[Milsurplus] [regenrx] Re: pentagrid detector sensitivity

J. Forster jfor at quikus.com
Thu Jan 5 22:15:44 EST 2012 

Rebecca-Eureka has no code wheels. It is not an IFF.

The AN/APN-2 Rebecca has 5 separate Tx frequencies. They are simple,
single RF pulses, in a fixed PRF train. There is no coding.

The AN/PPN-2 Eureka also has 5 separate Rx and 5 Separate Tx frequencies.
The PPN-2 is not supposed to be tuned to adjacent channels, This is a
nono: Tx= #2, Rx=#3.

The APN-2 display is a BC-929. It switches the Rx between two Yagi's,
boresighted left and right of the flight path. The pilot steers for equal
amplitude return from the PPN-2. Range is determined by the round-trip
time delay.

The Rebecca can be keyed to send Morse, BTW.

-John

===============




> Interesting!  I guess the reason for setting different pulse codes with
> the code wheels on the set is to enable distinguishing one path from
> another.
>
> In any case, why use a pentagrid converter as a triode??  Mike, W6MAB
>
>
>   ----- Original Message -----
>   From: Ray Chase
>   To: Michael A. Bittner ; regenrx at yahoogroups.com
>   Cc: milsurplus at mailman.qth.net
>   Sent: Thursday, January 05, 2012 6:39 PM
>   Subject: Re: [Milsurplus] [regenrx] Re: pentagrid detector sensitivity
>
>
>   The AN/PPN-2 is not an IFF set, it is a "pathfinder" beacon set used to
>   guide in airborne troops in WWII.  A marvel of electronics engineering
> and
>   packaging for that period of time.
>   Ray
>   ----- Original Message -----
>   From: "Michael A. Bittner" <mmab at cox.net>
>   To: <regenrx at yahoogroups.com>
>   Cc: <milsurplus at mailman.qth.net>
>   Sent: Thursday, January 05, 2012 8:48 PM
>   Subject: Re: [Milsurplus] [regenrx] Re: pentagrid detector sensitivity
>
>
>   > FWIW, the 1R5 (battery equivalent to the 6BE6) is used as a grounded
> grid
>   > UHF amplifier with grid-1 grounded and grids 2, 3 & 4 tied to the
> plate in
>   > the AN/PPN-2 IFF set.  BTW there's a PPN-2 on eBay right now with a
> BIN
>   > price of  $2,700.00.  Also, the Hallicrafters S-72 uses the 1R5 as its
>   > local oscillator in a conventional triode configuration with grids 2,
> 3 &
>   > 4 tied to the plate.  Why??  What's so great about the 1R5 that it's
> used
>   > as a GG amp or an LO??  Mike, W6MAB
>   >
>   >
>   >  ----- Original Message -----
>   >  From: davidpnewkirk
>   >  To: regenrx at yahoogroups.com
>   >  Sent: Thursday, January 05, 2012 5:12 PM
>   >  Subject: [regenrx] Re: pentagrid detector sensitivity
>   >  --- In regenrx at yahoogroups.com, "kyoritsu" <rikkyograsing at ...> wrote:
>   >  >
>   >  > Forgot to mention a couple of experiments I did with the 6BE6 as a
>   > regenerative detector.
>   >  >
>   >  > I tried injecting the signal on grid 3 (keeping the oscillator tank
> and
>   > grid leak on grid 1). Lyle Williams (The New Radio Receiver Handbook)
>   > wrote you could inject the signal into the screen grid of a pentode
>   > detector, and I wanted to see how this would work on the other control
>   > grid of a pentagrid. Well, it doesn't work. Of course, it can still
>   > oscillate but the only station I heard was one local AM broadcaster,
>   > regardless of where it was tuned or what band. I was hoping for
> antenna
>   > isolation.
>   >  >
>   >  > Also tried tying together the two control grids, 1 and 3. Sort of a
>   > belt and suspenders approach to regeneration, since the two screen
> grids
>   > are internally tied together in the 6BE6. This does work, but there's
> a
>   > clear reduction in gain.
>   >  >
>   >  > So far, the 6BE6 works best with grid 3 grounded. But since it is a
>   > converter tube, you could add a separate heterodyning oscillator
> circuit
>   > in addition to the usual regenerative detector, something that was
>   > suggested back in the 1930s and still comes up from time to time now.
>   >  >
>   >  > The 6BE6 goes into oscillation at a lower voltage than any of the
> RF
>   > pentodes I tried. It might be a candidate for a low B+ regen. Also,
>   > perhaps some of those extra grids could be put to work in space charge
>   > mode.
>   >
>   >  Some comments on these way-cool experiments. What's unusual about
> your
