Tagged: l-band

Discovery Dish April Manufacturing Update

This was posted over on our Discovery Dish Crowd Supply updates page and we are cross-posting here too.

It’s been over a month since our last update so we thought we’d share some of the recent progress. As mentioned in our last update, during the month of February all manufacturing was shut down due to the Chinese New Year holiday. In early March, staff returned to the factories and began making progress on finishing Discovery Dish.

We have a snazzy new logo, and we are working on obtaining some stickers to include with the feeds.

 

Dish Manufacturing Progress

The molds for the dish stamping machine were successfully created in March and the test stamps have come out great. The manufacturer is still tweaking the secondary mold that stamps the mounting and connecting holes, but we expect that to be completed shortly. Once that is done and tested, we can begin stamping the dish segments en masse.

The Dish mounting system was also finalized and we added 45-degree markers to it, which can help with aligning skew.

We are still awaiting the results of the anodizing tests, but they should be completed by the end of this month. Anodizing the dish is important as the dish must be a dark non-reflective matte color, so that it does not focus hot sunlight onto the feed point plastic head.

Feed Manufacturing Progress

PCB Upgrades

While waiting for the manufacturers to finish up with the molds, we’ve been further refining the PCB feed. Our final version of the PCB has now moved to a PTFE substrate with significantly lower loss at higher frequencies. This has yielded an over 1 dB increase in SNR at the GOES 1.69 MHz frequency.

The change to PTFE was not without problems. An interesting RF engineering problem occurred with the move to PTFE that we wanted to share. When moving to PTFE the only changes to the board layout are PCB trace width changes to keep the impedances matched. Other than that, the boards and layout are essentially identical. However, we discovered that the dual LNA design started oscillating when we moved the PTFE substrate. Oscillations can occur with LNAs when RF essentially bounces back and forth between the two LNAs, which causes undefined behavior in the LNA, such as poor gain, multiple spikes in the spectrum, and unexpected current draw values.

We found this quite odd because oscillations were not occurring in the original FR4 PCB, and the QPL9547 LNA is advertised as ‘unconditionally stable’ which means that it should never oscillate. However, we found that unconditionally stable guarantees may not apply to two-stage designs. In the end, the fix was simple, we just needed to add a damping resistor to one of the inductors on the circuit which reduces its Q-value. It seems that the change from FR4 to PTFE effectively increased the Q-value of this inductor so much, which in turn induced an oscillation in the circuit.

Discovery Dish Feed Head Enclosure

We’ve also refined the entire feed assembly. The feed arm pipe now has a ruler laser etched onto it so that mounting it at the correct distance is easy. A skew angle guide has also been added around the neck. A thumbscrew locking mechanism has been added to the feed head neck too, so that skew can easily be adjusted without the need for a screw driver or Allen wrench to loosen the set screw.

The PCB enclosure has been slightly refined and the injection molding die is currently in production and due to be completed in mid-May. While waiting for the die to be made, we’ve been testing different plastic mixes for the head enclosure to make sure that they are UV stable. The plastic mix has certain strict requirements and choosing the correct mix is crucial. It has to be RF-transparent with a low relative permittivity value, it has to endure direct sun, UV damage, and freezing weather, as well as be water-proof too.

S-Band Feed

Previously as noted in prior updates we were testing an S-band feed with the FR4 substrate. But we found that there was too much loss and the SNR values we got were not great. The move to PTFE substrate means that our experimental S-band feed is now working very well. We will be releasing this in the near future as an additional feed product that can be used with Discovery Dish. This feed will have a frequency range of 2.2 GHz - 2.3 GHz. This covers the main S-band weather satellites, other satellites like Coriolios and JASON as well as the many dump-only S-band satellites that transmit signals only over certain regions.

As requested by most people interested in an S-band feed, the S-band feed will not include a downconverter, so to use it you will either need an SDR like the HackRF which is capable of tuning to the S-band, or a third-party downconverter product.

Discovery Dish Outdoor Metal Enclosure Progress

Our enclosure set is now complete, and the final packing has almost been completed. The user manual can be found here Discovery Dish Outdoor Enclosure User Manual.pdf.

