Interesting callsign you have there to be doing that, unless you have > 13dB of cable and tuner losses before the feedpoint!

(For the non UK contingent, M6 prefix is a 'foundation' license limited to 10W).
73 Dan.

The gotcha with CATV gain blocks is that they are pretty much all **very** high bias class A with commensurate levels of heat generation.

I would have thought that a CFB video opamp (With suitable transformer on the front to make the impedances match and to optimize noise performance), followed by a push/pull class A stage to a few watts, followed by 50V LDMOS (Maybe MRFE6VP6300 or similar held back to maybe 17dB or so gain by feedback) would get you reasonable performance@250W or so if the details were right.

If you were feeling fancy, a modest relay controlled attenuator between the video opamp and the driver stage would allow the noise performance to be optimized when running reduced power.

One of these days I will have to prototype it.

If looking, there are similar high speed CFB opamps from all the usual suspects, and TAPR Hermes does the push/pull thing into a transformer to get a half watt from 4 or the things.

Regards, Dan.

Ah, no that would be 500% markup, not profit.

Unless you are a highly vertically integrated sales outfit with your own brand (Most supermarkets fit this description), your retail chain will be looking for ~100% markup to cover their costs in shop space, staff, overheads and all the rest (Yes including profit), so that cuts your 500% to 250% right there.

Now factor in local approvals (FCC,CE), and your need to handle warranty issues locally, add in distribution and stock holding costs, labor and legal bills, MARKETING, and sure you can make a reasonable markup on importing Chinese product, but it is in fact a surprisingly cutthroat game to be in (Your product is functionally the same as everyone elses, and you are only competing on price and marketing, no real opportunity to own a whole market there).   

There is money to be made, but I don't think it is all that massive, and it only works for product that you can reasonably shift in multiple container quantities.

Regards, Dan.

Look at the car audio crowd, those audio amps usually use some kind of forward converter, 12V in to somewhere in the +- 50V or so region at competitive power levels, usually half a dozen butch mosfets doing the half bridge thing and a big high flux toroid with a mess of windings.  

Or getting a little less crude about it, here is an app note for 385W @ 48V from a 12V supply, set up 3 of these as a 12 phase converter and you have your KW of DC.
http://cds.linear.com/docs/en/design-note/dn453f.pdf

For a KW of DC at any voltage you are going to be looking at somewhere around 100A@12V, the nice thing is that @50V you are only looking at 20A, which makes sizing cable for say 5% losses far more reasonable, mount the DC/DC right next to the battery and move the 50V to the RF deck down reasonable sized cables.

Hell a 12V 1kW inverter giving 120 or 240V AC out is not that expensive and is actually significantly more complicated then a humble 12V -> 50V boost converter.

And yes, I know about the overheads, that is why you allow a factor of three between parts and factory gate pricing for a rule of thumb.

Regards, Dan.

$6K, I could build a decent amp for 1/3rd of that!
Which of course is the point, to stay in business a good rule of thumb is that the factory gate price should be three times your parts cost (You can refine this once you know your real costs, but it is usually not too far off), so that $6K amp has probably got $2K worth of bits in it.

Lets see, if I was trying for a big amp like that today, I would probably be eyeballing the latest generation of freescales ldmos parts with some interest, and a 1.2KW rated part is about $300, so $600 for transistors, another couple of hundred for heatsinks, fans and such, add maybe $600 for the required very butch SMPSU, add the output filters, relays, magnetics and control and yea $2K in parts sounds about right.

Doing much the same exercise for the RM product gives about the same result, but it could have been so much better with relatively small changes, for all that 12V bipolar finals are technology that really needs to be retired. The car audio guys have shown that DC-DC converters of significant capacity are an affordable component in even that market, so why not do the same for an RF amp?

Both amps hit roughly the price points I would expect given the design parameters, and both are probably value for money in their own way, what you buy depends on your view of the value to put on the intangibles (Reliability, splatter, protection, efficiency).

Actually, IIRC Ferrari did have a few problems with cars that were only ever being used for the run to the shops and thus never getting up to temperature.....

Regards, Dan.

