New Project - Solid State Linear for HPSDR from FT-1000D Carcass

[K1JJ]

I finally settled on a linear amplifer for the HPSDR ~100mW 6-160M transceiver.  

Last week I swapped some gear for the PA final unit, the low pass filter assembly and the protection board from a dead FT-1000D.  (May the departed FT-1000D rest in peace)  The previous owner is a vely famous gangsta on this BB.

The solid state PA is good for 200W pep output at about 100mW drive.  The RF low pass filters are relay controlled for each band and will be auto-controlled by the HPSDR with a click of the mouse when bands are changed. Total screen control, no tuning required.

The thermal sensor, mounted on the PA heatsink, will turn on a 12V muffin fan when needed. I expect to use only about 40W pep to drive my tube amp, so it should rarely come on.

The finals run on 30 volts and I have measured my other station FT-1000D to be about -40db 3rd order IMD at 40W. So it is clean enough as a good driver.

I am adding a current limiting circuit for the 30V line that will shut the PA down if too much drive or preset power is exceeded.  In addition, the protection board will generate ALC for high SWR conditions, like any ricebox.

I think borrowing a brick and filter from a DOA ricebox is a good solution for  anyone looking for a low level SDR linear.

Still needs wiring and testing.


73,

T

Pic #2: PA Unit

Pic #3: LP Filters

[Mike/W8BAC]

Those are two very energetic pills. Two hundred real watts PEP? Sweet! Good luck with the project Tom.

[W1AEX]

That looks like some excellent engineering to "graft" that final stage into linear service with the HPSDR. It'll make a great driver for whatever fire breather you plan to follow it up with.

I made a few component changes to the bandpass board and added the missing band that you wanted right next to the 10 meter filter. Should work FB there now!

[K1JJ]

I made a few component changes to the bandpass board and added the missing band that you wanted right next to the 10 meter filter. Should work FB there now!

You vely, vely funny man, Rob!

Actually those written numbers are the aggregate IQ's of the various bands as estimated by the ARRL.   Your addition will be good for hangover mornings, tnx.

T

[W2VW]

Any source for those pcb coax connectors?

[W1ATR]

Looks pretty damn nice so far Vu. I would maybe think about getting better cooling on that pa board however. Maybe raise the board up a bit on higher standoffs and bend up a little shroud for that fan to get air pressure under that heat sink. My 1000d seems to be happiest at 35 watts carrier but it does get a bit warm evidenced by the little squirrel cage coming on during transmission.

Just a thought.
J

[K1JJ]

Thanks, Jared -

Yes, I plan to play around with a fan shroud to direct air directly at the heatsink and fins. I realize I should stand the heatsink up so the air flows naturally up. But I will be using it as a 40w pep maximum driver for my tube linear most of the time, so heat won't be a problem. We'll see. I can move it around later if need be.

My station FT-1000D's fan does come on during AM too. It's quite a compact, efficient design, really.

Dave: Which PCB coax connectors do you mean, the tiny 50 ohm ones about 1/8" diameter?  I am short two for the project - I axed HUZ to see if he left them in the rig by mistake. If you mean the 50 ohm phono-plug type, those are easy to make up from audio plugs.

T

[KD6VXI]

Tom,

Those teensie connectors that almost look like they where molded into the end of the coax when it was made are a BEAR to find.....  I've located them twice.

1.  GPS companies use them for interconnects...  Pulled a couple OLD (read BIG) GPS boards apart years ago.  They had them in it.

2.  WiFi Networking.  They are used fairly prolifically for interconnects in routers.

Mouser has them, as well as a few of the SPECIALTY WiFi companies.  They WiFi companies will also have pigtail adapters to make them go to about anything.  I have a couple pigtails here, one for SO connector on the opposite end, one for an N. 

If you want to go the adapter route, the EASIEST (just call and order) would be UniDAPT from RF Parts or your local Bird dealer...  I believe they have an adapter kit, I KNOW RF Parts sells one near their Bird stuff in last years catalog.

First time I saw them was taking apart a Military radio surplus in the 80s.  Was REALLY cool tech then



--Shane
KD6VXI

[W2VW]

Yes the 1/8" ones.

Thanks Shane.

[w5omr]

I made a few component changes to the bandpass board and added the missing band that you wanted right next to the 10 meter filter. Should work FB there now!

Actually those written numbers are the aggregate IQ's of the various bands as estimated by the ARRL.  

Glad you clarified -who- estimated the IQ by Band idea... that statement certainly isn't prevalent on 75m SSB!

[WA1GFZ]

You will fry that final with the fins down

[K1JJ]

You will fry that final with the fins down

No problem. I will get some 'L' brackets and mount the heatsink on its side with the fins aligned straight up. The fan will allow a better blast of air this way too.

T

[WA1GFZ]

My heat sink is 6 X 12 with 3 inch fins. It gets pretty hot during heavy bias.

[K1JJ]

Looks like you increased the final cores quite a bit.

Here's the new heatsink mounting. The fan air hits the heatsink fins hard and the air rushes up thru the fins. Vely FB flow.  This is how the sink was positioned in the actual FT-1000D rig.

T

[K1JJ]

Project update:

The ex-DOA FT-1000D linear transplant is wired up. The 13.8V, 9 volt regulated supply, T/R relays and all DC connections are working.  I still have to install the LP filter interface for the band relay switching. Awaiting parts.
The fan comes on when the heatsink gets warm.

  One word of caution. I almost made a fatal mistake. The Japanese plug for the 13.8V that goes to the PA unit board had the plus wire white and the negative wire red.  I wired it up as I figured it should be but before turning on the power I checked all connections for continuity and proper polarity. Sure enuff, the 13.8V was backwards and would have blown out some series stuff on the PA unit board. OUCH!  Bullet dodged.

