Dog Radio Studio 2, LPB RC-6A

It will come as an interesting story when you begin broadcasting with the LPB RC-6A, you will be one of few to report carrier current experience.

Following you I might have something ready by then to also begin CC broadcasting. It will take some time to get the right parts.

Tomorrow I will study the power poles and the transformer to try and guess how many houses are on the same circuit.

When I had the CC transmitter, the RC-6A,
I had no idea what to expect. And I had a real
commercial coupler, which was lent to me.

The day I decided to actually commit, and do
it, I wired the system for neutral injection and
was really excited.

I powered up the system, and found that the
LPB transmitter's audio (as received on a radio)
was badly distorted. Something was seriously wrong.
And this had previously not been the case.

So I tried to continue the experiment running just
a dead carrier. Unfortunately, interference on the
channel made it impossible to determine the results.

I'm interested in CC broadcasting for sure. But I'm
also interested in having a beautiful piece of vintage
broadcast gear up and running.

So,when the time comes, I sure will report what ever
happens. I've never done this before.

Best Wishes,
Bruce, Dog Radio Studio 2

Back in the RC-6A's prime, the coupler at that time was the LPB TCU-8. Not all that different from the TCU-30 and the tuning procedures were the same for the couplers. There was however a little addition added to the tuning instructions for the TCU-30 if connected with an RC-6A.

On the RC-6A, there is a neon bulb on the output tank. This works as your plate resonance "dip" indicator, only in opposite indication. Meaning that you tune the two final tuning inductors for a maximum illumination of the neon bulb. When tuned properly, the neon bulb should glow fully, and the power/swr meter in the coupler should indicate 5-8 watts of power when the coupler is in "Power" mode.

But...here is something they never mentioned in the tuning procedure for an RC-6A connected to the TCU-30.

After going through the tuning procedure once, return the function knob on the TCU-30 to "Power" and re-peak the plate resonance tuning inductors. Do the procedure at least 3 times for maximum resonance and coupling efficiency.

If the tuning on the RC-6A, when connected to a TCU-30, is not repeated at least a few times, the end result is an improper match between the RC-6A transmitter and the TCU-30 coupler and messy audio, such as distortion or band splattering.

The solid state LPB units do not have any tuning on the final output. They are hard configured for a 50 ohm output, and designed to interface to the TCU-30 coupler. Usually the tuning process for that is one or two times.

The RC-6A has an output that must be tuned to resonance. And like the bigger counterparts, requires frequent checking and re-peaking now and then. One of the neat things about that RC-6A, like its solid state counterparts, are not kiddie toys. They both are professional broadcast transmitters and perform exactly like their bigger cousins. In other words, treat them just as you would treat a 50KW behemoth when it comes to the maintenance and tuning and that RC-6A will provide the same level of performance.

RFB

Thanks RFB!

You have given me some VERY valuable info!

Right before the RC-6A went off to New Jersey,
I ran some tests into a dummy load at 860 kHz.
(860 is the only rock I have, and it's not a good
channel.)

Test number one showed some power out but with
almost no audio. That's when I decided to switch
the tubes - the 3 6AL11s - around. I finally got to
a combination where I was getting 6 watts out -
maybe a little more - with about 70 percent modulation.
I was pretty happy with that, because it meant things
weren't as bad as I thought.

That's when my friend came through Connecticut on
business, and picked up the RC-6A on his way home
to New Jersey.

I was under the impression that the neon bulb went
out when the final amp was tuned properly. (Somebody
gave me bad info, I guess.) This contradicted the fact
that when I was getting the 6 plus watts out on 860 -
the neon bulb WAS at full brilliance.

Thanks for the info on the coupler and the tuning
procedure. I may be able to get a coupler back
from a different friend when the RC-6A comes back.
Meanwhile, I can tell my friend in New Jersey about
the neon bulb resonance indicator, and how it
really works.

I have one other question that I'm sure you can confirm.

I believe some RC-6As were able to be operated
throughout the entire AM broadcast band -
540 to 1600 - and that some only covered the
bottom end.

Do you have any comments on that frequency
coverage issue?

Thank you very very much!

Bruce, Dog Radio Studio 2

"I believe some RC-6As were able to be operated
throughout the entire AM broadcast band -
540 to 1600 - and that some only covered the
bottom end."

