Ok Folks, at the end of a long saga of fiddling with an old technology tube
transmitter is this bit of satifying news:

A few days ago, I had a QSO with a fellow in Ohio, I received an email and
mp3 sound file from a fellow in Leeds, England, who had heard and recorded
my little 5 Watt signal and this way I could hear it too.

He gave it a 429-539 QSB and listening to it I was embarrassed by the less
than perfect code as well as the detectable chirp but oh well...

So now is the time to start the construction of that more advanced version
of a starter transmitter using two 807 as finals, who was mentioning that
design way back??

Anyways, hints of where to find the circuit diagram are welcome.

With a very chirpy 73

Uwe







in article , Uwe at
wrote on 4/8/04 4:42 PM:

in article , N2EY at
PAMNO wrote on 4/8/04 07:59:

In article , Uwe
writes:

Using the L/C meter I wound a proper coil, I checked the calibration of my
plate current meter, I did a more thorough check of the grid current (it is
between 1 and 2 mA) and so on and so forth.

I think you mean "screen current".

And I did connect a dummy load (even though they don't respond or send out
QSL cards when you tranmit into them).

Yup!

None of the thing did make any real difference and the dip, the elusive dip,
was in the order of magnitude of maybe 2 mA, nearly impossible to see on my
meter.

Then I changed the circuit around as you suggested, testing the RFC and I
got a dip the likes of which I had never seen. The meter went slowly from
about 30 mA to 50 mA and then dropped to about 25 mA, I couldn't miss it.

But what does it mean. I gather my RFC is not ok. What is wrong??

I used a Series 4590 high current filter inductor I had around, it has the
Digi Key number DN 4528.

The RFC you're using is not meant for the appliucation. It's intended for
much
lower frequencies. You can't tell that just by looking at it.

RF choke design is a matter of compromises. For example, the use of a
powdered
iron or ferrite core will raise the inductance. But that same core does not
work at all frequencies, and may saturate from DC current in the core.

The biggest problem is called "distributed capacitance". In order to get lots
of inductance, you put on lots of turns, closely spaced. But each turn has a
small amount of capacitance to the turns next to it. All these small
capacitances add up, and as the frequency is increased they become
significant
to the total reactance of the choke. At one or more frequencies the choke
will
actually resonate - these are called "self resonant" frequencies. At some
frequencies the choke may act like an inductor of much lower inductance, or
even like a capacitor, because of the self resonances. Self resonance in a
choke can be found with a suitable dip meter.

RF chokes that are meant for applications like the AC-1 are designed to have
self-resonant frequencies far from the amateur bands.

Happy about the dip but still not clear on the deeper reasons...

Hope this helps.

73 de Jim, N2EY

Yes this is all very helpful. Indeed I was thinking that it would have taken
me a very long time to figure this out by myself, if at all.

I put another choke in there, a Hammond 1535B, the self resonant min. frequ.
is 1.3Mhz.

I guess it does take some deeper inside what parameters to look for since
this one improves things slightly but not yet altogether (slightly more
pronounced dip).

Who carries the sort of chokes you were refering to?

73 Uwe

Uwe wrote:

Ok Folks, at the end of a long saga of fiddling with an old technology tube
transmitter is this bit of satifying news:

A few days ago, I had a QSO with a fellow in Ohio, I received an email and
mp3 sound file from a fellow in Leeds, England, who had heard and recorded
my little 5 Watt signal and this way I could hear it too.

He gave it a 429-539 QSB and listening to it I was embarrassed by the less
than perfect code as well as the detectable chirp but oh well...

So now is the time to start the construction of that more advanced version
of a starter transmitter using two 807 as finals, who was mentioning that
design way back??

Anyways, hints of where to find the circuit diagram are welcome.

With a very chirpy 73

Uwe







in article , Uwe at
wrote on 4/8/04 4:42 PM:


in article , N2EY at
wrote on 4/8/04 07:59:


In article , Uwe
writes:


Using the L/C meter I wound a proper coil, I checked the calibration of my
plate current meter, I did a more thorough check of the grid current (it is
between 1 and 2 mA) and so on and so forth.

I think you mean "screen current".


And I did connect a dummy load (even though they don't respond or send out
QSL cards when you tranmit into them).

Yup!

None of the thing did make any real difference and the dip, the elusive dip,
was in the order of magnitude of maybe 2 mA, nearly impossible to see on my
meter.