So a few more parts need to be added then I'm ready to plug it in for an RF test later this week. I'll dress out the wiring once tested.

The Mercury board receiver, which I pumped 200 watts into blowing the front end last month is back and repaired. The complete HPSDR transceiver is working FB now and ready for the new 200W linear.



T

[K1JJ]

Project Update:

I put 15V on the 1000D PA unit system including the LP filter. All the T/R DC and RF keying is working.  With 0 dbm drive (1 mW)  I got about 30 watts out.   Looks like it will work FB once I get the 30V on it. Still have related cabling and stuff to iron out first.


One problem I see is the internal antenna relay that feeds the receiver. This RX output shows a slight spike on the scope from the TX on unkey at times. It is as much as 15V.  I will need to sequence this so the TX shuts down completely before the RX comes on.  I once blew out a solid state R-1000 receiver front end because the sequencing was not right. It's easy to get a spark on unkey if we are not careful.

T

[K1JJ]

The 200W solid state linear amp continues to evolve. See below the small board on top which is for shutdown protection from high swr or excessive final current.  This is the same kit board used in the class E rigs as designed by Steve/QIX. It uses a Hall effect device for current sampling. This is a version of the K4HX/Taylor hybrid.

I also added idiot-proof polarity diodes on the inputs for various low voltage supplies.  Check out the digital volt and current meter.  A small buttom switches from Volts to Amps.

I am still awaiting a control board that will accept the digital band change commands from the HPSDR transceiver. This will switch the low pass filters in the final PA for band changes. All controlled by a mouse.

So far everything is working as it should.  It will eventually run at 30VDC making 200w pep out.  The project's on hold until some more low voltage supplies arrive next week.

I usually keep the wires "haywire" until all testing is finished, then bundle them up neatly later on.

I know what you thinking... "How can dummy like Tom Vu possibly make thing run without blowing up as usual?"  I no know answer to question. Maybe Vu-Konk-Fu vely strong this month.

T

[w3jn]

I liked your TMC better  

There's no denying the benefits of an absolutely silent amp, though.  You might need a thermostatically controlled fan.  Both my TransWorld high power solid state amps have them.

[WA1GFZ]

John,
That TMC amp is very cool. I was lucky to finally make a deal with a friend who had one. It is unmolested only missing a shield plate. I also bought a pair of new sealed 4CX350s. I was going to buy a Valiant as a medium power rig but the TMC is much nicer. Looked in the stash and found a nice NOS 2000VAC transformer good for at least 1KVA and have another to make the low voltages.
I'm thinking of rebuilding it with new caps and teflon wire.

[W2VW]

The TMC will ride again.

[WA1GFZ]

Gee Dave I could drive it with an HP8640B and use external modulation input.
That would be very clean. The TMC design is first rate.
If I didn't want the noise I could drop in quad 6146s or a pair of 4D32s on their side.

[K1JJ]

Hi Johnny,

There is already a thermostatically controlled fan in there. I just borrowed the device sensor output from the amp board and drove the new fan. Works FB with a soldering iron test...  The amp has redundant safety features now, including fuses for RF input, all power supplies, swr shutdown and final PA current electronic overloads protecting both the RF input to the amp -  and final output current.

This amp is almost as big as an FT-1000D box. Those Japanese really were good at squeezing this whole rig in - including the power supply. Amazing how they did it back in 1989.

The TMC certainly is a nicely built amp. However the blower noise is a problem. I tried a pair of 6146's, but the power out was too low in AB1. The amp needs a lot of different voltages, so the power supply takes some time to build. Maybe there will be one at Hoss for you to pick up, Frank.  I saw a complete unit with supply there two years ago for about $400. I tried to buy it but was already sold.

I added extra RF negative feedback to this TMC and it is even cleaner than stock.  I'd say it is as clean as the FT-1000D when the 1000D runs at 40w out.   At full power, the 1000D is no match for the TMC for IMD.

All in all, I'd much rather have the 1000D PA unit for the HPSDR operation due to auto band switching, silent operation and lack of dangerous supply voltages.  (As if there's no dangerous supplies in the shack here)

I know what you thinking - "How can dummy like Tom Vu keep from getting fried all these years?"  I no know answer, but maybe Vu-Kong-Fu vely strong last 40 year.

T

[W2VW]

Gee Dave I could drive it with an HP8640B and use external modulation input.
That would be very clean. The TMC design is first rate.
If I didn't want the noise I could drop in quad 6146s or a pair of 4D32s on their side.

Or "drop in" a pair of 4CX1500Bs as they are only fed voltage. Proportion the B+ up to keep the plate tank as-is. Plenty of dissipation maybe a quiet air system too?

[WA1GFZ]

The TMC needs +/-150 volts, High voltage for the final and Zener regulated screen vlotage. Then 120 VAC for the Fan had heater transformer. The only odd thing is the 6CL6 predriver has a grounded screen so you need a negative voltage on the cathode. The tracking predriver and triver tuning is cool.
Wow I have only ever seen one TMC at Deerfield and I now own it after about 10 years.
Dave I looked into dropping in a 4CX1500. One might fit if the socket is sub mounted.
HMMM, I have a socket. I would also add a second common contact on the tank switch. You only have about 4 3/4 inches of height to play with.

[K1JJ]

Frank, you will need a regulated grid bias too, even though there is no grid current. No sag whatsoever required.  There are relay switching requirements for the voltages too.  Also ant T/R relays needed.  Dave, the TMC you will be getting - I already installed these relays into the amp for voltage and RF ant switching. Just add fixed supply voltages and stir.

Dave, that C1 cap is at the limit for 2KV, so higher voltage is a problem with 1500's.  Maybe a vac variable.  (And a new fil xfmr for the finals)

T