[ARC5] Why "Noodling" About Sweep Tubes

[Jim Wiley]

Just the usual things. Parasitic suppressors on the plates (a 47-ohm 
2-watt carbon resistor wrapped with about 7 turns of #20 wire), a 
100-ohm 1-watt series resistor for each control grid, good grounding of 
the screens, good isolation between the grid and plate circuits, good 
bypassing of the plate and screen HV feeds, and of course careful 
neutralization. I seem to remember that it was a push-pull final, but I 
could be wrong about that part - it was, after all, 50 years ago.  The 
VHF version (6 and 2 meters) was definitely PP. I think I also remember 
running the screens at somewhat reduced voltage for HF service.  I was 
working for RCA at a mountain-top site in Western Alaska, and we had 
lots of spare parts.  We had dozens of 5763s and 5894s, but no 6AG7s, 
807s or 6146s.  Need I say more?

- Jim, KL7CC




On 10/23/2013 8:43 PM, Dennis Monticelli wrote:
> Jim,
>
> Thanks for the info on the 5894.  I have one of those but have been 
> reticent to use it fearing that the high gain at VHF might make it 
> tough to tame at HF.  Did you take any special precautions when you 
> built that multi-band HF rig?
>
> Dennis AE6C
>
>
> On Wed, Oct 23, 2013 at 7:55 PM, Jim Wiley <jwiley at gci.net 
> <mailto:jwiley at gci.net>> wrote:
>
>     The much better version of the venerable 829A, that fits the same
>     socket and runs from the same voltages, is the 5894A (also known
>     as the QQV06-40A and AX9003A).
>
>     Also inexpensive, because not many people know what they are,
>     particularly when labeled using the European numbering system.
>     Puts out more power than the 829B, mostly because it was designed
>     from the ground up as a VHF dual power tetrode,  so it is a bit
>     more efficient.
>
>      I built a HF rig using one and got around 150 watts output, 160
>     thru 10 meters.  Used another in a Johnson-Viking 6N2 and got an
>     easy 110 watts AM, 140 watts CW output. The 5894A works at full
>     power up thru 180 MHz and at reduced ratings thru 450 MHz.
>
>
>     - Jim, KL7CC
>
>
>
>     On 10/23/2013 6:21 PM, Kenneth G. Gordon wrote:
>
>         On 23 Oct 2013 at 18:36, Dennis Monticelli wrote:
>
>             I just remembered another tube. The 829B was very
>             expensive in the WW2 era but it's practically free at the
>             hamfests now. You find them mil grade NIB. I don't think I
>             paid more than $2 for mine. You can parallel the two
>             tetrode sections or use them push-pull. I think they're
>             good for 40W plate per section. 12V heaters and a 7 pin
>             socket (Septar?) that is worth more than the tube.
>
>         The 829B is one of my favorite tubes. The pulse version is the
>         3E29. I buy them as often as I see them for under $5 each.
>         They will output something like 100 watts at 2 meters. They
>         are, essentially, a pair of 807s in one envelope with far
>         shorter interconnecting leads, and reduced plate dissipation
>         rating since you can't really have 70 watts PD in that small
>         an envelope. They make a magnificent push-pull oscillator in
>         addition to being an excellent push-pull amp. Ken W7EKB
>
>
>