Are you sure about that? My recollection is  43 + 10 log P subject to not needing to exceed 50dB of suppression.
It is seldom the second that is the problem, except sometimes if trying to cover rather too many bands with a single filter, it is the third that gets you, because while in a well designed push pull stage the second might be close to -40dBc even before the filter, the third will usually be less the 20dB down on the carrier.
Most of what I see over here seems to be 5 pole (3 caps, 2 inductors), except on 6M where it is usually an elliptic to protect the broadcast band from the second harmonic.
Severe non linearity once you run the thing into the supply rail is a feature of ALL amplifiers, once the active device saturates at peak, gain starts to fall rapidly, just the way it is.
This is not quite the same problem as an insufficiently stiff bias supply on a bipolar stage where in effect the bias supply must be capable of sourcing Ic (ave) / Hfe without moving significantly over the full modulation envelope, for an amp designed for 300W, so ~600W DC input, say 45A or so @ 12V, that means the bias supply must be capable of sourcing at least an amp, and more likely several amps if the bias point is to remain invariant over the modulation envelope.
I am not quite sure that is correct.
The power output is limited by the supply voltage and the collector load impedance.

You set the collector load impedance based on the supply voltage and required output power, then wind the output magnetics to suit the target load impedance and SWR (Usually gives a design load of 75 ohms or so (1.5:1 on high Z for a nominal 50 ohm load), if you are failing to make the target power because of hitting the supply rail, then the answer is to slightly increase the turns ratio on the output transformer (Of course this lowers the collector load Z, but that is the trade off, the power has to come from somewhere).
THP seem to be staying in business last I looked.
Amen to that!
It is interesting that I can buy a cheap marine radio that does not need a mic gain control and just works, but that the ham gear seems to require this most abused of knobs, good quality ALC is well understood these days and the electronics is really not a big deal....

73 Dan.

Also as far as I can see the bias regulator does not look near stiff enough to supply the current required at rated output in class AB.

Low pass networks are actually the easy bit in solid state ham amps, it is envelope linearity that tends to be problematic, particularly in low voltage bipolar designs like this one, and no amount of filtering helps with that.     

I have never used one of these (or even had one on the bench) so I must reserve comment on measured performance, but the power demand numbers not adding up and the bias thing would worry me.

73 Dan.

Stanley are NOT what they once were....

Agree on the rest.
For more 'mechanical' tools, snap-on are nice but more money then god, probably not worth it unless you are a full time mechanic.

73 Dan.

I am not quite sure what exclusively for means in this context, and I will grant that it would not quite be turnkey, but if you took a hermes and pulled the anti alias filter, then preceded it with a suitable pair of BPFs and LNAs, you would come close by running it as a subsampler (The sample and hold bandwidth is ~700MHz).
The ADC noise figure does argue for quite a bit of front end gain, so you would need those filters.

Providing a VHF and UHF input path was one of the motivations for me trying to find the time to cook my own version.

73, Dan.

I am aware of the work, and was mainly bemoaning the missed opportunity to distribute a semi turn key radio with the required sampler, pad and relay preinstalled.

It is not an issue for you and me, but I get the feeling that the average purchaser of a 100D might be quite happy to upgrade the software and FPGA bitstream, but rather less happy to do the admittedly minor hardware hack required. 

I will probably end up getting a hermes, for all that what I would really like is an anglia logic board (The high speed IO port looks kind of interesting), as I am finding the time to spend with altium working up my own version is hard to come by.

Regards, Dan.

The annoying thing is that at almost no cost (AND without changing the PA in any way) the Anan radios could have provided a way to significantly improve the transmitter performance.

Adding a relay to switch the rx input to sample the forward power would have allowed either semi open loop adaptive predistortion (And could be done entirely in the baseband processing computer) or a cartesian loop (Really needs to be in the fpga), either of which should be good for 20dB improvement without breaking any sweat at all, and 30+db of improvement is possible.
-31dB ref PEP (From the Anan100D brochure) really is not great, -51 would be almost best in breed....
Even if nothing else, it would have allowed the waterfall to show the transmit spectrum as measured.

In the case of the 100D, it would have been possible to go one better, and sample both current and voltage at the aerial socket, which means that load mag Z and phase angle could be calculated. This opens up some interesting possibilities if one was to get smart with the drain power supply to the fets (This would obviously need PA changes).

Now granted, it is not a massive thing if starting with a hermes or similar to add that relay and appropriate attenuators and such, but it would have been nearly trivial to integrate onto the PA board in the ANAN series rigs and would have made all sorts of improvements only a software patch away.

