Hello All,
I'm trying to put together a satellite station and know that I need
a mast mounted pre-amp for my receive antenna. I'll be using
Lindenblad antennas for both transmitting and receiving. I'm looking
for opinions on a good pre-amp, company and models. I know I need a
unit with a low noise floor, sub 1 Db.
Thanks,
Rob Brown
kb8wws

Hi Rob

Thats a pretty wide open question... I don't have any model etc
recommendations for you, but since nobody has replied to your question...

Suggest you read up (web) and understand the implications of preamps,
then with understanding about gain, noise figure, IMD and power handling
go and compare various manufacturers models. Relying on empirical "it
worked well for me" from fellow amateurs is always fraught with danger!

Keep in mind that for some designs, best NF corresponds with really bad
performance in an adjacent strong signal environment. Fiddling with gate
bias current is a way to tune this to the best compromise.

You may also wish to review your choice of antennas. Higher gain and
steering may be something you'll need (eg for using the higher orbit
sats) and the wider pattern from the Lindenblad's may introduce more
terrestrial noise than you want. My next experiment for sat work will be
a quadrature fed interlaced 2/70 quad.. Cebik has some info on that..

If you are RX only you may even wish to build.

Cheers Bob VK2YQA

Rob Brown wrote:
I'm looking
for opinions on a good pre-amp, company and models. I know I need a
unit with a low noise floor, sub 1 Db.

On Aug 6, 7:11 am, Bob Bob wrote:
Hi Rob

Thats a pretty wide open question... I don't have any model etc
recommendations for you, but since nobody has replied to your question...

Suggest you read up (web) and understand the implications of preamps,
then with understanding about gain, noise figure, IMD and power handling
go and compare various manufacturers models. Relying on empirical "it
worked well for me" from fellow amateurs is always fraught with danger!

Keep in mind that for some designs, best NF corresponds with really bad
performance in an adjacent strong signal environment. Fiddling with gate
bias current is a way to tune this to the best compromise.

You may also wish to review your choice of antennas. Higher gain and
steering may be something you'll need (eg for using the higher orbit
sats) and the wider pattern from the Lindenblad's may introduce more
terrestrial noise than you want. My next experiment for sat work will be
a quadrature fed interlaced 2/70 quad.. Cebik has some info on that..

If you are RX only you may even wish to build.

Cheers Bob VK2YQA

Rob Brown wrote:
I'm looking
for opinions on a good pre-amp, company and models. I know I need a
unit with a low noise floor, sub 1 Db.

Bob,
Thanks for the info. I won't be able to install a tower or any other
large expense project at my QTH for the near future. The XYL isn't
too keen on our hobby and so the best I will be able to do is the pair
of Lindenblad antennas. I'm going with the Lindenblad antennas after
reading the section L.B. Cebik has on his extensive web site. Antenna
is omni-directional, has gain from 3 to 50 degrees, and I can build it
with simple hand tools. I'll start looking for more information about
the pre-amps on-line. I had looked at the AMSAT site, but they didn't
mention too many manufacturers for the pre-amps.
Thanks,
Rob Brown
KB8WWS

Rob,

As was pointed out, there are many options. Having been active on
satellites for 20+ years, I would recommend that you look at the SSB
Electronics units http://www.ssbusa.com/gaasfet.html and the ARR units
http://www.advancedreceiver.com/page2.html in that order. If you took
a poll of AMSAT members, I would be amazed if between the 2 they did
not constitute 75% or more used. Both do well in high noise areas.
The SSB units have some additional filtering, and adjustable gain.

While they are no longer sold in this country, if you come across a
Landwehr unit, it would be worth considering. My 2 meter unit keeps
on ticking 21 years later.

One thing to avoid is the units sold by major manufacturers such as
Icom. They probably have some use, somewhere, but for satellite ops
they soon get replaced as they have poor noise figures.

Finally, it is tempting to go with an RX-only unit. You will want the
capability to both receive and transmit on both antennas, which pretty
much means a switched unit, or some fancy relays. If you have short
runs of high quality cable, you can probably get by on 2 meters with a
unit in the shack. A mast mount is better, but for most things, one
in the shack, with the above qualifications, is good enough. The 70
cm unit need to be mounted remotely.




--
Alan
WA4SCA

"Rob Brown" wrote in message
oups.com...
On Aug 6, 7:11 am, Bob Bob wrote:
Hi Rob

Thats a pretty wide open question... I don't have any model etc
recommendations for you, but since nobody has replied to your question...

Suggest you read up (web) and understand the implications of preamps,
then with understanding about gain, noise figure, IMD and power handling
go and compare various manufacturers models. Relying on empirical "it
worked well for me" from fellow amateurs is always fraught with danger!

Keep in mind that for some designs, best NF corresponds with really bad
performance in an adjacent strong signal environment. Fiddling with gate
bias current is a way to tune this to the best compromise.

You may also wish to review your choice of antennas. Higher gain and
steering may be something you'll need (eg for using the higher orbit
sats) and the wider pattern from the Lindenblad's may introduce more
terrestrial noise than you want. My next experiment for sat work will be
a quadrature fed interlaced 2/70 quad.. Cebik has some info on that..

