HRPT weather satellite signals have much higher resolution than APT images; however, HRPT image reception is a little more complex than receiving APT images from passing orbital weather satellites. First, the operating frequency is much higher and second, it is important to have the ability to track the satellites. The image decoding also takes a lot more processing power. In this example, the RSP2 is being used with a 26 director element loop yagi (approximately 20 dBi and 6 ft in length) in conjunction with a 21dB gain LNA with a noise figure of 0.36 dB. Additionally, the cost of equipment and software is higher, so you will want to read through this article and get a good idea of all of the software and components, and related expenses, before starting.
The tracking system employed is a repurposed Meade Instruments DS2090AT mount with 497 controller. If you use one of these, be sure to obtain the latest version which has a blue band around it showing the position rather than a black band. Older versions of the mount may not work as well without some modification for this application (they may slip in vertical movement, given that the antenna is near the maximum out-of-balance weight for the newer mounts – if it should slip and tightening does not solve the problem, pull the vertical control portion apart and insert a rubber washer such that it is between the friction plate and the original gripping section; alternatively, you may be able to add some non-metallic weight to the back of the boom to better balance the antenna in the mount). Given that the diameter of a 90 cm telescope tube is near that of the loop yagi in the 1.7 GHz range and the antenna weight is comparable to that of a telescope tube, making use of a used telescope mount capable of tracking satellites worked well in this instance. Meade Instruments has downloadable software on its web site to allow uploading the most recent versions of software and TLE (satellite data) files to the 497 controller using an RS-232 serial cable. Refer to the Autostar™ Software Updater. Additionally, Meade has downloadable Autostar™ Suite software to enable using the mount to point to any position in the observable sky as well as to track orbital satellites passing overhead.
The LNA used is a TriQuint/Qorvo TQP3M9037-PCB evaluation PCBA which provides approximately 21dB gain with a noise figure of 0.36dB. The LNA in this image has been modified to apply a 10uH inductor 220 mA (PN 9250A-103-RC) and 33uF 25VDC capacitor (PN TAP336K025SCS) to supply power via the coaxial cable from the RSP2 using the RSP2’s BIAS-T feature on Antenna Port B. The TriQuint TQP3M9037-PCB evaluation PCBA only requires around 47mA at 5VDC. Operation off of the RSP2 Bias-T power can be used, if a band pass filter is not needed in your area. Be sure to use flexible (to allow the antenna mount to move properly), low loss cable, such as LMR-240 to connect the LNA (and filter) is used to go the short distance to the RSP2 (or a line driver, If the RSP2 will be mounted far away from the antenna).
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The antenna used is a 26 director element loop yagi antenna with center frequency at 1692.70 MHz. The antenna is applied for reception of HRPT signals as well as HRIT/LRIT signals from geostationary weather Satellites; however, for geostationary weather satellite image reception, you may need to apply additional loops (e.g., 32 director elements) which will likely make the antenna too heavy for the mount to position properly, unless additional weight is added to the back end. At 26 director elements, the antenna is at the limits of what the mount can support without additional weight on the backend to counterbalance the antenna. Using any type of metal to mount the antenna anywhere near the director elements will result in decreasing the gain of the antenna. This is why the antenna is mounted from behind the first reflector element. Using the standard Meade telescope clamshell to hold the antenna required additional reflector elements to offset the effects of the clamshell fixture on the signal and optimize the gain when the loop yagi antenna is mounted. The antenna mount is made from a PVC connector fitting that is made to connect two 3” PVC pipe ends. The PVC connector fitting was obtained at the local hardware store. You will need to modify the PVC connector fitting by using a drill with a small grinding head to remove enough of the inner rim to allow the antenna boom to fit tightly against the inner wall. You will also need to drill two small diameter bolt holes through the PVC and antenna boom and mount the boom inside the PVC with two bolts; make sure these holes are just barely wide enough to allow the bolts through (any excess will allow for play in the movement of the antenna when mounted and any potential play or variability in position needs to be kept to a minimum). Additionally, you will want to use some industrial strength glue to attach hard plastic alignment pieces on either side of the boom on the inside of and attached to the PVC fitting, following the boom and firmly up against it, but not glued to the boom. This will keep the screws from eventually widening the holes in the PVC and creating a loose fitting, once in operation. The antenna boom is long enough and heavy enough to put significant force on the mounting screws and PVC where the screws are mounted when moving, so you will want to keep the antenna boom from shifting where the screws attach the antenna boom to the PVC. The PVC is then removed and painted to prevent deterioration in the environment; then the PVC is reattached to the antenna boom firmly. Next, you will need to find 1/16” thick by 1” wide rubber strips, preferably with an adhesive backing to attach around each end of the PVC fitting. This will allow a firm fit in the 90mm clamshell mount. Do not remove the existing felt padding inside the clamshell. Now you can mount the antenna boom with attached PVC to the clamshell. Mount the linear-feed yagi loop antenna for a diagonal polarization as this will work reasonably well for linear polarized signal HRIT and LRIT geostationary satellite reception (GOES 13, 14, and 16) as well as work with RHCP orbital satellite signals as the satellites move along their orbital path. The boom used is a ¾” diameter and 6 ft long aluminum tube. Holes were drilled in the boom as indicated in the table below. The loops for the loop yagi antenna were made from aluminum sheets and carefully cut to size with holes drilled at each end for mounting. Mounting of the loops, excluding the driven element was performed using aluminum rivets. The driven element was attached by drilling a hole through the boom to pass the UT-141 through and the UT-141 (after attaching the SMA connector and bending to mate with the LNA) was then attached to the aluminum boom. This can be done, such as by using a small amount of conductive epoxy on either side of the boom where the UT-141 enters and exits.
