On 1 Mar 2007 21:16:22 -0800, wrote:

Dare I say that what is needed is that much overworked phrase
"paradigm shift"? It used to be that a "transceiver" was a radical
new thing, because everyone knew that you needed a separate Tx and
Rx. Oddly, with phased arrays, perhaps the transceiver becomes passe.

Hi Jim,

There may be life left in the transceiver to perform what you want
anyway. Just think more power.

I can sense that this discussion is leading back to a separation of
driver from amplifier. You could still use a power divider to feed
the remote amps at the various array locations. Say 10W at 10 active
antennas, each with a 100W rating.

This would preserve investment, and create and alternative to the
Henry market. Hams would have two purchase paths instead of
discarding their introductory base station and opting in for N number
of active arrays driven by a specialty item that looks like their old
rig gathering dust in the corner.

Of course, if you are talking about two or three elements, this shifts
the investment plan (but it still presumes you are willing to abandon
a prior investment). The cost-benefit of this is usually a steep
slope populated only by a few early adopters.


In fact, for HF, you can probably get away with smaller active
antennas for receive. There's no particular reason why the Tx
antennas and the Rx antennas have to be the same, since you're not
typically receiver noise figure limited.

There's no reason to expect you need a large transmit antenna for
solid state amps either. The native source resistance of a transistor
is quite low, and has to be transformed UP to match 50 Ohms. If you
had a radiation resistance of only several ohms (a very short
radiator) all you have to pay attention to is cutting Ohmic loss and
providing flexible inductance. Unfortunately, this may be a
performance killer - but if you are demanding multiband performance,
you will have to answer for this for any size array element.

There IS a strong signal IM
problem..so maybe active receive antennas aren't the right solution.

The same transceiver that survives IM would still handle it from
several phase active array elements. As you can see, redesigning a
new driver eventually leads you back to the gear you have. If you now
demand a separate receiver, separate driver, and separate active array
antennas, costs rise faster by the number of connections.

Adaptive nulling is a bit weird to
work with as a user, especially if you expect to control it. And, for
hams, they want a bit more control.

Programmable oscillators that shift immediately and start at any point
in the cycle (absolute phase AND frequency control) would be miles
further down the road.

These devices are NOT synthesizers NOR linear multipliers. They are
variable frequency look-up tables driving a DAC. You send the chip a
command of the frequency you want, and the phase angle; send the "go"
command, and the oscillator shifts from its existing frequency and
phase immediately to the new one (immediately being within one table
cell lookup).

When I looked into these 10 years ago, they (driver/DAC combination)
operated from the KHz up to about 16MHz and cost less than one XTAL
ordered to a single frequency. You still have the elemental clock osc
XTAL for processor and driver, but those litter the world for pennies.

Using this kind of technology is about the only reason I would trash
my current rigs and go for a custom driver (but it would have to
inhabit each array antenna's amp and thus render it a complete
transmitter. This would in turn cast all the features (like SSB
generation) into each of those elements. The unit cost of this would
climb because of feature creep, not component pricing.

What would be cool is to have a
3D panoramic display that somehow indicates not only the frequency
spectrum, but the angle of arrival.

This again, argues for small adaptive antennas. Now you need them in
layers.

73's
Richard Clark, KB7QHC

In fact, for HF, you can probably get away with smaller active
antennas for receive. There's no particular reason why the Tx
antennas and the Rx antennas have to be the same, since you're not
typically receiver noise figure limited.

Adaptive nulling is a bit weird to
work with as a user, especially if you expect to control it. And, for
hams, they want a bit more control.

Using this kind of technology is about the only reason I would trash
my current rigs and go for a custom driver (but it would have to
inhabit each array antenna's amp and thus render it a complete
transmitter. This would in turn cast all the features (like SSB
generation) into each of those elements. The unit cost of this would
climb because of feature creep, not component pricing.

What would be cool is to have a
3D panoramic display that somehow indicates not only the frequency
spectrum, but the angle of arrival.


When living in a residential area, as I do, canceling or reducing local qrm
and man made noise is your first interest!
Using an array is may be the only way to go. Either by using analog means
(phasers) or using digital signal processing. In DSP a lot more is possible.

