Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1] 2 Next   Go Down
  Print  
Author Topic: 2e26 tube PA  (Read 8927 times)
9A5BDP
Member

Posts: 110




Ignore
« on: November 13, 2012, 12:00:51 PM »

Hi there..

I have one Sylvania 2e26 tube that I want to integrate in my homebrew qrp all tube ssb transceiver project. TRX will be dualband 40/20m. Do any of you solder smoke lovers have some sudgestions regarding building such type of PA?

Available anode voltage will be around 250-300Vdc.
What is best operating point for that tube regarding low generation of harmonics, output power is not a issue if it is in qrp range 5..to max 10W.

Thanx in advance for advice..

73!
Logged
WB6BYU
Member

Posts: 13339




Ignore
« Reply #1 on: November 13, 2012, 12:28:56 PM »

It's rather like a small version of the 6146, and should use similar circuits.

There was a transmitter using one at 10 watts in the RSGB Radio Communications
Handbook
that was designed for NFD.  It actually required some design work to
keep the DC input below the 10 watt limit for that event.  That might be a good
starting point if you can find a copy of the handbook.
Logged
KB1GMX
Member

Posts: 782




Ignore
« Reply #2 on: November 13, 2012, 02:11:27 PM »

250-300V will limit you to _maybe_ 10W CW,  likely less.  For that tube its capabilities
were more around 450V and 20-23W.   Forcertain at 300V it's not going to be strained.
You will also have to figure out what the screen voltage ill need to be running that low.

For 300V you might try a 6AQ5 or 5763 for about 5-7W.

Find used copies of the Radio Amateurs Hanbook in the 1957 to 1968 range for
tube based transmitters.


Allison
Logged
9A5BDP
Member

Posts: 110




Ignore
« Reply #3 on: November 15, 2012, 12:40:21 PM »

My first idea was to use ordinary 807 tube but for sake of power consumption and qrp rules in my mind I finaly adopted idea with 2e26 tube on the end. One more reason to use this tube is that this tube is truly RF power amplifing tube no AF mimic RF operation (like EL84...).
Did any comercial maded HF rig (CB or ham) with 2e26 tubes ever worked with low plate voltage? I ask this because this tube is not so popular uk Europe ( or even replacement tube do not exist).
Beside of original idea for building truly tube qrp ssb rig I want to build at the end of this project one vibrator (choper) or even beter rotary-dynamo povered rig with lead acid batteries as an source of electricity.

73! and thanx for help
Logged
G3RZP
Member

Posts: 4721




Ignore
« Reply #4 on: November 15, 2012, 01:32:44 PM »

How many 2E26 do you have? If you need extra ones, contact me at peter.chadwick at ties.itu.int

The 'at' becomes '@' of course.
Logged
KA5N
Member

Posts: 4380




Ignore
« Reply #5 on: November 15, 2012, 03:32:39 PM »

There was a design for a single band AM transmitter with a 2E26 final written up in QST magazine back
in the late 1950's.  You selected the band you wanted.  It was widely copied and used.
A number of hams (including me) in Austin, Texas built copies for 10 meters and used
them on transmitter hunts (now called Fox Hunts) every saturday for several years.
Running 10 watts, they worked as well as any commerical mobile transmitter.  Of course the receiver was usually a commercial receiver , or a convertor for the auto BC set.  I had a homebrew receiver using germanium transistors.  
We had a blast.

Allen KA5N
Logged
WB6BYU
Member

Posts: 13339




Ignore
« Reply #6 on: November 15, 2012, 09:57:57 PM »

I found the information on the "WIRRAL Six-Ten NFD Transmitter" in the 5th Edition
(1982) of the Radio Communication Handbook.  It ran 250V on the anode and
screen to limit the tube to 10W DC (perhaps about 6W output.)  That's not to say
that is the optimum level - it might be better designed for 10W RF output running,
say, 300 to 350V on the anode, but it will give you a starting point at any rate.


Meanwhile, I found the table of linear amplifier data in my 1969 ARRL Handbook
which suggests running it at 500V anode and 200V screen with an idle current of 9mA.
Maximum signal DC plate current 45mA, about -25V bias on the grid, and maximum of
10mA screen current.  This gives a useful output power of 15W in SSB service.
« Last Edit: November 15, 2012, 10:20:20 PM by WB6BYU » Logged
WB6DGN
Member

Posts: 619




Ignore
« Reply #7 on: November 15, 2012, 11:22:35 PM »

The 2E26(A) was frequently used as the transmitter driver in commercial tube type two way radios.  I never liked the tube very much.  Its typical life expectancy was, at best, about half that of the 6146 that usually followed it and the 6146 was working a lot harder.  Often the 2E26 would be replaced two or three times before the final needed replacing.  This was pretty consistent regardless of the make or band of the transmitter (many manufacturers used that combo. at the time).  So, if the tube doesn't seem to last as long as it should, its probably not the circuit's fault.
Tom
Logged
9A5BDP
Member

Posts: 110




Ignore
« Reply #8 on: November 16, 2012, 12:07:23 PM »

Hi..

One thing that I want to say is that homebrewing comuniti are active and supportive one..thanx guys

Lets go from the end..life of 2e26 tubes are short? Please tell me more..did tube with short life powered from the PA HV pover supply? Maybe is problem with overdisipated anode...

10W dc is little bit low but who knows maybe will be higher? I think that is possibile to push my PSU otput to 300V after some recalculating resistors and capacitor enlargement.