Actually all of them are capable of covering the entire MW band, even the extended upper portion. The difference is with the output tank and coupling between the osc/buffer tube and the final/mod tube. There was a run of those RC-6A units that could cover the whole band right out of the box. Most however were built according to the customer's frequency requests. Those that did cover the whole band were designed for those who needed to change their frequency from one end of the band to another, and was more cost effective for both the customer and LPB to build a series of those RC-6A's capable of covering the whole band for those extreme frequency changes than to have two separate transmitter/coupler setups.

The solid state counterparts can also cover the entire band as well. They just have to have the final elliptical filter components changed for the particular part of the band and a small bias adjustment and of course, the crystal on the exciter.

LPB made all of them with field adjustment/change in mind. Reading their manuals, one would think they were ready to chop off anyone's fingers who dared to try to adjust anything or change anything. Mere words on paper is all that was, mostly to encourage the return of the unit to the factory for changes and repairs. But both the tube and solid state units are highly field serviceable.

RFB

"I was under the impression that the neon bulb went
out when the final amp was tuned properly. (Somebody
gave me bad info, I guess.) This contradicted the fact
that when I was getting the 6 plus watts out on 860 -
the neon bulb WAS at full brilliance."

The neon bulb is connected to indicate maximum RF energy at peak resonance and will illuminate fully when the plate is tuned properly. It functions opposite of a plate current meter where we want to see a "dip" in the meter indication.

The traditional plate current meter is looking at the tube's plate current draw. When off resonance, that current is more, and when tuned to resonance, the current is minimum at the resonance point..hence the "dip" in the meter reading.

The neon bulb looks at the output energy from the tuning tank. It sees nothing but RF energy at that output connector, and just like tuning a 3 meter stick with a grain of wheat bulb, the brighter the light bulb illuminates, the maximum RF energy is passing through that bulb, hence tuned to resonance.

Glad to pass on the info! 🙂

RFB

Back in 1979 or 1980, I had the opportunity
to own the "Scariest Ham Transmitter In My
Radio Life." (Echo Fade) LIFE... LIFe... LIfe...
Life... life....

It was a Heathkit Sceneca (Sp?) If you have seen
this beast, you should be scared. It was a big
green and silver vacuum tube monster. It was
supposed to transmit AM and CW (morse code)
on the ham radio six meter band (50 - 54 MHz)
or the two meter band (144 - 148 MHz.) It was
VFO controlled. Plate input was around 100 watts (?)

It lived in my friend Bill's closet for years and years.
He fed it small scraps of bread, potato chip crumbs,
and an occasional fly (during the summer time.)

One day, I expressed an interest in trying to transmit
a 2 meter uplink signal to the ham radio satellite
Oscar 7. I needed a transmitter. (For some reason,
every memory from there on is fuzzy.) I don't know how,
but this beast ended up on my ham radio desk.

I had to test it. I was young and really stupid. Not having
a load to terminate it's 50 ohm output, I put a 2 meter
rubber duck antenna (which had a PL-259 plug on it)
into the SO-239 socket on the back on the transmitter.

Then tune up. Look at the meter. Turn this knob, that
knob, look at the meter. Look. Tune. Look. Tune.
Look look tune.

Burning smell. Big burning smell.

I pulled the ham station master switch. Yup. I wasn't
totally dumb. I had a master switch. Now the power
was off everywhere.

I turned the transmitter around and looked at the 2
meter rubber duck antenna. The plastic was melted
and dripping onto the operating desk. There was a
big drip of plastic that was about to fall off of the
rubber duck but didn't.

This is how we learn (hopefully) about what RF energy can
do.

Fast forward ahead. I procured an 11 element 2 meter beam
antenna. Now I had a load that would at least be
able to handle that kind of power.

On the front of the transmitter was a big multimeter. It read
plate milliamps, grid current and plate VOLTAGE. This was
new. I had never seen a transmitter ever, where you could
read PLATE VOLTAGE. COOL!

So here we go again. Kind of like having an early Atlas Rocket
on the pad, filled and bulging with fuel and liquid hydrogen.
On internal power, ready to go.

Here we go! Press the transmit button.

