Posts by G0MJW

    The question was : when I adjust the POTY for optimum SWR moving plates does the circulation affected?

    Yes. PLEASE DO NOT ADJUST LIKE THIS FOR MINIMUM VSWR. HOW MANY TIMES MUST I REPEAT THIS ? The same point comes up again and again and again. If you tune like that the chances are you will produce a linear antenna. HF DXCC types old antenna lore does not apply! POTY is a complex antenna.

    Now to get those resonances right build accurately. Exactly 3.00 mm spacing. No deviations in sizes, correct connector type. To tune if required use a vector network analyser and look and what's happening on a Smith Chart. If that's too difficult, perhaps ask someone for help. Really it needs the proper tools. If you really can't find a VNWA find where it is matching. If it's high gently bend all four corners towards the reflector just a little. Do it evenly and symmetrically. See what happens. If it's really far off frequency the dimensions are not correct.

    Here is mine - before and after.



    I would suggest doing some research on the Lime boards. It strongly depends which frequency band output you have selected. Perhaps the newer one is detecting differently. It could also be broken or the match makes it appear so. But does it really matter that they are different as long as you know? I would not run the lime anywhere near peak output.

    It looks well made. A ruler will not be accurate enough. Do you have a 3mm drill bit for example?

    What you need to do is find something 3mm thick (exactly, not approximately) and put it between the plates to measure the spacing. A metal shim is good for this. If it is not 3mm then you need to make it 3mm by resoldering the patch with a blowtorch or hot air gun. If you use a damp cloth behind you can prevent the reflector and connector from unsoldering while you melt the solder on the patch.

    Some people found a slightly under 3mm (say 2.9mm) aluminium shim between the plates is a good way to get a 3mm spacing. The difference allows for it not being easy to ensure it is tightly compressed together when at 350c. When that's done you should have a good match but if not it is possible to adjust be very slightly bending the patch. However you really need to have access test equipment to do this. They are only $60 for a Nanovna working to 3 GHz, but I recognise that unlike in the UK, you can buy a lot of beer for $60 in OM, so perhaps the local radio club has something they can lend?

    Hi Bill

    The POTY spacing and dimensions are critical for it to work. 4mm spacing is a 25% error so far to far out. I would suggest re-soldering it with a temporary 3mm spacer to get it correct. Then you might need to bend a little to get best match. Starting from 4mm spacing would not be good. Perhaps you can show a more detailed image ? The critical spacing is the gap between the plates but also the way the connector is mounted matters. There should be no screws coming into the gap.


    Here is what I came up with last night. With this setup, I could hear the beacon and some QSOs, but signals were weak. On TX, I could not see my signal on the waterfall. So more work needed.

    My guess is that the problem is the position of the feed. The feed is now the same distance from the feed as it was in the original, where it was working well, but in the original the bottom of the reflector was touching the mount, now it is about 2 cm above, so it is not pointing to the same spot on the dish. Any way to fix this?

    73, bill

    The simple way to fix the height change to grab one side of the mount firmly with one hand, the end of the boom with the other and bend the boom to the right spot. Most LNB supports for inexpensive dishes are suitably flexible to do this.


    Oh dear - there is usually a much simpler way to make it fit on a standard holder Just replace the top plastic part with a much thinner bit of metal. Done. Not this but hopefully you get the idea.

    [Blocked Image:]

    But really think it is plumbing so use readily available fittings. One of these mounted on the boom.

    [Blocked Image:]


    Instead you could use a non-LNB solution based on a 10 GHz receive converter. It might be cheaper to spend 40 Euro on a POTY kit.

    DB6NT ? Several people have re-tuned transverters I believe. Of course the cost is quite high but there must be thousands of old 10 GHz receive converters lying around that are no longer used after the OM upgraded or lost interest in microwaves. You can of course also just modify the LNB with an SMA rather than the probe but that's quite advanced and needs skill.


    I would go with the wrong frequency. If there is 20W going out and not a lot back it's got to be going somewhere. The coax is short I assume, not 50m of RG213! Dish should be brad enough at 2.4 GHz to be aligned. Why don't you check the LO is correct with the SDR ?



    I think the problem here is getting information out of you as to exactly what the set up is is quite difficult. If you need help tell us exactly what the end-end configuration is and then we will have a chance of understanding what might be wrong.

    For example your earlier comment about SWR getting better after you moved the feed back does not make sense. Moving the feed should not significantly impact VSWR. We later find out there is a 20W PA in line, but I recall the LED is on the transverter - so where is this VSWR being measured? Is there also an LED on the amplifier? I don't think there is. Therefore you have now a good match from transverter to amplifier which is useful but does not relate to the feed. That amplifier does have forward and reverse power monitoring. This should tell you if you are getting the correct power out and what the reflected power is. Measure these voltages. Compare with the manual. Tell us the result.


    The pluto does not hold the settings unless you configured it to in that config file. Normally the router will assign the same IP to the same MAC address, unless you told it to do something different. This is usually the best way to ensure the IP remains the same.