Looking at the Dave Benson schematics is a good suggestion ... I would also
look at Elecraft who also has manuals online with schematics. I would also
look at the hfpacker amp (www.hfprojects.com). This was a project ran a
couple years ago to build an amp to basically take the QRP rigs in the 2.5
watt range to 30 watts or so. The design actually could do it with a watt
of drive but they put an attenuator in the front to allow flexibility with
different rigs that didn't have completely adjustable output power.

But I also have to ask the same question Tom asks. 80 is a noisy band, and
one that demands large antennas. To get past the noise you need power, and
that adds a lot of weight. Don't forget, you not only have the amp to carry
around, but you gotta carry the DC to run all this, too.

If you are line of sight, then you can go very high in frequency, but
certainly in the higher parts of the HF spectrum, the antennas are more
manageable and the bands are quieter, which means power is less of an issue.
You could even go to VHF but then the whole construction thing becomes more
challenging.

But then, if you are looking for a 100-200 mile path, then 80 probably is
the ticket, but you're going to have to constrain your playing to days when
the A index is low. Indeed, I would suspect you would want to be balooning
in the daylight - precisely when 80 is very noisy. So you better be paying
close attention to the propagation reports if you want to hear your baloon.

...

"Tom Bruhns" wrote in message
m...
Shouldn't be too difficult to come up with the brute-force answer, but
I have to ask: Why?

"Allan Butler" wrote in message
news:mRmEb.595184$Fm2.545419@attbi_s04...
Hi there.

Another Amateur that is involved with volunteering with schools and such
is
looking at launching a baloon with an HF transmitter on board. The band
of
operation is 80 meters. He is looking at some type of a beacon that will
send data via BPSK modulation and needs 10 to 20 watts of transmit power
at
the output port. For an input to the unit he has 0dBm or 1 milliwatt of
RF
at the operating frequency.

This looks like it would require 40 to 43 dB of gain to get to the level
that he needs for output.

Does anyone have suggestions of places to look on the web for application
notes and/or schematics for amplifiers along these lines?

I have done some searching on Google and found a few things but most of
them
take inputs of 30dBm or so and only take that level up to 40dBm. He still
needs to bridge the gap from 0 dBm to 30 dBm in that instance.

Any information that you can help with is greatly appreciated.

Al Butler
ka0ies

Here are the web page links for High Altitude Ballooning

http://users.crosspaths.net/~wallio/HABLinks.html

Ralph Wallio, W0RPK is a good resource
http://users.crosspaths.net/~wallio/

W9GB

This looks like it would require 40 to 43 dB of gain to get to the level
that he needs for output.

Does anyone have suggestions of places to look on the web for application
notes and/or schematics for amplifiers along these lines?

I have done some searching on Google and found a few things but most of them
take inputs of 30dBm or so and only take that level up to 40dBm. He still
needs to bridge the gap from 0 dBm to 30 dBm in that instance.

Hmmm. Seems to me that many of the VFO-and-mixer QRP CW/SSB
transmitter projects might have suitable designs... a few milliwatts
out of the mixer and bandpass filter, into a one- or two-gain-stage
driver which would then push power out to the final transistor(s).

Let's see. The Small Wonder Labs PSK-20 transmitters seem like a good
place to start looking. The schematic shows that the transmit
circuitry uses a Minicircuits TUF-1 mixer. According to the
Minicircuits web page, this takes as input a +7 dBm local oscillator
and up to 1 dBm of RF. It has a conversion loss in the 7-8 dBm range,
so you'd end up with somewhere around -6 dBm at most coming out of it.
The PSK-20 transmitter buffers this through a transistor, then through
a MAR-35M monolithic amplifier, and then through a 2SC1970 and
2SC1971, and ends up with 2.5 watts of power.

Seems to me that you could probably fiddle with this final stage a bit
(double up on the 2SC1971, heatsink 'em, run at a higher current
level, and adjust the driver circuitry to suit) and end up with 10
watts out.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Shouldn't be too difficult to come up with the brute-force answer, but
I have to ask: Why?

That is, why so much power? And why 80 meters? I'd think you'd want
to use a higher frequency so that the antenna would be easier, and if
the balloon is aloft and line-of-sight, even a watt should be more
than enough to hear it loud-and-clear. Sending up an amplifier and a
power plant that will run it at 10 watts output will take quite a bit
of balloon displacement. I think it may be worth asking some
system-design questions to see if he can reach a more optimal
solution.

Cheers,
Tom

Allan Butler wrote in message news:mRmEb.595184$Fm2.545419@attbi_s04...
Hi there.

Another Amateur that is involved with volunteering with schools and such is
looking at launching a baloon with an HF transmitter on board. The band of
operation is 80 meters. He is looking at some type of a beacon that will
send data via BPSK modulation and needs 10 to 20 watts of transmit power at
the output port. For an input to the unit he has 0dBm or 1 milliwatt of RF
at the operating frequency.