I use an array of 2 small active loop antennas.
The two phase coherent receivers are made using the front-ends of two
Elecraft K2´s and a Delta 44 soundcard in the PC. The software makes
the rest of the dual (SDR) receiver. No expensive hardware needed.
See: http://www.pa0sim.nl/Software.htm
(one of the windows shows the phase difference (TDOA), which helps
eg. selecting the correct phase for the phaser)

Even two antennas can be very effective against local qrm and even non
local qrm. I sure would like to try four antennas HI. It is easy to scale it
to four antennas/receivers, but I still have my qrl .....

73 de Jan PA0SIM

On 2 Mar, 10:41, "Jan Simons PA0SIM"
wrote:
In fact, for HF, you can probably get away with smaller active
antennas for receive. There's no particular reason why the Tx
antennas and the Rx antennas have to be the same, since you're not
typically receiver noise figure limited.

Adaptive nulling is a bit weird to
work with as a user, especially if you expect to control it. And, for
hams, they want a bit more control.

Using this kind of technology is about the only reason I would trash
my current rigs and go for a custom driver (but it would have to
inhabit each array antenna's amp and thus render it a complete
transmitter. This would in turn cast all the features (like SSB
generation) into each of those elements. The unit cost of this would
climb because of feature creep, not component pricing.

What would be cool is to have a
3D panoramic display that somehow indicates not only the frequency
spectrum, but the angle of arrival.

When living in a residential area, as I do, canceling or reducing local qrm
and man made noise is your first interest!
Using an array is may be the only way to go. Either by using analog means
(phasers) or using digital signal processing. In DSP a lot more is possible.

I use an array of 2 small active loop antennas.
The two phase coherent receivers are made using the front-ends of two
Elecraft K2´s and a Delta 44 soundcard in the PC. The software makes
the rest of the dual (SDR) receiver. No expensive hardware needed.
See:http://www.pa0sim.nl/Software.htm
(one of the windows shows the phase difference (TDOA), which helps
eg. selecting the correct phase for the phaser)

Even two antennas can be very effective against local qrm and even non
local qrm. I sure would like to try four antennas HI. It is easy to scale it
to four antennas/receivers, but I still have my qrl .....

73 de Jan PA0SIM- Hide quoted text -

- Show quoted text -

Jan,
the above is beyond me. I see it as an ideal addition to a Gaussian
array where you have two receive points or more on the antenna such
that the receiver could make the best choice which is polarity of
choice. At the same time allows you to disconnect two feed points to
concentrate on the desired feed. Of course all feeds can be connected
for recieve anyway to counteract fade. I believe that there is a niche
in ham radio for what you have there.
Thanks for sharing
Cheers and beers
Art

On Mar 1, 10:32 pm, Richard Clark wrote:

I can sense that this discussion is leading back to a separation of
driver from amplifier. You could still use a power divider to feed
the remote amps at the various array locations. Say 10W at 10 active
antennas, each with a 100W rating.

This probably the most practical thing.. and in fact what I'm working
on prototyping. The challenge is in the amplifiers (although the
recent FCC ruling doing away with the anti-CB amplifier rules will
help)

Most inexpensive amplifiers do not have "well behaved" properties at
RF (i.e. they change all their parameters as they heat up).. this
makes dealing with phasing and mutual coupling a bit challenging If
the output Z changes, then the network matching it to the element
needs to change..if the gain and phase through the amp changes, then
the drive needs to be adjusted.

Fortunately, the problems are solvable, at least in a theoretical
sense.


This would preserve investment, and create and alternative to the
Henry market. Hams would have two purchase paths instead of
discarding their introductory base station and opting in for N number
of active arrays driven by a specialty item that looks like their old
rig gathering dust in the corner.

Yes.. this is exactly the growth path I would envision.


There's no reason to expect you need a large transmit antenna for
solid state amps either. The native source resistance of a transistor
is quite low, and has to be transformed UP to match 50 Ohms. If you
had a radiation resistance of only several ohms (a very short
radiator) all you have to pay attention to is cutting Ohmic loss and
providing flexible inductance. Unfortunately, this may be a
performance killer - but if you are demanding multiband performance,
you will have to answer for this for any size array element.

