New transmitter is up and running :)

[WA1GFZ]

The KW matchbox can easily handle 3KW PEP unless you have a weird load.
Old KW rigs ran about 750 watts carrier.

[ke7trp]

Not these two.  They ran the T3 full tilt but it wont take the heat of this rig. Not even close.

I have run BIG SSB power through them with out ill effects.  It wont take this BIG MAUL.. HAHA
C

[W2PFY]

Hope to see some of you guys on 40 meters today

Will it do 20 meters & 10? Maybe you already posted what it will do but i'm toooooooooooooooooooooooo lazy to go back & read. And where are you located and what time do you operate?

l

[ke7trp]

Nope.. Just 40, 80 and 160.   The only bands an ole AMer needs.

C

[KM1H]

My monitor shows the 304's as white, that is asking for trouble if its true as thats a lot more than 600W PD out of the pair.

[ke7trp]

Its just the camera, They run a nice warm cherry color.  Class AB1,  125 mills idle.  About 750 to 800 watts for the pair at this voltage and current. Normaly, one low power, they only pop up 200 mills.  On High power and full modulated I only see 300 to 350 mils.  THe Transformer is 1 amp.  Read the attached 304Tl spec sheet and you can see I am running then way below specs.

 In class AB2, A pair of these will do 1800 watts. The modulator was built for full power and has the iron and PS to back it up. I just cant imagine what type of carrier needs 1800 watts of modulator though!

Neat tubes!  

I kinda wish I had two 450 THs in the final instead of the 4-400s.  I think it would have more "cool" factor.

C

[ke7trp]

Here are some more shots of the rig.  I figured out how to hook this EVO phone to my computer.

C

[W9GT]

Very nice rig Clark!  I have a pair of 6C21s (sort of like pulse-rated 450TLs)  that I would like to run in the RF and modulate them with a pr of 304TLs.  The cool factor should be quite high.  Those big bottles are really neat to see all lit up.  I have been planning that rig in my head for years.  I obtained some broadcast xmtr iron to do the chores.  Maybe I will finally get it built one of these days.

73,  Jack, W9GT

[W2PFY]

The only bands an ole AMer needs

20 can be fun but I think most of the old timers who used either gave up or are SK's.

what do you use as an audio driver? A cathode follower would be great for class AB-1 so your driver could be transformer-less for clean audio. I heard JJ on his driver transformer set up and his new J-Sweat fangeled driver and he sounded great on both set ups. Unless he AB'ed them, I don't think I would have noticed the difference.

[ke7trp]

I use the king 500 on 20 meters Phone.  WOrks great and gives me a good 250watts.   This rig is just for the low bands.

Robert W0vmc built the modulator for hifi.  It is Driven by an external Toa Amplifier.  There is no real limit to its audio bandwidth. It runs 20 to nearly 20,000 if uncapped.

The 450TH just looks cool!  I think you have a fine idea.

C

[ke7trp]

Ok.  I got the RF parts plate choke installed today. part number RFC-3.   1.5 amp 225uh- 4kv.  So far so good. I have not run 40 meters yet.  I am scared to do so.  This plate choke looks light duty to me. I did run full smoke into a dummy on 75 meters. No problem.  I also ran full legal limit tonight on the rig on 75 phone.  I had the tuner arc AGAIN but was told I had the audio up to high.  I put the rig back into the dummy load and reset all the audio rack and peak limiter so I was almost closing the carrier but not all the way.  Now the tuner does not arc. 

I just had a pleasant QSO with W1IA in NH from Arizona. He said I was booming in and sounding great on 3870.  I guess the rig is working now  

Right now I am trying to decide if I should put the rig on 40 tomorrow or if I should just let it be on 75 for now.  I hate to blow that plate choke out!  It was pointed out to me that in class C plate modulated phone, That choke is probably seeing ALOT more then 4kv voltage on it.  The HV is at 2300.  I need a less on how much that voltage increases when modulated.  I am going to grab a handbook from the 50s and read tonight to try to learn.

C

[W2PFY]

I believe at 100 percent mod, you will see twice the dc voltage imposed on the PA place so if you can do 125 percent or even higher, the voltage go's up more.

[ke7trp]

I read the 1964 hand book last night.  In AM, class C, The voltage is double at the carrier.  ITs doubled again at 100% mod.  So the total is 4 times over the HV supply.  On low power, I am running 2300 volts.  Nearly 10,000 volts!!!


C

[W2PFY]

ITs doubled again at 100% mod.

Are you sure? I think somewhere it reads that for 100 percent mod you need double the voltage.

[ke7trp]

According to that handbook, AM in class C doubles it. When you add the audio to 100%, its 4 times HV voltage. They show in the book 13,000 volts calulated from 3250 volts HV.

C

[W2PFY]

Sounds right.

[ke7trp]

Got the transmitter on 40 meters now. 95 % positive and 80 negative.  No arcs or sparks!!!!    7293

C

[W2PFY]

Recorded from Global tuners in Grand Junction, CO.

[ke7trp]

Cool. Sounds decent for a mic right into the rig!  THe audio has alot of his in it. I wonder how hard I was hitting that RXer? That was 95% mod on the gates mod monitor.

Thanks alot!!! 

40 is full of activity on AM right now. I am about 9 contacts deep and more are signing on.

C

[W2PFY]

You were doing 20 over sometimes. That was recorded in the 15 kc bandwidth.

The other guys were weak. Lots of noise on the receiver. I'm near Albany, NY.

 Your welcome!!

[ke7trp]

Cool!   There are a bunch of guys. Can you hear kd7HVL??? Frank is on a PRC174 backpack radio on battery power!  He is S9 over here.

C

[W2PFY]

No, too weak in that receiver.

[W2PFY]

I plugged my Sony headset right into the computer and gave those two clips a listen. That transmitter sounds damn good

I got a bunch of 304tls around here and a bunch of 450TH's and just about everything to build a HB. I think it will happen this winter. I have three mod transformers that can handle the power and I would be able to see which one sounds the best.

If your going to be on tonight on 75, let me know the time & freq, I'll try to record you on a local receiver.

[ke7trp]

I just did the same. I plugged my Beats headphones (studio quality) into the laptop and had a listen. WOW.  Full audio.  If anything there is to much bass.  Maybe I will try to use the onboard mixer EQ to cut some of that bass and boost the mid a touch. 

Your transmitter plans sound great.  I wanted 450THs also but was talked out of it.  The main reason is they are Triodes and you are going to have hell to pay to get them neutralized on multi band/freq operation.  If its a single band use them!

The plan right now is to switch to 75 meters in about a half hour.  The BC stations are going to take over 40 here shortly. 

Try Smeter.net for another RXer. I seem to hit that one loud.

C

[W2PFY]

If anything there is to much bass.

Your bass is fine. Maybe you have your EQ set up for more bass on your computer? set if flat and then give a listen.

450TH tubes can work on an all band transmitter. The secret is having a very small vacuum variable cap as a neutralizing cap (2-45uuf) and re-neutralize it from the front panel when making band changes. Once you have the settings noted, its just another step. I don't know how it would work for a pi net but if you had a balanced network in the grid circuit it may  work fine. An MBL 150 network in the grid would handle a 450TH. My Westinghouse is shunt fed to the final and has a balanced network in the PA final. Resetting the neutralizing cap becomes automatic.