The final set consists of:

  • 1x Metal Enclosure
  • 3x Custom metal cable glands
  • 1x Vent
  • 1x Electronics mounting board
  • 1x Pole mounting set (with hose clamps)
  • 1x Wall/DIN mounting set
  • 1x 10 mm x 10 mm x 8 mm thermal pad (to be placed under the electronics mounting board)
  • 1x 10 mm x 10 mm x 3 mm thermal pad (to be placed under electronics on top of the mounting board)
  • 1x Set of various screws and washers

(Note that there will be some minor changes from this image in sets going out of customers - the hose clamp will be shorter, and the mounting rails will be longer)

Meteor M2-4 Launch

We mentioned in our last update that a new weather satellite Meteor M2-4 was due to launch. The launch was successful and the satellite is now in orbit. The satellite was briefly turned on after launch, and we were able to receive HRPT images from it in the L-band. However, now it is currently in a testing phase so the transmitters are often turned off. We don’t know how much longer it will be in testing, but we assume it won’t be more than a few more months.

GOES-U / GOES-19 Launch Updates

We’ve been keeping an eye on the expected launch date for the next GOES satellite. Currently, it has been delayed from April 30, 2024, to the new date of June 25, 2024, when it will be launched on a Falcon Heavy from Kennedy Space Center, Florida.

Elektro-L4 Updates

In the last update, we mentioned that we were having some problems getting SatDump to receive Elektro L4 properly on computing devices that used ARM processors. After some investigation, we determined that this was a problem with buffer size settings in SatDump and we were able to suggest a fix in https://github.com/SatDump/SatDump/pull/616 which was implemented. New versions of SatDump have this problem fixed.

Driver Tweaks

We have been looking at the RTL-SDR drivers and have found a few tweaks that can improve performance at L-band frequencies. We’ve put a modified version of the librtlsdr/librtlsdr fork up our the rtlsdrblog GitHub at https://github.com/rtlsdrblog/librtlsdr. With this fork and the PTFE feed upgrades, we now get around 5-6 dB of SNR on GOES-18.

Antenna Rotator

The low-cost antenna rotator is finishing up with prototype testing, and we are now working on improving the design’s manufacturability.

Timeline

The ramping of progress from the Chinese New Year holidays to now has been a little slower than expected, but if everything goes perfectly to plan, we will be on time for shipping by the end of June. However, this is currently a best-case scenario. There are still a few manufacturing stages to get through like the final mass production, CE testing and sea freight shipping. Unfortunately, from prior manufacturing experience, there are always setbacks along the way that slow progress, so we are conservatively pushing our advertised timeline back by about 1-2 months. We apologize for any potential delays, but we are working hard to get the product out to you ASAP!

Customer Questions

We have had a few more customer questions over email which we’d like the answer publicly below:

Would it be practical to use this kit indoors to do hydrogen-line astronomy? I ask because I live in a flat in a block of retirement flats, and wouldn’t be able to place an aerial or dish outside, but could find space for a Discovery dish + rotation gear inside.

Unfortunately, indoor Hydrogen line astronomy is out of the question. The hydrogen line signal is just too weak to be seen indoors, and there would most likely be too much interference indoors as well.

What all do i need to purchase and get for the Discovery Dish for Radio Astronomy?

You’ll need these two components from the Discovery Dish Crowd Supply store:

  • Discovery Dish (Dish & Mount Only)
  • Hydrogen Line Discovery Feed

You will also need a software defined radio, such as an RTL-SDR Blog V3/V4 which can be purchased separately, a computer and somewhere to mount your dish (e.g. a mast/tripod etc).

Have you tested this for C-Band / Aero downlink reception?

Currently, we do not have a C-band feed, so we have not tested it for this purpose. Generally, a larger 1.2 m+ dish is required for C-band AERO, so the 70 cm Discovery Dish may not be suitable. We may test this with Discovery Dish in the near future just in case however.

I want to purchase a hydrogen antenna. Where should I buy it? Also, please tell me what is needed to observe seti radio waves.

The Discovery Dish (Dish & Mount) and Hydrogen Line Discovery Feed can be pre-ordered from the Discovery Dish Crowd Supply store. I’m not sure exactly what you are referring to with SETI radio waves. An alien signal could in theory be on any frequency, but the 1.42 GHz Hydrogen line frequency could be a good bet as it’s a universal frequency of interest that any technological civilization would be observing. Realistically the Discovery Dish would be too small to detect potential alien signals unless they were very strong.

