Rick report's on the status of his 5760 EME project --
I have been hearing well with increased moon noise, so the
receiver is working ok. To my chagrin, though, I found that I
have no TX. At 1st I thought it was the TWTA. But it seems
that I have lost the control cable for TX/RX, Hydraulics
on/off, and my AZ/EL control. The cable is buried under my
house and 100' long. So, when things settle down I will be
out rebuilding the control circuits. I want to update the
Microwave EME Directory and need input from everyone to keep
the list accurate. Please include your email address.
Stig writes -- Again this month I couldn't operate the
SW due to a combination of family commitments and high winds.
During the week after the SW while checking the on 432, I
found G4ERG and exchanged (549/559). No others were heard
that night at 432. On Saturday, 10 Feb I had tried to set up
some skeds on 13 cm. Paul, WA6PY was worked (429/449) for
initial #34. I am OZ4MM and looking for 13 cm skeds
for the March SW, if someone is interested?
Han's SSB Contest report We had bad WX with strong
wind and snow. Despite the WX, I QSO'd on 3 Feb at 1304 HB9Q
(54/53) JN47, 1623 G4CCH (54/54) IO93, 1819 OE9ERC (55/54)
JN47, 1833 GW3XYW (52/52) IO71, 1911 N2IQ (55/44), FN13, 2059
LX1DB (55/55) JN39, 2111 K5JL (55/54) EM15, 2117 K2DH (54/54)
FN13, 2133 F2TU (54/53) JN38, 2347 K0YW (56/55) DM67, 2351
KA0Y (55/54) EN41 and 2355 K2UYH (52/53) FN20, and 4 Feb at
0045 W5LUA (54/54) EM14 for a score of 13x2x6 = 312 points. I
also contacted on 23 cm on 6 Jan HA5SHF, G3LTF, WA1JOF and
ZS6AXT, on 7 Jan K0YW, KA0Y, W7GBI and OE9ERC, on 8 Jan W4AD,
VE6TA, K9BC and W6HD, on 9 Jan K0YW, DJ9YW, I0UGB and SM6CKU,
on 28 Jan G4CCH and SM2CEW, on 2 Feb KA0Y and on 4 Feb
SM2CEW, ZS6AXT and IK2MBB (from HB9SV's QTH).
Tonda, OK1DAI reports that he and OK1DAK operated
their club station during the EME SSB Contest. They QSO on 3
Feb at 1932 HB9Q (43/42) JN, 1936 OE9ERC (44/44) JN, 2008
N2IQ (54/54) FN20, 2022 G4CCH (44/44) IO, 2050 F2TU (43/43)
JN, 2112 LX1DB (54/54) JN, 2132 K5JL (54/53) EM, 2256 K0YW
(54/54) DM and 2340 KA0Y (54/52) EN for initial #184. All
QSOs were on 2-way SSB. They ended with a score of 6x18 for
108 points. Heard on SSB were OK1UWA, GW3XYW and K2DH.
Before the contest they completed their conversion from 75
to 50 ohm and eliminated that last piece of 75 ohm cable.
The results were even better than expected
As Tonda put it
It was like you put a new outstanding piece in an old
car." On 1296 they QSO'd on 10/11 Dec #177, K0YW #178,
W2UHI, K5JL, G4CCH, K5GW #179, W7SZ, WA6PY #180 and DL6LAU
#181, heard were OZ6OL, VE6TA and WA1JOF, in the Jan SW
WA1JOF (429/529) #182, and in the Feb SW before the contest
OK1UWA (O/O) #184, and heard IK2MMB, ON5RR,GW3XYW, K2DH,
VE6TA and VE6NA. On 5760 we worked on 3 Feb 3 at 1405 F2TU
(O/O) for initial #16 and the 1st F/OK QSO on 6 cm and 1501
F1ANH (O/O) #17. Nil was copied in sked with OH2AXH. A
circular pol feed was used in all skeds that delivered 1.4
dB of moon noise and CS/G noise of 4.5 dB. On 10368 we have
improved our system and now have 20 W at the WG rotatable
linear feed from a new TWTA. This produces good consistent
echoes on at least (O) level. The Moon noise was measured at
1.8 ~ 1.9 dB on Feb 7 with the same old 3.7 m dish., HB9BHU
was so kind to switch on at 2031and we easily QSO'd (O/M)
for initial #14.
