[ARC5] YG/ZB Demo

Mike Hanz aaf-radio-1 at aafradio.org
Mon Jul 4 18:01:11 EDT 2011


> Mike wrote of the YE/ZB:
>> The sector edge characteristics are not formed by narrow beam width,
>> but by precisely switching the audio coding at each angle desired.
> Still, Mike, if the YE beam is too wide, or the ZB is too close to the
> YE, multiple sector IDs would be received at the ZB.

Michael, Michael...how soon we forget. ;-)    Heh, heh...the answer is 
clearly stated in the NRL discussion of the system.  You use a 
combination of the RF gain control with the BFO turned on and that most 
magical of modern computers - the Mark I Mod I human brain and ear 
combination, to determine which beam is loudest.  I know we're all into 
perfect solutions to complex problems these days, but sometimes the 
simplest is best.  I don't know why you wouldn't use a control box...in 
fact it's required of the ARR-2 to select the channel number before the 
mission flight,  and RF gain as you approached the carrier.  Similarly, 
you'd need an ARA/whatever control box in addition to the ARR-1 pilot's 
control box distant/local switch to make gain adjustments for the ARR-1.

>> There is *no* discussion in the literature about these systems that
>> suggest you could *only* find the general vicinity of the battle group -
>> it was always about finding your particular *carrier*.
> But...it appears that the specific individual YE beacons of the carriers
> in a battle group were discriminated only by FREQUENCY in the 234 to 258
> MHz YE/ZB operating band.

That's correct.  And the implication is?  That brings up another 
question about the previous postulate - if you could only get in the 
general *vicinity* of an entire battle group that covered a 30 mile 
circle, why would each carrier have its own discrete frequency?  I can 
just imagine the flight groups coming back from a 250 aircraft raid to 
say four carriers, all demanding radar position reports and guidance 
back to *their* carrier...yeah, sure...that'll work great! :-)

> There's a pilot's report of YE/ZB use during the battle of Midway at:
>
>    http://www.cv6.org/company/accounts/jmccarthy/
>
> These statements indicate some intersting details of YE/ZB use:
>
> (1)  YE/ZB frequency was DIFFERENT for each carrier in the task group.
> (2)  YE/ZB sector IDs were IDENTICAL for each carrier in the task group.
> (3)  YE signal strength was controlled (reduced) on approach to reduce
>       multiple sector ID reception by lowering aircraft altitude.
> (4)  When the YE was very close on approach, all sectors were received
>       at the ZB.

I'd agree with that, but all the sectors wouldn't all be received with 
the same signal strength as the transmitting antenna rotated.  I'd also 
speculate that the backlobe of the antenna was pretty far down.  Of 
course, there are some pilots that couldn't find the broadside of a barn 
if it smacked them in the face, so there are probably varying degrees of 
aptitude in determining the loudest sector.  It's a little like swinging 
a loop antenna - despite a fairly broad angle indication, you can 
usually get the maxima or minima pretty close based on perceived signal 
strength, can you not?  At least it always seemed like you could with a 
bit of RF gain control jiggling.

> I think it is doubtful that a demo setup where the ZB antenna is physically
> close to the simulated YE, that one could avoid the situation described at
> the end of the quote above, where are sectors are received.

I rather like John's suggestion of using LEDs, though it might be 
interesting to try a TS-24 with a back reflector to the little whip and 
see if some dimensional adjustments could be made to achieve the goal.  
The manual suggests ten feet from the test set, so that's a good start.

> And it is
> essentially impossible to discriminate at the ZB and its BCB receiver on
> the basis of signal strength, except that as the signal grows stronger,
> more sector IDs are received.

Everyone is entitled to their speculation...some folks can hear patterns 
in noise better than others, just as some can distinguish patterns in 
images, or odors, or tastes better than others... :-)

  - Mike



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