If you are RX only you may even wish to build.

Cheers Bob VK2YQA

Rob Brown wrote:
I'm looking
for opinions on a good pre-amp, company and models. I know I need a
unit with a low noise floor, sub 1 Db.

Bob,
Thanks for the info. I won't be able to install a tower or any other
large expense project at my QTH for the near future. The XYL isn't
too keen on our hobby and so the best I will be able to do is the pair
of Lindenblad antennas. I'm going with the Lindenblad antennas after
reading the section L.B. Cebik has on his extensive web site. Antenna
is omni-directional, has gain from 3 to 50 degrees, and I can build it
with simple hand tools. I'll start looking for more information about
the pre-amps on-line. I had looked at the AMSAT site, but they didn't
mention too many manufacturers for the pre-amps.
Thanks,
Rob Brown
KB8WWS

Hi Rob

Have you considered joining AMSAT? There is a wealth of information on
HAM satellites within that organization. I consider Bob's advice about
preamps to be excellent. AMSAT Journal, Volume 28 Number 4, July/August
2005 has a good article on preamps for HAM satellite reception.
Cebik's text on Lindenblads implies that it needs to be located only a few
feet above ground in order to realize the "omni-hemispheric" pattern, so
line loss isnt likely to be reason enough to use a preamp with it anyway.

Jerry

Yeah thats always bad. I chose my XYL to fit in with my hobby grin

Of course height isn't as important for sat work than it is for
terrestrial. You can place small directive arrays on the rooftop and
steer them easily. I realize you are already Lindenblad bound but 2-3
element quads or helix antennas are still quite unobtrusive. Another
possibility is the egg beater type construction that with a simple
azimuth rotator will give you a few more dB gain than the "full" omni. I
personally went from a cross dipole to a Lindenblad in my first
satellite experiments with RS10. Was only running 3W SSB on 2m and it
was copyable on 10m down to 5 degrees elevation.

But back on the preamp front. I saw Alan's recommendation for the SSB
Electronics unit. No doubt there is a good reason for such a "high"
price, but I think I'd stick to building one from cheapish dual gate
FETs. Granted the NF isn't as low but with average rigs running 4-12dB
the improvement will still be significant. (Some rigs benefit from
changing PIN diode T/R switching to a coaxial relay. It really is
surprising) You may even want to do the maths of determining how much RX
signal you really need. A satellite is of course listening for signals
against a large amount of terrestrial noise whereas you are looking up
at essentially a cold RF sky. One of the reasons now doubt for the
disparity in ground station vs satellite RF output power.

Down East Microwave do a number of LNA's;

http://www.downeastmicrowave.com
and a 2m device;
http://www.downeastmicrowave.com/PDF/2mlna.PDF

I remember hearing good things about the company maybe 10 years ago.
They are a around $30-60 for RX only applications.

Sorry I ran out of time web searching. They aren't as prolific as I thought!

I apologize for waffling!

Cheers Bob



Rob Brown wrote:

Bob,
Thanks for the info.

On Aug 7, 8:28 pm, Bob Bob wrote:
Yeah thats always bad. I chose my XYL to fit in with my hobby grin

Of course height isn't as important for sat work than it is for
terrestrial. You can place small directive arrays on the rooftop and
steer them easily. I realize you are already Lindenblad bound but 2-3
element quads or helix antennas are still quite unobtrusive. Another
possibility is the egg beater type construction that with a simple
azimuth rotator will give you a few more dB gain than the "full" omni. I
personally went from a cross dipole to a Lindenblad in my first
satellite experiments with RS10. Was only running 3W SSB on 2m and it
was copyable on 10m down to 5 degrees elevation.

But back on the preamp front. I saw Alan's recommendation for the SSB
Electronics unit. No doubt there is a good reason for such a "high"
price, but I think I'd stick to building one from cheapish dual gate
FETs. Granted the NF isn't as low but with average rigs running 4-12dB
the improvement will still be significant. (Some rigs benefit from
changing PIN diode T/R switching to a coaxial relay. It really is
surprising) You may even want to do the maths of determining how much RX
signal you really need. A satellite is of course listening for signals
against a large amount of terrestrial noise whereas you are looking up
at essentially a cold RF sky. One of the reasons now doubt for the
disparity in ground station vs satellite RF output power.

Down East Microwave do a number of LNA's;

http://www.downeastmicrowave.com
and a 2m device;http://www.downeastmicrowave.com/PDF/2mlna.PDF

I remember hearing good things about the company maybe 10 years ago.
They are a around $30-60 for RX only applications.

Sorry I ran out of time web searching. They aren't as prolific as I thought!

I apologize for waffling!

Cheers Bob

Rob Brown wrote:
Bob,
Thanks for the info.

Bob,
Thanks for the links. Sorry about the late date of this post, but
this is the first time I've done anything at home except sleep! We
work to play, or that's the way I do it.
Thanks again,
Rob Brown
KB8WWS