Does anyone have schematic/plans for a Band III (175 - 240MHz) antenna
booster?

Thanks.

ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz) antenna
booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


--
Best Regards:
Baron.

"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz) antenna
booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

A google search turned up a few results, but mostly bipolar - most of the
bipolars I have with adequate fT are in scrap TV tuners, they're a bit
fragile!

I do have a small stash of SMD medium power bipolars, but they weren't
cheap.

What I had in mind was something simple with a BF991, the plan is to
re-radiate from the communal aerial who's socket is diametrically opposite
the radio and no easy way to route a cable.

The walls are plastered on steel mesh, so the room is pretty much a faraday
cage - no chance of feedback to the master aerial.

ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.
By the way, do do know that I'm not in the USA. I'm just up the road
from you. :-)

A google search turned up a few results, but mostly bipolar - most of
the bipolars I have with adequate fT are in scrap TV tuners, they're a
bit fragile!

I do have a small stash of SMD medium power bipolars, but they weren't
cheap.

BFR91's are good up there.

What I had in mind was something simple with a BF991, the plan is to
re-radiate from the communal aerial who's socket is diametrically
opposite the radio and no easy way to route a cable.

You might find that phase differences in the direct and re-radiated
signals cause problems.

The walls are plastered on steel mesh, so the room is pretty much a
faraday cage - no chance of feedback to the master aerial.

Mmm I've never seen that done in a domestic property. Its usually only
the corners that have a steel edging strip. The only other time that
I've seen steel used, is as re-enforcing in prefabricated concrete
construction or the old style window and door frames.

--
Best Regards:
Baron.

"Baron" wrote in message
...
ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.
By the way, do do know that I'm not in the USA. I'm just up the road
from you. :-)

ISTR before DVB-T STBs became all the rage, the US was still using Band III
for TV - I was hoping someone here would know whether its still the case.

In any event there should have been more Band III antenna boosters left over
on the web than I've found.


A google search turned up a few results, but mostly bipolar - most of
the bipolars I have with adequate fT are in scrap TV tuners, they're a
bit fragile!

I do have a small stash of SMD medium power bipolars, but they weren't
cheap.

BFR91's are good up there.

Quite likely some of the bipolars I've lifted from scrap tuners could be
those, but they're mostly unmarked.

Somewhere at the back of the garage I have some scrap boards from Hitachi
19" monitors for Sun Micro's, each video stage has a 1.3GHz TO126 MOSFET as
the grounded gate part of the cascode. But that'd be getting into the relms
of feeding back to the master aerial.

There's also some hi-res monitor CRT boards in the junk box that can handle
the frequency, but apart from the hassle of rigging a 90 - 110V HT it would
definately re-radiate a little too much!


What I had in mind was something simple with a BF991, the plan is to
re-radiate from the communal aerial who's socket is diametrically
opposite the radio and no easy way to route a cable.

You might find that phase differences in the direct and re-radiated
signals cause problems.

I think the secret is keeping it as simple as possible and using a moulded
co-ax connector on the input, it might be neccessary to put a tinplate
screen over the MOSFET, there's also the point of orienting the input and
output RFCs at right angles.


The walls are plastered on steel mesh, so the room is pretty much a
faraday cage - no chance of feedback to the master aerial.

Mmm I've never seen that done in a domestic property. Its usually only
the corners that have a steel edging strip. The only other time that
I've seen steel used, is as re-enforcing in prefabricated concrete
construction or the old style window and door frames.

Mum's house is the same, and that's 100 years older than my flat, I remember
something needed to be mounted on a wall and when I drilled a hole for the
rawl plug the drill just went through to a void behind, I had to use a large
drill to ram a hole through the mesh and use a very large rawl plug.

All the internal walls in my flat are breeze block with the plaster slapped
straight on, but all the external walls have the plaster on steel mesh.

ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.
By the way, do do know that I'm not in the USA. I'm just up the road
from you. :-)

ISTR before DVB-T STBs became all the rage, the US was still using
Band III for TV - I was hoping someone here would know whether its
still the case.

http://en.wikipedia.org/wiki/North_A...on_frequencies
Seems so. Like the UK its doing the DTV bit.

In any event there should have been more Band III antenna boosters
left over on the web than I've found.


A google search turned up a few results, but mostly bipolar - most
of the bipolars I have with adequate fT are in scrap TV tuners,
they're a bit fragile!

I do have a small stash of SMD medium power bipolars, but they
weren't cheap.

BFR91's are good up there.

Quite likely some of the bipolars I've lifted from scrap tuners could
be those, but they're mostly unmarked.

I've not had much luck using those. :-(
They don't seem to like being extracted. I suspect heat or static
damages them.

Somewhere at the back of the garage I have some scrap boards from
Hitachi 19" monitors for Sun Micro's, each video stage has a 1.3GHz
TO126 MOSFET as the grounded gate part of the cascode. But that'd be
getting into the relms of feeding back to the master aerial.

You won't have a lot of gain from one of those, maybe 6db if you're
lucky. Power devices like that aren't much good with small signal
levels.

There's also some hi-res monitor CRT boards in the junk box that can
handle the frequency, but apart from the hassle of rigging a 90 - 110V
HT it would definately re-radiate a little too much!


What I had in mind was something simple with a BF991, the plan is to
re-radiate from the communal aerial who's socket is diametrically
opposite the radio and no easy way to route a cable.

You might find that phase differences in the direct and re-radiated
signals cause problems.

I think the secret is keeping it as simple as possible and using a
moulded co-ax connector on the input, it might be neccessary to put a
tinplate screen over the MOSFET, there's also the point of orienting
the input and output RFCs at right angles.


A passive input/output is what is needed for that kind of bandwidth.


The walls are plastered on steel mesh, so the room is pretty much a
faraday cage - no chance of feedback to the master aerial.

Mmm I've never seen that done in a domestic property. Its usually
only the corners that have a steel edging strip. The only other time
that I've seen steel used, is as re-enforcing in prefabricated
concrete construction or the old style window and door frames.

Mum's house is the same, and that's 100 years older than my flat, I
remember something needed to be mounted on a wall and when I drilled a
hole for the rawl plug the drill just went through to a void behind, I
had to use a large drill to ram a hole through the mesh and use a very
large rawl plug.

Yes there is normally a void behind the plaster board, maybe an inch.
The trick is to use a plasterboard anchor. There are two major types,
one simply screws into a pilot hole and threads directly into the
plaster the other is a spring toggle. There are many plastic and metal
variants of both.

All the internal walls in my flat are breeze block with the plaster
slapped straight on, but all the external walls have the plaster on
steel mesh.

Interesting !

--
Best Regards:
Baron.

"Baron" wrote in message
...
ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.
By the way, do do know that I'm not in the USA. I'm just up the road
from you. :-)

ISTR before DVB-T STBs became all the rage, the US was still using
Band III for TV - I was hoping someone here would know whether its
still the case.

http://en.wikipedia.org/wiki/North_A...on_frequencies
Seems so. Like the UK its doing the DTV bit.

In any event there should have been more Band III antenna boosters
left over on the web than I've found.


A google search turned up a few results, but mostly bipolar - most
of the bipolars I have with adequate fT are in scrap TV tuners,
they're a bit fragile!

I do have a small stash of SMD medium power bipolars, but they
weren't cheap.

BFR91's are good up there.

Quite likely some of the bipolars I've lifted from scrap tuners could
be those, but they're mostly unmarked.

I've not had much luck using those. :-(
They don't seem to like being extracted. I suspect heat or static
damages them.


Pill style UHF transistors include the only examples I know of plastic
encapsulated germanium transistors, being PNP isn't neccessarily a clue as
PNP silicon transistors aren't exactly rare in TV tuners.

With UHF transistors, my Peak-Atlas transistor tester can't tell the
difference between Ge & Si.


