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Coto

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About Coto

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    Star Forming
  1. @Carl Reade 2 questions: 1) Is my single 30dB LNA sufficient, or must I necessarily get at least 1 in-line amplifier? Have you had any success without an in-line amplifier? 2) I am now about to paint the feed. Must I not paint the connector region at all, or can I also only have a tiny space unpainted where the 4 nuts are from the inside? In other words, must the entire connector plate make contact with the waveguide, or can only 4 nuts make contact (which will be in contact with the ground plate of the connector)? Is there any issue regarding "how much contact is enough"?
  2. EDIT: I had an issue/question but I figured it out.
  3. How can the absorption of electromagnetic energy by a conductive metal (antenna) be explained if electromagnetic radiation is interpreted as packets of energy (photons)? How can the interaction of photons with an antenna create an alternating electrical current?
  4. Adam: "You can us it with max 20V DC and 150mA current."
  5. It's based on 5V? Why did he say max 20V? And what do you think I should do? The only other bias-tee I have is this, but I'm not sure if it'll do or not: https://www.ebay.com/itm/RF-Divider-Biaser-Bias-Tee-10MHz-6GHz-for-HAM-radio-RTL-SDR-LNA-Amplifier-50VDC/113170701206?epid=21021845279&hash=item1a597fdb96:g:9Q0AAOSwvmxbWqtq Is the electronics chain I mentioned correct? Someone suggested the coax is probably 75 Ohms and it'll be a mismatch with the SMA cables.
  6. Carl, what's the specifications of your bias tee? Adam's Bandpass Filter [http://adsbfilter.blogspot.com/2015/06/hydrogen-line-1420-mhz-filter.html] (which I'm planning to use as a bias tee) seems to only be able to pass 150mA through the cable, yet, the LNA + in-line amps take up about 500mA. Am I misinterpreting Adam's words? Also, does your RTL-SDR get oversaturated by the high gain the LNA + 2x in-line Amplifiers output? Right now I'm trying to find the right cables to connect everything together. I would use a shielded 5-meter SMA to SMA extension cable but I've only got an unshielded SMA to SMA cable (I didn't know unshielded cables act as an antenna!). So here's my solution to avoid ordering a shielded SMA to SMA cable (which I've only found on ebay) and hold the build for another month or so: Is it a good idea to have the second In-line Amp after the long 5m cable? I'm mainly using it due to connectivity capabilities, cause I can't think of any other way of connecting the antenna to the SDR which is far away. *Are your in-line amps also F-Type? Thanks, Coto
  7. Alright, so the engineers built the feed for me: Might not be a factory-level construction, but I'm very happy for just €35 (he told me the next one would cost €60 because it came out harder than he thought haha). Question: Is it ok if I give it a good white paint (after a layer of primer paint)? I don't think I'll have any problem with reflectivity or something?
  8. How come the antenna probe connector's ground plate must be in contact with the feed, but it doesn't matter if the dish is also in contact? Antenna grounding is one of thing I really don't understand - why must the feed be in contact at all?
  9. Didn't know that, thanks. Is it OK that the feed is also in contact with the dish? A threaded rod (1-meter long screw) holds the feed into place which is held by the dish using 4 nuts in total (2 for the feed, 2 for the dish) end. Is that OK, or should I somehow isolate the feed-screw area with another material where electrical contact is made?
  10. So I am currently trying to find an engineer to craft the feed for me, so everything should be ready soon. Question: Should the antenna probe N-Type connector plate (GND?) be in contact with the metallic structure of the feed, or should I isolate it with some tape or something? Does it matter at all? Another question is, how conductive must the feed material be?
  11. Can anyone explain what antenna grounding is and if it's necessary in radio astronomy? I've heard about it being used in transmitting antennas but I'm not really sure if is used in receiving/radio astronomy antennas. Will I need to have wires or conductive metals going from my dish into the earth or something?
  12. Alright, my RTL-SDR V3 arrived and I want to connect it to my LNB and try some solar observations with my small dish. Now the LNB requires power (to run the down converter etc.) which means bias tee. We all know what happened when I last used a bias tee, so I need your guidance here. LNB -> F-type to SMA connector -> bias tee -> SDR Is this the right chain configuration? Thanks!
  13. The SBA430 LNA seems to be exactly what I want, and I found it at a cheaper price (80 GBP) sold by someone who no longer needs it. Hopefully he's still selling it!
  14. @Dave S Hi Dave, most LNAs from ebay and similar suppliers have unreliably bad characteristics (i.e. they say the NF very low or the gain is very high which is either not true because they're lying or their testing equipment is poor). The problem with most wide-band LNAs (as far as I understand the circuit of amplifiers) is that the wider the operating frequency, the lower the gain. Other than that issue, I could just use a bandpass filter, so I don't mind having a wide-band LNA as long as it covers my desired band and has a low noise-figure (NF) and reasonable Gain. Coto
  15. Hi all, I'm looking for an LNA at around 422 MHz. I'm basically trying to detect Pulsars using a very low-cost setup, like this guy managed to do: http://neutronstar.joataman.net/sites/iw5bhy_barga_3/index.html I'm looking to follow identical steps, but his LNA is no longer available. Anyone knows where I can get an LNA with similar characteristics (NF & Gain) to the author's LNA of choice? Thanks, - Coto P.S.: RTL-SDR V3 should arrive tomorrow. Hopefully connecting the Ku-Band LNB directly to the SDR should allow me to do some solar drift scans...
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