Jan has concluded he had antenna problems during the
Jan SW -- I only copied NC1I. Since Jan I have only heard
NC1I and surprisingly DL9NND. I climbed the roof and opened
some of the dipole boxes. I found water as well as melted
support parts. This surely did not contribute to a good
performance, although the VSWR has not changed? I have to
solve this water penetration problem very soon. I now have my
WEB-site up at:
PA0PLY's WEB Site
Timon (JO33j) is working on coming up on 23 cm EME,
and eventually also 10 GHz -- I have a 3 m Al dish and want
to put it up. I am interested in possible mount designs. [Try
contacting PA3CSG.] I would like to know if a PST71 rotator
(8.8 m2, rotating torque 42 kg-cm, breaking torque 52.325 kg-
cm and vertical load 1.450 kg) can handle my dish? [Timon can
be contacted at firstname.lastname@example.org or at:
PA9KT's WEB Site
Marko writes -- I wasn't QRV for
the autumn contest because WX was very bad both weekends. On
the 2nd contest weekend the heavy rain even caused a big
landslide 80 km from here that killed 6 people. The winds
were also high, but my dish survived for now (knock on
wood). My next planned 3 cm activity will be for the DUBUS
spring contest. [Marko also sent in comments on circular pol
see the Technical section of this NL.]
Peter reports excellent conditions both on 432 and
1296 during the Feb SW -- On 432 I worked UA6LGH, VK4AFL,
DK3WG, JH4JLV, RA3LE, DL9NDD, I5CTE, K1FO, OH2DG, NC1I,
K4EME, OE3JPC, UA3PTW, SM3AKW, G3HUL, WB0GGM, KJ7F and UA6LGH
again. I listened to N1BUG running with PA3CSG. Signals were
again very good from Paul, with a pronounced peak at 6-8 degs
elevation at his end. On 1296 I did not enter the SSB Contest
as I run my amplifiers in class C. I came on Sunday night for
some CW QSOs and worked OE9ERC, DJ5MN, OZ6OL, F5PL, ZS6AXT
and IK2MMB/HB9SV (huge signal!). Everything worked well over
the weekend and I was pleased to see the dish track properly
at -30 degs C temperature.
Carl has been working on his 2.3 GHz system and was
happy to test it on 3 Feb I QSO'd at 2000 ZS6AXT (559/559),
2320 OE9XXI (569/559), 2330 OE9ERC (579/559) and 2335 HB9SV
(559/559), on 4 Feb WA6PY (M/M) on sked, and 10 Feb JA4BLC on
2304/2424. I did not take part in the SSB Contest mainly due
to my efforts on 13 cm. On 432 I worked on 3 Feb at 2100
SM2CEW, 2110 K1FO, 2127 UA6LGH, 2138 K5WXN, 2145 G4ERG and
2155 G3HUL, on 4 Feb at 0019 NC1I, 0056 G4YTL, 1407 VK4AFL,
2354 OZ6OL, 2358 UA3PTW, and on 5 Feb at 0033 AL7OB with a
Tor expects to be QRV very soon on EME both on 144 and
432 MHz. He is interested in operating procedure, and can be
reached at email email@example.com. [See G3SEK's Procedures
at the end of the Jan 2001 NL].
Doug is making progress on his dish I had a good day
re-counter balancing the dish. It was a remarkable day in
that there was hardly a breeze. It required 480 kg to get
balance and provide enough back force to get the hydraulics
to bring the dish off the horizon. We had 2 x 60 liters oil
drums of concrete (3 x 40 kg bags) and had to add another 2 x
60 liters in rubbish bins! A friend is going to weld a couple
of 60 and 20 liter cans together to replace the rubbish bins.
Its not presently a real pretty sight, but it works! I
ordered a garden shed for the 'dish shack'. I expect to have
it completed in 3 weeks. I will then have to extend the
cables and ducting to it. I also have to build a dish feed
platform as the feed point is 18' off the ground. It is fun
to wave the dish around. The gearing and speed control work
great. The Az motor (20 V @ 85 A) is PWM controlled. El is
hydraulic and uses a HP single phase electric motor. One of
the digital 0.5° sensors is fitted (El) ready to be cabled.