Indeed, yes.. fortunately, you already need to have an adjustable
impedance transformer (because the feed point Zs change with frequency/
steering), and even more fortunately, you don't need a broadband
match.. All you need is a few kHz, so a single L and C might do it,
"good enough".

There IS a strong signal IM
problem..so maybe active receive antennas aren't the right solution.

The same transceiver that survives IM would still handle it from
several phase active array elements. As you can see, redesigning a
new driver eventually leads you back to the gear you have. If you now
demand a separate receiver, separate driver, and separate active array
antennas, costs rise faster by the number of connections.

But it turns out that you want a different kind of phasing for receive
than for transmit (not only a different pattern, but it turns out
you'd like to do it a different way... null formation being one
reason).. that pushes you away from a simple adjustable LC phasing
network for the receive array. For receive, you'd also like it fast
(and, potentially, multiple beams at once).


Adaptive nulling is a bit weird to
work with as a user, especially if you expect to control it. And, for
hams, they want a bit more control.

Programmable oscillators that shift immediately and start at any point
in the cycle (absolute phase AND frequency control) would be miles
further down the road.

That's available now.. it's a DDS. And you can buy a radio off the
shelf that has these capabilities (the FlexRadio SDR1000), although,
there are a couple difficulties with the flex (for one, they didn't
bring the sync input to the DDS out to the connector). You can buy a
eval board from Analog Devices for $200.

ordered to a single frequency. You still have the elemental clock osc
XTAL for processor and driver, but those litter the world for pennies.

Interestingly, in a very much higher budget arena (deep space comms
and ranging), they're also doing this. Until recently, you had to
special order the crystal for your spacecraft radio (with 18+ month
lead time!!), so if you had a channel reassignment, it was a real
problem. (One of the Mars Rovers and the Mars Reconnaissance Orbiter
are on the same channel.. wasn't supposed to be a problem because the
rover was not planned to survive long enough)




Using this kind of technology is about the only reason I would trash
my current rigs and go for a custom driver (but it would have to
inhabit each array antenna's amp and thus render it a complete
transmitter. This would in turn cast all the features (like SSB
generation) into each of those elements. The unit cost of this would
climb because of feature creep, not component pricing.

Kind of depends where you divide up the building blocks. The raw
exciter cost (DDS plus mod plus D/A converter for modulation) is quite
low.


Jim

On 2 Mar 2007 11:33:57 -0800, wrote:

Hi Jim

Most inexpensive amplifiers do not have "well behaved" properties at
RF (i.e. they change all their parameters as they heat up).. this
makes dealing with phasing and mutual coupling a bit challenging If
the output Z changes, then the network matching it to the element
needs to change..if the gain and phase through the amp changes, then
the drive needs to be adjusted.

If you are interested in a design for yourself, and maybe a production
run of a few hundred, then look to the HF/10M/6M/2M surplus repeater
market from Motorola and RCA designs of the 70s and 80s. Dirt cheap
decks with enough elbow room to make mods.

Fortunately, the problems are solvable, at least in a theoretical
sense.

One doesn't usually see fortunately paired with theoretical.
ironically this is how this thread started - was with a pig in the
poke explanation passing for science

All you need is a few kHz, so a single L and C might do it,
"good enough".

So, this daydream is on one band only?

But it turns out that you want a different kind of phasing for receive
than for transmit (not only a different pattern, but it turns out
you'd like to do it a different way... null formation being one
reason).. that pushes you away from a simple adjustable LC phasing
network for the receive array. For receive, you'd also like it fast
(and, potentially, multiple beams at once).

Ah, there's always a big but (as PeeWee Herman would say).

Programmable oscillators that shift immediately and start at any point
in the cycle (absolute phase AND frequency control) would be miles
further down the road.

That's available now.. it's a DDS. And you can buy a radio off the
shelf that has these capabilities (the FlexRadio SDR1000), although,
there are a couple difficulties with the flex (for one, they didn't
bring the sync input to the DDS out to the connector). You can buy a
eval board from Analog Devices for $200.

