Date: Sun, 26 Dec 2010 22:06:08 -0600
From: "Jeff Blaine" <keepwalking188@yahoo.com>
Subject: Re: [Amps] 572B AMP PLANS
To: "Hsu" <hsu4qro@gmail.com>, <amps@contesting.com>
Message-ID: <0FB28AAD039F4D3B93D503C58EB78222@8710w>
Content-Type: text/plain; charset="iso-8859-1"
Hsu,
The 813 looks nice. But I am very impressed with the GI7B. I really work that
tube hard - both in the RTTY contesting and on the
bench (one time, I ran the pair for 20 minutes key down at rated power) for
simple endurance test on the amp. Finally had to stop
out of worry the DL was going to explode. hi hi.
If I am needing to use glass, I think I prefer the 3500Z if you have high
enough plate voltage available. I'm not sure what the
3-500z looks like at 2500V.
Good luck!
73, Jeff AC?C
www.ac0c.com
## I have 4 x Drake L4B's.... and the no load is 2650 vdc on RX... and with
800ma cxr... the B+ drops down to 2490 vd. Since
I added a 50 ohm-50W WW glitch R in series with the B+, I lose another 40 vdc
across the glitch R. The pair of 3-500Z's just
last a Looong time. IMD is superb.
## IF you hb a linear, and are doing it to.... 'save money', I usually find
the savings are not there. I will usually end up with vac input
and output relay's.. and vac relay for bias, vac caps, and nice metal work.
I end up with a better overall product that does what I want,
and am happy with it. IMO, after building everything from pair's of 813's
to 4 x 572B's... to 4 x 811A's to single and dual 4-1000's, single 3-500Z's
etc, my conclusion after doing this since 1972 is that it's just as easy to
build a big amp as a small one.
## building a 4 x 572B linear these days is plane nuts. Add up the cost of
[a] 4 x tubes [b] 4 x sockets [c] 4 x anode connector's, [d] 4 x suppressors,
etc, and you may as well use a single or dual GS35B...or a single YC-156.
A YC-156 goes for $200-$300.... and No socket required, and NO suppressor
required.
Just whack a hole in the chassis..and bolt it it. Easy to drive [17w = 1.5
kw.... 150w=7.5 kw 200w = 10 kw... it makes for a versatile tube. Linearity
is superb,
and it laughs at 100% duty cycle modes.
## a few fellow's here in town back in the mid 70's had 30L1 amps. They
would ALL burn holes right through the 811A anodes. Several more had new
SB-200's.
The fellow's with the SB-200's would be buying 572b's every 2 x years. In
the long term.... you save nothing using these 'toy tubes' . And none of em
were used on
RTTY/FM or any 100% duty cycle data node..... they just won't last at all.
## The bandswitch's and tank circuits in most of these amps are a poor joke as
is. Beware, the current ratings for multi-tech switch's are for 60hz..and
NOT RF freqs,
esp the higher bands. If you want a heavy duty bandswitch, either use a
bigger switch, and /or parallel 2 or more wafer's. If you parallel mutiple
wafers, it has to be
done correctly. Tank coi taps go to wafer #1..and the output of the assy is
on wafer #2. That way the RF current will divide equally between the 2 x
wafers.
Switch contacts and tank coils, etc... on 29.7 mhz will only handle 1/4
what they will handle on 1.8 mhz. [29.7 /1.8= 16.5 sq rt of 16.5 = 4.1 ]
You can use the same
formulae between any 2 x ham bands.
later... Jim VE7RF
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|