Posts by PA1EW

    My Kuhne up-converter 2424A was returned this week after succesfull modification. I made some contacts that showed improved stability, even with the higher power-levels.

    So, now i could start testing my dual-band helix feed, together with a portable setup with 60cm offset dish on a tripod. Everything experimental and only practical tests done today.

    Several parts are re-used from the home-station. Downlink (Octagon LNB with mini-GPSDO and IF 435MHz ) was first set up and dish heading optimized. Using temporarily RTL-SDR for this test.

    Last test was TX Uplink-only (RX via Amsat-UK webSDR) with the combined dual-feed at a power level of abt 10-12W ( estimated 10W at the feed). FT817 used for driving the upconverter. First results showed strong uplink of some dB above the FSK-beacon, so a nice signal. Real measurements still to be done but this seems to work OK for portable use, as intended.

    Checking the up-and downlink combined (full-duplex) will follow after finishing the (compact) portable equipment construction that will serve demonstration purposes as well. My dualband patch-feed is also waiting to be tested. Hope the weather stays OK...

    73 Ed

    Very nice!. Perhaps you can consider, instead of the bag, using a suitable transparant cilinder (PE-PP) with top-cap slid over the whole dual band feed and leaving the under-side open. With this in place you are still able to view the beautifull internals and avoid condensation being built-up.

    73 Ed

    Did anyone test the new performance of a modified 2424 A, without using the external reference?. I am curious if one can use up to full power without degradation by "FM-ing".

    My unit is to arrive tomorrow and can't wait to have it back..

    73 Ed

    DD0KP Thanks Heiner, I am very curious how my patch will perform. Once I have the Kuhne up-converter back I can start testing ( and getting back on-air!).

    I think when your helix was properly built it should work as good as the patch. Anyway, whishing you good luck with the new patch-feed!. I now can see some pro's and con's and some depending on preference as well.

    73 Ed

    G0MJW Yes, it is silvered indeed. Just a very thin layer applied with rubb-on chemical process from a bottle with (toxic!) liquid containing silver. I used this also on my helix copper wires. It is more for the "looks" and perhaps does a good job regarding skin-effects.

    73 Ed

    Finished soldering my patch and RL measurements. After the first results (spot-on frequency) I tried a few times to resolder the patch radiator to obtain the "magic double-dip", but this I could not get in any way. When re-checking the information I realised that it may not appear at all (?). The main thing seems to be that the RL dip is not very deep, but instead a broad, shallow one. This was achieved with abt. 19dB so it should produce proper LHCP.

    Hope that my Kuhne blackbox returns soon after modification so I can continue with on-air tests.....

    It is not clear to me in which ways the patch can be "tweaked" ?.

    Mine is waiting to be soldered soon.

    73 Ed

    Hi David,

    I did not use this LNB model before, but perhaps have some hint how to use it without further modifications to make it work as a dual band feed.

    I have done some measurements with an Octagon Twin PLL (27MHz) and a 5,25 turns LHCP helical combination (G3RUH/G6LVB design). The interaction is very small between them: SWR of the helical, mounted as depicted below, is abt 25dB and watching the strenght of a beacon the LNB signal degradation was <1dB when the Helical with reflector was slid over the LNB frontcover. All this was done at the focus-point of an offset dish. Yes, I know the helix is not exactly in focus, but the error seems acceptable.

    I was not able to finish actual transmission tests as my Kuhne MKU2424A Up-converter currently is back to the company for the modifications...

    Several people do have good results with similar constructions.

    73 Ed PA1EW

    DK1MG Hello Hans-Jochen, as said by others 5 ... 10W should work alright with a 22dBi antenna. I can't find a reference to either LHCP or RHCP polarisation for it?. It must be RHCP of course, but I am almost sure this is correct.

    Another problem to look for is the N-connectors used on your cable(s). Any small error in mounting will cause a lot of extra attenuation at 2.4GHz. Could be a good idea to measure the cable(s) on a good SWR-analyzer.
    Do you know the antenna SWR with coaxial cables connected?. If not, measure- or ask someone else to all this do for you... Wishing you good luck!

    73 Ed PA1EW

    I did not try the HELI2400 antenna, but did see the very nice construction for real several times now (last time, they were all sold out..) I do not have any connection to this supplier, but you can be sure to buy quality. I do have some other ANJO antenna and these have a high mech. standard and good RF performance.

    When I would have problems with installing a dish, this antenna would be my 1st choice ( OK, it is not cheap but I would consider the investment).

    73 Ed PA1EW

    I removed the (naked) Octagon LNB from my RX dish and started to assemble the Helix-combination version-1. The plastic box houses the mini-GPSDO. Measured Helix Return Loss in feedpoint of a dish is abt 25dB. Just want to find out how much ERP-degradation, if any, the non-optimal positioning of the Helix in this way provides. Also influence on RX LNB to be checked.... To be continued.

    P.s. a weather-proofing solution with a PP-box seems to fit well

    73 Ed PA1EW

    Hello Martin, thanks for the info. Good to have you here!.

    I have just finished a similar construction G3RUH/G6LVB's design for the 5.25 turns helix and measured good RL. Only the cover frontpart of the Octagon will protrude the hole in the aluminum reflector plate, so I do not expect much influence from it. Hope to test this one soon.

    Another plan is to use a narrow 23mm rocket-LNB with dielectric lens more closely next to the helix. Already found that LNB attenuation from the helix in this way is very low.

    At this moment my station is separate TX offset dish 110cm + 5,25 helix LHCP and RX offset dish 78cm + modified Octagon OTLSO + GPSDO 27,841846MHz for IF 435MHZ

    73 Ed PA1EW

    Thanks Lucio, today I bought a cake box that is made from PP5 and is microwave safe. When I can I will test it on receive before I fit it.

    Unfortunately the power amplifier has died for some reason and I cannot transmit at present.

    Mike G4CDF


    Sorry to hear your power amp died. Wish you good luck fixing it!.

    73 Ed PA1EW