Somewhere at the back of the garage I have some scrap boards from
Hitachi 19" monitors for Sun Micro's, each video stage has a 1.3GHz
TO126 MOSFET as the grounded gate part of the cascode. But that'd be
getting into the relms of feeding back to the master aerial.

You won't have a lot of gain from one of those, maybe 6db if you're
lucky. Power devices like that aren't much good with small signal
levels.

If I was going to use one of those I'd make it the grounded gate in a
cascode with a more lively FET type device in the common source section, but
I'm pretty sure I don't need that kind of output power.


There's also some hi-res monitor CRT boards in the junk box that can
handle the frequency, but apart from the hassle of rigging a 90 - 110V
HT it would definately re-radiate a little too much!


What I had in mind was something simple with a BF991, the plan is to
re-radiate from the communal aerial who's socket is diametrically
opposite the radio and no easy way to route a cable.

You might find that phase differences in the direct and re-radiated
signals cause problems.

I think the secret is keeping it as simple as possible and using a
moulded co-ax connector on the input, it might be neccessary to put a
tinplate screen over the MOSFET, there's also the point of orienting
the input and output RFCs at right angles.


A passive input/output is what is needed for that kind of bandwidth.


Could be one of those lateral thinking moments - A dual gate MOSFET gives
its best into an inductor but parasitic capacitance will cause an unwanted
resonance.

I'm thinking low value (less than 10 Ohms) WW resistor - its as inductive as
a small RFC but with sufficient resistance to wreck its Q figure.


Many years ago when resistors were little ceramic tubes inhabited by an
end-capped carbon rod and sealed at each end with cement, it was common
practice to wind RFCs on these resistors, but I'm not sure what's the
different between shunt and series parasitic resistance in an RFC.




The walls are plastered on steel mesh, so the room is pretty much a
faraday cage - no chance of feedback to the master aerial.

Mmm I've never seen that done in a domestic property. Its usually
only the corners that have a steel edging strip. The only other time
that I've seen steel used, is as re-enforcing in prefabricated
concrete construction or the old style window and door frames.

Mum's house is the same, and that's 100 years older than my flat, I
remember something needed to be mounted on a wall and when I drilled a
hole for the rawl plug the drill just went through to a void behind, I
had to use a large drill to ram a hole through the mesh and use a very
large rawl plug.

Yes there is normally a void behind the plaster board,

Its definately not plaster board.

ian field Inscribed thus:

Pill style UHF transistors include the only examples I know of plastic
encapsulated germanium transistors, being PNP isn't neccessarily a
clue as PNP silicon transistors aren't exactly rare in TV tuners.

With UHF transistors, my Peak-Atlas transistor tester can't tell the
difference between Ge & Si.

:-)

If I was going to use one of those I'd make it the grounded gate in a
cascode with a more lively FET type device in the common source
section, but I'm pretty sure I don't need that kind of output power.

Here see if this suits.
If the attachment doesn't show I'll mail it to you.


A passive input/output is what is needed for that kind of bandwidth.

Could be one of those lateral thinking moments - A dual gate MOSFET
gives its best into an inductor but parasitic capacitance will cause
an unwanted resonance.

I'm thinking low value (less than 10 Ohms) WW resistor - its as
inductive as a small RFC but with sufficient resistance to wreck its Q
figure.

Many years ago when resistors were little ceramic tubes inhabited by
an end-capped carbon rod and sealed at each end with cement, it was
common practice to wind RFCs on these resistors, but I'm not sure
what's the different between shunt and series parasitic resistance in
an RFC.


Yes I remember that trick well. Particularly anode suppressors on
6146/6L6 PA's. I've burnt one or two up as well.

--
Best Regards:
Baron.

Baron Inscribed thus:

ian field Inscribed thus:

Pill style UHF transistors include the only examples I know of
plastic encapsulated germanium transistors, being PNP isn't
neccessarily a clue as PNP silicon transistors aren't exactly rare in
TV tuners.