Then I changed the circuit around as you suggested, testing the RFC and I
got a dip the likes of which I had never seen. The meter went slowly from
about 30 mA to 50 mA and then dropped to about 25 mA, I couldn't miss it.

But what does it mean. I gather my RFC is not ok. What is wrong??

I used a Series 4590 high current filter inductor I had around, it has the
Digi Key number DN 4528.

The RFC you're using is not meant for the appliucation. It's intended for
much
lower frequencies. You can't tell that just by looking at it.

RF choke design is a matter of compromises. For example, the use of a
powdered
iron or ferrite core will raise the inductance. But that same core does not
work at all frequencies, and may saturate from DC current in the core.

The biggest problem is called "distributed capacitance". In order to get lots
of inductance, you put on lots of turns, closely spaced. But each turn has a
small amount of capacitance to the turns next to it. All these small
capacitances add up, and as the frequency is increased they become
significant
to the total reactance of the choke. At one or more frequencies the choke
will
actually resonate - these are called "self resonant" frequencies. At some
frequencies the choke may act like an inductor of much lower inductance, or
even like a capacitor, because of the self resonances. Self resonance in a
choke can be found with a suitable dip meter.

RF chokes that are meant for applications like the AC-1 are designed to have
self-resonant frequencies far from the amateur bands.


Happy about the dip but still not clear on the deeper reasons...

Hope this helps.

73 de Jim, N2EY

Yes this is all very helpful. Indeed I was thinking that it would have taken
me a very long time to figure this out by myself, if at all.

I put another choke in there, a Hammond 1535B, the self resonant min. frequ.
is 1.3Mhz.

I guess it does take some deeper inside what parameters to look for since
this one improves things slightly but not yet altogether (slightly more
pronounced dip).

Who carries the sort of chokes you were refering to?

73 Uwe




See if you can get a copy of the ARRL Handbook from the '40s or '50s.
'60s will get you some 807's, some 1625's (still cheaper than 807's at
Antique Electronics Supply!), and some 6146's.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

"Uwe" wrote in message
...

So now is the time to start the construction of that more advanced version
of a starter transmitter using two 807 as finals, who was mentioning that
design way back??

You almost have to put those 807s in push-pull, for aesthetic reasons. That
is easier to do with plug-in coils than with a bandswitch. Then you need a
dual variable to tune the dual coils. Swinging link to adjust coupling to
the antenna. This stuff shows up at hamfests sometimes. You may find
someone's old homebrew rig for sale and you can salvage the parts from it.
The Handbooks Tim mentioned will have all the info you need. I started out
with a 1953 Handbook but I can't remember what projects were in it anymore.
They're all over eBay, don't pay too much. Tim's also right about the 1625
tubes. They're the same as 807s except for the filament voltage and socket.

My second transmitter (the first was a single 6V6) used an 807W, a compact
version of the full-size bottle, as the PA. I used a Calumet baking soda can
for a shield.

While you're cruising the hamfests, look for an RCA Transmitting Tube
manual, a small paperback. They're fun to read and there's some application
info in them, as well as the usual datasheets.

I used to use a mercury-wetted relay to key my tube rigs. They're really
fast and make a nice ticking sound when you're keying. They also isolate you
from the keyed voltage and allow the use of most modern keyers. Definitely
in keeping with the period, too. They look like octal vacuum tubes with
metal bulbs but they're shiny, not black. 24 VDC is a common coil voltage.

Do you hang out on the boatanchors group? You might be able to turn up some
parts and lots of info over there.

(Note that I have quit trying to convert you to solid-state! You are
obviously a lost cause. : Have fun.)

73,

"PM"

in article ,
Paul_Morphy at wrote on 5/3/04 11:29 PM:


"Uwe" wrote in message
...

So now is the time to start the construction of that more advanced version
of a starter transmitter using two 807 as finals, who was mentioning that
design way back??

You almost have to put those 807s in push-pull, for aesthetic reasons. That
is easier to do with plug-in coils than with a bandswitch. Then you need a
dual variable to tune the dual coils. Swinging link to adjust coupling to
the antenna. This stuff shows up at hamfests sometimes. You may find
someone's old homebrew rig for sale and you can salvage the parts from it.
The Handbooks Tim mentioned will have all the info you need. I started out
with a 1953 Handbook but I can't remember what projects were in it anymore.
They're all over eBay, don't pay too much. Tim's also right about the 1625
tubes. They're the same as 807s except for the filament voltage and socket.