Tune. Tune. Tune. Tune. Gee, I think I'll look at
the plate voltage. Hmmm. Why does it go from about
800 volts down to 650 volts when I transmit?

That seems weird. Hmmmmmm.

Tune tune tune. the plate voltage is getting more
erratic. "I don't like this." I said in my head.

Tune tune tu-

BAAAAAAAAAAAAAAAAAAAAAAAAAAAAAMMMMMMMM!!!!!!!!!!!!!!!!!!!!

I was in a daze.

Through the daze, I heard my father yell down the stairs, "Are you alright??"

Through my dry mouth and throat, I managed to shout. "I'm OK!!!!"

Time passed.

And the Green Silver Beast went into the closet. My closet!
And I wasn't around much anymore. Life had really picked
up speed.

My little brother was left with the task of feeding the monster
potato chips, loaves of bread, and lots of flies. It was
HUNGRIER now.

Some time after that, I finished college, moved out. Got an
apartment, a job, and spent too much time trying to understand what
the opposite sex was trying to tell me.

So much time, in fact, that I forgot about the Green and Silver
Beast in the closet.

The years passed.

1983.

One particular day in 1983, my Dad was outside doing yard work. The neighborhood
trash truck came down the street.

The garbage man saw the 2 meter 11 element beam that was STILL on
the roof of my dad's house.

The conversation went something like this.

Trash Man: "Hey, is that a CB antenna?"

My Dad: "I don't know, but my son's got some old radio equipment
he doesn't want."

A few minutes went by. Then it happened.

My Dad gave the trash man the Green and Silver Monster out of the
closet.

In parting, the trash man said, "I'm sure I can probably use this
as a linear amp for the out of CB band," i.e., 26 to 27 MHz, or so.

"Yup, thanks mister. This will be a great afterburner for my CB
out of band rig!"

Then the garbage truck went off into the distance, stopping briefly
every once in a while, until it was out of sight.

And as for the trash man:

May God have mercy on his soul.

Best Wishes,
Bruce, Dog Radio Studio 2

Back in 1979 or 1980, I had the opportunity
to own the "Scariest Ham Transmitter In My
Radio Life." (Echo Fade) LIFE... LIFe... LIfe...
Life... life....

It was a Heathkit Sceneca (Sp?) If you have seen
this beast, you should be scared. It was a big
green and silver vacuum tube monster. It was
supposed to transmit AM and CW (morse code)
on the ham radio six meter band (50 - 54 MHz)
or the two meter band (144 - 148 MHz.) It was
VFO controlled. Plate input was around 100 watts (?)

It lived in my friend Bill's closet for years and years.
He fed it small scraps of bread, potato chip crumbs,
and an occasional fly (during the summer time.)

One day, I expressed an interest in trying to transmit
a 2 meter uplink signal to the ham radio satellite
Oscar 7. I needed a transmitter. (For some reason,
every memory from there on is fuzzy.) I don't know how,
but this beast ended up on my ham radio desk.

I had to test it. I was young and really stupid. Not having
a load to terminate it's 50 ohm output, I put a 2 meter
rubber duck antenna (which had a PL-259 plug on it)
into the SO-239 socket on the back on the transmitter.

Then tune up. Look at the meter. Turn this knob, that
knob, look at the meter. Look. Tune. Look. Tune.
Look look tune.

Burning smell. Big burning smell.

I pulled the ham station master switch. Yup. I wasn't
totally dumb. I had a master switch. Now the power
was off everywhere.

I turned the transmitter around and looked at the 2
meter rubber duck antenna. The plastic was melted
and dripping onto the operating desk. There was a
big drip of plastic that was about to fall off of the
rubber duck but didn't.

This is how we learn (hopefully) about what RF energy can
do.

Fast forward ahead. I procured an 11 element 2 meter beam
antenna. Now I had a load that would at least be
able to handle that kind of power.

On the front of the transmitter was a big multimeter. It read
plate milliamps, grid current and plate VOLTAGE. This was
new. I had never seen a transmitter ever, where you could
read PLATE VOLTAGE. COOL!

So here we go again. Kind of like having an early Atlas Rocket
on the pad, filled and bulging with fuel and liquid hydrogen.
On internal power, ready to go.