With UHF transistors, my Peak-Atlas transistor tester can't tell the
difference between Ge & Si.

:-)

If I was going to use one of those I'd make it the grounded gate in a
cascode with a more lively FET type device in the common source
section, but I'm pretty sure I don't need that kind of output power.

Here see if this suits.
If the attachment doesn't show I'll mail it to you.


A passive input/output is what is needed for that kind of bandwidth.

Could be one of those lateral thinking moments - A dual gate MOSFET
gives its best into an inductor but parasitic capacitance will cause
an unwanted resonance.

I'm thinking low value (less than 10 Ohms) WW resistor - its as
inductive as a small RFC but with sufficient resistance to wreck its
Q figure.

Many years ago when resistors were little ceramic tubes inhabited by
an end-capped carbon rod and sealed at each end with cement, it was
common practice to wind RFCs on these resistors, but I'm not sure
what's the different between shunt and series parasitic resistance in
an RFC.


Yes I remember that trick well. Particularly anode suppressors on
6146/6L6 PA's. I've burnt one or two up as well.

Ooops ! Wrong picture. :-)

--
Best Regards:
Baron.

"Baron" wrote in message
...
Baron Inscribed thus:

ian field Inscribed thus:

Pill style UHF transistors include the only examples I know of
plastic encapsulated germanium transistors, being PNP isn't
neccessarily a clue as PNP silicon transistors aren't exactly rare in
TV tuners.

With UHF transistors, my Peak-Atlas transistor tester can't tell the
difference between Ge & Si.

:-)

If I was going to use one of those I'd make it the grounded gate in a
cascode with a more lively FET type device in the common source
section, but I'm pretty sure I don't need that kind of output power.

Here see if this suits.
If the attachment doesn't show I'll mail it to you.


A passive input/output is what is needed for that kind of bandwidth.

Could be one of those lateral thinking moments - A dual gate MOSFET
gives its best into an inductor but parasitic capacitance will cause
an unwanted resonance.

I'm thinking low value (less than 10 Ohms) WW resistor - its as
inductive as a small RFC but with sufficient resistance to wreck its
Q figure.

Many years ago when resistors were little ceramic tubes inhabited by
an end-capped carbon rod and sealed at each end with cement, it was
common practice to wind RFCs on these resistors, but I'm not sure
what's the different between shunt and series parasitic resistance in
an RFC.


Yes I remember that trick well. Particularly anode suppressors on
6146/6L6 PA's. I've burnt one or two up as well.

Ooops ! Wrong picture. :-)

That schematic has the Elektor look about it.

Is the 4007 being used as a varicap?

ian field Inscribed thus:


"Baron" wrote in message
...
Baron Inscribed thus:

ian field Inscribed thus:

Pill style UHF transistors include the only examples I know of
plastic encapsulated germanium transistors, being PNP isn't
neccessarily a clue as PNP silicon transistors aren't exactly rare
in TV tuners.

With UHF transistors, my Peak-Atlas transistor tester can't tell
the difference between Ge & Si.

:-)

If I was going to use one of those I'd make it the grounded gate in
a cascode with a more lively FET type device in the common source
section, but I'm pretty sure I don't need that kind of output
power.

Here see if this suits.
If the attachment doesn't show I'll mail it to you.


A passive input/output is what is needed for that kind of
bandwidth.

Could be one of those lateral thinking moments - A dual gate MOSFET
gives its best into an inductor but parasitic capacitance will
cause an unwanted resonance.

I'm thinking low value (less than 10 Ohms) WW resistor - its as
inductive as a small RFC but with sufficient resistance to wreck
its Q figure.

Many years ago when resistors were little ceramic tubes inhabited
by an end-capped carbon rod and sealed at each end with cement, it
was common practice to wind RFCs on these resistors, but I'm not
sure what's the different between shunt and series parasitic
resistance in an RFC.


