The AM Forum

An update on the 1929 TNT Type 45 Push-Pull.

Completed the Plate RF Choke and leads, including making some brass solder tabs.  Dug out and cleaned up an ammeter for the Plate built mount from brass stock.  Rearranged the antenna matching section to better match the original schematic and layout.  

I would like to add a meter for the Grid tank, but don't want to complicate things until I have the rig working.  I have is DC ammeters.  I need to do a bit more figuring with the circuit as to where it would be placed.  

Photos from similar self oscillating rigs show Grid Ammeters but not exactly where.  I think it should be in the center tap off the grid coil on the lower voltage side of the Grid Leak Resistor, i.e. between the resistor and the Grid Coil.

I'm going through a beautifully clean Heath HP-23b power supply, just need to verify the resistors are still up to spec.  Previous owner re-capped it with nice Nichicon caps.   The crying shame is the seller shipped it in a box of peanuts so the case is catty wampus.  ;)

I need 2.5v at 2.7A  for my Type 45 filaments.  Located a suitable transformer at Radio Shack (who says they don't stock anything?  My RS is great!!!).  Need to put it on the variac and confirm the output.  I will tap the 12v filaments and use the two unused pins on the HP-23b octal socket.  Then build a power cord.

Rainy and snowy weekend expected for Md, so good for indoors play.  cheers, bill.

Very nice work, OM. :D

The Hammy variable is just the right vintage, too.

73DG

Looking good! Been running my 45 tnt the last few days getting ready for the BK weekend. I am no good at contesting but love the sound of the old rigs.
I used  vintage car heater control available at many auto store to cut the 6 volts to 2.5 . However since you have two why not just go for 5 volts?
All the best
Don

Thanks Don.

They need to be paralleled per the circuit for the Grid tank to work.  The Type 45 require 2.5volts. I've already tested the filament circuit with power and they warm up nicely.



I'm reading your modulator experiments carefully!  I've got a number of carbon mics including T-13 Candlesticks, a British WWII model, and a fancy lozenge shape RCA double button desktop mic.

bill

The loop modulator deal is astounding.
Don

Bill,

Your work looks excellent.  I like the TNT topology.  Mine uses just a single 210 and has always worked great. 

You can see some of the pictures including mine on Steve - VE7SL wonderful website. 

My next breadboard will be a Hartley for 40M using a 203. 

Fun stuff and its good your having fun with it.

http://members.shaw.ca/ve7sl/tnt.html

This weekend starts the AWA Bruce Kelly event using 1929 and earlier transmitters.  Its a fun time for sure. 

http://www.antiquewireless.org/awa-on-the-air.html


73,
Joe - W3GMS     

Excellent work Gents !!

And here is my 1929 Hartley built to Bob W2ZM article in the OTB in 1998 . It uses a 27 Tube. Not sure if I will have time to fire it up this weekend but look forward to hearing the  your TNT's on the air !


Rick

Link coupling works best with these old rigs.  You can loosely couple to the antenna and the effect of the wind blowing the antenna and causing frequency shifts is greatly reduced. 

73,
Joe, GMS

I've been pounding my hands off, but not even 1 BK activity qso.....  ;D

Just kidding, It would be an absolute miracle if my Hartley with 1.5watt input would cross the Atlantic on 80m....

Built about 14 years ago, according to layouts that were used in Holland and EU countries late 20's.
The tube is a Philips B406. An (af) output triode with 3watt dissipation.
http://www.vintageradio.nl/Buizen/b406.htm
I ran (it's been a long time ago I fired this little monster up) it at 120v DC. Even with a pw signal I was able to contact a few west EU countries....

It might be a bit off topic, but I just wanted to show the pics...  :)

Thanks for posting John!  Nice to see rigs from Europe with local parts.  The transformer with the taps is not common here.  Bill

Guys,

Very nice looking rigs and it is nice to see one from "across the pond".  I really like the early European tube style.

This is a topic I am starting to follow because I want to build a transmitter of appropriate vintage to go with my Aero "International 4" receiver as soon as I get it working.  Now that the snow is falling more inside projects are the  plan :)

I love those breadboard rigs. This is one of my all time favorites (all though probably not 1929 vintage).

That is gorgeous Steve!  Kind of like some of the very nicely designed sports car that look fast even sitting still.

It's not mine. Wish it was!

That is a beautiful breadboard what appears to be an amplifier to me.  Looks like an HDVL coil at the top and that was not around in 29.  Regardless, its a great looking rig.  Notice the AK knobs on it.   Not sure whats below the grid coil in the box.  

Joe - GMS

Very nice old buzzard transmitter!  You just can not beat those old buzzard plate RF chokes!!   

With the Hi Q plate networks required for the self excited transmitter, looking at the coil is often misleading to what frequency its on.  It looks like that amount of inductance would almost hit 160M.  My TNT uses about 4uh for 80M.

73,
Joe, W3GMS

 

Great looking rig (although probably not 1929 vintage).

That's twice in one week, Steve.

Just letting you know that there are folks out here reading this stuff ;D

What is twice in one week?

Really nothing, just trying to be funny, ALTHOUGH I thought you would see it.

Fred

Very well observed Joe... ;)

When building this little rig, I had no idea how much inductance I would need. That is why I gave the coil "enough" turns.
Had to short some, to get it working on 80m...

Martin, PA4WM