Have you silver plated it?
Posts by G0MJW
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For SSB Class AB is quite sufficient. No need for nearly Class A.
I agree but that is not an answer that is universal. SSB is not the only mode being used via OQ-100 so it depends. If you are doing DATV, which is where you need the larger powers this amplifier can generate, you might need more bias, or not, there is a sweet spot between current and spectral regrowth.
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Currently I use the 30W Spectrian module which is probably not much more than 20W at 2.4Ghz.
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Mine is 26W out of the box. Just turn down the bias on PA and driver and it runs much cooler. Also only command it on when transmitting.
Simples !
Dave
The bias level is a compromise between efficiency and linearity. Need to find the sweet spot.
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Hello OM's,
can someone explain to me what a square waveguide is good for at a LNB?
73's! Peter, DJ7GP
Look up square waveguide - you might just as well ask about a round one.
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I think you are correct, the values are different in the final article in the
BATC CQ-TV 263, maybe Mike G0MJW could give some comments?
I 'am still awaiting the BATC PCB and have to reorder some components also because of the different schematic component values
73 de Frank PH2M
This was all about getting DC in without getting 750 MHz and 25 MHz out. It is supposed to be a low pass filter. The 220nH is blocking the IF, The 10uH the reference. They may have been the wrong way round in an earlier diagram but they are OK in CQTV. It was supposed to be published last year but got bumped.
Well, that's what it is supposed to do but if you know better please do it.
Mike
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But when I check the origin, I also have this double-dip but far more deep >30dB compared to my week 11dB - but maybe as proposed fine-tuning will help.
I am not sure exactly what you mean but the dip ought to be 16-20 dB, no more as if it is it means both resonances are the same frequency and that's not s good for circular - (still pretty good though). The main thing is your amplifier is happy and you are a good signal into the satellite.
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Looks OK to me - the spurious resonance around 1.9 GHz is the reflector resonating and that varies depending on its size. The other resonance looks to be in the right place. It could be a little better match but there is the expected double dip. A little light bending will probably help improve the VSWR if it is a problem for your PA. The two dips are a little high - the aim is to have them evenly either side of the operating frequency.
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The same amount of heat dissipated, just in a different place. It might be easier just to use a larger dropper resistor rather that a regulator as the current is constant
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We could migrate to the pub / bar if the weather is nice.
Or even if the weather is not nice
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You need to consider the slant path attenuation - there is a very good ITU-R P series recommendation on this. P.618. https://www.itu.int/dms_pubrec…18-12-201507-S!!PDF-E.pdf
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DD4YR, are you sure ?.
I think the 2 Helixes act as an array and have a joint focus point which is right between the 2 helices. Thus it should fit very well.
Kind regards
Matthias
What he said.
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The maximum gain depends on the area of the dish, the actual gain depends on how well it is illuminated. You are doing well if you get 60-70% efficiency. The helix must be matched in gain to the focal length of the dish (and it must be at the focus). There will be additional loss from feed blockage for a prime focus dish. See W1GHZ excellent online papers.
If you dish gain is 25dB, then expect 23 dB in practice, if your feed radiation pattern is well matched to the dish.
2.4 GHz Gain
0.6m 21-22 dB
0.9m 24.5-25.5 dB
1.2m 27-28 dB
1.5m 29-30 dB
1.8m 30.5 - 31.5 dB
2.4m 33-34 dB
Mike
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Dear Bernard,
I understand your frustration, but we discussed this before the launch and concluded that this would not be a good idea.
Apart from legal and regulatory issues, we are currently not supporting the idea of remote access or "relaying" via Internet to the satellite using a transmit gateway.
Sorry...73s Peter
I agree - I would go further it is a bad idea for transmit - it is also pointless - transmit on internet over a satellite you cannot receive? Where is the skill and self training in that?
Mike
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HB9SKA Hi Thomas. I can only speak about the Octagon Quad LNB Green which I have. Before modification, It drifted quite a bit for the first 15 minutes or so and then became manageable - only slight re-tuning required then. I suspect that the dual output version (for which I sent the link) will be the same as it also has a 25MHz Xtal. None of them are going to be rock stable on their own but these are acceptable. 73 Russ.
Thay will be rock stable by definition surely, but the rock itself is the issue by the time it is multipiled by 390. Hence the replacement with an external LO. That is almost essential for narrow modes but there are other solutions - e.g. correction based on the beacon. Wideband is a different matter. You may be better off not locking if it increases the phase noise.
Mike
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It is still pretty strong.
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That is what the Bias-T reference injector I designed for BATC is for
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"UPLINK - PATCH VS HELIX - WHAT'S BETTER" aka how long is a piece of string? It depends - the patch is not optimum for a 0.6 f/D dish, though it isn't that bad. It is better for a dish 0.4 to 0.5. A helix, depending on the length may be better but it may also impact 10 GHz more. It needs simulating or measuring.
The patch performance can be easily improved for longer dishes, but at a much higher level of complexity. You maybe gain a dB or two. For EME, or on RX that would really matter but for QO-100 TX you are in practice gaining very little, less than half an s-point or, for many just having to back off the PA a little less to avoid being too strong.
Mike
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I designed a PCB for a TCXO with Remcos' crystal filter and PSU. The phase noise was OK but that particular TCXO was not stable enough. A GPS locked source from LEO Bodnar is a much better solution.
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I would build it as it is and just not use the waveguide, but if you really don't need it to be dual band you have a lot more options.
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The length of the tube is not critical. It is acting as waveguide which has a very low loss.
The differences in the inner diameters will work OK. Ideally it should be a smooth transition but a small step will not introduce much loss.
Yes - it works with prime focus - 0.5 f/D