I’ve seen a small home made 3D-printed dish called a ‘heliocone dish’ being used for HRPT. How is Discovery Dish different?

The heliocone 3D printer design going around is a great DIY solution for L-Band polar orbiting HRPT satellites. But it has some limitations as it cannot receive the weaker geostationary satellites due to its smaller size and use of a circular polarized feed. It also cannot receive satellites using the opposite circular polarization. It also cannot receive satellites on different frequencies or the Hydrogen Line without designing a new helical feed and using a different LNA+filter combo. Discovery Dish is a more of a general purpose ‘does-it-all’ and ‘ready to use’ out-of-the-box dish. With our dish and feeds you can receive the L-Band polar orbiting HRPT satellites as well as the geostationary satellites. You can quickly swap out the feed for a different feed that covers a different band as well.

 

Receiving Unintentional Voice Transmissions from GPS Satellites

Over on dereksgc's YouTube channel we've discovered a few more recent interesting videos from his satellite decoding series that people may be interested in. One from two weeks ago shows how it's possible to receive voice transmissions on navigation satellites such as GPS.

Many navigational and meteorological satellites carry a search and rescue (SAR) repeater which is intended to receive UHF emergency locator beacons and rebroadcast them in the L-band or higher. However the repeaters appear to be picking up all sorts of other signals from the ground, including voice transmissions. Dereksgc notes that the theory is that there are some land based communications systems in some countries that are sharing frequencies that emergency locator beacons use, or that malicious pirates may be actively using these SAR repeaters for their own communications.

Dereksgc shows examples of retransmitted signals on the Beidou, GLONASS and Elektro-L satellite downlinks at 1.5442 GHz and at 2.226 MHz for the GPS satellites. He also shows what sort of satellite dish and feed setup you need. In the video he uses a HackRF as the SDR, but you could also use an RTL-SDR for the satellites that transmit at 1.5442 GHz.

Receiving voice transmissions from GPS satellites || Satellite reception pt.10

RTL-SDR Blog L-Band Patch, Bullseye, YouLoop Sale

This Black Friday we are offering a discount on our L-Band Patch, Bullseye and YouLoop antennas in our store and marketplace listings! The sale will run until the end of November.

Our L-Band patch is an active design for receiving L-band satellites such as Inmarsat, Iridium, GPS and other satellites that transmit between 1525 - 1660 MHz (please note that you cannot use it for weak signals that require a dish like HRPT or GOES).

The Bullseye LNB is a TCXO stabilized LNB for the QO-100 geostationary amateur satellite and other Ku-band satellites.

The YouLoop is a super portable passive HF/VHF loop antenna designed for super low NF/MDS receivers like the Airspy HF+ Discovery.

  • L-Band Patch Antenna: US $59.95 $49.95
  • Bullseye LNB: US $29.95 $24.95
  • YouLoop: US $39.95 $31.96

Pricing includes free shipping to most countries. Please note that pricing does not include VAT and/or taxes which may be added for your country.

Lon.TV Demonstrates Decoding Various Digital Signals with RTL-SDR

Tech YouTuber Lon.TV has recently uploaded a video demonstrating how to identify and decode various digital transmissions with an RTL-SDR dongle. In the video he explains how to use VB Cable to pipe audio from SDR# into various decoders, and then goes on to show DMR, APRS, POCSAG, L-Band AERO, FT8, and JS8/JS8CALL all being decoded via an RTL-SDR Blog V3 dongle.

Software Defined Radio Part 2 - Decoding Digital Transmissions with an RTL-SDR USB Radio

SignalsEverywhere tests our RTL-SDR Blog Active L-Band Patch Antenna

Sarah from the SignalsEverywhere YouTube channel is back this week with a video review and demonstration of our RTL-SDR Blog Active L-Band patch antenna, which is designed for receiving Inmarsat and Iridium satellites between 1525 - 1660 MHz with an RTL-SDR or other bias tee capable SDR.

In the video Sarah demonstrates the patch antenna in action running in SDR++, discusses some of the features and compares it against another patch antenna. She goes on to briefly show JAERO receiving and decoding an 8400bps AERO voice channel.

