[ARC5] OT: X-15 Radios

[Scott Johnson]

I don't think  UHF DF in the cockpit was a big priority with this program.  The ARA-25 works well if it is properly maintained (especially with the later PIN diode switched antenna).  I know there were very high speed AT-256 surrogates produced with a ceramic center insulator, rather than the early phenolic or later Teflon.  ( I have one somewhere, I have no idea what aircraft it was from).   I would guess thy want to produce the least amount of drag, so it was probably mounted somewhere where the boundary layer was fairly deep.  The loop probably peered through a flat ceramic matrix radome in the belly, as on most aircraft.

Scott V. Johnson W7SVJ
5111 E. Sharon Dr.
Scottsdale, AZ 85254-3636
H (602) 953-5779
C (480) 550-2358
scottjohnson1 at cox.net
scott.johnson at ieee.org

-----Original Message-----
From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> On Behalf Of Roy Morgan
Sent: Saturday, December 1, 2018 8:17 PM
To: ARC-5 <arc5 at mailman.qth.net>
Subject: Re: [ARC5] OT: X-15 Radios

I can tell of a system that worked:

I was copilot on the photographers helicopter as Apollo 7 came back to a water landing near Bermuda.  Our aircraft (the SH-3D *) had been fitted with two antennas, one on each main landing gear strut, and presumably some sort of receiver (possibly the normal UHF radio, I don’t remember that part of the installation).  Each antenna was a small yagi and was fastened to the strut on each side.  This was a temporary installation for the event.

The returning space capsule had a beacon transmitter on it that was transmitting both during the last phase of descent (by parachute) and while in the water.  I assume that all three or four helos in the greeting flight were able to home in on the thing as it came down and floated in the water.  It did land within a mile or so of the target location.

The weather was good with plenty of visibility, so finding the thing was not a big challenge.  I have no idea of the expected accuracy of the bearings we got.  I can assume that the antennas and receivers were tested before the actual recovery of the space capsule.


More about the helicopters and pictures:

* If you catch a glimpse of the President’s helicopter on the news - it’s the same aircraft and you can see the strut on the main landing gear.

The Wikipedia entry for “Helicopter 66” 

https://en.wikipedia.org/wiki/Helicopter_66

has a picture that shows the antenna (It looks to be VHF size, not a ULHF as I tell above). Here is the picture from Apollo 8:
https://en.wikipedia.org/wiki/Helicopter_66#/media/File:Helicopter_66_Apollo_8.jpg
Showing the astronauts getting off the helo.

This photo shows the Apollo 7 event I was on - this picture was almost certainly taken from my helo.  You can see the antenna on the strut but the image is very fuzzy:
https://upload.wikimedia.org/wikipedia/commons/f/f2/Apollo_7_recovery_with_SH-3_Sea_King_1968.jpg


Roy


> On Dec 1, 2018, at 8:10 PM, Brian Clarke <brianclarke01 at optusnet.com.au> wrote:
> 
> Is that really the best? For such an expensive system?
> When you get equal signals from two antennas, they can be pointing many degrees off alignment because of the insensitivity –…

> From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On Behalf Of bob at vanirmail.com
> 
> Subject: Re: [ARC5] OT: X-15 Radios
>  
> Hi Mike.  
>  
> If I were designing this DF system for the X-15  I would install small titanium stub antennas on each wing with the fuselage shielding one antenna from the other.   

Roy Morgan
K1LKY since 1958
k1lky68 at gmail.com




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