[Amps] i was reading on here

Wed Dec 7 22:53:03 EST 2016

Down At Dayton this year Palstar came out with LDMOS dual BLF578 amp they were waiting FCC acceptance of it.
N9IWW

-----Original Message-----
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Sent: Wednesday, December 7, 2016 10:32 PM
To: amps at contesting.com
Subject: Amps Digest, Vol 168, Issue 37

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Today's Topics:

   1. Re: SS amps and auto-tune. Is it even necessary? (Leigh Turner)
   2. Re: Pulls? (RAY FRIESS)
   3. Re: Pulls? (Jeff AC0C)
   4. Re: SS amps and auto-tune. Is it even necessary? (qrv at kd4e.com)
   5. Re: SS amps and auto-tune. Is it even necessary? (Leigh Turner)

----------------------------------------------------------------------

Message: 1
Date: Thu, 8 Dec 2016 11:11:50 +1030
From: "Leigh Turner" <invertech at frontierisp.net.au>
To: "'AMPS'" <amps at contesting.com>
Cc: <leigh.turner at ieee.org>
Subject: Re: [Amps] SS amps and auto-tune. Is it even necessary?
Message-ID: <9876C98E73CE419A91C28B9E4D9EF638 at Invertech>
Content-Type: text/plain;	charset="iso-8859-1"

I agree with the spot-on-the-mark sentiment summary expressed below. 

A very fine QRO legal-limit S.S. amp with decent IMD specs can be homebrewed by the savvy hands-on experimentally inclined (not many of us left?) amongst the ham radio fraternity.

Jim is right about the complexity and cost of "everything else" particularly implementing the requisite diplexer based harmonic terminating auto-switched HF multi-band LPF capable of handling up to 2.5 kW under potentially high VSWR conditions. In terms of dollars per Watt the modern LDMOS FET active devices per se are very cheap.

If one is designing a monoband S.S. QRO amp then some complexity and associated cost savings can be had.

Adequate heatsinking and dealing with the demanding thermal issues (the Achilles heel of LDMOS and MOSFET RF power devices) and efficient heat extraction is the other principal challenge. This has a big impact on semiconductor MTBF.

It can all be done; but not cheaply :-(

Cheap, reliable / good MTBF, no time limit QRO, low IMD, are mutually exclusive design goals. The pragmatist has to take their pick which parameters they value most; choosing them all is an expensive exercise even for the resourceful homebrewer; commercially we are talking over $10K ++ for a high-end S.S. amplifier. 

Leigh
VK5KLT

-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Catherine James
Sent: Thursday, 8 December 2016 3:45 AM
To: amps at contesting.com; Jim Thomson
Subject: Re: [Amps] SS amps and auto-tune. Is it even necessary?

On Wed, 12/7/16, Jim Thomson <jim.thom at telus.net> wrote:

 ##? The low cost of the LDMOS is the least of the issues involved.???Its everything else that?s involved with the SS amp. 
 ##  Jim???VE7RF

Yep, that's it in two sentences.  That's why I can't get excited about cheap SS finals until I see a complete, commercialized SS amp using them, said amp to be affordable and reliable. Right now they are for experimenters.

73,
Cathy
N5WVR
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------------------------------

Message: 2
Date: Thu, 8 Dec 2016 00:44:18 +0000
From: RAY FRIESS <rayfrijr at msn.com>
To: "amps at contesting.com" <amps at contesting.com>
Subject: Re: [Amps] Pulls?
Message-ID:
	<DM5PR01MB2746FEAD9434342366587049CA840 at DM5PR01MB2746.prod.exchangelabs.com>

Content-Type: text/plain; charset="iso-8859-1"

Speaking of pulls ..   I was a broadcast engineer about 35 years ago and we would regularly pull tubes when they were down to about 90% of their rated readings in the transmitter.  We would throw them out and replace them with new ones, until I started saving the pulls and taking them home.

As a result, I have about a dozen 4-125 and 4-250 tubes which were primarily used in the modulator section of our 5 KW transmitter.   They have been in storage at my home ever since and are still, for all intents and purposes, brand new.  They look brand new even, considering that they were replaced when they were at 85 to 90% efficiency.  I kept them thinking they would work great for ham linears for anyone who was building a linear.

If there is any interest, let me know.....   Most of them I rewrapped in their original padding and put back in their original boxes and stored in a safe place.

________________________________
From: Amps <amps-bounces at contesting.com> on behalf of Catherine James <catherine.james at att.net>
Sent: Wednesday, December 7, 2016 9:50 AM
To: amps at contesting.com
Subject: Re: [Amps] Pulls?

And how do you find these deals when broadcast stations with older transmitters do a pull?

I hear a lot of discussion around how great pulls are as an affordable source of good tubes, but it is always vague and never tells us how we can get in on the fun.  Is this one of those "you have to know somebody" situations?

73,
Cathy
N5WVR

--------------------------------------------
On Wed, 12/7/16, Fuqua, Bill L <wlfuqu00 at uky.edu> wrote:

 Subject: RE: [Amps] Pulls?
 To: "Catherine James" <catherine.james at att.net>
 Date: Wednesday, December 7, 2016, 4:25 AM

   Most pulls today are from broadcast stations using older transmitters. Also, from SK estates.
 73
 Bill wa4lav
 ________________________________________
 From:
 Amps [amps-bounces at contesting.com]
 on behalf of Catherine James [catherine.james at att.net]
 Sent: Tuesday, December 06, 2016 11:13 PM
 To: Amps Group
 Subject: [Amps]
 Pulls?

 Where do you guys get your tube pulls?