I am very interested to find some data regarding pi (collins) anode network for antenna tuning purpose. If any of you have some practical data (published somwhere or not) or even actual buildin article please send it to me, I will be very happy with that..

My email is pozarikus #at# gmail dot com

Keep the soldering iron hot Smiley

73!
Logged
N3QE
Member

Posts: 2288




Ignore
« Reply #9 on: November 16, 2012, 02:45:01 PM »

The 2E26(A) was frequently used as the transmitter driver in commercial tube type two way radios.  I never liked the tube very much.  Its typical life expectancy was, at best, about half that of the 6146 that usually followed it and the 6146 was working a lot harder.  Often the 2E26 would be replaced two or three times before the final needed replacing.  This was pretty consistent regardless of the make or band of the transmitter (many manufacturers used that combo. at the time).  So, if the tube doesn't seem to last as long as it should, its probably not the circuit's fault.

In my experience with 6146 variants in ham equipment, the driver tube (6CL6 in Heathkits, 12BY7A in Kenwoods, etc.) always seemed to have a rather short life too. I would guess, it's biased class A?

When 6CL6's are used in CW transmitters chains (wonderful doublers/triplers) they last forever. Of course that's biased deep class C.

And when 6CL6's are used in vintage VFO's they aren't dissipating much power at all so not a fair comparison.

Tim.
Logged
WB6BYU
Member

Posts: 13339




Ignore
« Reply #10 on: November 16, 2012, 09:18:45 PM »

Quote from: 9A5BDP

...I am very interested to find some data regarding pi (collins) anode network for antenna tuning purpose...




This is fairly easily calculated by the formulas in the standard handbooks.

For a tetrode class AB linear amplifier the plate load resistance (RL) is given by
2 * ( Va - Va_min) / I_peak

Va is the anode DC voltage, and Va_min is the minimum voltage on peaks.  Usually
this would be a bit less than the screen voltage for good performance.

I_peak is the peak anode current, which is 1.4 times the average (not to be
confused with the reading on voice peaks, of course.)

So for the recommended conditions given above (500V anode, 200V screen,
maximum current 45mA) we might use 185V as the minimum anode voltage,
so the plate load impedance is (500 - 185) / (0.045 * 1.4) = 5K ohms.

Then the reactances of the pi-network components are calculated using
some standard formulas that are too awkward to try to type here.  But
the same copy of the RSGB Radio Communications Handbook has
a list of reactances for a Q of 12 for various load impedances, so it looks
like:

XC1 = 417 ohms
XL = 437 ohms
XC2 = 75 ohms

should get you pretty close.

[Disclaimer:  it wouldn't hurt to have someone who is more familiar with
tubes check my calculations here.]

With lower plate voltage you may need to use two tubes in parallel to get
sufficient output power.

Logged
9A5BDP
Member

Posts: 110




Ignore
« Reply #11 on: November 17, 2012, 02:03:50 PM »

Thanx for math that you provided. I finaly got one free day from work so I will make some calculations and graph exercise on tube datasheets.
How stabile must be screen voltage for PA stage? I saw somewhere that in past is some VR tubes used for that purpose (also for suplying stabile voltage to VFO).

Logged
WB6DGN
Member

Posts: 619




Ignore
« Reply #12 on: November 17, 2012, 06:24:06 PM »

Quote
Lets go from the end..life of 2e26 tubes are short? Please tell me more..did tube with short life powered from the PA HV pover supply? Maybe is problem with overdisipated anode...

Wow!  That's taxing my memory just a bit; its over 50 years ago.  As I recall, the drivers were biased Class C as it is a CW type (FM) transmitter.  The plate supply of the 2E26 was generally fed from the mid voltage supply and was, typically, in the range of 250 to 300 volts (don't ask the current, I'd only be guessing!) .  Normally the high voltage supply fed only the plate(s) and screen(s) of the final PA amplifier(s).  The single 2E26 would feed one or two 6146 tubes or, in some cases, a single 5894 (or variant) for the higher power version.
That configuration seemed to be, at the time, almost an industry standard as General Electric, Motorola and Link all used it in their VHF Lo and High band radios at one time or another.  In the older Link HiBand radio, that single 2E26 even fed an 829B for a (supposed) 50 watt output.  As expected, that rarely happened, though.
Unfortunately, that's about all that I can recall.  Sure wish I'd kept some of that old equipment.  In my experience, that was the fun stuff to work on unlike the current breed of "throw-away" gear.
One final comment.  Over the years, various tubes would gain a reputation as to their life expectancy.  The 6146 and, especially, the 5894 were quite highly regarded but the 2E26, 829B and 2C39 were some of the ones regarded as "losers".  Obviously, the design of the circuits that those tubes operated into were equally or even more significant in that appraisal, but the tube seemed to be the item that garnered all the praise or condemnation as the case may be.
Tom
Logged
KQ6Q
Member

Posts: 988




Ignore
« Reply #13 on: November 22, 2012, 07:51:35 PM »

The Gonset Communicators of the 50's used a 2E26 final on 6m and 2m. They weren't pushed very hard, the units had a power supply that worked on AC or 12V DC with a Vibrator.
Logged
KD0REQ
Member

Posts: 971




Ignore
« Reply #14 on: November 23, 2012, 11:24:11 AM »

2E26s weren't a bad tube, but they ran quite hot in that envelope, and if you hit a pretty good bump, as driver in things like Motorola business band sets locked in the trunk, they would short.  yes, short life.  I always though the interns designed that one while the paid tube engineers were doing the 6146 family.
Logged
Pages: [1] 2 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!