Yes I remember that trick well. Particularly anode suppressors on
6146/6L6 PA's. I've burnt one or two up as well.

Ooops ! Wrong picture. :-)

That schematic has the Elektor look about it.

Shrug.

Is the 4007 being used as a varicap?

I assume that you are referring to D3. That is a reverse voltage
protection diode. There are no varicaps in that circuit at all.

If you look the amplifier can be powered via the signal output cable.

--
Best Regards:
Baron.

Baron wrote:

ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.


That would be 'high band' VHF in the US which runs from 174 to 216
MHz

I've used this style of amplifier for at least 25 years:

http://www.mcmelectronics.com/product/33-917&cid=prodCrossSell

Which works from 5 MHz to 950 MHz


They sell the power supply separately, or you can build your own:

http://www.mcmelectronics.com/product/DISTRIBUTED-BY-MCM-PS-10-/33-915

This is a typical one piece amp:

http://www.mcmelectronics.com/product/33-290&cid=prodCrossSell


A simple, DIY amp can be built on a piece of single sided PC board
with one of the monolithic amps from Minicircuits

http://www.minicircuits.com/pages/app_notes.html They sell individual
amp hybrids, hybrid assortment kits and development kits.

Most are designed for 50 ohm, but a six hole ferrite bead (Like those
used in baluns) are easy to make a 5 turn to six turn RF transformer
which will convert the impedance to about 72 ohms.

You should have little or no problem finding a local source, since
they are used in a lot of commercial radio equipment.


By the way, do do know that I'm not in the USA. I'm just up the road
from you. :-)

A google search turned up a few results, but mostly bipolar - most of
the bipolars I have with adequate fT are in scrap TV tuners, they're a
bit fragile!

I do have a small stash of SMD medium power bipolars, but they weren't
cheap.

BFR91's are good up there.

What I had in mind was something simple with a BF991, the plan is to
re-radiate from the communal aerial who's socket is diametrically
opposite the radio and no easy way to route a cable.

You might find that phase differences in the direct and re-radiated
signals cause problems.

The walls are plastered on steel mesh, so the room is pretty much a
faraday cage - no chance of feedback to the master aerial.

Mmm I've never seen that done in a domestic property. Its usually only
the corners that have a steel edging strip. The only other time that
I've seen steel used, is as re-enforcing in prefabricated concrete
construction or the old style window and door frames.

--
Best Regards:
Baron.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

"Michael A. Terrell" wrote in message
m...

Baron wrote:

ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.


That would be 'high band' VHF in the US which runs from 174 to 216
MHz

I've used this style of amplifier for at least 25 years:

http://www.mcmelectronics.com/product/33-917&cid=prodCrossSell

Which works from 5 MHz to 950 MHz


Do you have any schematics for a VHF high band booster?

My junkbox might do better to provide a DG MOSFET such as a BF991.

"Michael A. Terrell" wrote in message
m...

Baron wrote:

ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.


That would be 'high band' VHF in the US which runs from 174 to 216
MHz

I've used this style of amplifier for at least 25 years:

http://www.mcmelectronics.com/product/33-917&cid=prodCrossSell

Which works from 5 MHz to 950 MHz


Just out of curiosity - what frequency could I squeeze through a 2N7000 as
the grounded gate section of a cascode?

ian field Inscribed thus:

Just out of curiosity - what frequency could I squeeze through a
2N7000 as the grounded gate section of a cascode?

Probably 100Mhz or thereabouts.

--
Best Regards:
Baron.

"Baron" wrote in message
...
ian field Inscribed thus:

Just out of curiosity - what frequency could I squeeze through a
2N7000 as the grounded gate section of a cascode?

Probably 100Mhz or thereabouts.

--
Best Regards:
Baron.


Obviously I was hoping for a little more.

There are schematics floating about the web for Ham rigs using an IRF510 PA,
maybe 40 or 80m.

ian field wrote:

"Michael A. Terrell" wrote in message
m...