My second transmitter (the first was a single 6V6) used an 807W, a compact
version of the full-size bottle, as the PA. I used a Calumet baking soda can
for a shield.

While you're cruising the hamfests, look for an RCA Transmitting Tube
manual, a small paperback. They're fun to read and there's some application
info in them, as well as the usual datasheets.

I used to use a mercury-wetted relay to key my tube rigs. They're really
fast and make a nice ticking sound when you're keying. They also isolate you
from the keyed voltage and allow the use of most modern keyers. Definitely
in keeping with the period, too. They look like octal vacuum tubes with
metal bulbs but they're shiny, not black. 24 VDC is a common coil voltage.

Do you hang out on the boatanchors group? You might be able to turn up some
parts and lots of info over there.

(Note that I have quit trying to convert you to solid-state! You are
obviously a lost cause. : Have fun.)

73,

"PM"





Paul, I may be a lost cause but I did, after we talked about it, buy the
Experiments in RF design book-great stuff and I also continue to work on my
stamps based controllers even though I can't find a single tube in there...

Thanks for your help

Uwe

Restored Ameco AC-1 on eBay; $177 and three days left!

http://cgi.ebay.com/ws/eBayISAPI.dll...=30944894 96&
rd=1

"RadioGuy" wrote in message
...
Restored Ameco AC-1 on eBay; $177 and three days left!


http://cgi.ebay.com/ws/eBayISAPI.dll...=30944894 96&
rd=1

And the reserve price hasn't been met! Silly hams.

73,

"PM"

And the reserve price hasn't been met! Silly hams.

Whatever floats your boat. I have seen many give thousands for a restored car
that cost very little new. Different people have different interests, doesn't
necessarily mean they are silly.
I bought an AC-1 in 1962 for about $19. I built it and when I finally got it
working, I had the tubes in the wrong sockets, I had the most fun I have had in
40 years of ham radio.
Would I give $300 for a restored AC-1, no, nor would I give $25,000 for a
restored '66 Mustang. There are many that would. Are coin, stamp, or fill in
the blank collectors silly?
73 Gary N4AST

Final eBay bid on AC-1; $238.49 and reserve not met!

http://cgi.ebay.com/ws/eBayISAPI.dll...=30944894 96&
rd=1

----------

JGBOYLES wrote in message
...
And the reserve price hasn't been met! Silly hams.

Whatever floats your boat. I have seen many give thousands for a
restored car
that cost very little new. Different people have different interests,
doesn't
necessarily mean they are silly.
I bought an AC-1 in 1962 for about $19. I built it and when I finally
got it
working, I had the tubes in the wrong sockets, I had the most fun I have
had in
40 years of ham radio.
Would I give $300 for a restored AC-1, no, nor would I give $25,000 for
a
restored '66 Mustang. There are many that would. Are coin, stamp, or
fill in
the blank collectors silly?
73 Gary N4AST

Final eBay bid on AC-1; $238.49 and reserve not met!

http://cgi.ebay.com/ws/eBayISAPI.dll...=30944894 96&
rd=1

----------

JGBOYLES wrote in message
...
And the reserve price hasn't been met! Silly hams.

Whatever floats your boat. I have seen many give thousands for a
restored car
that cost very little new. Different people have different interests,
doesn't
necessarily mean they are silly.
I bought an AC-1 in 1962 for about $19. I built it and when I finally
got it
working, I had the tubes in the wrong sockets, I had the most fun I have
had in
40 years of ham radio.
Would I give $300 for a restored AC-1, no, nor would I give $25,000 for
a
restored '66 Mustang. There are many that would. Are coin, stamp, or
fill in
the blank collectors silly?
73 Gary N4AST

And the reserve price hasn't been met! Silly hams.

Whatever floats your boat. I have seen many give thousands for a restored car
that cost very little new. Different people have different interests, doesn't
necessarily mean they are silly.
I bought an AC-1 in 1962 for about $19. I built it and when I finally got it
working, I had the tubes in the wrong sockets, I had the most fun I have had in
40 years of ham radio.
Would I give $300 for a restored AC-1, no, nor would I give $25,000 for a
restored '66 Mustang. There are many that would. Are coin, stamp, or fill in
the blank collectors silly?
73 Gary N4AST