There is no backlash and even when tipped over the dish needs
a hell of a shove to see the slightest movement. The sheer
size and weight of the installation has me a little edgy. It
will take time for me to gain confidence in the system.
Trevor writes -- Activity on 432 has been fairly good
with initials ON5OF, KA0Y, WB0GGM and UA6LGH in recent weeks.
Conditions have been typically quite variable especially
during the Feb SW. Faraday ranged from zero to 90 degs over
short periods of time. I worked AL7OB with his new dish [good
picture of it on his web site] and a hugely improved signal
over the previous yagi array. With spring approaching in the
Northern hemisphere, I look forward to increasing activity. I
can usually make myself available outside of weekends for any
tests, skeds, etc. I feel there are many suitable days each
month that are under utilized.
Willie was on 70 cm the past SW. He worked on 4 Feb at
0000 PA4FP very good (O) signal, but Frank didn't hear
Willie, 0030 G4YTL (339/O) for initial #300, 0145 K1FO
(579/579), 0259 AL7OB (339/O) #301 and 0530 VK4AFL (O/O) -
very good signal #302. Willie had good echoes all evening. He
will be back on 23 cm in a month or two. For skeds on 70 cm,
Shep has serious health problems and will shutting
down on 70 cm shortly. He wants to provide Montana to all
that need his rare state before he is QRT. Stations wanting
skeds should contact him at email w7hah@montana. com. Shep
worked on 7 Jan N2IQ, on 8 Jan DF3FI for initial #220, on 10
Jan KJ7F #221, and on 27 Jan W7SZ #222.
Larry writes -- Thanks to the "big" stations I had a
good time during the 23 cm EME SSB Contest. The following
contacts were made all via SSB/SSB: OE9ERC, HB9Q, KA0Y,
K0YW, G4CCH, N2IQ, W6HD, K2UYH and K5JL for a score of 9x2x7
= 126 points. Prior to the contest I worked W7HAH on 70 cm
for new State and had a 2nd "FSK" QSO with W7LHL on 23 cm.
[See the Technical report on this ground breaking QSO
promised last month at the end of this NL.]
Paul has moved to 13 cm I QSO'd on 11 Jan WA1JOF in
an extra sked on 1296. For the 3/4 Feb SW I moved to 13 cm
and worked W5LUA, OE9XXI, OE9ERC, SM3AKW and JA4BLC. I did
not hear G3LQR. W7GBI, LX1DB and DL6LAU were not QRV. SM3AKW
told me that HB9SV was calling me. I heard him (M) copy, but
to short to identify callsigns. My biggest problem is
frequency calibration and moon aiming without hearing my own
echoes. I am also getting interference from noise (10-15 dB)
with maxims every 35-50 kHz during evening hours. JA4BLC is
very strong now, and the noise was not a problem. Does
anybody have experience with a similar noise problem? It
looks like wideband modulation - spread spectrum. It covers
2304, 2320 and is strongest at 2424. I will stay on 13 cm in
March. I will setup 10 GHz equipment for April - May. Then I
plan to mount my 70 cm feed on the same 2.4 m dish and see
how many stations I will be able to work on 432. I will be
available for skeds on 13 cm on 2 March from 2000 until
2400, then EL is to high for my dish mount, on 3 March from
0300 until 0700, and from 2100 until 0100 on 4 March, from
0400 until 0800, and on 4 March from 2200 until 0130 on 5
John is still not QRV on 70 cm. The WX has not been
good for tower work. He was active in the SSB Contest and
QSO'd HB9Q, K5JL, G4CCH and LX1DB on 2-way SSB. He CWNR
OE9ERC and heard others. John has been working on an GS9b amp
for 13 cm. He is also working on an GI7b HPA.
John missed his Feb JA skeds due to Hi VSWR from an
ice storm. He did work DL8OBU for initial #84, OH2DG #85 and
G4ERG #86, only a partial with KL7HFQ and nil from YO2IS and
UA6LGH. He reports hearing ON5OF, PA4PF and G4YTL - worked
for #87 after the SW. John will be active on random during
the March SW, but is also interested in skeds.
