[Milsurplus] NDB's and tank radios

[frledda at att.net]

WAAS GPS provides for precision approaches, called LPV.  

 

LPV Precision GPS approaches are everywhere and replacing costly ILS.  This is mostly happening on smaller city owned airports, when maintaining the existing ILS is becoming difficult.  ILS CAT II and CAT III are here to stay, for now.  Larger airports are keeping their ILSs, but also adding GPS approaches. Attached is a current precision LPV GPS app plate for DFW; this approach is as accurate as an ILS approach. LPV GPS approaches are easier to fly and less demanding for ATC, as there is no need for RADAR vectors to intercept the ILS localizer.

 

NDBs are great, but there are very few users.  Since the AA Cali crash, airlines do NOT allow pilots to do NDB approaches (rightly so), and new GA avionics does not include any ADF receiver.

 

I agree that availability of GPS may be a problem,  but there are enough VORTAC and ILS to properly navigate.  Big jets still have inertial nav. At the same time, the industry is developing new precision navigation technology for GPS denied environments.

 

Best, Francesco K5URG

 

 

From: milsurplus-bounces at mailman.qth.net <milsurplus-bounces at mailman.qth.net> On Behalf Of Charlie L.
Sent: Thursday, December 4, 2025 4:41 PM
To: milsurplus at mailman.qth.net
Subject: [Milsurplus] NDB's and tank radios

 

The rate of NDB shutdowns may be slowing or stopping.  It is still the least expensive navigation aid out there, and pilots still like a needle that swings around and says to fly 'thataway', as opposed to discerning what his screens tell him.. Small municipal and county airfields can afford an NDB with minimal expense and maintenance, compared to an ILS.  The FAA is also backing off on turning off VOR and TACAN equipment, a mountain top VOR near me slated for shutdown has been resurrected and money spent on improvements.  Apparently the military is also  finding out TACAN can not be fooled like GPS.  The only difference in a standard VOR/TACAN station, VORTAC, and a VOR/DME only (Distance Measuring Equipment) is the rotating antenna is turned off and power reduced to 1KW out.  When the solid state second generation VORTAC came online in the mid 80's, the TACAN ran at 5KW out, the same as the old tube set that used a SAL89 Klystron with 12KV on the cathode, but the fancy solid state system started blowing amplifiers, of which three were 10 at 500 watts each, fed by a 1 to 10 splitter at 100 watts in, and then into  a 10:1 combiner for 5KW out, but they started to burn up and it was too expensive to fix, so reduce power to 1KW.  GPS still cannot be used for a precision approach landing due to ground reflections, which are multiplied on an approach over water, so  V/UHF ILS gear is still the norm, the latest model being installed right now the ILS 420.  It has only two adjustments, the rest are software.  A few years ago, an ILS could have 100 pots to turn to align it and its monitors.

 

Probably the biggest failure in the tank radios depicted in Fury, was in the crystals.  The crystal used in those radios was notorious for going bad, many not even making it across the pond to the ETO, just going bad in transit.  I had a complete unused set for that radio in the felt lined box, and checked all 100 of them, only two worked.  I swapped them all to the new AF4K crystal guy for a good 160 meter crystal. 

 

Charlie in NC

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