3cm receive only system
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Dave Brown
I want to set up a receive only 3cm system to monitor beacons etc.
I understand that there are a few LNBs that use a crystal controlled LO and some of these are being used (with mods) to receive QO-100. As this application is 3cm receive only I believe I should be able to use the LNB, mechanically unmodified? I have no real limitations as regards IF frequency as long as its below 2GHz . I'm looking for recommendations as to which of the few LNBs available that fall in this category I should get. If I can get away with no LO mods so much the better but happy to eventually use an external frequency source if I find stability inadequate. Had a trawl through earlier posts re QO-100 etc but no clear picture has emerged re which LNB might be best for this application. 73 Dave, ZL3FJ Christchurch, NZ
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eightyelectric
I have modified several of these, and the 4 output versions, for use on q100, and 10.368 GHz. https://www.ebay.co.uk/itm/Octagon-Twin-PLL-Satellite-LNB-OTLG-0-1dB-Technology-Sensitive-25-MHZ-Crystal-/202622912037?_trksid=p2349624.m46890.l49292 Paul G6UAJ Sent from my Galaxy
-------- Original message -------- From: Dave Brown <2c39a@...> Date: 18/02/2021 21:48 (GMT+00:00) To: UKMicrowaves@groups.io Subject: [UKMicrowaves] 3cm receive only system I understand that there are a few LNBs that use a crystal controlled LO and some of these are being used (with mods) to receive QO-100. As this application is 3cm receive only I believe I should be able to use the LNB, mechanically unmodified? I have no real limitations as regards IF frequency as long as its below 2GHz . I'm looking for recommendations as to which of the few LNBs available that fall in this category I should get. If I can get away with no LO mods so much the better but happy to eventually use an external frequency source if I find stability inadequate. Had a trawl through earlier posts re QO-100 etc but no clear picture has emerged re which LNB might be best for this application. 73 Dave, ZL3FJ Christchurch, NZ
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Colin G4EML
Dave,
The problem is that the supply of LNBs is very unpredictable. Even those with the same part number often have different insides.
The Octagon LNBS were at one time very popular but QO-100 has caused the supply of those to dry up.
Basically any PLL type LNB will probably do what you want but there is always an element of chance when ordering. Feed it with 18 V via a Bias T and listen on 618 MHz with a SDR Dongle.
You can get away without modifying if you are happy to cope with quite a lot of drift. The frequency can be expected to be off by 100s of KHz at 10GHz with temperature drift. But it is normally fairly slow so you can still receive beacons OK. If you have a strong beacon to act as a marker it is not too much of a problem to compensate for the drift but if you only have weak beacons then you may struggle to find them. It is fairly easy to modify most LNBs to feed in an external high stability reference, once you do that they work very well. I have had one on my mast without a dish for some years now and I can often hear beacons by rain scatter.
Colin G4EML
From: Dave Brown
Sent: 18 February 2021 21:48 To: UKMicrowaves@groups.io Subject: [UKMicrowaves] 3cm receive only system
I want to set up a receive only 3cm system to monitor beacons etc. I understand that there are a few LNBs that use a crystal controlled LO and some of these are being used (with mods) to receive QO-100. As this application is 3cm receive only I believe I should be able to use the LNB, mechanically unmodified? I have no real limitations as regards IF frequency as long as its below 2GHz . I'm looking for recommendations as to which of the few LNBs available that fall in this category I should get. If I can get away with no LO mods so much the better but happy to eventually use an external frequency source if I find stability inadequate. Had a trawl through earlier posts re QO-100 etc but no clear picture has emerged re which LNB might be best for this application. 73 Dave, ZL3FJ Christchurch, NZ
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eightyelectric
They can also be used modified, but the drift due to temparature is more than I could live with. Sent from my Galaxy
-------- Original message -------- From: "eightyelectric via groups.io" <Eightyelectric@...> Date: 18/02/2021 22:10 (GMT+00:00) To: UKMicrowaves@groups.io Subject: Re: [UKMicrowaves] 3cm receive only system I have modified several of these, and the 4 output versions, for use on q100, and 10.368 GHz. https://www.ebay.co.uk/itm/Octagon-Twin-PLL-Satellite-LNB-OTLG-0-1dB-Technology-Sensitive-25-MHZ-Crystal-/202622912037?_trksid=p2349624.m46890.l49292 Paul G6UAJ Sent from my Galaxy -------- Original message -------- From: Dave Brown <2c39a@...> Date: 18/02/2021 21:48 (GMT+00:00) To: UKMicrowaves@groups.io Subject: [UKMicrowaves] 3cm receive only system I understand that there are a few LNBs that use a crystal controlled LO and some of these are being used (with mods) to receive QO-100. As this application is 3cm receive only I believe I should be able to use the LNB, mechanically unmodified? I have no real limitations as regards IF frequency as long as its below 2GHz . I'm looking for recommendations as to which of the few LNBs available that fall in this category I should get. If I can get away with no LO mods so much the better but happy to eventually use an external frequency source if I find stability inadequate. Had a trawl through earlier posts re QO-100 etc but no clear picture has emerged re which LNB might be best for this application. 73 Dave, ZL3FJ Christchurch, NZ
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Hi Dave
The German Octagon (PLL version) was quite good without mods, but it needed 30-45 minutes to stabilise. I have changed over to the 'Bullseye 10KHz' which claims 2 ppm TCXO stability. It certainly is far better than the Octagon, and after 2-3 minutes power applied, stayed within the QO-100 NB beacon frequency, and didn't need re-tuning on a typical SSB or CW signal. In fact, I had slightly more initial drift from the SDRplay (Mk 1) which is my IF (~739 MHz) receiver. 73 Martyn G3UKV On 18/02/2021 21:48, Dave Brown wrote:
I want to set up a receive only 3cm system to monitor beacons etc. I understand that there are a few LNBs that use a crystal controlled LO and some of these are being used (with mods) to receive QO-100. As this application is 3cm receive only I believe I should be able to use the LNB, mechanically unmodified? I have no real limitations as regards IF frequency as long as its below 2GHz . I'm looking for recommendations as to which of the few LNBs available that fall in this category I should get. If I can get away with no LO mods so much the better but happy to eventually use an external frequency source if I find stability inadequate. Had a trawl through earlier posts re QO-100 etc but no clear picture has emerged re which LNB might be best for this application. 73 Dave, ZL3FJ Christchurch, NZ
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