Ivo reports -- Since the WX was thunderstorms every
night, I did not manage to get on 6 cm during the Feb SW. In
fact both SW nights were clear, but quite windy from a cold
front. So I went to 13 cm on Saturday and worked SM3AKW
(559/559) - very good signals from Carl for the 1st time,
then HB9SV with the same reports. The sked listed for WA6PY
were well after my Moon window ended. I did not hear anybody
else. On Sunday I changed to 23 cm, to give out some points
in the SSB Contest, but only one station was heard on SSB.
[The contest was already over!] I worked DF4PV, DJ5MN,
OE9ERC, OZ6OL, SM2CEW, IK2MMB/HB9, W2UHI, G4CCH, K5JL, KA0Y
and K0YW - all with good signals. CWNR was F1PYR and heard
was F5PL. We had strong winds, thus it was chopping the
signals sometimes. All stations on CW, no SSB, although not
much activity in my window. The WX improved on Tuesday 6
Feb. I installed my 6 cm assembly into the dish feed. The
main changes are the addition of an IMU circular pol horn
and power upgraded to 40 W. The initial position of the horn
gave about 0.6 dB Moon noise. My echoes were up to (549). On
Wednesday I moved the horn a bit and the result was bit
worse. (To change the horn position is quite an exercise, it
takes well over an hour!) Since Peter OE9PMJ asked for sked
that night, I did not change it. And in the evening I got
him straight away, with (559) signals. He gave me (449) for
initial #8 on 6 cm. After that I worked Reinhilde, OE9YTV
#9. Signals were clear CW, so that I could use my 200 Hz AF
filter without problems. However, whether in SSB BW or 200
Hz, signals were excellent even with my low Moon noise. I am
not sure whether Peter is also using circular pol. I will
see in future QSOs whether there will be now any frequency
spreading as happened with linear pol. After final
optimization of the horn position I will try to measure how
much power is induced into the 6 cm horn from 23 and 13 cm
horns and if the level is acceptable, I will leave the 6 cm
assembly permanently installed, so that I would have 3 bands
(23, 13 and 6 cm). The offset installation of 23 and 13 cm
has worked well for me. Change from band to band takes just
a minutes. Of course the dish must be repositioned, by some
5 degrees in EL for the offset. The gain loss for dishes of
5 m or more is virtually negligible.
I had planned to operate 432 the 1st evening of the
Feb SW and 1296 the 2nd for the SSB Contest. Things do not
always turn out the way you plan. On Friday night I checked
out my system, and discovered a very high VSWR. In trouble
shooting the problem I found that the T-R relay at the dish
was not getting voltage. Cable problems are not new as my
dish has been up for > 25 years and most of the cables have
been in place that long. The T-R relays, however, have always
worked. In the dark and cold, (it was raining with some snow
mixed in), it would have been very difficult to fine the
break. I ran a spool of wire from my shack to the feed of the
dish and got the relays working in a very temporary way. I
then found that my preamp was not working. I had voltage to
the feed, so I ran a clip lead to the preamp. I made it on
just in time for an extra sked with DL5LF at 0100. I copied
Frank (O) for the 1st few periods, but he did not copy me.
After this sked it was near the end of my Eur window and the
WX was not that good, so I gave up for the evening. The next
day I found one of the control cables had sheared at the back
of the dish. I made repairs and had everything back to
normal, but had to modify my plans to operate the SSB
contest. I had to attend an awards program at the college; I
had intended to skip in favor of the contest. It occurred
during my Eur window. Fortunately, KC2TA and KB2TIS, whom
frequently operate contests with me, were available to keep
the station on the air. I was able to operate after 0300 and
was hoping for some JA/VK activity that never appeared. We
did QSO on 3 Feb at 2101 HB9Q JN (55/53), 2110 F2TU JN
(55/43), 2126 LX1DB JN (56/56), 2130 KA0Y EN (55/55), 2132
K5JL EM (55/55), 2134 OE9ERC (56/54) JN, 2140 N2IQ (57/57)
FN, 2146 K2DH FN (55/55), 2158 K0YW DM (55/55), 2205 IO G4CCH
(55/55), 2248 IO GW3XYW (53/53), 2256 WA9OUU EM (55/53), 2318
K4QI FM (54/54) and 2355 OZ6OL JO (53/52), and on 4 Feb at
0026 W5LUA EM (54/54), 0354 W6HD CM (54/54), 0400 W7BBM DM
(549/55) and 0410 W7SZ CN (54/53) for (18x2+1x1)x10 for 370
G4RGK, DAVID DIBLEY
KB0PYO is collecting the pieces to put his 15' dish on the
air. Mark might have it operational by this fall.
