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