OK, Analog Devices is a star performer. I built a tube version of
this DDS back in '68 when it was called a coherent detector (could
have been called many names depending on where you developed the audio
output).

However, this is NOT what I was referring to, as that is distinctly
different. This is a software controlled oscillator whose frequency
and phase is immediately settable (within on clock, this is in the
nanosecondS range). If you need to phase each array element
independently to phase steer the combined system (also to take care of
phase matching through mutual coupling), the software solution spring
immediately to the front for a solution.

However, as I pointed out, it means N individual drivers following
those oscillators so that each can be phase controlled for the system
combination. The downside finds our current investment sitting in the
corner again, and our investing more design effort into SSB
generation, and hence, feature creep.

ordered to a single frequency. You still have the elemental clock osc
XTAL for processor and driver, but those litter the world for pennies.

Interestingly, in a very much higher budget arena (deep space comms
and ranging), they're also doing this. Until recently, you had to
special order the crystal for your spacecraft radio (with 18+ month
lead time!!), so if you had a channel reassignment, it was a real
problem. (One of the Mars Rovers and the Mars Reconnaissance Orbiter
are on the same channel.. wasn't supposed to be a problem because the
rover was not planned to survive long enough)

The software oscillator I described in the previous post would solve
that for the same cost as the custom XTAL.

If you are looking for a design and a market, I cannot think for the
life of me why that hasn't happened yet.

73's
Richard Clark, KB7QHC

On Mar 2, 12:15 pm, Richard Clark wrote:

If you are interested in a design for yourself, and maybe a production
run of a few hundred, then look to the HF/10M/6M/2M surplus repeater
market from Motorola and RCA designs of the 70s and 80s. Dirt cheap
decks with enough elbow room to make mods.

Or, perhaps the HF Superpacker Pro.. 100+Watts..20dB or so gain.


Fortunately, the problems are solvable, at least in a theoretical
sense.

One doesn't usually see fortunately paired with theoretical.
ironically this is how this thread started - was with a pig in the
poke explanation passing for science

A heck of a lot better than "theoretically there is NO solution..."
girn

All you need is a few kHz, so a single L and C might do it,
"good enough".

So, this daydream is on one band only?

1 adjustable L, 1 adjustable C.. covers all bands. For ham
applications, you only need to have the match and phase adjust at one
frequency at a time, and over a fairly small bandwidth, so the Q of
the matching circuit can be high. Not like a generic wideband phased
array where you need to have a wideband match, and do something like
true-time-delay processing.



OK, Analog Devices is a star performer. I built a tube version of
this DDS back in '68 when it was called a coherent detector (could
have been called many names depending on where you developed the audio
output).

However, this is NOT what I was referring to, as that is distinctly
different. This is a software controlled oscillator whose frequency
and phase is immediately settable (within on clock, this is in the
nanosecondS range).

That is precisly what a DDS does.. It has a phase accumulator where
you can adjust the phase increment per clock. The output of the phase
accumulator goes to a sine lookup table and then to a DAC. A typical
part might have a 48 bit phase accumulator and a 12 bit DAC.

Check out, for instance, the AD9858..

You might not be able to update the phase increment or absolute phase
in a nanosecond, but it's pretty fast (there's some pipeline delay
too.).. I'd say you could clock in a new configuration and have the
new RF appear no more than 100ns later.

If you need to phase each array element
independently to phase steer the combined system (also to take care of
phase matching through mutual coupling), the software solution spring
immediately to the front for a solution.

Well, software for the calculations, but perhaps not for all the RF
processing. You still need to adjust Ls and Cs for the match, unless
you're willing to design a fairly unusual amplifier: ideally, it would
act like a current source with a lot of voltage compliance that can
tolerate a very reactive load.. so you're essentially synthesizing the
L and/or C with an active device.. doable, but not too hot on power
efficiency these days.

Interestingly, in a very much higher budget arena (deep space comms
and ranging), they're also doing this. Until recently, you had to
special order the crystal for your spacecraft radio (with 18+ month
lead time!!), so if you had a channel reassignment, it was a real
problem. (One of the Mars Rovers and the Mars Reconnaissance Orbiter
are on the same channel.. wasn't supposed to be a problem because the
rover was not planned to survive long enough)

The software oscillator I described in the previous post would solve
that for the same cost as the custom XTAL.

