[Elecraft] Tower Climber RF Safety

[Wes]

Before my electronics career with Hughes Aircraft I worked for a time in the 
automotive machine shop my dad managed.  Having an interest in VHF radio and 
access to a machine shop, I built several high power 144 MHz amps both for 
myself and a number of other local hams.  After moving to Hughes, I worked for a 
time on TOW Missile and then moved on to the Phoenix Missile program. For folks 
who haven't watched the Top Gun movies, (you really should) Phoenix and the F-14 
were a marriage.

Phoenix had a feature called MOAT (Missile on Aircraft Test) wherein after (six) 
missiles were loaded onto F-14s a quick functional test was performed on the 
flight deck to verify that the system was ready to shoot. before launching the 
aircraft. When F-14s were deployed on the Enterprise aircraft carrier there 
started to be a lot of MOAT failures, necessitating the aircraft returning to 
the hanger deck, the missile being downloaded and retested on an onboard test 
set, where the failures couldn't be duplicated.

Someone a lot smarter than I hypothesized that the SCANFAR Radar system 
(https://grokipedia.com/page/SCANFAR) was upsetting the MOAT.  The ERP of the 
system was about 1.5 MW at about 225 MHz. The Phoenix Program Manager didn't 
believe in calculating or simulating anything, he wanted lab testing.  With my 
VHF background I was tasked with designing and building an amplifier that would 
take the output of an HP-608 generator and develop 300+ watts to be used into a 
10 dB Yagi pointed at a test missile, in a lab setting.  This was calculated to 
be equivalent to the RF levels impinging on the missile on the flight deck.  I 
agreed to build the amp but told them in no uncertain terms I didn't want to be 
anywhere near this when testing.  All I could think of was all of those sailors 
on the flight deck getting lit up by that radar.

Wes  N7WS

   ps.  I'm as old as Jim and all is this is from failing memory so I can't be 
held to any of it :-)

On 9/7/2026 2:26 PM, Jim Brown via Elecraft wrote:
> On 9/7/2026 1:44 PM, Kurt Pawlikowski via Elecraft wrote:
>> I thought some of you might find this of interest. It applies directly to 
>> Cell Tower climbers and RF safety, but might be a cautionary tale for RF 
>> exposure for us (and maybe someone nearby our antenna!). Not *exactly* 
>> amateur related.
>
> The nature of UHF antennas is VERY different from those we use at HF. They 
> have very high gain, concentrating their energy in a narrow beam in the 
> horizontal plane, and which can focus a LOT of RF power into the body of a 
> climber who is in front of them. Much less below them, although that can still 
> be a lot if there are enough transmitters at the site for the combined energy 
> is great.
>
> It's pretty hard to have significant RF exposure unless we're running high 
> power into an antenna that's very close to us (like a few yards).
>
> 73, Jim K9YC
> ______________________________________________________________