Baron wrote:

ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.


That would be 'high band' VHF in the US which runs from 174 to 216
MHz

I've used this style of amplifier for at least 25 years:

http://www.mcmelectronics.com/product/33-917&cid=prodCrossSell

Which works from 5 MHz to 950 MHz

Do you have any schematics for a VHF high band booster?


You need more than a schematic. Layout is critical at VHF if you
want a stable, low noise preamp.

The websites that had construction details that I could remember are
all gone. Some of those Mini Circuits MMIC hybrids are low noise, high
gain amplifiers for a couple dollars. All you need is 5 to 15 volts, a
couple capacitors and a resistor or inductor to isolate it from the
power supply. To duplicate its performance with discreet parts would
require careful layout on a PC board, or inside a metal shield with
standoffs to hold the parts.


My junkbox might do better to provide a DG MOSFET such as a BF991.


Why dual gate? You don't need a mixer.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

ian field wrote:

"Baron" wrote in message
...
ian field Inscribed thus:

Just out of curiosity - what frequency could I squeeze through a
2N7000 as the grounded gate section of a cascode?

Probably 100Mhz or thereabouts.

--
Best Regards:
Baron.


Obviously I was hoping for a little more.

There are schematics floating about the web for Ham rigs using an IRF510 PA,
maybe 40 or 80m.


40 meters is 7 MHz.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

"Michael A. Terrell" wrote in message
news

ian field wrote:

"Michael A. Terrell" wrote in message
m...

Baron wrote:

ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.


That would be 'high band' VHF in the US which runs from 174 to 216
MHz

I've used this style of amplifier for at least 25 years:

http://www.mcmelectronics.com/product/33-917&cid=prodCrossSell

Which works from 5 MHz to 950 MHz

Do you have any schematics for a VHF high band booster?


You need more than a schematic. Layout is critical at VHF if you
want a stable, low noise preamp.

The websites that had construction details that I could remember are
all gone. Some of those Mini Circuits MMIC hybrids are low noise, high
gain amplifiers for a couple dollars. All you need is 5 to 15 volts, a
couple capacitors and a resistor or inductor to isolate it from the
power supply. To duplicate its performance with discreet parts would
require careful layout on a PC board, or inside a metal shield with
standoffs to hold the parts.


My junkbox might do better to provide a DG MOSFET such as a BF991.


Why dual gate? You don't need a mixer.


It pretty much behaves like a cascode and lowers input capacitance.

A BF991 has much lower capacitance than any JFETs I have that can handle the
frequency, and the lowest power single gate MOSFET I have is the 2N7000 -
which I've already been told won't handle the frequency.

ian field wrote:

"Michael A. Terrell" wrote in message
news

ian field wrote:

"Michael A. Terrell" wrote in message
m...

Baron wrote:

ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.


That would be 'high band' VHF in the US which runs from 174 to 216
MHz

I've used this style of amplifier for at least 25 years:

http://www.mcmelectronics.com/product/33-917&cid=prodCrossSell

Which works from 5 MHz to 950 MHz

Do you have any schematics for a VHF high band booster?


You need more than a schematic. Layout is critical at VHF if you
want a stable, low noise preamp.

The websites that had construction details that I could remember are
all gone. Some of those Mini Circuits MMIC hybrids are low noise, high
gain amplifiers for a couple dollars. All you need is 5 to 15 volts, a
couple capacitors and a resistor or inductor to isolate it from the
power supply. To duplicate its performance with discreet parts would
require careful layout on a PC board, or inside a metal shield with
standoffs to hold the parts.


My junkbox might do better to provide a DG MOSFET such as a BF991.


Why dual gate? You don't need a mixer.

It pretty much behaves like a cascode and lowers input capacitance.

A BF991 has much lower capacitance than any JFETs I have that can handle the
frequency, and the lowest power single gate MOSFET I have is the 2N7000 -
which I've already been told won't handle the frequency.


Does the data sheet for that part have a sample layout or test
configuration?