Well.. not the same cost as a custom rock. The rock may have a long
delivery time, but it's not particularly more expensive than a
standard frequency. The DDS doesn't come for zero power, either, so
you have a tradeoff of more DC power for flexibility (power
consumption is a very big deal in deep space exploration). And, then,
there's also the whole radiation tolerance issue.


If you are looking for a design and a market, I cannot think for the
life of me why that hasn't happened yet.

Systems like this exist, but not in the ham market. Oddly, it seems
that hams balk at forking out more than $100K for a system that does
all this. The challenge is in getting it in a ham friendly format.
The hardware's not expensive, it's all that software and system
integration. But, 10 years from now, when the early adopters have
cobbled together their systems from bits and pieces, and some of the
concepts become more familiar, I think you'll see someone make the
investment to do the development to create an off the shelf product.
Clearly, there is SOME market for $10K ham widgets or things like
IC7800s and big towers with arrays of SteppIRs wouldn't exist.





73's
Richard Clark, KB7QHC

On 3 Mar 2007 12:04:50 -0800, wrote:

On Mar 2, 12:15 pm, Richard Clark wrote:

If you are interested in a design for yourself, and maybe a production
run of a few hundred, then look to the HF/10M/6M/2M surplus repeater
market from Motorola and RCA designs of the 70s and 80s. Dirt cheap
decks with enough elbow room to make mods.

Or, perhaps the HF Superpacker Pro.. 100+Watts..20dB or so gain.

Hmm, some 5-10 years ago me and my buddy were up to our hips in GE
MASTR IIs for one tenth the price of the HFSP. We could buy them
cheaper yet if we purchased by the pallet. Well, I suppose it's a
case of "that was then, this is now...."

So, this daydream is on one band only?

1 adjustable L, 1 adjustable C.. covers all bands. For ham
applications, you only need to have the match and phase adjust at one
frequency at a time, and over a fairly small bandwidth, so the Q of
the matching circuit can be high. Not like a generic wideband phased
array where you need to have a wideband match, and do something like
true-time-delay processing.

You might have to. I don't think an L tuner is going to have the
flexibility to look into the mutual coupling, as well as the delay, as
well as the match and be scalable to 3D. (May as well dream in
technicolor and surround sound.)

Check out, for instance, the AD9858..

Yes, things have sped up by 10 fold since I last visited this topic.

If you need to phase each array element
independently to phase steer the combined system (also to take care of
phase matching through mutual coupling), the software solution spring
immediately to the front for a solution.

Well, software for the calculations, but perhaps not for all the RF
processing. You still need to adjust Ls and Cs for the match, unless
you're willing to design a fairly unusual amplifier: ideally, it would
act like a current source with a lot of voltage compliance that can
tolerate a very reactive load.. so you're essentially synthesizing the
L and/or C with an active device.. doable, but not too hot on power
efficiency these days.

Ever hear of a gyrator?

The problem of solutions off the shelf is that they have been dumbed
down to the most generic market.

Consider your suggestion of the HFSP. Looking at the schematics
reveals the same old stale Class AB design WITHOUT neutralization.
It seems that feedback is an anathema to designers that have to pay
the piper called a commodity market. If they built a 20dB amp, and
then discarded 10dB of that gain for stability and source resistance
control - THEN you would have engineering. The 10dB cast back into
the amp loop was called "noise gain" by HW Bode; and this cured so
many ills of stability, distortion, noise, dampening, regulation...
that it its absence cheats us all of superior performance for the sake
of squeeking every dB of slop into the antenna. What would the world
be like without that filter deck following the amp? Amplifiers are
perfectly capable of delivering a low distortion HF sine wave - if you
designed it in, that is.

Early adopters are not being served there.

A solid state inductor/capacitor (AKA Gyrator) is technically a budget
buster for the chintz market; but if you design to the mission, then
there you are. To invest in digital oscillators, and then short sheet
the product with a limp re-hash Amp deck out of the 60s is not going
to ignite a new product venture.

73's
Richard Clark, KB7QHC