Posts by G8UGD

    I know this is an old thread, but I have one of the same units, an older synthesised device built around a MC151xx device with an EPROM that holds the programming data, for the APT format 2.4KHz tone system.

    I may have some informations/circuits somewhere on the unit and will try to find it just in case the original poster is still wanting information. No gaurantees.

    Cutting small groves in the track and fitting caps or even a resistor would still be possible. I measured the input current at just over 15 Volts in to the step up unit when transmitting it was 0.96 Amps so the unit is dissipating 15 Watts. I have a small fan I will connect to the fins if I can figure a mounting method.

    I have no larger amps at present, so just hope to get on SSB initially, need to test the POTY next.

    G8AGN I saw your response this morning so I set about putting something together as yours was the second one indicated with direct connection. I eventually etched a board, not done that in a long time, I did not follow any rules as I have no software for this just made something up. This is the board mounted on a heat sink.

    I have not put +5 dBm into the unit yet as the Hackrf I have limits at around -2 dBm but it looks like it has 26 or 27 dB gain. So for a first attempt at this in a very long time I am happy.

    Thanks all for your assistance.

    OK, I had assumed there would be some drift over time, otherwise they would not included the external port. For RX I would initially be relying on the SDR console locking to the beacon to remove the LNB drift, all guesswork until I actually get the unit and try it.

    The 5MHz oscillator I have has a spec of <=2 x 10-9ppm over -30 to +70 degree C, which I believe is better then most of the small TXCO's. Awaiting a MHL1336 and hope to provide a small 3 watt type amp and see if the will suffice.

    Hope to meet up on air!


    I am a beginner here and hope to be able to make SSB contacts at some point. I have ordered the BU500 and notice in some of the information that the reference can either be 10MHz or 26MHz. I was wondering if there is any option to select other standards. I have a 5MHz crystal oven style frequency standard that was used for quasi-sync PMR systems at UHF and would like to use that. I guess if not I could add a frequency doubler to go from 5 to 10 MHz. The 5 MHz standards crop up quite often.