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

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!

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

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

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?

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?

xpyttl wrote:

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?

I was a little distracted by the main path of the conversation that we were
having so I didn't ask at that time why they wanted 80 meters for a beacon
from that high. I also realize that it is going to take a fair amount of
battery to keep this thing going for any period of time.

These people do a lot with GPS. Maybe they are hoping to pass GPS location
data to the ground crew after the payload lands so that they can go right
to it and pick it up. I have no idea what they are doing with antenna ideas
or anything like that.

Now, what was his phone number? :-)

In the mean time thanks for the information. I will get to looking at it
and pass it on.

Al Butler
ka0ies

xpyttl wrote:

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?

I was a little distracted by the main path of the conversation that we were
having so I didn't ask at that time why they wanted 80 meters for a beacon
from that high. I also realize that it is going to take a fair amount of
battery to keep this thing going for any period of time.

These people do a lot with GPS. Maybe they are hoping to pass GPS location
data to the ground crew after the payload lands so that they can go right
to it and pick it up. I have no idea what they are doing with antenna ideas
or anything like that.

Now, what was his phone number? :-)

In the mean time thanks for the information. I will get to looking at it
and pass it on.

Al Butler
ka0ies

Dave Platt wrote:

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.


Thanks for the information. I will check it out and pass it on to the
persons that were looking for it.

Al Butler
ka0ies