Transister based RF Amplifier

A

amstereo

Guest
Hi all, 2nd query today, this one is abit higher in my list of items i need.

What i am in need of is an RF Amplifier where i can input oh about
100milli-watts of .5 - 1.5 MHz signal and on the other side I magically get
5 watts (more the merrier)

The only problem I have Is i suck at building kits. I had plans for a 5 watt
rf amp, however, I could not obtain the required componant values.

What I'm asking for, is, would anyone with the knowledge of rf amps beable
to piece me one up or put me on to easy to follow plans that also have the
componant listings. It's a simple amplifier, I was thinking of using high
voltage mosfets (48volt) in a push pull configuration cause many mosfets can
do 1 mhz no problems. But I'm not sure exactly what to do. assistance please
:) thanks for viewing.
 
On Sat, 10 Jan 2004 02:35:37 +1000, "amstereo"
<amstereo@optushomeDOTcompanyDOTaustralia> wrote:

Hi all, 2nd query today, this one is abit higher in my list of items i need.

What i am in need of is an RF Amplifier where i can input oh about
100milli-watts of .5 - 1.5 MHz signal and on the other side I magically get
5 watts (more the merrier)

The only problem I have Is i suck at building kits. I had plans for a 5 watt
rf amp, however, I could not obtain the required componant values.

What I'm asking for, is, would anyone with the knowledge of rf amps beable
to piece me one up or put me on to easy to follow plans that also have the
componant listings. It's a simple amplifier, I was thinking of using high
voltage mosfets (48volt) in a push pull configuration cause many mosfets can
do 1 mhz no problems. But I'm not sure exactly what to do. assistance please
:) thanks for viewing.
Click to expand...
Hello ,
have a look here http://w1.859.telia.com/~u85920178/index.htm
for some ideas that may help you. There is a lot of good reading on
that site. Click on "Projects" then click on "Transmitter Circuits"
Check out the valve Tx project. That should be easy if you are
having trouble with small components. You are talking broadcast
band here. The coil will be big anyway.

You remind me of my school days walking into a chemist shop
and asking for flowers of sulphur for a cut on my pet rabbit's leg,
charcoal and salt petre and then being told to bugger off by the
pharmacist. Half a dozen shops later we had the ingredients.

I don't know if you are a young lad or a grown up but no one
can stop you playing around with radio. The best place to pick
up parts and help is a Ham radio club. Lots of fun with like minded
people. Best to leave the broadcast band alone and join a
radio club.

Regards,
John Crighton
Hornsby
 
"John Crighton" <john_c@tpg.com.au> wrote in message
news:3fff008f.2636213@News.CIS.DFN.DE...
On Sat, 10 Jan 2004 02:35:37 +1000, "amstereo"
amstereo@optushomeDOTcompanyDOTaustralia> wrote:

I don't know if you are a young lad or a grown up but no one
can stop you playing around with radio. The best place to pick
up parts and help is a Ham radio club. Lots of fun with like minded
people. Best to leave the broadcast band alone and join a
radio club.
Click to expand...
Well you can come very close to the broadcast band (1.8 MHz) with a ham
licence. To
make things easier, you can buy crystals for 1.843 MHz which is sometimes
used
for AM transmissions and tweak your broadcast receiver to pick it up.

Better still, go down to your newsagent right now and pick up the
December-January
issue of Amateur Radio magazine. There's a great article on a 1.8 MHz AM
transmitter
to build. It's a little more complicated than you were probably thinking
of, but it's 20 watts
output.

http://www.alphalink.com.au/~parkerp/160.htm has info on 1.8 MHz activity
around Melbourne.

Regards, Peter

PS: The best I've done with 500mW of AM is about 30km. But the normal range
is nearer 5-10km.
 
"amstereo" wrote


What i am in need of is an RF Amplifier where i can input oh about
100milli-watts of .5 - 1.5 MHz signal and on the other side I magically
get
5 watts (more the merrier)



**** Pirating on the AM band again ,are we?
Brian Goldsmith.
 
the thing is, i've already got a transmitter (c-quam am stereo) that I want
to use it's output to drive the input of an amplifier type device, and get
more out of it, I can use it just above the broadcast band (crystal is 4x
frequency) 1800 = 7200.

a Whole transmitter isn't requred, just the amplifier stage.

I'm a youngins, but i have an interest in AM transmition. its more of a
chalenge getting the antanna right and things like that.
 
No, Testing out a few theories in relation to signal strength vs antanna
hight vs antanna configuration. I also have to keep phasig issues to a
minimum, because i am using am-stereo, which is a phase modulated stage
clipped on to a regular transmission. Wronge antanna configs screw the
phasing up. That why i'm doing this.
 
"amstereo" <amstereo@optushomeDOTcompanyDOTaustralia> wrote in message
news:3fff599b$0$27240$afc38c87@news.optusnet.com.au...

I'm a youngins, but i have an interest in AM transmition. its more of a
chalenge getting the antanna right and things like that.
Click to expand...
For best results aim to maximise the ground wave. This means a vertical
antenna with a low-loss matching network. A capacity hat and a ground plane
(eg tin roof) is important.

Length is desirable, but some people have put out potent signals with a
short top-loaded vertical on their car!

My good results were with a 9 metre wire held vertical on a pole. A good
ground was used (earth wire clipped onto a metal fence encircling sports
oval). A thicker rod (not wire) and a capacity hat would have improved
results further.