If you live in an area with high level terrestrial interference near the frequency of interest, you may wish to further employ a filter such as a Sysmocom or similar L-Band cavity filter with a pass band of 1525 MHz to 1750 MHz. If you place a filter between the LNA and the RSP2, you will need to provide 5VDC power directly to the LNA and may not wish to apply the Bias-T modification described above, since the filter will not pass the DC voltage through.
Once you have the hardware setup, you can do some initial testing to see how well you are receiving the HRPT signal. Using the SDRuno software that came with the RSP2, set the sample rate for 6 Msps. Set the RF gain to maximum. You should be able to see a signal similar to the following. Note that the center peak should be at least 30dBm on a pass having an elevation of at least 38 degrees and will be up to around 50dBm during a satellite pass.
In order to determine when the orbital satellite will be in position to start tracking, it is helpful to apply Orbitron software to start tracking as satellite begins passing your ground location. Orbitron software is available here: http://www.stoff.pl/ . Note that unless the antenna is at a relatively high position above ground such that there are no obstructions, you will need to determine when to start the pass by doing some testing. Typically, you will start the pass after the ground station is a little bit inside the coverage area for the satellite as indicated by Orbitron. To determine when to setup and get ready for orbital satellite passes, the following web site is helpful. You can obtain ten-day predictions for passes: http://www.n2yo.com/satellites/?c=3 .
Once you have the HRPT signals coming in at the appropriate levels, you will need decoding software and an HRPT image reader. HRPT decoding software is available from USA-Satcom for a fee. Contact USA-Satcom here: http://usa-satcom.com/contact/ . Here is an image of the HRPT decoder software under operation with the RSP2:
Note that the Meade DS2090AT mount does not have a DDE interface, so you will need to manually tell the mount when to initiate the track and it will follow the satellite from there. If you have a DDE compatible mount available, then you can make use of the DDE control in the USA-Satcom HRPT decoder.
You will need a PC with a fast Intel i7 CPU to run the USA-Satcom decoder software. Check with USA-Satcom for recommended processing requirements for the HRPT decoder software. The CPU applied in this example is an Intel i7 quad core 2.90GHz (3.90GHz peak).
Once you have the HRPT signals received and decoded, you will need to then open the stored files for viewing. This can be done with ReadHRPT software available at: http://www.satsignal.eu/software/hrpt.htm . You can generate gray scale and basic false color images with the base version of ReadHRPT. To obtain full color images, you will need the upgraded version for a fee.
NOAA HRPT images can be decoded using the above software. To view images from Meteor M2, additional MetFY3x processor software is needed from here: http://www.sat.cc.ua/page5.html .
Some Satellites for tracking and viewing images:
NOAA 19 - 1698.00 MHz
NOAA 18 – 1707.00 MHz
NOAA 15 – 1702.50 MHz
Meteor M2 – 1700.00 MHz
Note: Not all satellites always transmit for the entire orbit, so you may not be able to receive HRPT signals from all of the above satellites in your area. The NOAA satellites are usually very consistently transmitting, so you may want to start attempting to receive signals from those first and then attempt receiving images from other satellites in the above list.
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HRIT and LRIT Low-Cost System
https://www.sdrplay.com/community/viewt ... f=5&t=3262
HRIT and LRIT Geostationary Weather Satellite Image Reception
https://www.sdrplay.com/community/viewt ... f=5&t=2674
Orbital Weather Satellite APT Image Reception
https://www.sdrplay.com/community/viewt ... f=5&t=2529
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Here is a picture of the painted PVC bracket with 1/16 inch thick rubber tape applied to the outer edges to allow for a tight fit in the clamshell holder of the mount.
Here is a picture of the loop Yagi antenna attached through the PVC mounting bracket. Note that the PVC mounting bracket is exactly centered between reflector elements 1 and 3.
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Author not affiliated with any sources of components. Links:
TQP3M9037-PCB: https://www.mouser.com/ProductDetail/Qo ... n0eg%3D%3D
50 ft USB extender cable: https://www.ebay.com/itm/50FT-High-Spee ... 2749.l2649
1/16 inch thick by 1 inch wide rubber strips (adhesive backing): https://rubbersheetwarehouse.com/collec ... 1540356803
Additional notes: Total loop Yagi antenna weight is 11.6 ounces with 26 director elements (30 total elements). The DS2090AT mount works reasonably well with an unbalanced load up to around 10 ounces of unbalance. The telescope tube that is normally used with and typically balanced on the mount weights 55 ounces (3.4 lbs). The loop Yagi antenna in this article is not balanced on the mount. Mounting it at or near its balance point on the half metallic clamshell causes a reduction in gain, so the loop Yagi antenna from the first reflector element forward is mounted in front of the clamshell.
If you order a 50 ft USB cable and it does not have a large ferrite bead on each end and an active transceiver in the middle, it may not work well for this application. Be aware of this when you order a USB extension cable for SDR applications. Check with the company offering the cable, before you purchase.
Reason: No reason
Reason: No reason