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Author Topic: Which Amp To Buy?  (Read 23696 times)
W3RSW
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Posts: 606




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« Reply #30 on: May 30, 2014, 11:38:52 AM »

Fun thread.
Not an original thought but we all seem to pick our currently owned or more/easily used amps.
So I'll throw in my pre-owned, "certified" Alpha 89 gotten from rF Concepts via HRO for a little over $3k.  Existing 3cx800a7's yield 1.5 k with very little grid drive as they were spec'd from low grid drive lots.

Agree with others. --yes it's a tank, manually tuned and safety controlled by good "old fashioned" 7400 series chips, etc., no microprocessor or complicated logic trail. R.F. C. keeps just about spare everything for this amp, and even the bulk of those components are available from Mouser, et. al. If company goes out of business.

Back lit dials, full light show from reasonably stepped and calibrated LED's along with the already mentioned heavy duty construction. Mine came with strapping P. Dahl xformer.

And yeah, I do run it at around 1.2 kW pep out using two tone set up. The amp is simply designed to be reasonably efficient at 1.0 to 1.5 or so kW output.

Like many I seem to run it in one band that usually needs it the most, hence other than modest changes, tuning isn't too much an issue.

I do like the Acom rigs though and if going for a new amp would seriously consider one of their 1kw or a little more powerful tube models other than having some misgivings about the complications of having tetrodes and potential problems of Mother Russia's ex satellites manufacturing the amplifier, (especially these days redux) not to mention the additional control and power supply complexity of using tetrodes, heh, heh.

Yeah, I know Ian, Wm3SEK and others like tetrodes but I am simply fascinated with the oxide cathode, focused anode, high mu Eimac series as being the epitome of tube evolution.  Sorry they dropped the 8873, 8875 and hope for continued production of the 8874, 8877 and 3cx800 a7. Won't have to worry in my lifetime or for next generation however, given that amp manufacturers seem have finally put decent operating and safety limit circuitry in new amplifiers along with the exceeding long lifetime of these types of tubes when properly used.

Well OSHA types and legal harpies effectively eliminated the beryllium oxide 8873's ( like We were going to sit and file down to dust the heat sink all day.)  Dentron et. al. Burned Eimac to death over their 8875's with over usage of warranty replacement by hoping hams were smart enough not to full wick every knob and by dumb full scale grid meter design.  So I wish long life to the remaining series of 88's.

My Alpha 89 will definitely be pre-owned by another one of these days at reasonable cost to him and with reasonable reimbursement to me, unless my family has dumpster or yard sale thoughts. Grin
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Rick, W3RSW
KA4WJA
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Posts: 1098




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« Reply #31 on: May 30, 2014, 12:47:50 PM »

Yes, a fun thread!!
And, I seem to recall a "caution" about that Beryllium (?) oxide in the SB-230 construction manual...and we all laughed and said, "the guy who runs too high power using that, might DIE".... Smiley

If we could figure out a way for the new radios to spray Beryllium oxide dust out the front panel if you turn the mic gain too high, it wouldn't take too long before the on-air splatter issues would be reduced... Smiley Smiley




Speaking of tubes...Smiley

I have a Tempo 2002 (running a pair of 8874's on 144mhz) and a Alpha 77sx (running a pair of 8877's on HF).....and I have spare pairs of 8874's (NOS) and 8877's (working FB pulls)...
(and my old SB-221 w/ a pair of almost 35 yr old Eimac 3-500z's)
All still working fine...

I have no worries myself....but some have asked me...
So, here's my question...

We know that there are sources (China) for 8877's, etc. and plenty of NOS Eimac 8877's...
But, isn't Eimac still manufacturing 8877's / 3CX1500's?  and 3CPX-1500's?
....I am simply fascinated with the oxide cathode, focused anode, high mu Eimac series as being the epitome of tube evolution.  Sorry they dropped the 8873, 8875 and hope for continued production of the 8874, 8877 and 3cx800 a7. Won't have to worry in my lifetime or for next generation however, given that amp manufacturers seem have finally put decent operating and safety limit circuitry in new amplifiers along with the exceeding long lifetime of these types of tubes when properly used.
The reason I ask this directly is just last month I had a conversation with an MRI service technician (who had no clue about ham radio), and he said he still services MRI's, etc. "with tubes in 'em"....and said all he does, is "un-plug everything...remove the old tube, put in the new one....and hook everything back up....and then do a re-cal"...
I described the 8877 and he said "yep, that sounds like it" (although, I assume he was using the 3CPX-1500, pulse-rated tube)
When I asked him about the source of the tubes, he said he didn't know....but remarked that his boss "orders a case or two every month or so"....
I have no way of knowing whether any/all of what he said was factual....we were all just sitting waiting on a delayed flight, killing time talking....

So, what is the straight dope here...
Is Eimac still making 3CPX-1500's??  and 8877/3CX-1500's??
Anyone know for sure?



73,

John, KA4WJA
« Last Edit: May 30, 2014, 12:51:29 PM by KA4WJA » Logged
KF4R
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Posts: 5




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« Reply #32 on: May 30, 2014, 01:35:20 PM »

Just a FYI, Ameritron has now announced ALS- 1306 at Dayton, to be available next month. The same amp as the 1300 but with 6 meters.
Bob KF4R
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W3RSW
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Posts: 606




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« Reply #33 on: May 30, 2014, 04:16:06 PM »

John,
Yep, still making them.  I said "hope they continue" for those three. It's the 8873 and 8875 that they quit making.  Also meant to say the spacer (heat conductive but HV insulated, amazing material) between the tube and heat sink is the piece that contained the BeO2 (or whatever the valence combo is.). The 8873 is fine, just like all the others, silver plated, but with a finless cylindrical anode, as you know.

