Posts by G0MJW

    "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

    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

    DIY MiniTiouner

    TEST OK

    I bought two FTS - 4334 lv. Using universal circuit board made a MiniTiouner v2.Is easy to succeed.Thank you for all the people who create MiniTiouner.Is you let me feel the infinite pleasure.

    A lot of design work there - I could have sent you the Kicad files for the V2 PCB which wold have saved you having to make all those new footprints. Still it's done now. I think it would be useful to add some features in a V3 based on what we have learned in the last couple of years. Move the FTDI chip to the board rather than use a plug in module. Add some switching to the IO. Enable both tuners at the same time. Revise the PSU. Header for OLED. Perhaps even do the 22kHz stuff

    Located 28,2E and turned antenna a small push west. Found transponder quite easily.


    73

    With a little trigonometry it should be easy. Once you are aligned on Astra at 28.2E all you need to do is calculate the angular offsets - e.g. 2 degrees to the south, 0.5 degrees higher (this depends on your location of course). Then measure the length of the feed arm. Say it is 100cm long from the pivot point, then 2 degrees is (close enough) 100*sin(2) = 3.5cm. All you need to do is find some way to mark the position for Astra and move it accordingly to get to BADR.


    Mike

    A very good and respectable motivation for sure, but if we are honest 99% of all hamradio operators don't do this. Going full duplex as suggested for satellite operations is very helpful here but the round trip time is messing with the brain. It needs a bit of practice to cope with a delayed version of own voice.

    You need experience of politics - speak regardless of what you hear is the secret.

    dg0opk I hope my post didn't offend you in any way. I never said that my source of information was your article about LNB mods. Just trying to find out why there is so much difference between TXCO from same series but not the same frequency.

    DD0KP I hope is not the case because i bought it from digi-key, part number CW654CT-ND Connor-Winfield #D75F-025.0M , paid 14.49$ + taxes...

    My intention is to help other hams not to spend money and (most important) time trying to use D75F 25MHz TCXO, like the one in the picture from my last post, with RT320M. It could be a both-side problem , TCXO+LNB, not figure-it out by now. I will try to send a e-mail to ConnorWinfield to get the whole picture.....


    73 de YO9HZN

    Mine is pretty useless too. Came from Digikey I think. Exactly the same symptoms. Putting it in an isolated thermally stable environment prevents this but I might as well use an OCXO in that case. Here is my PCB - perhaps it is not ideal but good enough I think.

    I don't really care about return loss as long as it is good enough. It is not an indicator of good antenna performance. A dummy load has an excellent return loss. The circular polarisation relies on two resonances and the bandwidth and hence broadband return loss suffers, but it is still over 20 dB in the band of interest.

    I have built a PCB to mount and filter the D75F TCXO (see twitter) using an idea from Remco on filtering the supply and with a crystal filter and buffer on the output for low phase noise. Unfortunately like several others here that TCXO does not seem to be suitable for SSB. It hunts up and down about a mean frequency. It is a lot more stable if kept in a sealed constant temperature environment - which rather defeats the point.


    Does anyone have a list of TCXOs are are or are not suitable?


    Note - personally I use a GPS reference. This is looking at options for those who don't want to spend €100 on one of those.


    Mike

    Very nicely made, however I should point out a few things for it to work better. Firstly your S-band patch is linearly polarised so you will lose 3 dB. Not necessarily a problem with that amplifier. Secondly the "phase centre" of your two feeds look to be a long way apart - that is unless the 10GHz horn is acting as a director at 2.4 GHz but I don't think it is the right size for that. This means you can have one or other feed at the dish focus, but not both. Ideally you would want both at the focus, but if that is not possible, then make sure it is the 10 GHz one.

    Meanwhile, last year I designed another feed that is circularly polarised on 2.4 GHz and has the 10 GHz phase centre much closer to the 2.4 GHz phase centre.


    There are a few Twitter posts from me on it and some other designs for different pipe sizes, different patch shapes and with additional directors e.g https://twitter.com/TheRealMike/status/1077166330195951616


    I have updated the dimensions since then and we have iterated with various builders. The latest version is here.





    Here is the pattern at 2.4 GHz. Simulated but seems about right from the test units.



    What is not obvious from the drawing is that the 10GHz feed is replaced by the dielectric lens from a rocket style LNB. This allows it to match the dish but also does not interfere with the 2.4 GHz pattern. The third image below shows that feed on a test patch very similar to the one you have built. I also did a design with a small horn but the size of that horn has to be limited - see twitter.


    ...and it will be written up, eventually.



    73 Mike G0MJW