If you're over water you can do well. My best result was contacting the USA
with 5 watts and approx 100 m of wire as an antenna from St Kilda Pier.
That was using Morse code - AM would not do as well at that power level.

Peter
 
I get very little distance out of my little transmitter, 1km was the max i
could get - only under powerlines though.

I've got 100mw to work with as it sits, not much. I don't get it, why can a
CB on 12watts sideband hit south australia from ipswich in qld, and a lower
frequency transmission can't get down the road well?

I've toyed with carrier current, but i get a 50hz hum in the right channel.
 
Hi,
Well with 1 Mhz that's 75m for a 1/4 wavelength. If you are not using an
antenna of that length then your effeciency is going to be bugger all. Even
if you use a non resonant length with a matching network, most of the power
will be dissipated in the matching network as opposed to being radiated. If
your not anywhere near resonance the radiation impedance will be between
less than an ohm to a few ohms tops.

If you wanted to use L antenna variants you would still require a vertical
height of about 30 to 50m depending on which variant you use.

That's why those antennas right next door to me as so bloody big, not to
mention they use 10kW to get a decent signal around the place.

You could try using a weather balloon or similar to support a 1/4 wave
vertical for tests.

And of course you do have your experimental license don't you?

Greg


"amstereo" <amstereo@optushomeDOTcompanyDOTaustralia> wrote in message
news:3fff7404$0$25560$afc38c87@news.optusnet.com.au...
I get very little distance out of my little transmitter, 1km was the max i
could get - only under powerlines though.

I've got 100mw to work with as it sits, not much. I don't get it, why can
a
CB on 12watts sideband hit south australia from ipswich in qld, and a
lower
frequency transmission can't get down the road well?

I've toyed with carrier current, but i get a 50hz hum in the right
channel.
Click to expand...
 
"amstereo" <amstereo@optushomeDOTcompanyDOTaustralia> wrote

No, Testing out a few theories in relation to signal strength vs antanna
hight vs antanna configuration. I also have to keep phasig issues to a
minimum, because i am using am-stereo, which is a phase modulated stage
clipped on to a regular transmission. Wronge antanna configs screw the
phasing up. That why i'm doing this.

**** All this on the broadcast band?All within the law?

Brian Goldsmith.
 
I don't use frequencies that interfere with radio stations, i use empty
ones, and only during the day time. signal doesn't travel far in the day
time. This is my own personal guidelines. I've seen PC power supplies that
generate enough noise that the signal from the power supply travels further
than my transmitter does.
 
"amstereo" <amstereo@optushomeDOTcompanyDOTaustralia> wrote

I don't use frequencies that interfere with radio stations, i use empty
ones, and only during the day time. signal doesn't travel far in the day
time. This is my own personal guidelines. I've seen PC power supplies
that
generate enough noise that the signal from the power supply travels
further
than my transmitter does.


**** And Greg wrote "And of course you do have your experimental license
don't you?"

Well,do you?

Brian Goldsmith
 
nah, i' havn't even got a drivers licence yet.

were talking flea power at the moment (like the FM bugs, 'cept on am.)

havnt found how 2 get an experiment licence yet, care to elaberate?
 
Hi,
There is a scientific licence that may be applicable, about $50/yr. I think
there may also be some provisions for short term testing licence? I do
recall some amateurs with a test transmission down in the kHz region years
back and they obtained an experimental licence for that.

look here for more info.

http://www.aca.gov.au/aca_home/publications/reports/info/science.htm

You will probably need to apply for a non assigned scientific licence given
the frequencies you are using, else you may need to drop the freq or raise
it as the ABA may also have some input.

Just give the local ACA office a call, they'll be able to direct you in the
right direction.

I do not believe there is a class license for those FM bugs etc, so they are
not legal to use.

Good luck.

Greg

"amstereo" <amstereo@optushomeDOTcompanyDOTaustralia> wrote in message
news:4000b7d0$0$27240$afc38c87@news.optusnet.com.au...
nah, i' havn't even got a drivers licence yet.

were talking flea power at the moment (like the FM bugs, 'cept on am.)

havnt found how 2 get an experiment licence yet, care to elaberate?
Click to expand...
 
"gcd" <gcdmelbSPAM@austarmetro.com.au> wrote in message
news:4000e75e@news.comindico.com.au...

I do not believe there is a class license for those FM bugs etc, so they
are
not legal to use.
Click to expand...
Oh yes there is! See
http://www.aca.gov.au/aca_home/legislation/radcomm/class_licences/lipd.htm

and download the rtf file.

Thus our little transmitters are safe : )

Regards, Peter
 
Hi,
yes there is an entry there for 88-108. But c'mon 10uW EIRP? I reckon your
bug radiates much more than that!. I remember the old Jostky kit (is that
how it was spelt? - sigh - 1980's i'm getting old) , and it must have put
out out at least 20mW perhaps even more, used a 2n3866 output. S'pose some
of those designs in 101 fm bugs may meet the spec though.

Greg


"Peter Parker" <parkerp@NOSPAMalphalink.com.au> wrote in message
news:4001bf2d@news.alphalink.com.au...
"gcd" <gcdmelbSPAM@austarmetro.com.au> wrote in message
news:4000e75e@news.comindico.com.au...

I do not believe there is a class license for those FM bugs etc, so they
are
not legal to use.

Oh yes there is! See
http://www.aca.gov.au/aca_home/legislation/radcomm/class_licences/lipd.htm

and download the rtf file.

Thus our little transmitters are safe : )

Regards, Peter
Click to expand...
 
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