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: Prev 1 ... 6 7 8 9 10 [11] 12 13 Next   Go Down
  Print  
Author Topic: Basic L/R VHF Parasitic Oscillation Suppressor Design  (Read 28403 times)
W8JI
Member

Posts: 9304


WWW

Ignore
« Reply #150 on: October 20, 2011, 03:32:53 AM »

AG6K says:
Quote
  I use Matshitas because they can dissipate 12w for 1-hour in still air, and they can light cigars.


What is the part number of your special resistor , Rich?

Who is Matshitas?
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #151 on: October 20, 2011, 04:53:10 AM »

AG6K says:
Quote
  I use Matshitas because they can dissipate 12w for 1-hour in still air, and they can light cigars.


What is the part number of your special resistor , Rich?

Who is Matshitas?

  They are not "special" they are their standard 3W-rated line of MF and MOF resistors. .   Matsushita Electric is a Japanese company.  Their brand name in the U.S. is Panasonic.  IME they make under-rated electronic components.
cheers Tom R.
Rich
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #152 on: October 20, 2011, 05:07:45 AM »

Tom:  I normally wind such coils over a piece of correct size wood dowel rod.  This is what I'm going to suggest to the operator in Cyprus. 


That's the best method.


Quote
If I was to construct this replacement suppressor I would wind the two 100 ohm resistors in parallel....side by side and then wind the coil on dowel rod and then solder it to the parallel resistor combination which, looking from the end, would form a triangle.  Do you find this an acceptable method?(The original suppressor is a 47 ohm 2W resistor with 3.5t of wire over the resistor.)

This isn't that critical so long as there is enough inductance. The amp will either oscillate in a test, or it won't.

  IME push-pull* VHF oscillations are reliable, but push-push VHF oscillations like to surprise you.
*  push-pull VHF osc. occurs only in multi-tube amps,  makes no bang,  the anodes get orange-hot during the event, and unlike push-push osc. they do not damage tubes and other amp parts.   

Quote
He has to be careful though up on ten meters because the SB200, with loading control nearly meshed, can oscillate up on ten meters!

  now there's a new one!

Quote
Since the OY resistors are 100 ohm each his parallel combination will be 50 ohms at 4W.  Since the resistors are 10% tolerance, he'll probably be OK.

I'll suggest to him to start out with 5t of wire for the coil.  Do you suggest any correction(s) here?

That should be good.
[/quote]
Logged
W8JI
Member

Posts: 9304


WWW

Ignore
« Reply #153 on: October 20, 2011, 05:51:59 AM »

AG6K says:
  I use Matshitas because they can dissipate 12w for 1-hour in still air, and they can light cigars.


What is the part number of your special resistor , Rich?

Who is Matshitas?

Rich then said:
Quote
  They are not "special" they are their standard 3W-rated line of MF and MOF resistors. .   Matsushita Electric is a Japanese company.  Their brand name in the U.S. is Panasonic.  IME they make under-rated electronic components.
cheers Tom R.
Rich

So they are really not matshitas, but either Matsushita or Panasonic.
Rich also said:
Quote
  "small" ? they occupy about 50% more space than OYs. Will OYs dissipate 12w for 1-hour in still air and stay within ±10%?
Rich, ag6k

The Panasonic 3 watt
http://industrial.panasonic.com/www-data/pdf/AOA0000/AOA0000CE18.pdf
is .271 inches by .591 inches

The OY resistor is .276 inches by .886 inches.

How does the Panasonic occupy 50% more space than the OY resistor?Huh What type of space or math is this?

Also, the resistors that came in your kit for a 3-500Z amplfier are .235 x .65 inches. That kit raises the VHF Q of the anode system, and increases the SRF of the anode system. How is .235 x .65 larger than .276 x .886 inches?
 
73 Tom
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #154 on: October 20, 2011, 06:36:57 AM »

AG6K says:
  I use Matshitas because they can dissipate 12w for 1-hour in still air, and they can light cigars.


What is the part number of your special resistor , Rich?

Who is Matshitas?

Rich then said:
Quote
  They are not "special" they are their standard 3W-rated line of MF and MOF resistors. .   Matsushita Electric is a Japanese company.  Their brand name in the U.S. is Panasonic.  IME they make under-rated electronic components.
cheers Tom R.
Rich

So they are really not matshitas, but either Matsushita or Panasonic.
Rich also said:
Quote
  "small" ? they occupy about 50% more space than OYs. Will OYs dissipate 12w for 1-hour in still air and stay within ±10%?
Rich, ag6k

The Panasonic 3 watt
http://industrial.panasonic.com/www-data/pdf/AOA0000/AOA0000CE18.pdf
is .271 inches by .591 inches

Quote
The OY resistor is .276 inches by .886 inches
.

  then I was wrong about the volume of the OYs.  Apparently Matsushita uses materials that can operate at higher temps than Ohmite's.  Are you not impressed by lighting cigars?