Here we go! Press the transmit button.

Tune. Tune. Tune. Tune. Gee, I think I'll look at
the plate voltage. Hmmm. Why does it go from about
800 volts down to 650 volts when I transmit?

That seems weird. Hmmmmmm.

Tune tune tune. the plate voltage is getting more
erratic. "I don't like this." I said in my head.

Tune tune tu-

BAAAAAAAAAAAAAAAAAAAAAAAAAAAAAMMMMMMMM!!!!!!!!!!!!!!!!!!!!

I was in a daze.

Through the daze, I heard my father yell down the stairs, "Are you alright??"

Through my dry mouth and throat, I managed to shout. "I'm OK!!!!"

Time passed.

And the Green Silver Beast went into the closet. My closet!
And I wasn't around much anymore. Life had really picked
up speed.

My little brother was left with the task of feeding the monster
potato chips, loaves of bread, and lots of flies. It was
HUNGRIER now.

Some time after that, I finished college, moved out. Got an
apartment, a job, and spent too much time trying to understand what
the opposite sex was trying to tell me.

So much time, in fact, that I forgot about the Green and Silver
Beast in the closet.

The years passed.

1983.

One particular day in 1983, my Dad was outside doing yard work. The neighborhood
trash truck came down the street.

The garbage man saw the 2 meter 11 element beam that was STILL on
the roof of my dad's house.

The conversation went something like this.

Trash Man: "Hey, is that a CB antenna?"

My Dad: "I don't know, but my son's got some old radio equipment
he doesn't want."

A few minutes went by. Then it happened.

My Dad gave the trash man the Green and Silver Monster out of the
closet.

In parting, the trash man said, "I'm sure I can probably use this
as a linear amp for the out of CB band," i.e., 26 to 27 MHz, or so.

"Yup, thanks mister. This will be a great afterburner for my CB
out of band rig!"

Then the garbage truck went off into the distance, stopping briefly
every once in a while, until it was out of sight.

And as for the trash man:

May God have mercy on his soul.

Best Wishes,
Bruce, Dog Radio Studio 2

Sorry guys, I must have hit the
button twice.

By the way, I'm sure the trash man
was OK and the transmitter really
didn't eat stuff. But the rest is
true and it was fun to write about it.

Bruce, Dog Radio Studio 2

P.S. Oh yeah, that's liquid oxygen,
not liquid hydrogen. Man, I'm getting old!

I recall that particular VHF unit from Heathkit. A workhorse and reliable.

A rubber duck antenna? Plastic dripping onto the floor?!

Now that must have been something to see! 😉

RFB

That's cool that you remember that
RFB.

Maybe the Seneca I had wasn't so good.
I just looked it up and saw that it could
do 140 watts DC in on 6 meters. That's
a fair amount for a kid in 1979, that
didn't know what he was doing. The rubber
duck with the big plastic drip, that had solidified
and was still hanging there - was a great
conversation piece among our neighborhood
radio group. (In other words, they thought it
was crazy, but funny at the same time.)

Actually, in trying to make the story
humorous, I left out one part.

I actually did get a signal up and back
through one of the early OSCAR satellites.
I'm not sure which one, maybe it was
OSCAR 8, actually. The receiver was a
Hammarlund HQ-140X, with a 10 meter
preamp on it. The uplink signal wasn't stable,
in other words, it was very wiggly, for
lack of a better term. But I was really
glad that the satellite heard the signal
and sent it back down to me on ten meters.

I'm glad you remember the Seneca, too.

Best Wishes,
Bruce, Dog Radio Studio 2

There is a NASA satellite due to drop this weekend. Get your catcher's mit on, maybe you can grab some spare parts as it plunges down.

Yeah, I heard about that! I'll have
to check it out. I think that they
don't really know where it's coming
down.

Maybe I can get my kid's trampoline
out and grab a few parts real quick.

Guess I'll need some ice, too. That
things gonna be HOT!

Bruce, Dog Radio Studio 2

"I think that they
don't really know where it's coming
down."

Anyone actually believe they cannot track this thing when NORAD can track junk 10cm long and has a tag on everything up there...as they have proven many times as well as declared it many times?

They are not as helpless as they want everyone to believe.

RFB