YO2IS is looking for Oceania on 70 cm for WAC. Szigy need one
more QSO to bring him to initial #150.
VE3BQN is QRT on 23 cm EME. Ted has moved and is retired.
W6HD will be QRV on 3 cm soon.
ON4ANT has a new email address .
VE1ALQ had WX problems and was unable to be active in the SSB
Contest. Darrell's address is incorrect. It should be Darrell
Ward, 3 Windsong Crt., Brandy Point Est. (optional), Grand
Bay-Westfield NB, Canada E5K 2S5.
WA1JOF is working on 6-tube amp for 1296. Don finally worked
DJ5MN on Sunday of the SW.
K5WXN worked KL7HFQ and EA8FF for 2 initials on 70 cm EME in
VE6TA worked 4 stations during SSB Contest. Grant missed his
WA9OUU sked and had a partial with HA5SHF (M/-).
W7MEM now has 900 W on 432 and is interested in skeds, but
also needs better T-R relays.
W5ZN is working on a 70 cm array.
ON5OF is QRV again, although still in a cast. He worked
VK4AFL on Sunday on the SW, but heard nil from AL7OB.
G4YTL is looking for skeds.
RA3LE will be on 432.005 with 8 yagis and 1 kW every weekend
looking for random QSOs.
RW3PF is looking for 70 cm skeds.
DK3WDG will active on 432 in the March SW.
W5LUA worked 8 on 23 cm in the SSB Contest plus WA6PY on 2304
and a new one on 10 GHz.
W2UHI reports having fun on the SSB in the contest.
K5JL made 25 QSOs with his new TS-2000 during the SSB
K2DH fixed his Az drive problem and was on for the SSB
Contest and made 18 QSOs.
WA8WZG was iced up also and missed the contest. Tom still
needs to fix his El-Az control cables where rodents are
W4RDI missed the contest.
K5WXN reports good results on 432 in Feb, but lots of QSB
from polarity and libration.
K8ISK is interested in getting on 1296 EME from his home QTH.
KA0RYT is temporarily QRT on 70 cm.
KJ7F heard nil in sked with AL7OB.
DJ5MN reports nil from WA8WZG in last SW but did work WA1JOF.
He is making progress on 10 GHz.
CT1DMK will be on 70 cm for the March SW, and will move up to
6 cm and 3 cm during the DUBUS Contest.
K4EME worked in Feb on 432 NC1I, SM2CEW, K1FO, DL9NND,
DL8OBU, KL7HFQ and AL7OB.
K6IBY is QRV again on 70 cm and will be active on random
during the March SW.
UA9FAD QSO'd on 432 in Feb DL8OBU, AL7OB and G4ERG to bring
him to initial #140.
PA3CSG has a new email address .
RA3LE worked on 70 cm EA3DXU, OZ6OL, DJ3FI and UA3PTW in Feb.
UA3PTW added on 432 RA3LE, G4YTL, OZ6OL, AL7OB and EA8FF.
PA5ZBU has sent me (K2UYH) a packet of CDs from the RIO2000
EME Conference. These are for sale at $US10. Let me know if
you want one and I will get you a copy.
KB0PYO has a matching pair of (2 and 70 cm) amplifiers for
sale or possible trade. Both PAs use the 4CX1600u/GS23b and
were built by Steve Gross, N4PZ. Both include full metering,
blowers (1 on 2 m and 2 on 432), filament and grid supplies.
Mark is asking $1100 for the 2 m amp and $2000 for the 432
amp plus shipping. He will consider trades. Contact Mark at
W1ZX has for Sale an MFJ-784 Super
DSP filter for $US100+s,
JPS NRF-7 Noise Remover & Audio
Filter for $US50+s,
HP431B Power Meter with head for
HP415E SWR Meter - brown color unit (a later model
unit, not gray in color) for $US65+s,
Noise Com Noise Diodes
NC305, glass package for $US33+s, and
AIL Hot-Cold Load
Generator, Type 70 (needs some work) for $US25+s. Call Willie
at 301 645 5584 between 2000-2300 EST, FAX 301 645 6853, 24
hrs, or email to: W1ZX
KA0RYT is looking for Ultem.