This looks like it would require 40 to 43 dB of gain to get to the level
that he needs for output.

Does anyone have suggestions of places to look on the web for application
notes and/or schematics for amplifiers along these lines?

I have done some searching on Google and found a few things but most of them
take inputs of 30dBm or so and only take that level up to 40dBm. He still
needs to bridge the gap from 0 dBm to 30 dBm in that instance.

Any information that you can help with is greatly appreciated.

Al Butler
ka0ies

Allan Butler wrote:

OK here is what is going on as far as I know now.

The 3.5 MHz transmitter is to study sea wave propagation at that frequency
over sal****er at a defined altitude. I am not 100% certain what that means
but I will ask for more detail.

As to legality I will ask the person that I am getting the information for
what they have done in the way of research on this part. This group is
normally very good on researching these matters. It might be that they will
actually have the transmitter commanded from a UHF control link. I just
don't know for certain.

I will also pass on the information about the organizations that are doing
the balloon launches. It is always helpful to learn from other people.

Thanks for all the information so far folks. If there is anymore avaialble
please post it here to the news group so that we can all learn from each
other.

Al Butler
ka0ies

On Fri, 19 Dec 2003 16:57:48 GMT, Allan Butler
wrote:

Allan Butler wrote:

OK here is what is going on as far as I know now.

The 3.5 MHz transmitter is to study sea wave propagation at that frequency
over sal****er at a defined altitude.

Well then you're stuck with 80 meters. But I'd guess 5W output would
be plenty for your purposes. However, I'd be very interested in the
type of antenna you eventually settle on for this unusual purpose.
Nothing really springs to mind as being particularly suitable...
--

"I expect history will be kind to me, since I intend to write it."
- Winston Churchill

Paul Burridge wrote:
On Fri, 19 Dec 2003 16:57:48 GMT, Allan Butler
wrote:

Allan Butler wrote:

OK here is what is going on as far as I know now.

The 3.5 MHz transmitter is to study sea wave propagation at that frequency
over sal****er at a defined altitude.

Well then you're stuck with 80 meters. But I'd guess 5W output would
be plenty for your purposes. However, I'd be very interested in the
type of antenna you eventually settle on for this unusual purpose.
Nothing really springs to mind as being particularly suitable...

Zeppelin Antenna comes to mind. It was invented for this purpose.
If you can do with a wire antenna hanging off the baloon about 60m
down is another story.

Kind regards, Eike

Paul Burridge wrote:
On Fri, 19 Dec 2003 16:57:48 GMT, Allan Butler
wrote:

Allan Butler wrote:

OK here is what is going on as far as I know now.

The 3.5 MHz transmitter is to study sea wave propagation at that frequency
over sal****er at a defined altitude.

Well then you're stuck with 80 meters. But I'd guess 5W output would
be plenty for your purposes. However, I'd be very interested in the
type of antenna you eventually settle on for this unusual purpose.
Nothing really springs to mind as being particularly suitable...

Zeppelin Antenna comes to mind. It was invented for this purpose.
If you can do with a wire antenna hanging off the baloon about 60m
down is another story.

Kind regards, Eike

On Fri, 19 Dec 2003 16:57:48 GMT, Allan Butler
wrote:

Allan Butler wrote:

OK here is what is going on as far as I know now.

The 3.5 MHz transmitter is to study sea wave propagation at that frequency
over sal****er at a defined altitude.

Well then you're stuck with 80 meters. But I'd guess 5W output would
be plenty for your purposes. However, I'd be very interested in the
type of antenna you eventually settle on for this unusual purpose.
Nothing really springs to mind as being particularly suitable...
--

"I expect history will be kind to me, since I intend to write it."
- Winston Churchill

"Allan Butler" wrote in message
news:mRmEb.595184$Fm2.545419@attbi_s04...
Hi there.

Another Amateur that is involved with volunteering with schools and such
is
looking at launching a baloon with an HF transmitter on board. The band
of
operation is 80 meters. He is looking at some type of a beacon that will
send data via BPSK modulation and needs 10 to 20 watts of transmit power
at
the output port. For an input to the unit he has 0dBm or 1 milliwatt of
RF
at the operating frequency.

This looks like it would require 40 to 43 dB of gain to get to the level
that he needs for output.

Does anyone have suggestions of places to look on the web for application
notes and/or schematics for amplifiers along these lines?

I have done some searching on Google and found a few things but most of
them
take inputs of 30dBm or so and only take that level up to 40dBm. He still
needs to bridge the gap from 0 dBm to 30 dBm in that instance.

Any information that you can help with is greatly appreciated.

Al Butler
ka0ies

Here are the web page links for High Altitude Ballooning

http://users.crosspaths.net/~wallio/HABLinks.html

Ralph Wallio, W0RPK is a good resource
http://users.crosspaths.net/~wallio/

W9GB