>   > using the 6BE6 as a replacement for the 6BZ6 is that grid 1 of the
>   > 6BE6--which, per the 6BZ6 basing, its its control grid--is its
> _oscillator
>   > grid_. Grid 3 on the 6BZ6 is the tube's signal control grid; the 6BE6
>   > specs in the RCA Receiving Tube Manual say that with the tube's grid 1
>   > grounded and signal fed in at grid 3, the BE6's transconductance (7.25
>   > millisiemens in this connection) is almost that of the 6BZ6 (8 mS)
> under
>   > more or less the same operating conditions (and with its grid 3, its
>   > suppressor grid, grounded). I'd be interested in learning how the 6BE6
>   > operates as a regenerative detector with its grid 1 grounded and its
> grid
>   > 3 serving as its only control grid. Perhaps we can find manufacturer
> specs
>   > for the 6BE6 operating as an amplifier, with grid 1 as control and
> grid 3
>   > grounded; but the tube was designed for grid 3 to be the signal
> gozinta.
>   >
>   >  Yes, the more grids a tube has, the generally more noisy it is--in
>   > small-signal operation. (Small-signal operation is when an active
> device
>   > is operated in such a way that the incoming signal is small enough not
> to
>   > shift its dc operating point--that is, when the device is amplifying
>   > linearly.) When a tube operates as an amplitude-self-limiting
> oscillator
>   > it's in large-signal mode because its dc operating point--its dc
> bias--has
>   > shifted as a result of the presence of the signal it's generating and
>   > handling. A regenerative detector operates in large-signal mode both
>   > non-oscillating (it must be operating nonlinearly to "detect" AM) and
>   > oscillating (in which state it amplitude-self-limits, commonly by
>   > grid-cathode conduction).
>   >
>   >  So although it seems facile to consider that a pentagrid regenerative
>   > detector might be or should be noisier than a detector with fewer
> grids,
>   > we can't directly that from what we know about the relative noisiness
> of
>   > tubes with differing numbers of grids operating *small*-signal.
>   >
>   >  Another thing to keep in mind when evaluating different tube types
> that
>   > can be plugged into a given basing hookup is that in most screen-grid
>   > detectors, only the embedded triode consisting of the tube's cathode,
> grid
>   > 1, and grid 2 does the RF amplification/oscillation. The specification
>   > conveying the most significance to builders of such detectors, the
>   > grid-1-to-grid-2 amplification factor (mu, pronounced mew), is only
> rarely
>   > included in tube specifications. (If "triode connnected" data is
> available
>   > for a given pentode or tetrode--"triode connected" in this case
> usually
>   > meaning "by connecting the plate and grid 2 [screen] together"--the mu
>   > reported can, per Lankford-Smith in the Radiotron Designer's Manual,
> be
>   > taken as closely equivalent to the grid-1-to-screen mu.)
>   >
>   >  The variation from type to type of grid-1-to-screen mu is the main
> reason
>   > you've encountered significant regen-control-setting variation for
>   > critical regeneration across the various types you've tried. The RCA
> 6AK6
>   > data doesn't include its triode-connected mu; as an example, though
> the
>   > 6F6 pentode has a mu of 7 when triode connected. In contrast to this,
> the
>   > 6AU6, a sharp-cutoff pentode with transconductance about half that of
> a
>   > 6BZ6, has a mu of 40 when triode-connected. So, yes, I'd expect that
> you'd
>   > have to turn up your regeneration "considerable" with a 6AK6 relative
> to a
>   > 6BZ6 or a 6BZ6.
>   >
>   >  That you had to turn up regeneration with the 6AK6 does not
> necessarily
>   > mean that this tube is "worse" as a detector than the BZ6 or BE6; it
>   > merely means it's different--for as I've reported earlier in this
> forum, I
>   > find that tubes with lower grid-1-to-screen mus are generally more
>   > frequency-pulling-resistant in the presence of strong signals than
> tubes
>   > with higher mus when they're all compared as oscillating detectors.
>   >
>   >  Best regards,
>   >
>   >  Dave
>   >  amateur radio W9VES
>   >
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