On Jan 18, 8:20*am, BV wrote:
Hi

Got a pair of MRF648 and would like to build a 100W 70cm PA running at
13,8V.
I have been looking for constructions/idéeas on Google without luck.
Anybody able to help me?

If You got an article i can use, please mail it to me: bv(--at..)
mailme.dk

MRF648 data:

DESCRIPTION:
The ASI MRF648 is Designed for
12.5 V UHF large signal amplifier
applications up to 512 MHz.

FEATURES:
. Internal Input Matching Network
. PG = 4.4 dB at 60 W/470 MHz
. OmnigoldT Metalization System

MAXIMUM RATINGS
IC * * * * * * *11 A
VCBO * * * 36 V
VCEO * * * 16 V
VEBO * * * *4.0 V
PDISS * * * *175 W @ TC = 25 °C
TJ * * * * * * * -65 °C to +200 °C
TSTG * * * * -65 °C to +150 °C
?JC * * * * * *1.0 °C/W

73 de OZ1BV, Brian

Hi Brian,

My Motorola data book says these are designed for class C (e.g. FM)
amplifier service, not linear. I suppose you should expect to get a
little less PEP power out of them in linear service, for good
linearity.

The Moto data sheet has a test circuit; I could scan it, if it would
be any use to you. The microstrip dimensions are for glass-teflon
board, er=2.55, 1/16" (1.6mm) thick. Of course, the test circuit is
for a single transistor, not a pair. It is solidly class C: the base
and emitter are both at DC ground.

Cheers,
Tom

Hi Tom

Hi Brian,

My Motorola data book says these are designed for class C (e.g. FM)
amplifier service, not linear. *I suppose you should expect to get a
little less PEP power out of them in linear service, for good
linearity.

The Moto data sheet has a test circuit; I could scan it, if it would
be any use to you. *The microstrip dimensions are for glass-teflon
board, er=2.55, 1/16" (1.6mm) thick. *Of course, the test circuit is
for a single transistor, not a pair. *It is solidly class C: *the base
and emitter are both at DC ground.

Cheers,
Tom- Skjul tekst i anførselstegn -

- Vis tekst i anførselstegn -

This is correct, but I found out that Tokyo Hy-Power HL-120U uses
these transistors in this PA. If they are able to make a 100W linear
amp i hope to be able to do the same:-)
(The list where I figured out what transistor type is udes in PA's:
http://www.electronicpool.de/en/funkgeraetetypen.html)

I have not been able to find a schematic for HL-120U. It would be nice
to see how they designed the bias circuit.

Medt 73 de OZ1BV, Brian

"BV" wrote in message
...
Hi Tom

Hi Brian,

My Motorola data book says these are designed for class C (e.g. FM)
amplifier service, not linear. I suppose you should expect to get a
little less PEP power out of them in linear service, for good
linearity.

The Moto data sheet has a test circuit; I could scan it, if it would
be any use to you. The microstrip dimensions are for glass-teflon
board, er=2.55, 1/16" (1.6mm) thick. Of course, the test circuit is
for a single transistor, not a pair. It is solidly class C: the base
and emitter are both at DC ground.

Cheers,
Tom- Skjul tekst i anførselstegn -

- Vis tekst i anførselstegn -

This is correct, but I found out that Tokyo Hy-Power HL-120U uses
these transistors in this PA. If they are able to make a 100W linear
amp i hope to be able to do the same:-)
(The list where I figured out what transistor type is udes in PA's:
http://www.electronicpool.de/en/funkgeraetetypen.html)

I have not been able to find a schematic for HL-120U. It would be nice
to see how they designed the bias circuit.

Medt 73 de OZ1BV, Brian

You will find that the Mirage linears used the same family of
transistors as well.

pete