[eagle] Re: AO-51 Multiband Antenna???

Bill Ress bill at hsmicrowave.com
Mon Sep 3 21:47:49 PDT 2007


Hi Tom,

Thanks to you also for such a fine detailed description.

I have a two fold interest in learning more about what was planned. One, 
was getting information on what, if any, wideband antenna configuration 
was planned - for a potential CubeSat application I working with some 
folks on.

Now the other is the Pave Paws discussion Juan et. al., have been having 
today.

So, what you have said about the sensitivity of the SQRX and its ability 
to hear signals over its whole input band (.5 to 1300 MHz as you stated) 
leads me to the following suggestion.

On one of the passes just west of California (an Beale AFB), lets set 
the SQRX on one of the suspected Pave Paws frequencies and have what it 
hears transmitted down to a bunch of us on the West Coast to track and 
record what we hear and how the SQRX responds to what could be some high 
level signals. Might have to use the 2.4 GHz down link since the 435.3 
Tx would probably block the SQRX if its trying to listen in the 70 cm 
satellite band.

Any merit in the thought?

Tom Clark, K3IO wrote:
> Bill Ress wrote:
>> Maybe I'm a bit confused. In my Gould "ECHO" book (Version 1.1 - May 
>> 2004) on page 31, Figure 18 "ECHO satellite tray and component layout" 
>> it shows the VHF, the 4 element UHF turnstile and the L and S band 
>> antennas - - - but it also shows a "multiband antenna" feeding a switch 
>> and then the SQRX receiver. The other side of the switch is fed from the 
>> L band LNA. The SQRX can tune from 10 to 1300 MHz, and somehow I 
>> remember a 28 MHz SSB uplink test. Could be I've got the satellites or 
>> modes mixed up.
>>
>> By the way, that Figure 18 is the only place I can see the "multiband 
>> antenna" referenced so maybe it's an error. Figure 16, on page 30 shows 
>> the other side of the switch being fed by the VHF antenna. That's 
>> probably the right representation.
>>   
> Since I was the provider of a part of this, let me try to straighten 
> out the confusion.
>
> There are 3 physical antennas on Echo; #1 & 2 are on the "bottom" and 
> #3 is on the "top":
>
>    1. A 4 element "droopy dipole" 70 cm TX antenna; each element is a
>       canted ¼-wave monopole. The 4 elements are fed from a microstrip
>       hybrid that feeds the 4 elements at phases of 0,90,180 & 270
>       degrees. Opposite elements are out of phase (i.e. the hybrid
>       acts as a balun). 2 ports are fed from the 2 70cm TX with
>       opposite senses of circular.
>    2. The combined L-S antenna; L-band can be used for RX thru the
>       SQRX, S-band is TX.
>    3. A single 18" monopole made with a piece of piano wire stuck into
>       an SMA connector.
>
> I believe the confusion is about #3. This is the 2M RX antenna. The 
> coax passes thru a -10dB direction coupler, thence into an LNA and a 
> 4-way power splitter to feed the 4 separate 2M RX.
>
> The directional coupler was added at the last minute (provided by me, 
> glued in place by Chuck Green). Originally the plan had been to use a 
> hi-Z 10M preamp (fabricated by Stan) to provide for a 10M RX with the 
> SQRX (SQ = "SpaceQuest") in SSB mode. However, 2 days before it left 
> the USA, Lyle, Chuck, Mark and I decided that the performance was not 
> good, so we elected to use a passive directional coupler instead. 
> Although the 18" whip is a poor match at 10M, we decided it worked 
> better than the Hi-Z preamp, and it meant that the 18" whip could be 
> used anywhere in the 0.5-1300 MHz range covered by the SQRX (albeit 
> with marginal sensitivity).
>
> Since this scheme allows the SQRX to work on 2M, Drew has done some 
> excellent work using the SQRX to do a global map of the 2M environment 
> as seen from space. Not surprisingly, the RFI levels are quite high 
> over south-east Asia (high power cordless phones & fisherman using 2M 
> hardware. I was quite surprised to see that the area over Darfur was 
> also a hot spot!
>
> The relay Bill noted is a SPDT SMA coax relay that selects either the 
> 18", -10dB spigot or L-band from the L/S diplexer.
>
> 73, Tom



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