Sorry, I forgot that is a Philips part. Their data sheet is fairly
useless.

http://www.datasheetcatalog.org/data...ps/BF991_2.pdf

How about modifying the front end of a junk TV tuner?


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.

"Michael A. Terrell" wrote in message
m...

ian field wrote:

"Michael A. Terrell" wrote in message
news

ian field wrote:

"Michael A. Terrell" wrote in message
m...

Baron wrote:

ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.


That would be 'high band' VHF in the US which runs from 174 to 216
MHz

I've used this style of amplifier for at least 25 years:

http://www.mcmelectronics.com/product/33-917&cid=prodCrossSell

Which works from 5 MHz to 950 MHz

Do you have any schematics for a VHF high band booster?


You need more than a schematic. Layout is critical at VHF if you
want a stable, low noise preamp.

The websites that had construction details that I could remember are
all gone. Some of those Mini Circuits MMIC hybrids are low noise, high
gain amplifiers for a couple dollars. All you need is 5 to 15 volts, a
couple capacitors and a resistor or inductor to isolate it from the
power supply. To duplicate its performance with discreet parts would
require careful layout on a PC board, or inside a metal shield with
standoffs to hold the parts.


My junkbox might do better to provide a DG MOSFET such as a BF991.


Why dual gate? You don't need a mixer.

It pretty much behaves like a cascode and lowers input capacitance.

A BF991 has much lower capacitance than any JFETs I have that can handle
the
frequency, and the lowest power single gate MOSFET I have is the 2N7000 -
which I've already been told won't handle the frequency.


Does the data sheet for that part have a sample layout or test
configuration?

Sorry, I forgot that is a Philips part. Their data sheet is fairly
useless.

http://www.datasheetcatalog.org/data...ps/BF991_2.pdf

How about modifying the front end of a junk TV tuner?


VHF high band tuners are a bit rare in the UK, the band IV/V tuners are a
bit fiddly.

I might try a cascode with a 3819 CS and a 2SK619 as the GG, I was thinking
of a WW resistor to masquerade as the drain load RFC - low Q should squash
any resonance due to parasitic capacitance.

Hitachi datasheets are rubbish too - they say the 2SK619 is a high frequency
MOSFET but don't specify how high.

"Baron" wrote in message
...
ian field Inscribed thus:

Just out of curiosity - what frequency could I squeeze through a
2N7000 as the grounded gate section of a cascode?

Probably 100Mhz or thereabouts.

Having scribbled a rough schematic I've decided on a cascode with a 3819
input and a 2SK619 output driving a WW resistor masquerading as a low Q RFC.

Possibly the simplest way of setting up the operating conditions, is to use
a single transistor current source instead of a source resistor for the
3819 - any reccomendations on what's a suitable current setting?

"Michael A. Terrell" wrote in message
news

ian field wrote:

"Baron" wrote in message
...
ian field Inscribed thus:

Just out of curiosity - what frequency could I squeeze through a
2N7000 as the grounded gate section of a cascode?

Probably 100Mhz or thereabouts.

--
Best Regards:
Baron.


Obviously I was hoping for a little more.

There are schematics floating about the web for Ham rigs using an IRF510
PA,
maybe 40 or 80m.


40 meters is 7 MHz.

Hitachi won't tell me how fast the 2SK619 "high frequency MOSFET" will go,
but I've birdsnested the cascode with a 3819 in the common source section
and a 1mA current source instead of a source resistor.

This should allow me to study the DC behaviour of the circuit, but it was
gone 2am by the time I built it so I put it aside and turned in - I can
fire it up at the next tinkering session.

ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Just out of curiosity - what frequency could I squeeze through a
2N7000 as the grounded gate section of a cascode?

Probably 100Mhz or thereabouts.

Having scribbled a rough schematic I've decided on a cascode with a
3819 input and a 2SK619 output driving a WW resistor masquerading as a
low Q RFC.