If you're interested, this antenna has also been reviewed by Frugal Radio, Tech Minds, and Mike from SDRplay

The patch is currently in stock in our store for $49.95 shipped worldwide, or on Amazon USA for US customers. We note that previous problems (as explained in our earlier post) with cracks in the plastic in the latest batch with grey enclosures have been resolved now, and units shipping now are without defect.

What can you do with this antenna?

The Best L Band Antenna for The Money PERIOD

RTL-SDR Blog Active L-Band Patch Antenna for Inmarsat, Iridium, GPS Back in Stock

Just a quick note to say that the second batch of our Active L-Band Patch Antenna for receiving Inmarsat, Iridium and other L-Band satellites is now in stock, available to be shipped from our warehouse in China from early next week. Amazon will be stocked within the next 1-2 months as the freighter will take time to arrive.

Please see our store for ordering details.

Apologies as we've had to temporarily suspend sales of this product as a manufacturing defect has been discovered in this batch. The defect is that on a number of units the plastic around the screws is cracking, and this was caused by a factory worker over torqueing a pneumatic screwdriver.

The antenna itself will work fine, and it probably won't even affect weather tightness, but it is certainly a defect. If your unit already shipped out and your unit has these cracks, please let us know at [email protected] and we will get the factory to ship you a replacement enclosure. For unshipped units we will be issuing a refund within the next few days.

Update: The units have been repaired and are available for shipping again.

Pricing remains the same at US$49.95 including free worldwide shipping to most countries. A reminder to EU customers: please order from our Aliexpress or eBay stores as due to the new IOSS laws we need to now use those marketplaces to collect and remit VAT upon your purchase, instead of upon import at the border.

This second batch comes in a gray color as feedback from the previous batch indicated that a lighter color is preferred to avoid excess heating from the sun.

If you are hearing about this patch antenna for the first time, please see our original release post for more information. In short this is an amplified patch antenna designed to be used with bias tee capable SDRs that can provide 3.3V - 5V power, such as our RTL-SDR Blog V3 dongle, Airspy, SDRplay or HackRF.

The antenna allows for reception of L-band satellites that transmit between 1525 - 1660 MHz, such as Inmarsat, Iridium and GPS. Please note it is *not* for receiving weaker signals like HRPT and GOES which require a dish antenna.

The patch comes with useful mounting accessories including a window suction cup, bendable tripod and 3M RG174 coax cable. The patch and active circuitry is enclosed in a weather proof enclosure.

What can you do with this antenna?

Frugal Radio: A Review of the NooElec Inmarsat Patch Antenna Bundle

In his latest video Rob from Frugal Radio has reviewed the NooElec Inmarsat Patch Antenna Bundle. The US$79.95 bundle includes a PCB patch antenna, Inmarsat SAWBird LNA, SMA DC Block, SMA Barrel adapter and SMA pigtail. In the video Rob tests the bundle out on various AERO signals using the JAERO software, before moving on to compare the bundle with our own RTL-SDR Blog Active L-Band Patch antenna. The comparison results show that our $49.95 L-band antenna is better by about 5-6dB in SNR.

Our RTL-SDR Blog Active L-Band Patch antenna set is available on our store. However, please note that this antenna is currently in short supply due to the global electronics supply chain shortage. We expect to be sold out within a few days but we are aiming to be able to restock within 1-2 months from now.

Review : NooElec L Band Inmarsat Patch Antenna Bundle

Frugal Radio: Review of our RTL-SDR Blog L-Band Patch Antenna

Over on YouTube Rob from Frugal Radio has uploaded a video reviewing our new L-Band Patch antenna which we released for sale late last month. The patch is currently on a release sale for US$44.95 including free standard airmail shipping to most countries. We will be ending the sale this Wednesday at which point the price will go to US$49.95, still with free standard airmail shipping to most countries. The patch can be purchased from our web store at www.rtl-sdr.com/store.

In the video Rob demonstrates the patch receiving Inmarsat signals strongly, and decodes a few AERO signals using JAERO. He shows that the patch works on any RTL-SDR with bias tee capability as well as an Airspy Mini. Lastly he compares the unit against the SDR-Kits patch.

We note that we are also supplying a kit for a giveaway to Frugal Radio subscribers that we will announce in an upcoming video coming out a few days time.

RTL-SDR updated L-band patch antenna review - perfect for your SDR radio!

UPDATE: Giveaway information now available in the latest video below.

RTL-SDR L-Band Patch Antenna Giveaway