Fergus,
Me tinks you are avoiding the answer that you don't want!!!! I have a UPS
SL70 transponder, and what an excellent peice of kit it is. It sounds to me
that we have virtually identical installations. Standard lollipop antenna
with about a 5" diameter aluminium (aluminum in american)ground plane
installed behind the baggage bay, lower fuselage. Mine works a treat so far
and has done since installation. So, IMHO, the problem you have is not in
the installation configuration - you have a fault. Cabling , connectors or
the SL70 box itself. Sorry I can't be more comforting.
regards
MP
----- Original Message -----
From: "Fergus Kyle" <VE3LVO@rac.ca>
Subject: Re: Europa-List: Transponder issues
>
>
> PS: I was wrong once before. I thought I was wrong, but I was wrong - I
was
> right.
>
> ----- Original Message -----
> From: "Fred Fillinger" <n3eu@comcast.net>
> To: <europa-list@matronics.com>
> Subject: Re: Europa-List: Transponder issues
> | Fergus Kyle wrote:
> | >The only way to increase the radiation is to turn the flat disc
> | > of alu into a cone at up to 45deg from the axis of the 'spike'
> | > this might tune the antenna more closely to the 50ohm characteristic
> | > of cable and spike. You should not have to place the spike on the
> | > exterior to improve it.
> | > ...
> | > PS: - maybe the metal nearby 'blanked' your reply - try changing
> | > direction if you get a complaint.
> |
> | Ferg, I agree with your analysis technically, but FAA requires only
> | 125 watts to pass the test, which means their equipment must be able
> | to accept some lower output, may be even 50W. The SL-70 puts out
> | 250W, not "nominal" but minimum. These things have to 100% reliably
> | work in the enroute IFR environment, where in the U.S., at least, they
> | have paint you with two radar sites, and one of which can be a
> | backstop "super site" in each sector, capable of receiving your
> | interrogation at MEAs of only 'bout 3,000' AGL a couple hundred miles
> | away, a rather enormous path loss.
> |
> | Tweaking impedance or radiation pattern I think is unlikely to fix
> | anything, especially if ATC can receive your interrogations, under
> | that antenna "law of reciprocity" thing!
> |
> | Reg,
> | Fred F.
>
> Beats me, Lieutenant,
> Fred,
> You de man. I know nothing of the technical side of ATC's
> regime, so you are probably right about the power business. Although, I
> understood that the average power out was miniscule when the pulse was at
> 250W minimum but the pulse is very short thus reducing the average.
> Otherwise the power output could sterilize us all....... That's the limit
of
> my ken.
> Nevertheless I understood the question to be, "what do I do to
> the antenna?" I couldn't see moving it to the belly (outside understood)
as
> achieving much, whereas revision in situ seemd more efficient - providing
as
> you say, it is in a proper site/alignment to start with. Also the comment
on
> 'ground plane' seemed ominous.
> I concluded that ATC eggheads would have used the same
> technology as hams who bounce tiny signals off the moon and catch one
> millionth of the outbound signal on return - and these at ATC freqs
> (approx). That's 500,000 miles and two atmospheres. I see the loss of
signal
> due topgraphy but not path length.
> You did not comment on directivity/blanking. You don't suppose
> those periods of ATC non-reception to be this cause? It seems outlandish
but
> such things do exist methinks. What would you propose?; I am interested in
> your thoughts.............
> Cheers, Ferg
>
>
|