Possibly the simplest way of setting up the operating conditions, is
to use a single transistor current source instead of a source resistor
for the 3819 - any reccomendations on what's a suitable current
setting?

Difficult one ! Probably in the 3 to 6 ma range. The max for a 2n3819
is about 20 ma. Though I don't see the advantage of a cascode
arrangement.

--
Best Regards:
Baron.

"Baron" wrote in message
...
ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Just out of curiosity - what frequency could I squeeze through a
2N7000 as the grounded gate section of a cascode?

Probably 100Mhz or thereabouts.

Having scribbled a rough schematic I've decided on a cascode with a
3819 input and a 2SK619 output driving a WW resistor masquerading as a
low Q RFC.

Possibly the simplest way of setting up the operating conditions, is
to use a single transistor current source instead of a source resistor
for the 3819 - any reccomendations on what's a suitable current
setting?

Difficult one ! Probably in the 3 to 6 ma range. The max for a 2n3819
is about 20 ma. Though I don't see the advantage of a cascode
arrangement.

Its usual practice to run a JFET at less than IDSS(min) - which is 2mA for
the 3819, although most of the examples I have are well toward the (max) end
of the published spec, if I need more current I can pad the emitter resistor
in the current source until I reach the limit of the JFET in place.

An attractive solution is the DG MOSFET which behaves like a cascode and
gives good gain with less risk of instability and much reduced input
capacitance, the DG also allows very easy gain control - but I'm not sure
whether that applies to my discrete cascode.

Possibly most important of all is the top half of a cascode is a grounded
gate stage, which is a configuration that gets the highest frequency
response out of any given transistor used in that position.

"Michael A. Terrell" wrote in message
news

ian field wrote:

"Michael A. Terrell" wrote in message
m...

Baron wrote:

ian field Inscribed thus:


"Baron" wrote in message
...
ian field Inscribed thus:

Does anyone have schematic/plans for a Band III (175 - 240MHz)
antenna booster?

Thanks.

65Mhz ! Thats a pretty big bandwidth to cover.


Is Band III still used for TV in the US?

I don't know ! The guy that will know is Michael in SED.


That would be 'high band' VHF in the US which runs from 174 to 216
MHz

I've used this style of amplifier for at least 25 years:

http://www.mcmelectronics.com/product/33-917&cid=prodCrossSell

Which works from 5 MHz to 950 MHz

Do you have any schematics for a VHF high band booster?


You need more than a schematic. Layout is critical at VHF if you
want a stable, low noise preamp.

The websites that had construction details that I could remember are
all gone. Some of those Mini Circuits MMIC hybrids are low noise, high
gain amplifiers for a couple dollars. All you need is 5 to 15 volts, a
couple capacitors and a resistor or inductor to isolate it from the
power supply. To duplicate its performance with discreet parts would
require careful layout on a PC board, or inside a metal shield with
standoffs to hold the parts.


Last night DAB reception was unusually bad, so I figured I had nothing to
lose trying out my birdsnested booster. The 2N3819/2SK619 cascode only gave
a very slight improvement, so I tried a 2N7000 in place of the 619, the
result was indistinguishable. Next I tried a BF991 with its gates tied
together (I would have tried the 991 on its own in a normal configuration,
but the 12V wall-wart is actually pushing out 20V, right on the ABS-MAX for
the 991) this gave a bit more improvement but still a long way short of good
enough.

The best so far was a 2x 2N3819 cascode - the real improvement came when I
swapped from the radio to the TV socket. I think I may have identified a
flaw in using a WW resistor as a low Q RFC - the resistor has end caps which
are like a shorted turn at each end. So still needing a bit more
improvement, I might try actually winding some air cored coils and see if
they work better.

Since I was using the TV aerial socket I decided to check for TVI with a
little Casio pocket TV, much to my surprise it now gives 4 clear channels
instead of just one that was too grainy to see much. It didn't get channel
5, but that's higher up the band and the 3819s run out of steam about
450MHz.