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

[WA1GFZ]

I just checked the 4CX1500 tube height. Min tol is 4.6 inches. With the plate at the bottom of the socket that puts it at 4.7 inches. It might be tuff getting that tube inside the covers. I bet a third 4CX350 would easily fit.

[W2VW]

Very interesting. I'll wait to be able to see up close how much fun might be involved.

I'm gonna miss the bipolar sand power drift.....

[Steve - K4HX]

After all that, you might as well build one from scratch.

[WA1GFZ]

That was my plan but looking under the hood it would be hard to duplicate the quality in a 5 1/4 inch rack that runs Valiant power. So I was thinking of rebuilding it with new components and teflon wire. I don't think a 4CX1500 would fit but a third 4CX350 or even some other tubes would fit as long as they are not too tall. I'm thinking an additional loading cap on the lowest band would allow lower impedance operation by just selecting the next higher band on the tank coil. Higher voltage plate tune would be limited to lower C and may not be worth the trouble to install a vacuum cap. I wouldn't push the pi network over 1kw with that band switch.

[K1JJ]

TMC Swiss cheese...    


Steve, I was talking with a guy that wants to do an FT-1000 MKV PA unit conversion for his HPSDR. He said it was a 200W unit. I thought only the FT-1000D had 200W PA's and MKV's were 100W.  He sent me this link.  His FT-1000 MKV must be a rarer production unit.

http://forums.qrz.com/showthread.php?252770-FT1000MP-Mark-V-200W

T

[Steve - K4HX]

Some of the later FT1000 (whatevers) were 200 watt units. I forget which, if I ever knew.

[w3jn]

FT-1000MP MKV is 200W, FT-1000MP MKV Field is 100W.  The "Field" runs off 13.8V whereas the straight MKv has a 28V power supply.

Why they made so many different versions of that radio is beyond me.

[K1JJ]

Oh, so that's why they called it a "field".   It probably belonged out there PW using 13.8V devices... :-)

The 28V MKV  200w PA units might become more common as the years go on and the rigs crap out.  It's really a nice PA strip.

T

[WA1GFZ]

Dave,
There is an error in the PA500 schematic. A padder is switched in parallel with the loading cap on the lowest band. Last night I was looking at the switch to see how hard it is to add another common. Looks like I just need to grind a a contact rivet out. I don't know th evalue of the cap but it is a door knob. 

[W2VW]

Thanks Frank. We can continue this at Hosstraders over a beer or three.

[WA1GFZ]

Sounds good Dave.
I don't like the design of the LV supply. Way too funky for my simple mind.
I plan to use a 300VCT transformer with a bridge to generate plus and minus 150 VDC.

[W2ZE]

Also, the mark V does 75 watts class A outpoot.

[Mike/W8BAC]

Hay Tom, I have been wondering lately how the HPSDR project is going as well as the FT-1000 rf deck integration. This is my busy travel season so I haven't been on the air much. If it's up and running I'll hear it soon. How about an update and maybe some pictures?

Mike

[WA1GFZ]

Gee Dave VW We talked a couple times and totally forgot about the PA500.
I did find a couple 4CX250Bs Friday.

[K1JJ]

Hay Tom, I have been wondering lately how the HPSDR project is going as well as the FT-1000 rf deck integration. This is my busy travel season so I haven't been on the air much. If it's up and running I'll hear it soon. How about an update and maybe some pictures?

Mike

Hi Mike,

I was showing Steve/K4HX the HPSDR and 1000D module linear here this weekend. It's to the point of working as expected with remote mouse control of the LP filters and using a full QIX overload board failsafe system. If the swr climbs too high, drain current exceeds a certain preset value or the heatsink gets too warm there is preventative action.

The only thing left to do is to ramp it up beyond 50 watts to 200w out. I've been testing it carefully to be sure there are no hidden bugs.

We'll post some final shots soon.

TNX for axing, OM.

T

[K5UJ]

The 28V MKV  200w PA units might become more common as the years go on and the rigs crap out.  It's really a nice PA strip.

Probs there:  The FETs are expensive, there are two of them, and I think they are around $120 each but worse, they may not be made anymore and are unobtainium now.  The 28 v. supply is some kind of weird switching design and prone to crap out.  Yaesu wanted an insanely high price for replacements so some ops who lost theirs resorted to buying separate Astron 13.8 and 28 v. linear supplies.

OTOH it IS a solid PA.   Once, I ran mine on a DL for testing and did not know the internal fan was not on.  It had gotten hung up in the top speaker's wire.   After 15 or 20 minutes I just happend to put my hand on the heat sink because I make a habit of checking it.  It was hot as hell.  Yikes; I killed the tx and put a fan on the sink and got it cooled down and saved the PA, then got the internal fan working again.  Now when I run a 40 w. carrier with it I have outboard fans on the sink in addition to the stock fan.

The class A option is a bad idea if you ask me--the rig runs way hot, even if you run it at the peak power for class A to get the most efficiency.   It will sit there and tx all day at 20 w. serving as an amp exciter though.

Rob

[K1JJ]

Rob,

The FT-1000D uses bipolars, not FETS, that cost about $69 each based on a first check:

http://www.datasheetcatalog.org/datasheet/motorola/MRF422.pdf
http://www.pacificsemi.com/search.php?partno=MRF422

Yes, you are correct - I was advised not to run them A1 hot cuz of past failures.  Being bi-polars, they clean up very well when the amp is run at about 35 watts out. That's all I need to drive my tube amp. At 150-200w, they run at the normal -31db 3rd, which is too dirty for me. At 35w they seem about -40db 3rd or so, which is clean enuff for my IPA use.

I use an external 22-48V switching supply. We will see if it causes any switching hash IMD later on. If so, I will go to an analog PS.

I have a big fan on them that comes on with the sensor.

We'll have to see how it works out in the HPSDR service, but shud be FB.

T

[W2VW]

Gee Dave VW We talked a couple times and totally forgot about the PA500.
I did find a couple 4CX250Bs Friday.

I was still  completely brain dead from working overnights and a few other things.
Plenty of time to talk again when I do some work on the thing.