OZ9AAR is looking for the design of a 23 cm solid-state amp
see K3AX's report.
K3AX has a 225 W 23 cm solid-state PA for sale. See Harry's
report in this NL for details.
VE3BQN has a 23 cm 4 tube PA for sale. Contact Ted at email
N2IM is interested in 1296 and 5760 EME and is looking for
designs or to buy feeds for these bands. Charlie can be
reached at email at: N2IM
DJ5MN is looking for waveguide for 3 cm.
VE6NA is still looking for 6 tube amp for 23 cm.
W7MEM is looking for 2 SPDT Transco relays or equiv.
There was has been quite a bit of discussion on
the use of circular polarization for Microwave EME incited
by S57UUU's paper from the RIO2000 EME Conference. Marko,
S57UUU wrote: "It is true that it is harder to make a
circular feed than a linear, but it is not that much harder.
The losses are negligible. Discrete 90 deg hybrids and
cables are definitely not the way to make circular pol on 10
GHz. I would almost bet that the losses can be below 0.01 dB
for the 'squeezed tube' polarizer described by W2IMU
(reprinted in '96 EME conference proceedings). A PTFE
quarter-wave plate (my favorite) has maybe 0.1 dB. The
linear orthogonal (commercial WR-75 units from 11 GHz TVRO
can be used) and add about 0.1 dB. Using separate feeds for
RX/TX as I do [see -
spares you even
that. So 0.5 dB is an extremely pessimistic value. Even with
0.5 dB, the loss in S/N is less than 1.4 dB typical (signal
goes down .5 dB, .5 dB of loss at 300 K gives you 37 K of
noise - adding that to 160 K (70 K preamp, 30 K antenna, 60
K Moon/3 m dish - very optimistic values) gives a 0.9 dB
increase in noise). 1.4 dB is less than the approx. 2 dB we
are loosing on average with linear pol because of geometry.
I have described this in my Rio paper, also available at
circular will in- crease our signals and make them more
consistent. When listening to US stations on 3 cm linear
pol, I can see quite well the signal dip caused by geometry.
I do not believe that significant polarization can happen at
the Moon. It is DEPOLARISATION that happens, and that is as
detrimental to linear as it is to circular. This is also
described in my Rio paper. The bi-static case cannot be that
different from the mono-static. The Earth as seen from the
Moon is 2 deg across - and that is limb to limb. EU-USA is
more like one deg max. So the impact angle is less than one
half deg. That is negligible compared to the 7 degs average
slope of the lunar terrain (as determined by RADAR)."
Kent, WA5VJB responded: "The problem is that a Right Hand
Circular pol (RHCP) signal is reflected off the moon as a
Left Hand Circular pol (LHCP). If all 3 cm stations went to
RHCP we would all be cross-polarized. A RHCP station can
work a LHCP station, but each station would not be able to
hear their echoes. I am afraid simple circular polarization
is not the answer."
Charlie, G3WDG added: "You would need to have 2 orthogonal
probes in the feedhorn, one for LHCP the other for RHCP,
much like the IMU horn has, where the polarizing is done
with a phase delay section using a waveguide section loaded
with screws. I have not seen the Rio paper, and do not know
whether a practical feed design has been published. An
apology in advance if this paper has discussed the issues I
want to raise below. If the polarizer section is done with a
length of suitable dielectric, the losses would probably be
acceptable. The consequence of this from a practical point
of view is that we would likely end up using coax to feed
the probes in the horn. This requirs transitions to be made
if there is any waveguide in the system (e.g. to bring the
TWTA power to the feed, or waveguide input preamps). Since
most preamps are coaxial input, this is not much of a
problem. Where losses would arise, though, is in the
protection relay, which you would almost certainly need to
switch the preamp over to a 50 ohm load while in TX. I don't
think many people would risk relying on the isolation in the
feed (difficult to get > 25-30 dB) to stop burning up the
preamp. A waveguide switch would be better than a relay, but
then 2 transitions would be needed, and it all gets a bit
bulky and complex to have at the feed! It was this type of
reasoning, including the simplicity of a linear feed, which
led to the (almost) universal adoption of LP by 10 GHz EME
ops. I think it would be desirable for those seeking to
change the standard to try CP out in practice and compare
signal levels to linear. If there is ANY significant
reduction in system performance I would personally not want
to trade that for the only advantage I can see that CP
offers, namely the elimination of geometric rotation. I have
on occasions had to adjust pol angle, but not that often to
justify the extra work that building and installing a CP
feed would entail. I do not agree that on average using LP
costs us 2 dB as is claimed. It depends on the geometry of
the path and can be zero if you can rotate your linear feed.
