor from that source...
Bob..VK3ZL..
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