Quote
How does the Panasonic occupy 50% more space than the OY resistor?Huh What type of space or math is this?

  it wasn't bad math Tom, it was bad data.

Quote
Also, the resistors that came in your kit for a 3-500Z amplfier are .235 x .65 inches.

  close

Quote
That kit raises the VHF Q of the anode system,


  according to you but Not according to a HP 4191A.  A factory stock TL-922's VHF suppressor Q measures 5.5@100MHz.  Our stupid retrofit kit lowers the 922's VHF suppressor Q to 1.5@100MHZ with a trade-off of <0.1db at 28MHz.
Rich, ag6k


Quote
and increases the SRF of the anode system. How is .235 x .65 larger than .276 x .886 inches?
 
73 Tom
Logged
W8JI
Member

Posts: 9304


WWW

Ignore
« Reply #155 on: October 20, 2011, 08:37:27 AM »

  then I was wrong about the volume of the OYs.

Why not start actually looking things up before giving answers? It's a good thing to do.

Quote
Apparently Matsushita uses materials that can operate at higher temps than Ohmite's.  Are you not impressed by lighting cigars?

 No, and "apparently" is not a data point. It is a guess.


Quote
  it wasn't bad math Tom, it was bad data.

It was no data. You answered authoritatively without even looking.

W8JI wrote:
Quote
That kit (the Measures kit) raises the VHF Q of the anode system,


Quote
  according to you but Not according to a HP 4191A.  A factory stock TL-922's VHF suppressor Q measures 5.5@100MHz.  Our stupid retrofit kit lowers the 922's VHF suppressor Q to 1.5@100MHZ with a trade-off of <0.1db at 28MHz.
Rich, ag6k

Wrong.

You only consider the suppressor as the sole impedance of the anode system, and don't even consider that correctly. It is the SYSTEM impedance that matters, and the suppressor is a small part of that.

If we look at the system Q and remove the original suppressor and replace it with your actual as-shipped suppressors, the system's VHF Q and SRF of the anode system increases. Both are undesirable.

Also, the suppressors you sent to be measured were not the suppressors you actually sell. They were duplicates of the stock suppressor wound with nichrome, not the magic hairpins you actually ship out. Not only were they not the ones you actually use, you also altered N7WS's conclusions, which actually said they were identical at VHF. N7WS's conclusions make sense, because they were duplicates of the stock suppressor except with nichrome. The nichrome primarily reduces HF Q...not VHF Q.... in the parallel combination.

 
73 Tom  

« Last Edit: October 20, 2011, 08:55:38 AM by W8JI » Logged
AG6K
Member

Posts: 1




Ignore
« Reply #156 on: October 20, 2011, 10:50:52 AM »

  then I was wrong about the volume of the OYs.

Quote
Why not start actually looking things up before giving answers? It's a good thing to do.

Quote
Apparently Matsushita uses materials that can operate at higher temps than Ohmite's.  Are you not impressed by lighting cigars?  No, and "apparently" is not a data point. It is a guess.

  What happens to an Ohmite OY 2w resistor when it dissipates 12w in still air for 1-hour?  And the supremo-test: can they light a cigar?

Quote
  it wasn't bad math Tom, it was bad data.

Quote
It was no data. You answered authoritatively without even looking.

  obviously, but after all, this is only a hobby.

Quote
W8JI wrote:
That kit (the Measures kit) raises the VHF Q of the anode system,


Quote
  according to you but Not according to a HP 4191A.  A factory stock TL-922's VHF suppressor Q measures 5.5@100MHz.  Our stupid retrofit kit lowers the 922's VHF suppressor Q to 1.5@100MHZ with a trade-off of <0.1db at 28MHz.
Rich, ag6k

Quote
Wrong.
You only consider the suppressor as the sole impedance of the anode system, and don't even consider that correctly. It is the SYSTEM impedance that matters, and the suppressor is a small part of that.

  pse describe "the SYSTEM" Tom R.:  tnx .  .  As I see it, one end of each of the two TL-922's parasitic suppressors connects  to each 3-500Z's anode and the other end connects to the DC blocker, which connects to the Tune-C - which is grounded to the chassis;  Since the Tune-C exhibits  c. 11 ohms of XC at the VHF parasitic resonance when the 922 is operated at 7.2MHz, and that cancels some the 120MHz XL in the wiring, to me this does not look like an esoteric "SYSTEM"  than can only be understood by "recognized amplifier experts".