If CP is to be adopted widely (and let us not end up in a
mess where some are on linear and others on circular!), then
2 things need to happen. Firstly, practical designs for
feeds need to be published so that others can copy them, and
secondly the decision needs to be ratified at IARU level,
since there is an IARU standard in existence which
recommends LINEAR pol for EME use above 3 GHz. The RSGB
wrote a paper on this some years ago (which I wrote on
behalf of the Microwave Committee of the RSGB). This was
adopted (I can't remember at which meeting, but it was at
least 5 years ago I think), and is thus the "official"
standard. Most EME ops are currently using linear. An
unorganized switch to CP would not, in my opinion, be
productive in increasing activity as there would be residual
uncertainty in peoples' minds to put them off. EME
conferences are a good place to sound out ideas, but I don't
think they're a representative forum for reaching decisions
of international significance. That's one of the things IARU
exists for!" After reading Marko's paper, Charlie wrote: "I
have now had a look at the paper. The arguments in the paper
are well known and have been aired before when the matter
was debated years ago. I personally don't think anything has
changed to justify changing the IARU standard. The fact that
the proponents have not yet been able to show us how to
build a simple horn, I think justifies the comment that
there is yet no reason to change. BTW I am a firm supporter
of CP on 23 and 13 cm!"
TECHNICAL INFO FOR 23 CM EME QSO via DSP (FSK) Between W7LHL
and W7SZ: A brief description of this QSO that took place on
9 Jan (possibly the 1st of it's kind) was reported by W7SZ
in the Feb NL. The system used by both parties was designed
by Bob Larkin, W7PUA. The central element is his DSP-10 (144
MHz) transceiver featured in Sept~Nov 99 QST and on his WEB
DSP-10 WEB Site
transceiver is computer controlled and includes waterfall
display and EME friendly functions including: AZ/EL display,
Auto Doppler shift of Rx, Auto echo display and the FSK mode
called PUA43, which was used for this QSO. The system's
ability to dig into the noise results from long-term
integration, separating signal from noise. With this as
background, "PUA43" is the transmission of up to 43 tones,
one at a time. Each tone represents an alpha or numeric
character. Characters must fall into a spectral bin,
adjustable from 2 to 9 Hz wide. Each character's tone is
sent for 2 seconds and repeated once or twice per minute for
long as one wishes. To further improve reliability, there is
a random frequency "stir" to eliminate the effect of
birdies. This requires that both sked stations have their
computer clocks synchronized. The Frequency accuracy was
accomplished via a GPS controller (July 98 QST) steering a
10 MHz VCXO. Output of the OSC is buffered and power divided
to feed the DSP-10 transceiver and "lock" the 23 cm txvtr.
Unlike many FSK systems, this is not an all-or-nothing copy
of text. A process called "message estimation" is used to
determine the most likely characters. The confidence level
of a received character is noted by it's color and improves
with integration time. The improvement over aural copy is
yet to be fully established, but various experiments (non-
EME) have shown it to be 20 dB or more, depending on the
operators patience. The software to implement these EME
functions is still in Beta test. However, Bob is close to a
formal release. One problem experienced during this 1st EME
QSO was error between predicted and actual Doppler. Both
W7LHL and W7SZ had to correct by 9 Hz to be in sync during
the contact. This correction was established via the Auto
Echo mode prior to QSO. A 2nd "FSK" QSO between W7LHL (10'
dish) and W7SZ (12'dish) was completed on 18 Jan. Both
stations again using 50 W. However, based on the margin,
QSOs should be possible at significantly lower power levels.
More tests are planned.