ubitx 5 and boatanchor Collins amp #ubitx #v5 #linear-amp

Dean Souleles

Hi all - 

ubitx 5 continues to perform well.  Got digital modes working great and also making contacts on SSB phone. 

My question - does anyone have any experience using ubitx to drive an old-school vacuum tube  linear amp.  I have a Collins 30L-1 (4 811 tubes) that I use with my Kenwood.  Is it possible or even a good idea to try to make it work with the ubitx.  I need to figure out what it would take to bring out the PTT to drive the TX/RX control on the amp.  With the Kenwood I bought a commercial interface that plugs directly into the accessor port of the Kenwood.

Any thoughts or ideas would be greatly appreciated!




Last year I fed my BitX40 into a homebrew grounded grid sweep tube amp.(which I think is more boat-anchorish than Collins, no offence.)  This amp has spent nearly 20 years sitting in a shed in Hawaii, thus the rust and conversion of anything nickel into a living organism. But I drug it out and turned on the generator, and placed my life in Pelee's hands.  As I remember, with 6 watts out of the BitX40, I was approaching 100w Input on the amp .  I tested it out with another ham maybe 80 miles away.  He heard no distortion of loss of quality when the amp was on.  

Dean Souleles

That's great, that it worked so well.  I know I need to put a beefier relay in to switch the amp to TX.  I know I need to put a diode across the relay coil to protect the uBITx  I'm looking fir advice / schematic on wiring the relay and where to connect to the uBITx to pick up PTT to switch on the relay.

The external commercial relay I have on the Kenwood by radiodan will work if I replace the kenwood cable, but I'd prefer to build it in to the case.

The PTT picture you sent was just a thumbnail and I couldn't make out any details.



Jim Strohm

Dean, your 30L-1 likes to see 50 watts or more to start to make good power.  While it should amplify the output from a ubitx, it's a kilowatt-class amp with only 10 or 12 dB gain. 

So with the nominal 10 watts out of a a ubitx, you'd see about 100 watts out of the 30L-1, which is hardly worth lighting the filaments for -- at 25 watts per filament, you do the math. 

You'll need an amp better suited to the semi-QRP output of the ubitx, and capable of handling the higher output on lower frequencies and lower output on higher frequencies. 

I'm not saying you can't use your 30L-1 with a ubitx.  However, you may want to track down a "two-pill" CB amp to put between the ubitx and the 30L-1.


Dean Souleles

Hi Jim,

Gotcha - that makes a lot of sense.  Or if I only want 100-150 watts out I could just use the 2 pill - and leave the Collins for my benchtop station.

Thank you,