Quote
If we look at the system Q and remove the original suppressor and replace it with your actual as-shipped suppressors

  chortle.  "Actually"  Cecilia L. only solders suppressors together for people who are too feeble to do the job themselves.

Quote
the system's VHF Q and SRF
of the anode system increases. Both are undesirable.

  Guffaw!  System here, System there, it's Systems everywhere! 

Quote
Also, the suppressors you sent to be measured were not the suppressors you actually sell.

  This is getting funnier and funnier.

 
Quote
They were duplicates of the stock suppressor wound with nichrome,

  I did not build the low-Q suppressor N7WS tested, I sent him the components and he built it.

Quote
not the magic hairpins you actually ship out.

  On request we occasionally ship completed suppressors with coil inductors but Cecilia just told me that she has never made one with a U-inductor.  Afterall, U-L supps are rare since they are bad news when used on two-holer amplifiers due to the cross-coupling dilemma.

 
Quote
Not only were they not the ones you actually use, you also altered N7WS's conclusions, which actually said they were identical at VHF.

  Identical?  See for yourselves folks at:
http://www.somis.org/Rp-comp.html
  It is beginning to appear that that this discussion with Tom is morphing into a hydra-headed monstrosity from beyond reality.

Quote
N7WS's conclusions make sense, because they were duplicates of the stock suppressor except with nichrome. The nichrome primarily reduces HF Q...not VHF Q.... in the parallel combination.

 Tom R. moves the suppressor from outside the output Pi-network to inside it - perhaps nobody will notice?

Quote
73 Tom

  .  Rich, ag6k
Logged
AB5Q
Member

Posts: 202




Ignore
« Reply #157 on: October 23, 2011, 06:48:10 AM »

Quote
AG6K -  Tom R. moves the suppressor from outside the output Pi-network to inside it - perhaps nobody will notice?

Please elaborate.
Logged
G3RZP
Member

Posts: 4328




Ignore
« Reply #158 on: October 23, 2011, 06:57:13 AM »

QuoteAG6K -  Tom R. moves the suppressor from outside the output Pi-network to inside it - perhaps nobody will notice?

So did STC in their 1961 transmitters running 30 and 80 kW output.
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #159 on: October 23, 2011, 09:18:29 AM »

Quote
Thanks.

W8JI's web page about de-junking a TL-922 shows how simple it really can be in practice.

73 de Jim, N2EY

  A stock 922 has VHF suppressors with a Q of 5.5 at 100MHz.  Would it be better or worse to have suppressors with a Q of 2 at 100MHz Jim?  Rich, ag6k
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #160 on: October 23, 2011, 09:26:23 AM »

Quote
QuoteAG6K -  Tom R. moves the suppressor from outside the output Pi-network to inside it - perhaps nobody will notice?

So did STC in their 1961 transmitters running 30 and 80 kW output.

  Was the VHF suppressor after the Tune-C Peter ?  tnx  Rich, ag6k
Logged
G3RZP
Member

Posts: 4328




Ignore
« Reply #161 on: October 23, 2011, 09:37:04 AM »

Yes. It had a separate tap on the variable inductor.
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #162 on: October 23, 2011, 09:52:13 AM »

Quote


View Profile Personal Message (Online)

Ignore
   
   
RE: Basic L/R VHF Parasitic Oscillation Suppressor Design
« Reply #161 on: Today at 09:37:04 AM »
   
Reply with quoteQuote
Yes. It had a separate tap on the variable inductor.

  Since the output HF Pi-network's L is essentially a RFC at VHF, how could a VHF suppressor function there   Peter?
Logged
G3RZP
Member

Posts: 4328




Ignore
« Reply #163 on: October 23, 2011, 11:25:48 AM »

Depends on the situation. Parasitics will often show up towards minimum on the tuning C: in that case, the impedance at 70 MHz (which was what they were worrying about) was pretty small. And in big transmitters, a 50 ohm 100 watt resistor with one connected to the plate and the other to nowhere can be a very effective suppressor.

You mustn't think that one size fits all.
Logged
AG6K
Member

Posts: 1




Ignore
« Reply #164 on: October 23, 2011, 01:41:06 PM »

Quote
Quote
AG6K -  Tom R. moves the suppressor from outside the output Pi-network to inside it - perhaps nobody will notice?

Please elaborate.

  VHF parasitic osc. suppressors are normally outside the HF output Pi-network.   
Logged
Pages: Prev 1 ... 6 7 8 9 10 [11] 12 13 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!