At 04:35 PM 8/4/2008, w7lrd@comcast.net wrote:
Next question- which probably would be more aimed at a EME bb. I have a 12 foot TVRO I am building a patch feed for 1296, and feed it through 50 feet of LMR400 to my IC-1271A. I want to see if I am able to "hear" EME signals. Of course if I am able to, you can guess what my next effort will be. This will be a cheapie effort as I am only using stuff I already have. I do have a KJ6KO L band 70 watt amp. 73 Bob W7LRD Seattle
Bob,
Regarding 1296-eme: The 12-foot dish will do fine on eme and the 70w amp will do fine as a start, especially if you use JT65C.
Is your patch feed circular polar? EME on 1296 is RHCP in transmit and LHCP in receive. The switch of polarity sense is due to the fact that reflection at the moon reverses the sense of polarization. This might be difficult to achieve with a patch feed. Many eme stations are going to the septum feed since it produces both senses of circular polarization and eliminates the need for a high power coax relay. See http://www.ok1dfc.com/EME/emeweb.htm for septum designs.
50-feet of LMR-400 will lose a lot of power at 1296 (2.4dB loss); only 42w will reach the dish. You can solve this two ways: upgrade to 1-5/8-inch hardline (61w will reach the dish) or mount the amplifier at the dish (on the back side would work well). Then use a 10-12 foot 1/2-inch hardline to the feed so that 95% of the power reaches the feed. Typical stations on 1296 eme run a minimum of 150w and average 200-300w. I understand from talking with Gordy, WA6ZKY, that a 150w amp is being developed by KJ6KO. I probably let the cat out of the bag so my appology to Greg.
73 Ed - KL7UW
----- Original Message ----- From: "Edward Cole" kl7uw@acsalaska.net To: w7lrd@comcast.net; "AMSAT-BB" AMSAT-BB@AMSAT.Org Sent: Tuesday, August 05, 2008 8:24 AM Subject: [amsat-bb] Re: brain picking time
At 04:35 PM 8/4/2008, w7lrd@comcast.net wrote:
Next question- which probably would be more aimed at a EME bb. I have a 12 foot TVRO I am building a patch feed for 1296, and feed it through 50 feet of LMR400 to my IC-1271A. I want to see if I am able to "hear" EME signals. Of course if I am able to, you can guess what my next effort will be. This will be a cheapie effort as I am only using stuff I already have. I do have a KJ6KO L band 70 watt
amp.
73 Bob W7LRD Seattle
Bob,
Is your patch feed circular polar? EME on 1296 is RHCP in transmit and LHCP in receive.
Hi Ed, KL7UW
It is best to specify to Bob that on 1296 MHz the dish in transmit must radiate RHCP in direction of the moon so that the patch or any other feed must radiate LCHP in direction of the surface of the dish.
The switch of polarity sense is due to the fact that reflection at the moon reverses the sense of polarization.
OK So that on receiving the wave coming from the moon is received LHCP over the surface of the dish but the dish reverse by reflection the signal in direction of the feed that must be made RHCP polarized on receiving.
In addition a TVRO dish works well with a patch feed if the F/D ratio of the dish is ranging from 0.35 to 0.45
might be difficult to achieve with a patch feed.
W0LMD make a patch feed for RHCP and LHCP but never I tested it
Since the target of Bob is to see if he is able to only "hear" EME signals at 1296 MHz without to complicate his life I suggest at the very beginning to build only a patch feed RHCP polarized.
To receive a 1296 EME signal with a 12 foot TVRO and a IC-1271A it is strictly necessary to connect directly to the patch connector a low noise preamplifier with a NF in the order of 0.5 dB
Since the gain of a low noise EME preamplifier for 1296 MHz is in the order of 30 dB or more then 50 feet of LMR400 connected from the output of the preamplifier up to the input of the IC-1271A will not deteriorate the overall NF of the system that will be only a little bit higher than 0.5 dB
73 Ed - KL7UW
73" de
i8CVS Domenico
Domenico,
You said it well. I forgot to mention that polarity sense will reverse upon reflection at the dish surface, so the feed sense should be Rx=RHCP; Tx=LHCP. In other discussions about using a patch for eme, concern has been about sidelobe performance and high power rating of the patch if full QRO eme is considered. Up to 200w it probably is OK.
I assumed that Bob was savy enough about microwave weak-signals to know that on eme a preamp is not a luxury but an absolute necessity. LMR-400 would be fine for connection from the preamp to the receiver in the shack, if at least 15-dB net gain is left after the cable loss is subtracted. More gain is desirable if the receiver NF is high. A preamp of 0.3 dBNF is standard at 1296 for eme.
I have a WD5AGO two-stage preamp with 0.30dBNF and 31-dBgain bought from Radio Astronomy Supply.
73 Ed - KL7UW
At 05:54 PM 8/5/2008, i8cvs wrote:
----- Original Message ----- From: "Edward Cole" kl7uw@acsalaska.net To: w7lrd@comcast.net; "AMSAT-BB" AMSAT-BB@AMSAT.Org Sent: Tuesday, August 05, 2008 8:24 AM Subject: [amsat-bb] Re: brain picking time
At 04:35 PM 8/4/2008, w7lrd@comcast.net wrote:
Next question- which probably would be more aimed at a EME bb. I have a 12 foot TVRO I am building a patch feed for 1296, and feed it through 50 feet of LMR400 to my IC-1271A. I want to see if I am able to "hear" EME signals. Of course if I am able to, you can guess what my next effort will be. This will be a cheapie effort as I am only using stuff I already have. I do have a KJ6KO L band 70 watt
amp.
73 Bob W7LRD Seattle
Bob,
Is your patch feed circular polar? EME on 1296 is RHCP in transmit and LHCP in receive.
Hi Ed, KL7UW
It is best to specify to Bob that on 1296 MHz the dish in transmit must radiate RHCP in direction of the moon so that the patch or any other feed must radiate LCHP in direction of the surface of the dish.
The switch of polarity sense is due to the fact that reflection at the moon reverses the sense of polarization.
OK So that on receiving the wave coming from the moon is received LHCP over the surface of the dish but the dish reverse by reflection the signal in direction of the feed that must be made RHCP polarized on receiving.
In addition a TVRO dish works well with a patch feed if the F/D ratio of the dish is ranging from 0.35 to 0.45
might be difficult to achieve with a patch feed.
W0LMD make a patch feed for RHCP and LHCP but never I tested it
Since the target of Bob is to see if he is able to only "hear" EME signals at 1296 MHz without to complicate his life I suggest at the very beginning to build only a patch feed RHCP polarized.
To receive a 1296 EME signal with a 12 foot TVRO and a IC-1271A it is strictly necessary to connect directly to the patch connector a low noise preamplifier with a NF in the order of 0.5 dB
Since the gain of a low noise EME preamplifier for 1296 MHz is in the order of 30 dB or more then 50 feet of LMR400 connected from the output of the preamplifier up to the input of the IC-1271A will not deteriorate the overall NF of the system that will be only a little bit higher than 0.5 dB
73 Ed - KL7UW
73" de
i8CVS Domenico
participants (2)
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Edward Cole -
i8cvs