 I see many, many mentions of pulls from medical or other devices,  but I have never seen these offered. Have they dried up? Or  do they all go up on eBay at crazy prices?

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------------------------------

Message: 3
Date: Wed, 7 Dec 2016 20:31:11 -0600
From: "Jeff AC0C" <keepwalking188 at ac0c.com>
To: <amps at contesting.com>
Subject: Re: [Amps] Pulls?
Message-ID: <A9A474FCFCA34787A1D21DD0A06D9917 at w520>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
	reply-type=original

I don't think PULL has a generic meaning.  How can you generalize with so many different tubes in so many different applications and with different thresholds for determining when to swap?  You can find stories on both ends - success and fail.

My only experience with pulls is with some YC156 that K5AND Dick sent to me to test in my amp as he was thinking about selling those.  I have a new
(NOS) tube here for reference and 3 out out of the 4 pulls exhibited exactly the same power output with exactly the same Ig as the new tube.  I don't know how much "life" would be left in them from a ham amp standpoint but they were 100% as far as I could determine.  The 4th had some sort of internal short.  My experience with the YC156 pulls is pretty good based on this single data point.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message-----
From: RAY FRIESS
Sent: Wednesday, December 07, 2016 6:44 PM
To: amps at contesting.com
Subject: Re: [Amps] Pulls?

Speaking of pulls ..   I was a broadcast engineer about 35 years ago and we 
would regularly pull tubes when they were down to about 90% of their rated readings in the transmitter.  We would throw them out and replace them with new ones, until I started saving the pulls and taking them home.

As a result, I have about a dozen 4-125 and 4-250 tubes which were primarily 
used in the modulator section of our 5 KW transmitter.   They have been in 
storage at my home ever since and are still, for all intents and purposes, brand new.  They look brand new even, considering that they were replaced when they were at 85 to 90% efficiency.  I kept them thinking they would work great for ham linears for anyone who was building a linear.

If there is any interest, let me know.....   Most of them I rewrapped in 
their original padding and put back in their original boxes and stored in a safe place.

________________________________
From: Amps <amps-bounces at contesting.com> on behalf of Catherine James 
<catherine.james at att.net>
Sent: Wednesday, December 7, 2016 9:50 AM
To: amps at contesting.com
Subject: Re: [Amps] Pulls?

And how do you find these deals when broadcast stations with older 
transmitters do a pull?

I hear a lot of discussion around how great pulls are as an affordable 
source of good tubes, but it is always vague and never tells us how we can 
get in on the fun.  Is this one of those "you have to know somebody" 
situations?

73,
Cathy
N5WVR

--------------------------------------------
On Wed, 12/7/16, Fuqua, Bill L <wlfuqu00 at uky.edu> wrote:

Subject: RE: [Amps] Pulls?
To: "Catherine James" <catherine.james at att.net>
Date: Wednesday, December 7, 2016, 4:25 AM

   Most pulls today are from broadcast stations using older transmitters. 
Also, from SK estates.
73
Bill wa4lav
________________________________________
From:
Amps [amps-bounces at contesting.com]
on behalf of Catherine James [catherine.james at att.net]
Sent: Tuesday, December 06, 2016 11:13 PM
To: Amps Group
Subject: [Amps]
Pulls?

Where do you guys get your tube pulls?

I see many, many mentions of pulls from medical or other devices,
but I have never seen these offered. Have they dried up? Or
do they all go up on eBay at crazy prices?

_______________________________________________
Amps mailing list
Amps at contesting.com
http://lists.contesting.com/mailman/listinfo/amps
Amps Reflector - Contesting.com Ham Radio Mailing 
Lists<http://lists.contesting.com/mailman/listinfo/amps>
lists.contesting.com
Welcome to the Amplifier mailing list! This list is intended for the 
exchange of information on HAM RADIO Amplifiers related topics ONLY. Our 
goal is to keep ...

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------------------------------

Message: 4
Date: Wed, 7 Dec 2016 22:14:24 -0500
From: "qrv at kd4e.com" <qrv at kd4e.com>
To: 'AMPS' <amps at contesting.com>
Subject: Re: [Amps] SS amps and auto-tune. Is it even necessary?
Message-ID: <5848D010.5010901 at kd4e.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I respectfully disagree - unless one demands only a
full-legal amp.

SB-200's (and many similar power-level amps) sold like
crazy in the past & are still being resold daily.

A 600w SS amp is not expensive to build - a 1.5KW is.

Might we divide the discussion that way, please?

It would be helpful to direct some attention to the
positive opportunities via new devices to provide Hams
with affordable entry-level 160-10m SS amps.

WDYT?

Thanks - David KD4E

> It can all be done; but not cheaply :-(
>
> Leigh VK5KLT

------------------------------

Message: 5
Date: Thu, 8 Dec 2016 14:01:30 +1030
From: "Leigh Turner" <invertech at frontierisp.net.au>
To: "'AMPS'" <amps at contesting.com>
Subject: Re: [Amps] SS amps and auto-tune. Is it even necessary?
Message-ID: <1902DA76358F4F0EBC154A12B4209A7A at Invertech>
Content-Type: text/plain;	charset="us-ascii"

Yes, fully agree David; if we bifurcate the S.S. amp design and build
endeavour to less than 600 Watt PEP, and no time limit 1.5 kW, then it's an
entirely different ballgame whereby things become very doable at a price
entry-level hams can afford.

Leigh
VK5KLT

-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of qrv at kd4e.com
Sent: Thursday, 8 December 2016 1:44 PM
To: 'AMPS'
Subject: Re: [Amps] SS amps and auto-tune. Is it even necessary?