73 Dan.

We are indeed having fun, particularly as I found a local guy who can mount fine pitch BGA and QFN for me on prototypes (hint, look for someone who repairs Playstation and X box units, the better end of these guys will have a proper BGA rework station).

My version is taking shape in Altium, a sort of Hermes variant along the lines of the 100D but set up for cartesian feedback on transmit and with the finals (pair of VRF151) drain supply derived from a buck converter so the drain supply can be made to track the envelope (and output impedance) for better power efficiency and less heat.

I have also moved the main anti alias filter into the RX BPF filtering so that subsampling will work for reception on the 2M & 70cm bands without needing a transverter (The 2208 has a sample and hold bandwidth out to 700Mhz). Transmit on these bands will need a different PA of course.

The neat thing about NIOS II is that while it is not itself a very good processor, it can tie into application specific FPGA logic, so expensive things like FFTs can be pushed out to dedicated hardware in the gate array. 

Now if only the bigger FPGAs (and especially the good AD chips) were a bit cheaper.....

Regards, Dan.

The flex appeared (at least in the hardware I saw) to have relay switched bandpass filters ahead of the ADCs, while the 100D uses a combination of the transmit LPF and switched HPFs on ADC1, with the second converter having only an anti aliasing filter....

The flex runs the ADCs at 250 Msamples/second vs 125M for the Hermes derived designs, possibly an issue on 6M where good aliasing performance is a big ask of the filters, this difference does however explain the larger slice count on the 100D as the FPGA area per slice will be about 1/4 - 1/2 that of that for the flex all else being equal.

The flex supports synchronous sampling at least for government users, but will apparently not support it for our market, this according to some discussion at the UK national rally last year (Something about ITAR regs in the US).
A pity, as electronically steered beam forming has interesting possibilities, especially if multiple receivers were widely geographically dispersed and locked to gps or similar (Think long baseline interferometry or HF radar).  The Anan hardware and software looks somewhat more amenable to having this sort of thing grafted on.

Finally, the Hermes/Anan rigs look to be hackable in a way the Flex is not.

73, Dan.

Software is hard, and worse is the next best thing to impossible to estimate reliably, real time software is an order of magnitude harder, realtime on a multitasking general purpose machine is harder again (And is just plain nasty to debug).

A big part of the issue is that the compute hardware out there is just so very variable, and even things like network cards (and their drivers) can be 'interesting', I have had a so called gigabit chipset start randomly dropping frames for no apparent reason, most unwelcome when trying to use UDP to move low latency audio around.

It might work here on my development box, but that is no guarantee that it will do the job on your packard bell laptop with a fan full of fluff that your mate has overclocked for you and has Norton AV hiding in the background fiddling with every system call I make, and storms of SMI exceptions trying to keep the poor thing from melting.

PCs provide a lot of cheap compute power, but low and deterministic latency is not their strong point.

Never underestimate the pain of going from a prototype to a product, especially when MS Windows is in any way involved.

What could be interesting is investigating the possibility of using a small dedicated compute board as a baseband processor for the anan/hermes radios, possibly itself with FPGA support or using CUDA or something, this would sit as a shim between the userland devices and create the the very high bandwidth I/Q data stream for the radios as well as doing the FFTs and suchlike, allowing the controls to run in a rather less time constrained environment.

I am thinking something like a TMS320C6xxx or SHARK, a Gb network port for the radios and a second network interface for the user network. The DSPs can handle the baseband processing without breaking a sweat, and can do it with negligible latency as they can work sample by sample in interrupt context rather then having to do blockwise processing like a PC does. As memory serves Hermes at least lets you select the amount of decimation in the CIC chain so it may well be practical to run at baseband bandwidths limited only by the network bandwidth to the radio.

This is essentially where the 6000 series is trying to go, but I want something hackable, including having the VHDL/Verilog be hackable, however good the supplied API may be, sooner or later you will hit something it will not let you do, and that sort of defeats the point of an SDR for me.

73, Dan.

Alas it is not quite that simple....

Frequency is the rate of change of phase, so to increase the frequency by say 5Khz you have to cause the RATE OF CHANGE of phase to increase by 2 * pi * 5000 radians per second.

Just adding a fixed phase shift does not do it, you have to make the phase shift increase with time.

Fortunately if you simply place an integrator between the modulation input and the phase modulator you get exactly the required behavior, so it is not an insurmountable problem, but that integrator does mean that the response is dependent upon the modulating frequency.

HTH.

73 Dan.