You can buy the three series, 8877, etc. still made from Richardson Electronics, CPI's favored outlet. ...but h'ain't cheap no mo.
$890 per 3cx800a7 last quote I got with a month or so wait until production run is made.

Ought to sell them by the Troy ounce.  Hey, not to far out of the realm due to the silver and gold in them, not to mention the extremely close tolerances and very small dimensions of the components, especially the grid to cathode spacing with the grid wires critically spaced between cathode emission bands. The better centered, the lower the grid current requirements since theoretically the grids only provide a voltage field to direct and control the electron stream on its way to a much farther away spaced anode.  If spacing is perfectly equidistant then the current required is small. Gain is greatly determined by the ratio of the grid to anode spacing over the grid to cathode spacing.  With a gain of 200, that's quite an achievement.

Can't imagine how Eimac produced them so relatively cheaply in the 70,s, for Hams no less. We sure killed the goose on that one.  Denny should've been lynched from Eimac's perspective. We had a great ride from our perspective, but da train was comin' down de tracks.

I'm enjoying them while I can.

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Rick, W3RSW
W8JX
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Posts: 13268




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« Reply #34 on: May 31, 2014, 05:31:58 AM »

The realty is that is does not cost anywhere near 900 to make a 3cx800. It's a captive market with one supplier controlling most of it and they squeeze out as much profit as possible.
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--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
W3RSW
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Posts: 606




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« Reply #35 on: May 31, 2014, 06:25:25 AM »

"Everybody knows that."
Left you some room. Grin

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Rick, W3RSW
K8KVN
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Posts: 68




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« Reply #36 on: May 31, 2014, 07:33:03 PM »

I'm surprised no one has mentioned QRO Tech made right here in Ohio.

You know, those look like nice amps.
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KA5PIU
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Posts: 446




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« Reply #37 on: June 01, 2014, 09:07:21 PM »

Hello.

What I look for are old marine radio amps.
They are commercial grade and FCC type accepted, and frequently CHEAP!
Most will run on 100 to 260 volts, with something like 30 taps on the transformer.
And the transformer is very forgiving, and well protected.
The tubes are run well within the ratings, well within the ratings.
For example, the RCA Radiofone super10 has a 4cx5000 tube in it.
At 1.5 kW, the thing will last forever!
Oh, and did I say A 4cx5000?
No, it has 2!
There are switches to drive 1 or 2 tubes, and you can pick witch one.
I got it for scrap value.
It will happily dim your house lights on 220.
True, it is the size of a gun safe, but it does work.
Quiet? not with the normal fans, but at 1.5 kW, you can slow things down, way down.
The power supply is normally always on, and can provide a host of voltages for your radio.
But, that is but another avenue.
Whatever the case, look at what has the highest value for you.
In my case, $100 for an old marine box was what I went for.
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W3RSW
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Posts: 606




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« Reply #38 on: June 02, 2014, 05:39:03 AM »

Yeah, fire that baby up on 500kHz ! Just don't send SOS unless the FCC's at the door.  Grin
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Rick, W3RSW
KA5PIU
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Posts: 446




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« Reply #39 on: June 02, 2014, 05:47:29 AM »

Yeah, fire that baby up on 500kHz ! Just don't send SOS unless the FCC's at the door.  Grin


That was my first thought, test the auto alarm sender.
There is this fire alarm like pull station. Lips sealed
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N3QE
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Posts: 5593




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« Reply #40 on: June 02, 2014, 06:21:20 AM »

For example, the RCA Radiofone super10 has a 4cx5000 tube in it.
At 1.5 kW, the thing will last forever!
Oh, and did I say A 4cx5000?
No, it has 2!

Do you have a picture? All the "RCA Radiophone" trademarked units I remember seeing were truly crufty CB sets marketed for marine use. They were crufty beyond belief even compared to other early tube CB sets, the microphone I remember coming with the set was a perfectly square box.

What you are describing sounds more like the "RCA Ampliphase" which I know were used shipboard for SW broadcasting.

Tim.
« Last Edit: June 02, 2014, 06:36:53 AM by N3QE » Logged
KA5PIU
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Posts: 446




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« Reply #41 on: June 02, 2014, 06:30:47 AM »

For example, the RCA Radiofone super10 has a 4cx5000 tube in it.
At 1.5 kW, the thing will last forever!
Oh, and did I say A 4cx5000?
No, it has 2!

Do you have a picture? All the "RCA Radiophone" units I remember seeing were truly crufty CB sets marketed for marine use. They were crufty beyond belief even compared to other early tube CB sets, the microphone I remember coming with the set was a perfectly square box.

What you are describing sounds more like the "RCA Ampliphase" which I know were used shipboard for SW broadcasting.

Tim.

RCA used "Carfone" for its mobile applications.
And, the marine model was "Radiofone".
This has nothing to do with what is inside, it is just a marketing name.
http://vintageadsandbooks.com/radio-corporation-america-1962-super-carphone-150-2-way-vintage-ad-y107.html
As you can see, not an average RCA carfone, but a Super Carfone 150!
And, why pictures? there is a youtube of it.
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N3QE
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« Reply #42 on: June 02, 2014, 06:42:48 AM »

As you can see, not an average RCA carfone, but a Super Carfone 150!

RCA Carfone 150 was a decent high-band mobile FM radio of its era. The ones I recall used 6146's in the finals and a lot were converted to mobile or fixed ham use by the 70's.
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